JP7624911B2 - Refrigeration Cycle Equipment - Google Patents

Description

This relates to a refrigeration cycle device that performs defrost operation on a heat exchanger.

Frost may form on the heat exchanger of a refrigeration cycle device installed outdoors. For example, in an air conditioner, which is a type of refrigeration cycle device, frost forms on the heat exchanger of the outdoor unit when the outdoor air temperature is low during heating operation, for example when the outdoor air temperature falls below freezing. When frost forms on the heat exchanger of a refrigeration cycle device, the performance of the refrigeration cycle device decreases. To prevent such a decrease in performance, a defrosting operation is performed to remove the frost that has formed on the heat exchanger, as described in Patent Document 1 (JP Patent Publication 2011-247582).

Some heat exchangers in refrigeration cycle devices are equipped with multiple heat transfer tubes, as described in Patent Document 1, for example. Some refrigeration cycle devices such as the one described in Patent Document 1 are equipped with a heat exchanger in which multiple paths are formed so that the refrigerant split into multiple heat transfer tubes flows in parallel.

In a heat exchanger with multiple paths, the way the frost melts during defrost operation may differ for each path depending on how the frost forms on each path and the heat supply conditions for each path. If the timing at which the frost melts differs significantly for each path, the timing to end the defrost operation will be set longer to match the path that ends defrosting the latest.

The challenge with such refrigeration cycle devices is to shorten the time required for defrost operation.

The refrigeration cycle device of the first aspect includes a heat exchanger, a flow rate adjustment mechanism, and a controller. The heat exchanger has multiple paths for dividing the refrigerant that performs the refrigeration cycle. The flow rate adjustment mechanism adjusts the flow rate of the refrigerant flowing through the multiple paths. The multiple paths include a first path and a second path that requires a longer time to defrost than the first path when the flow rate is not adjusted during defrost operation. The controller adjusts the flow rates of the refrigerant in the first and second paths using the flow rate adjustment mechanism during defrost operation, thereby reducing the flow rate of the refrigerant in the first path and increasing the flow rate of the refrigerant in the second path.

In the refrigeration cycle device of the first aspect, by adjusting the refrigerant flow rates in the first and second paths using the flow rate adjustment mechanism during defrost operation, the flow rate of the refrigerant flowing through the second path can be increased, making it possible to bring the time required for defrosting the first path closer to the time required for defrosting the second path, thereby shortening the overall time required for defrost operation.

The refrigeration cycle device of the second aspect is the refrigeration cycle device of the first aspect, and is provided with a temperature sensor that measures the temperature of the refrigerant flowing through the first path. The controller determines the completion of defrosting from the measurement result of the temperature sensor, and controls the flow rate adjustment mechanism to increase the flow rate of the refrigerant through the second path when it is determined that the defrosting of the first path is completed.

In the refrigeration cycle device of the second aspect, the temperature sensor of the first path can determine the appropriate timing for the controller's control, and the configuration for determining the appropriate timing for the controller's control can be realized with a simple configuration.

The refrigeration cycle device of the third aspect is the refrigeration cycle device of the first or second aspect, and is provided with a timer that counts the operation time of the defrost operation. The controller controls the flow rate adjustment mechanism to reduce the flow rate of the refrigerant flowing through the first path or increase the flow rate of the refrigerant flowing through the second path during the defrost operation according to the operation time of the defrost operation.

In the refrigeration cycle device of the third aspect, the timer can determine the appropriate timing for the controller's control, and the configuration for determining the appropriate timing for the controller's control can be realized with a simple configuration.

The refrigeration cycle device of the fourth aspect is the refrigeration cycle device of any one of the first aspect to the third aspect, in which the controller controls the refrigeration cycle to increase the proportion of gas components in the refrigerant flowing through the heat exchanger to a level higher than that of the heating operation, thereby performing defrost operation. The first path is located higher in the direction of gravity than the second path.

In the refrigeration cycle device of the fourth aspect, in the lower flow path in the direction of gravity where a large amount of liquid components with a large mass flow, the flow of the refrigerant is poor and frost is difficult to melt. However, by increasing the flow rate of the lower second path, the amount of heat supplied to the second path can be increased, and the time for defrost operation can be reliably shortened.

The refrigeration cycle device of the fifth aspect is a refrigeration cycle device of any one of the first aspect to the fourth aspect, in which the heat exchanger has a first flat multi-hole tube through which the first path passes and a second flat multi-hole tube through which the second path passes.

In the refrigeration cycle device of the fifth aspect, the flow rate varies greatly in a flat multi-hole pipe with a small flow cross-sectional area for each passage, so the time required to defrost the second pass can be significantly reduced, resulting in a noticeable effect in reducing the defrost time.

The refrigeration cycle device of the sixth aspect is a refrigeration cycle device of any one of the first aspect to the fifth aspect, in which the flow rate adjustment mechanism includes at least one of a first valve arranged in the first path for adjusting the flow rate of the refrigerant flowing through the first path, and a second valve arranged in the second path for adjusting the flow rate of the refrigerant flowing through the second path.

In the refrigeration cycle device of the sixth aspect, the flow rate adjustment mechanism is configured with at least one valve, and the flow rate adjustment mechanism can be realized with a simple configuration.

The refrigeration cycle device of the seventh aspect is the refrigeration cycle device of the sixth aspect, in which the flow rate adjustment mechanism includes both the first valve and the second valve. The controller adjusts the first valve and the second valve in a direction to bring the flow rates through the first path and the second path closer together during cooling operation or heating operation.

The refrigeration cycle device of the seventh aspect can shorten the defrost operation time and improve the efficiency of cooling or heating operation.

1 is a circuit diagram illustrating an example of an air conditioner according to the present disclosure. FIG. 2 is a partially enlarged perspective view for explaining an example of a heat exchanger of an air conditioner. FIG. 3 is a schematic cross-sectional view showing an example of a connecting header of the heat exchanger of FIG. 2. FIG. 3 is a schematic partial cross-sectional view for explaining paths of the heat exchanger of FIG. 2 . 5 is a graph for explaining temperature increases in the first path and the second path during a defrost operation. FIG. 11 is a partially enlarged perspective view for explaining another example of a heat exchanger for an air conditioner. FIG. 7 is a schematic partial cross-sectional view for explaining paths of the heat exchanger of FIG. 6 . 5 is a flowchart showing an example of a flow rate control operation in a defrost operation in the first embodiment. 9 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 8 is performed. 1 is a perspective view showing a specific example of an outdoor unit of an air conditioner according to the present disclosure. FIG. 11 is a schematic cross-sectional view for explaining an air flow in the outdoor unit of FIG. 10 . 11 is a schematic perspective view showing an example of a heat exchanger provided in the outdoor unit of FIG. 10. 11 is a schematic perspective view showing another example of a heat exchanger provided in the outdoor unit of FIG. 10 . FIG. 13 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 12 according to the first embodiment. FIG. 14 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 13 according to the first embodiment. 10 is a flowchart showing another example of the flow rate control operation in the defrost operation in the first embodiment. 17 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 16 is performed. FIG. 5 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 2 according to the second embodiment. FIG. 7 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 6 according to the second embodiment. 10 is a flowchart showing an example of a flow rate control operation in a defrost operation in the second embodiment. 21 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 20 is performed. FIG. 10 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 2 according to a third embodiment. FIG. 7 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 6 according to a third embodiment. 13 is a flowchart showing an example of a flow rate control operation in a defrost operation in the third embodiment. 25 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 24 is performed. FIG. 10 is a schematic partial cross-sectional view for explaining an example of a path of the heat exchanger of FIG. 2 according to a fourth embodiment. 13 is a flowchart showing an example of a flow rate control operation in a defrost operation in the fourth embodiment. 28 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 27 is performed. 13 is a flowchart showing another example of the flow rate control operation in the defrost operation of the fourth embodiment. 30 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 29 is performed. 13 is a schematic partial cross-sectional view for explaining a specific example of a path of the heat exchanger of FIG. 12 according to the fourth embodiment. FIG. 32 is a flowchart showing another example of the flow rate control operation in the defrost operation of the heat exchanger shown in FIG. 31 . 33 is a graph showing an example of a change in the refrigerant flow rate in each path when the flow rate control operation shown in FIG. 32 is performed.

First Embodiment
(1) Overall Configuration In the following, the refrigeration cycle device will be described using an air conditioner 1 shown in Fig. 1 as an example. The air conditioner 1 is a device capable of cooling and heating the interior of a building or the like by performing a vapor compression refrigeration cycle. The air conditioner 1 has an outdoor unit 2, indoor units 3a and 3b, communication pipes 4 and 5 connecting the outdoor unit 2 and the indoor units 3a and 3b, and a controller 23 that controls the components of the outdoor unit 2 and the indoor units 3a and 3b (components of the air conditioner 1). The refrigerant circuit 6 of the air conditioner 1 is configured by connecting the outdoor unit 2 and the indoor units 3a and 3b via the communication pipes 4 and 5. A vapor compression refrigeration cycle is performed by circulating a refrigerant through the refrigerant circuit 6. In a vapor compression refrigeration cycle, a refrigerant mainly made of gas is compressed (the pressure of the refrigerant is made high), heated, condensed by heat dissipation to liquefy, decompressed and expanded to evaporate a part of the liquid refrigerant (the pressure of the refrigerant is made low), and the remaining liquid refrigerant is evaporated and vaporized, and the refrigerant removes heat. In this disclosure, a refrigerant mainly made of gas is called a gas refrigerant, and a refrigerant mainly made of liquid is called a liquid refrigerant. The concept of gas refrigerant includes a refrigerant in a gas-liquid two-phase state in which a small amount of liquid refrigerant is mixed in a gas refrigerant, and the concept of liquid refrigerant includes a refrigerant in a gas-liquid two-phase state in which a small amount of gas refrigerant is mixed in a liquid refrigerant.

The outdoor unit 2 is installed outdoors (on the roof of a building or near a wall of a building, etc.) and constitutes part of the refrigerant circuit 6. The outdoor unit 2 has an accumulator 7, a compressor 8, a four-way valve 10, a heat exchanger 11, an outdoor expansion valve 12 as an expansion mechanism, shut-off valves 13 and 14, and an outdoor fan 15. The devices of the outdoor unit 2 that constitute the refrigerant circuit 6 are connected by refrigerant pipes 16 to 22.

The indoor units 3a and 3b are installed indoors (such as in a living room or in the attic space) and constitute part of the refrigerant circuit 6. The indoor unit 3a has an indoor expansion valve 31a, an indoor heat exchanger 32a, and an indoor fan 33a. The indoor unit 3b has an indoor expansion valve 31b as an expansion mechanism, an indoor heat exchanger 32b, and an indoor fan 33b. The indoor heat exchangers 32a and 32b are composed of, for example, flat multi-hole pipes 63 (see Figures 2 and 6) and heat transfer fins 64 (see Figures 2 and 6).

The connecting pipes 4 and 5 are refrigerant pipes that are installed on-site when the air conditioner 1 is installed in a building or other installation location. One end of the connecting pipe 4 is connected to the shutoff valve 13 of the outdoor unit 2, and the other end of the connecting pipe 4 is connected to the liquid side ends of the indoor expansion valves 31a and 31b of the indoor units 3a and 3b. One end of the connecting pipe 5 is connected to the shutoff valve 14 of the outdoor unit 2, and the other end of the connecting pipe 5 is connected to the gas side ends of the indoor heat exchangers 32a and 32b of the indoor units 3a and 3b. In this disclosure, the liquid side end is, in other words, an inlet/outlet through which the liquid refrigerant flows, and the gas side end is, in other words, an inlet/outlet through which the gas refrigerant flows.

The controller 23 is configured by communication connection with control boards (not shown) provided in the outdoor unit 2 and the indoor units 3a and 3b. For convenience, the controller 23 is illustrated in FIG. 1 at a position separate from the outdoor unit 2 and the indoor units 3a and 3b. The controller 23 controls the components of the outdoor unit 2 and the indoor units 3a and 3b. In other words, the controller 23 is configured to control the overall operation of the air conditioner 1. The controller 23 controls, for example, the opening degree of the outdoor expansion valve 12 and the indoor expansion valves 31a and 31b. For example, if the compressor 8 is capable of changing its rotation speed, the controller 23 controls the rotation speed of the compressor 8. Also, for example, if the outdoor fan 15 and the indoor fans 33a and 33b are capable of changing their rotation speed, the controller 23 controls the rotation speed of the outdoor fan 15 and the indoor fans 33a and 33b.

The controller 23 is realized by, for example, a computer. The controller 23 includes, for example, a control arithmetic unit and a storage device. The control arithmetic unit can be a processor such as a CPU or a GPU. The control arithmetic unit reads a program stored in the storage device and performs predetermined image processing and arithmetic processing according to the program. Furthermore, the control arithmetic unit can write the results of the calculation to the storage device and read information stored in the storage device according to the program.

(2) Operation of the Air Conditioner The air conditioner 1 is configured to be capable of performing cooling operation, heating operation, and defrost operation. The air conditioner 1 may be configured to be capable of performing operations other than the three types of operation described above (for example, fan operation, dehumidification operation). The air conditioner 1 may be capable of only heating operation and defrost operation, without performing cooling operation. In the cooling operation and defrost operation, the air conditioner 1 circulates the refrigerant through the compressor 8, the heat exchanger 11, the outdoor expansion valve 12 and the indoor expansion valves 31a and 31b, and the indoor heat exchanger 32a and 32b in this order. In the heating operation, the air conditioner 1 circulates the refrigerant through the compressor 8, the indoor heat exchanger 32a and 32b, the indoor expansion valves 31a and 31b, the outdoor expansion valve 12, and the heat exchanger 11 in this order. The defrost operation is performed during the heating operation to melt the frost that has adhered to the heat exchanger 11. In the present disclosure, the defrost operation in which the refrigerant flows in the opposite direction to the refrigerant circulation direction in the refrigerant circuit 6 during the heating operation may be referred to as a reverse cycle defrost. The cooling operation, the heating operation, and the defrost operation are controlled by the controller 23.

During cooling operation and defrost operation, the four-way valve 10 is switched to the connection state shown by the solid line in FIG. 1. The connection state shown by the solid line in FIG. 1 is a state in which the compressor 8 and the heat exchanger 11 are connected, and the accumulator 7 and the connecting pipe 5 are connected. In the refrigerant circuit 6, the low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor 8, compressed to the high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor 8 is sent to the heat exchanger 11 through the four-way valve 10. In the heat exchanger 11, the high-pressure gas refrigerant sent to the heat exchanger 11 exchanges heat with the outdoor air (outdoor air) supplied as a cooling source by the outdoor fan 15, dissipates heat, and becomes a high-pressure liquid refrigerant. At this time, the heat exchanger 11 functions as a refrigerant radiator. The high-pressure liquid refrigerant that has dissipated heat in the heat exchanger 11 is sent to the indoor expansion valves 31a and 31b through the outdoor expansion valve 12, the shutoff valve 13, and the connecting pipe 4. The refrigerant sent to the indoor expansion valves 31a and 31b is decompressed to the low pressure of the refrigeration cycle by the indoor expansion valves 31a and 31b, becoming a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the indoor expansion valves 31a and 31b is sent to the indoor heat exchangers 32a and 32b. The low-pressure gas-liquid two-phase refrigerant sent to the indoor heat exchangers 32a and 32b exchanges heat with indoor air supplied as a heat source by the indoor fans 33a and 33b in the indoor heat exchangers 32a and 32b, and evaporates. The indoor air cooled by the indoor heat exchangers 32a and 32b is supplied to the room, thereby cooling the room. The low-pressure gas refrigerant that has evaporated in the indoor heat exchange sections 32a and 32b is sucked back into the compressor 8 via the connecting pipe 5, the shutoff valve 14, the four-way valve 10, and the accumulator 7.

During heating operation, the four-way valve 10 is switched to the connection state shown by the dashed line in FIG. 1. The connection state shown by the dashed line in FIG. 1 is a state in which the compressor 8 and the connecting pipe 5 are connected, and the accumulator 7 and the heat exchanger 11 are connected. In the refrigerant circuit 6, the low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor 8, compressed to the high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor 8 is sent to the indoor heat exchangers 32a and 32b through the four-way valve 10, the shutoff valve 14, and the connecting pipe 5. The high-pressure gas refrigerant sent to the indoor heat exchangers 32a and 32b exchanges heat with the indoor air supplied as a cooling source by the indoor fans 33a and 33b in the indoor heat exchangers 32a and 32b, dissipates heat, and becomes a high-pressure liquid refrigerant. The indoor air heated by the indoor heat exchangers 32a and 32b is supplied to the room, thereby heating the room. The high-pressure liquid refrigerant that has released heat in the indoor heat exchanger 32a, 32b is sent to the outdoor expansion valve 12 through the indoor expansion valves 31a, 31b, the connecting pipe 4, and the closing valve 13. The refrigerant sent to the outdoor expansion valve 12 is decompressed to the low pressure of the refrigeration cycle by the outdoor expansion valve 12, becoming a low-pressure two-phase gas-liquid refrigerant. The low-pressure two-phase gas-liquid refrigerant decompressed by the outdoor expansion valve 12 is sent to the heat exchanger 11. The low-pressure two-phase gas-liquid refrigerant sent to the heat exchanger 11 exchanges heat with the outdoor air supplied as a heat source by the outdoor fan 15 in the heat exchanger 11, evaporating and becoming a low-pressure gas refrigerant. At this time, the heat exchanger 11 functions as a refrigerant evaporator. The low-pressure refrigerant evaporated in the heat exchanger 11 is sucked back into the compressor 8 through the four-way valve 10 and the accumulator 7.

During heating operation, if the controller 23 detects frost on the heat exchanger 11, the air conditioner 1 performs a defrost operation to melt the frost on the heat exchanger 11. For example, when the temperature of the refrigerant at a predetermined point of the heat exchanger 11 becomes lower than a predetermined temperature, the controller 23 determines that the condition for starting defrosting of the heat exchanger 11 has been reached. In defrost operation, as in cooling operation, the four-way valve 10 is switched to the connection state shown by the solid line in FIG. 1 to make the heat exchanger 11 function as a radiator of the refrigerant. By supplying high-temperature and high-pressure gas refrigerant to the heat exchanger 11, the frost on the heat exchanger 11 can be melted. In other words, in defrost operation, the ratio of gas components of the refrigerant flowing through the heat exchanger 11 is higher than in heating operation due to the refrigeration cycle. The defrost operation is performed, for example, until it is determined that defrosting in the heat exchanger 11 is complete when the temperature of the refrigerant in the heat exchanger 11 or the temperature at a predetermined location in the heat exchanger 11 becomes higher than a predetermined temperature. Alternatively, the defrost operation is performed, for example, until a defrosting time set in consideration of the state of the heating operation before defrosting has elapsed. After the defrost operation is completed, the operation returns to the heating operation.

(3) Heat exchanger 11
(3-1) Two-row heat exchanger 11
As shown in FIG. 2, the heat exchanger 11 includes a plurality of flat multi-hole tubes 63 and a plurality of fins 64. The flat multi-hole tube 63 is a flat tube having a flat portion 63a that serves as a heat transfer surface and a plurality of passages 63b formed therein. Each passage 63b is a small through hole through which the refrigerant flows. The fin 64 shown in FIG. 2 has a plurality of elongated notches 64a formed at a distance from each other. The fin 64 also has a plurality of fin main portions 64b sandwiched between adjacent notches 64a and a long edge portion 64c that extends continuously in the row direction. Each of the flat multi-hole tubes 63 is inserted into each notch 64a. A ventilation passage through which air flows is formed between the flat multi-hole tubes 63 of adjacent rows inserted into the notches 64a. The shape of the fin 64 shown here is an example, and fins having other shapes may also be used. 2 has a configuration in which two rows of flat multi-hole tubes 63 cross the air flow. Each row includes, for example, three or more stages of flat multi-hole tubes 63.

As shown in FIG. 3, two rows of flat multi-hole tubes 63 are connected to the connecting header 90. The flat multi-hole tube 631 of the first row 11A is arranged on the windward side, and the flat multi-hole tube 632 of the second row 11B is arranged on the leeward side. The refrigerant flowing through the flat multi-hole tube 631 of the first row 11A flows from the flat multi-hole tube 631 of the first row 11A to the flat multi-hole tube 632 of the second row 11B via the connecting header 90. When flowing in the opposite direction to the above-mentioned refrigerant direction, the refrigerant flowing through the flat multi-hole tube 632 of the second row 11B flows from the flat multi-hole tube 632 of the second row 11B to the flat multi-hole tube 631 of the first row 11A via the connecting header 90. In other words, the refrigerant that flows through the flat multi-hole tube 631 of the first row 11A or the flat multi-hole tube 632 of the second row 11B is turned back at the connection header 90.

Note that, although the configuration in which the refrigerant flows in a folded manner in the connecting header 90 is described here, the heat exchanger 11 to which the present disclosure is applied can also be configured so that the refrigerant flows in the same direction through the flat multi-hole tubes 631 in the first row 11A and the flat multi-hole tubes 632 in the second row 11B without folding the refrigerant.

As shown in FIG. 4, the heat exchanger 11 includes a first path PA1 and a second path PA2. Since the flat multi-hole tubes 63 are arranged in many stages in the heat exchanger 11, it is necessary to finally distribute the refrigerant to each stage. However, if the refrigerant supplied to the heat exchanger 11 is distributed to all the flat multi-hole tubes 63 at once, problems such as uneven flow of the refrigerant will occur, so the refrigerant is divided into multiple groups, with multiple stages as one group. For example, the first path PA1 is configured as one group of m stages (m is an integer), and the second path PA2 is configured as one group of n stages (n is an integer). m and n may be the same number or different numbers. One heat exchanger 11 may have multiple first paths PA1 and multiple second paths PA2. In addition, there may be other paths (third path, fourth path, ...) with different numbers of stages other than the first path PA1 and the second path PA2.

In FIG. 4, the flow of the refrigerant during defrost operation is indicated by arrows. In the first path PA1, the refrigerant flowing through one second refrigerant distribution pipe 76 is divided into m pipes and flows into the m-th stage of the flat multi-hole tube 63 of the first row 11A. The refrigerant flowing through the m-th stage of the flat multi-hole tube 63 of the first row 11A is turned back at the connection header 90 and flows through the m-th stage of the flat multi-hole tube 63 of the second row 11B to the one first refrigerant distribution pipe 72 of the first path PA1. In the second path PA2, the refrigerant flowing through one second refrigerant distribution pipe 76 is divided into n pipes and flows into the n-th stage of the flat multi-hole tube 63 of the first row 11A. The refrigerant flowing through the n-th row of flat multi-hole tubes 63 in the first row 11A is turned around by the connection header 90, passes through the n-th row of flat multi-hole tubes 63 in the second row 11B, and flows into one first refrigerant distribution tube 72 in the second path PA2.

Comparing the first path PA1 and the second path PA2, the second path PA2 takes longer to defrost than the first path PA1 when the flow rate is not adjusted during defrost operation. Figure 5 shows the temperatures of the outlet pipes of the first path PA1 and the second path PA2. Figure 5 shows the temperatures of the outlet pipes of the first path PA1 and the second path PA2 during defrost operation when the first path PA1 and the second path PA2 are not adjusted by the flow rate adjustment mechanism 100 (see Figure 4), which will be described later. As shown in Figure 5, when the flow rate is not adjusted during defrost operation, the temperature rise of the second path PA2 during defrost operation is smaller, and the second path PA2 takes longer to defrost than the first path PA1.

The reason why the second path PA2 takes longer to defrost than the first path PA1 when the flow rate is not adjusted during defrost operation will be briefly explained below. For example, when the stage direction of the heat exchanger 11 is aligned with the vertical direction, condensation water flows downward due to gravity, so that more frost forms on the flat multi-hole tubes 63 of the lower path than on the flat multi-hole tubes 63 of the upper path. In this case, the upper path corresponds to the first path PA1, and the lower path corresponds to the second path PA2. The second path PA2, which has a lot of frost, requires more heat to defrost than the first path PA1, and takes longer to defrost.

For example, in defrost operation with a small circulation volume, the pressure difference (differential pressure) of the refrigerant between the inlet and outlet of each passage 63b of the flat multi-hole tube 63 becomes very small. If the differential pressure of the flat multi-hole tube 63 is small, the liquid refrigerant accumulated in the passage 63b of the flat multi-hole tube 63 is poorly discharged, the flow rate of the refrigerant decreases, and the time required for defrosting becomes longer. If the second path PA2 is poorer at discharging liquid refrigerant than the first path PA1, the second path PA2 will take longer to defrost than the first path PA1 unless the flow rate is adjusted during defrost operation.

For example, the flat multi-hole tubes 63 in the lower stage of the heat exchanger 11 radiate more heat to surrounding components such as the bottom frame 42 (see Figure YY). If the second path PA2 radiates more heat per unit time to surrounding components than the first path PA1, the second path PA2 will take longer to defrost than the first path PA1 unless the flow rate is adjusted during defrost operation.

(3-2) Single-row heat exchanger 11
Configurations that can be used for the heat exchanger 11 of the present disclosure include a single row configuration shown in Fig. 6 and a configuration with three or more rows (not shown) in addition to the two row configuration shown in Fig. 2. The heat exchanger 11 shown in Fig. 6 also includes a plurality of flat multi-hole tubes 63 and a plurality of fins 64. The heat exchanger 11 shown in Fig. 6 is configured such that one row of flat multi-hole tubes 63 crosses the air flow. Each row includes, for example, three or more stages of flat multi-hole tubes 63.

As shown in FIG. 7, a row of multiple flat multi-hole pipes 63 is connected to the connecting header 90. The multiple flat multi-hole pipes 63 are connected to a header collector pipe 80. The header collector pipe 80 and the connecting header 90 are hollow cylindrical members with both ends closed. The internal space of the header collector pipe 80 is divided by multiple partition plates 81 into spaces that separate the refrigerant flowing in the first path PA1 and the second path PA2. The internal space of the connecting header 90 is divided by multiple partition plates 91 into spaces that flow the refrigerant in the first path PA1 and the second path PA2.

The internal space of the header collecting pipe 80 between the two partition plates 81 is divided into two spaces by the partition plate 82. The internal space of the header collecting pipe 80 between the partition plate 81 and the end of the header collecting pipe 80 is divided into two spaces by the partition plate 82. One of the two spaces divided by the partition plate 82 is a space through which gas refrigerant flows, and the other is a space through which liquid refrigerant flows. A first refrigerant distribution pipe 72 is connected to the space through which the liquid refrigerant flows in the header collecting pipe 80. The refrigerant divided by the distribution unit 71 flows in the first refrigerant distribution pipes 72. A second refrigerant distribution pipe 76 is connected to the space through which the gas refrigerant flows in the header collecting pipe 80. The refrigerant divided by the distribution unit 75 flows in the second refrigerant distribution pipes 76.

The refrigerant split by the splitter 71 flows through each first refrigerant split pipe 72 into each space in the header collecting pipe 80 where the liquid refrigerant flows. In each space in the header collecting pipe 80 where the liquid refrigerant flows, the refrigerant is further split and flows through each flat multi-hole pipe 63 to the connecting header 90. In the connecting header 90, the refrigerant that has passed through the multiple flat multi-hole pipes 63 is first combined and then split into multiple flat multi-hole pipes 63 connected to the space in the header collecting pipe 80 where the gas refrigerant flows. The refrigerant that flows from the multiple flat multi-hole pipes 63 into each space in the header collecting pipe 80 where the gas refrigerant flows is combined and flows into each second refrigerant split pipe 76.

When flowing in the opposite direction to the above-mentioned refrigerant direction, the refrigerant divided at the dividing section 75 flows through each second refrigerant dividing pipe 76 into each space in the header collecting pipe 80 where the gas refrigerant flows. In each space in the header collecting pipe 80 where the gas refrigerant flows, the refrigerant is further divided and flows through each flat multi-hole pipe 63 (gas side flow path GC) to the connecting header 90. In the connecting header 90, the refrigerant that has passed through the multiple flat multi-hole pipes 63 is once combined and then divided into multiple flat multi-hole pipes 63 (liquid side flow path RC) connected to the space in the header collecting pipe 80 where the liquid refrigerant flows. The refrigerants that flow from the multiple flat multi-hole pipes 63 into each space in the header collecting pipe 80 where the liquid refrigerant flows are combined and flow into each first refrigerant dividing pipe 72. Note that here, a configuration in which the refrigerant flows by turning it back at the connecting header 90 is described, but the heat exchanger 11 to which the present disclosure is applied may be configured to flow the refrigerant without turning it back.

As shown in FIG. 7, the heat exchanger 11 includes a first path PA1 and a second path PA2. A plurality of stages are divided into a plurality of groups. For example, the first path PA1 is composed of m stages (m is an integer) as one group, and the second path PA2 is composed of n stages (n is an integer) as one group. m and n may be the same number or different numbers. In FIG. 7, the first path PA1 is composed of 18 stages of flat multi-hole tubes 63, and the second path PA2 is also composed of 18 stages of flat multi-hole tubes 63. The liquid side flow path RC, in which the liquid refrigerant mainly flows, is composed of four stages of flat multi-hole tubes 63 among the first path PA1 and the second path PA2, and the gas side flow path GC, in which the gas refrigerant mainly flows, is composed of the remaining 14 stages of flat multi-hole tubes 63. The boundary between the liquid side flow path RC and the gas side flow path GC is indicated by a two-dot chain line. In the heat exchanger 11 shown in FIG. 7, when the first path PA1 and the second path PA2 are compared, the second path PA2 takes longer to defrost than the first path PA1 when the flow rate is not adjusted during defrost operation. The reason why the second path PA2 takes longer to defrost than the first path PA1 is the same as that of the two-row heat exchanger 11 already described, so the explanation is omitted.

(4) Configuration for Flow Rate Control in Defrost Operation (4-1) Configuration for Flow Rate Control of Heat Exchanger 11 with Two-row Configuration As shown in Fig. 4, the flow rate adjustment mechanism 100 includes a first valve 111 provided in the first refrigerant diversion pipe 72 which is the outlet of the liquid refrigerant of the first path PA1. The first valve 111 may be an on-off valve which only opens and closes, or may be an electrically operated valve which can adjust the opening degree.

The air conditioner 1 includes a first temperature sensor 121 attached to the first refrigerant distribution pipe 72 of the first path PA1 and a second temperature sensor 122 attached to the first refrigerant distribution pipe 72 of the second path PA2. The first temperature sensor 121 is a temperature sensor that measures the temperature of the refrigerant flowing through the first path PA1, and transmits the measured value to the controller 23. More specifically, the temperature of the refrigerant measured by the first temperature sensor 121 is the temperature of the refrigerant in the first path PA1 after heat exchange in the heat exchanger 11. The second temperature sensor 122 is a temperature sensor that measures the temperature of the refrigerant flowing through the second path PA2, and transmits the measured value to the controller 23. More specifically, the temperature of the refrigerant measured by the second temperature sensor 122 is the temperature of the refrigerant in the second path PA2 after heat exchange in the heat exchanger 11.

(4-2) Configuration for flow rate control of single-row heat exchanger 11 As shown in Fig. 7, the flow rate adjustment mechanism 100 includes a first valve 111 provided in the first refrigerant distribution pipe 72 which is the outlet of the liquid refrigerant of the first path PA1. The first valve 111 in Fig. 7 may also be an on-off valve which only opens and closes, or may be an electrically operated valve which can adjust the opening degree.

The air conditioner 1 shown in FIG. 7 includes a first temperature sensor 121 attached to the first refrigerant distribution pipe 72 of the first path PA1 of the heat exchanger 11 with a single row configuration, and a second temperature sensor 122 attached to the first refrigerant distribution pipe 72 of the second path PA2. The first temperature sensor 121 is a temperature sensor that measures the temperature of the refrigerant flowing through the first path PA1 of the heat exchanger 11 with a single row configuration, and transmits the measured value to the controller 23. More specifically, the temperature of the refrigerant measured by the first temperature sensor 121 is the temperature of the refrigerant in the first path PA1 after heat exchange in the heat exchanger 11 with a single row configuration. The second temperature sensor 122 is a temperature sensor that measures the temperature of the refrigerant flowing through the second path PA2 of the heat exchanger 11 with a single row configuration, and transmits the measured value to the controller 23. More specifically, the temperature of the refrigerant measured by the second temperature sensor 122 is the temperature of the refrigerant in the second path PA2 after heat exchange in the heat exchanger 11 with a single row configuration.

(4-3) Flow Control in Defrost Operation The operation of flow control in defrost operation will be described with reference to the flow chart shown in Fig. 8. The operation of flow control in defrost operation of the heat exchanger 11 with a two-row configuration is the same as the operation of flow control in defrost operation of the heat exchanger 11 with a single-row configuration, so they will be described together.

At the start of defrosting, the flow rate of the refrigerant in the first path PA1 shown by the solid line in FIG. 9 and the flow rate of the refrigerant in the second path PA2 shown by the dashed line are adjusted to be, for example, substantially the same. However, the flow rates of the refrigerant in the first path PA1 and the second path PA2 do not have to be the same at the start of defrosting. For example, the flow rate of the refrigerant in the second path PA2 may be set to be greater than the flow rate of the refrigerant in the first path PA1.

When the defrost operation starts, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1 with the stored first set temperature Td1 (step S1). When the frost on the first path PA1 melts away, the measurement value of the first temperature sensor 121 becomes greater than the first set temperature Td1. When the measurement value of the first temperature sensor 121 is equal to or lower than the first set temperature Td1 (No in step S1), the controller 23 keeps the first valve 111 open. Because the first valve 111 remains open, the flow rates of the refrigerant in the first path PA1 and the second path PA2 do not change from the time when defrosting starts, as shown in FIG. 9.

When the measured value of the first temperature sensor 121 becomes greater than the first set temperature Td1 (Yes in step S1), the controller 23 closes the first valve 111 (step S2). Here, a case where the first valve 111 is an on-off valve is described. When the first valve 111 is closed, the refrigerant does not flow through the first path PA1 (the flow rate of the refrigerant becomes 0). Before and after the opening and closing of the first valve 111 during defrost operation, the controller 23 does not change the rotation speed of the compressor 8, the outdoor expansion valve 12, and the indoor expansion valves 31a and 31b, so the amount of refrigerant flowing into the heat exchanger 11 is substantially constant. The refrigerant flowing into the heat exchanger 11 is divided into the first path PA1 and the second path PA2, so that by closing the first valve 111, the refrigerant that was flowing through the first path PA1 flows through the second path PA2. By closing the first valve 111, the refrigerant that was flowing through the first path PA1 flows into the second path PA2, and the flow rate of the refrigerant flowing through the second path PA2 increases. Here, an example is described in which the amount of refrigerant flowing into the heat exchanger 11 during defrost operation is substantially constant, but the amount of refrigerant flowing into the heat exchanger 11 may be configured to change during defrost operation.

After the first valve 111 is closed, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2 with the stored second set temperature Td2 (step S3). The second set temperature Td2 may be the same as the first set temperature Td1, or may be different. When the frost on the second path PA2 melts and disappears, the measurement value of the second temperature sensor 122 becomes greater than the second set temperature Td2.

When the measurement value of the second temperature sensor 122 is equal to or lower than the second set temperature Td2 (No in step S3), the controller 23 continues the defrost operation with the first valve 111 closed. When the measurement value of the second temperature sensor 122 is greater than the second set temperature Td2 (Yes in step S3), the controller 23 ends the defrost operation.

If the first valve 111 is an on-off valve, an operation to close the first valve 111 is performed in step S2. However, if the first valve 111 is an electrically operated valve, an operation to reduce the opening degree may be performed. Also, when reducing the opening degree of the first valve 111 in step S2, the controller 23 may control the opening degree to a predetermined small opening degree all at once, or may control the opening degree to be gradually reduced over time.

(5) Specific Application to Air Conditioners (5-1) Specific Configuration of Outdoor Unit Figures 10 and 11 show a specific example of the outdoor unit 2. The outdoor unit 2 shown in Figure 10 is an upward-blowing type heat exchange unit that draws in air from the side of the casing 40 and blows air out from the top of the casing 40. The outdoor unit 2 is provided with a casing 40 that houses devices such as an accumulator 7, a compressor 8, a heat exchanger 11, and an outdoor fan 15. The casing 40 also houses components of the outdoor unit 2 other than the accumulator 7, the compressor 8, the heat exchanger 11, and the outdoor fan 15, but these components are not shown in Figures 10 and 11. The casing 40 has a shape based on a rectangular box. The casing 40 has a bottom frame 42 suspended on a pair of mounting legs 41, four pillars 43 extending vertically from the corners of the bottom frame 42, a fan module 44 attached to the upper ends of the four pillars 43, and a panel 45.

The fan module 44 is located above the heat exchanger 11 (above in the direction of gravity). The fan module 44 constitutes a part of the casing 40 above the four pillars 43 and forms the top surface of the casing 40. The fan module 44 is a module in which the outdoor fan 15 is housed in a rectangular box with openings on the top and bottom. The opening on the top surface of the fan module 44 is the air outlet 40d, and the air outlet 40d is provided with an air outlet grill 46. The outdoor fan 15 is disposed in the casing 40 facing the air outlet 40d, and is a blower that takes in air from the air inlets 40a, 40b, and 40c into the casing 40 and discharges it from the air outlet 40d. The panel 45 is spanned between the pillars 43 on the front side. The panel 45 does not have an air inlet. The air inlets 40a, 40b, and 40c are formed on the side of the casing 40. Additionally, an air outlet 40d is formed on the top surface of the casing 40.

The bottom frame 42 forms the bottom surface of the casing 40, and the heat exchanger 11 is attached to the bottom frame 42. The compressor 8 and the accumulator 7 are also provided on the bottom frame 42. The heat exchanger 11 shown in Figures 10 and 11 has a roughly U-shape in plan view, and is disposed so as to face three sides of the casing 40. The heat exchanger 11 faces three intake ports 40a, 40b, and 40c. The bottom frame 42 is in contact with the lower end portion of the heat exchanger 11, and functions as a drain pan that receives drain water generated in the heat exchanger 11 during cooling operation or defrosting operation.

As shown by the two-dot chain line arrows in FIG. 11, in this outdoor unit 2, air is drawn into the casing 40 through the heat exchanger 11 from the three sides where the suction ports 40a, 40b, and 40c are formed. In addition, the air drawn into the casing 40 is blown out of the casing 40 from the air outlet 40d on the top surface of the casing 40 by the outdoor fan 15, as shown by the two-dot chain line arrows in FIG. 11.

12 shows an example of the heat exchanger 11 of FIG. 10 in a two-row configuration. The heat exchanger 11 is provided with two header collecting pipes 70, 80 and a connecting header 90. The header collecting pipes 70, 80 shown in FIG. 12 are hollow cylindrical members with both ends closed. The internal space of the header collecting pipes 70, 80 is divided by a plurality of partition plates 79, 89 into spaces that divide the refrigerant flowing in a plurality of paths. A first refrigerant distribution pipe 72 is connected to each space divided by the partition plate 79 so as to correspond to each path, and a second refrigerant distribution pipe 76 is connected to each space of the header collecting pipe 80 divided by the partition plate 89 so as to correspond to each path. The internal space of the connecting header 90 is divided by a plurality of partition plates (not shown) into nine spaces through which the refrigerant of the plurality of paths flows. The heat exchanger 11 of FIG. 12 has nine paths. The refrigerant flows substantially horizontally through the heat exchanger 11. Nine paths are arranged vertically. Each path includes multiple stages of flat multi-hole tubes 63, as shown in FIG. 4.

An example of the heat exchanger 11 of FIG. 10 in a single row configuration is shown in FIG. 13. This heat exchanger 11 is provided with one header collector pipe 80 and a connecting header 90. The header collector pipe 80 and the connecting header 90 shown in FIG. 13 are the same as those described using FIG. 7, so their description will be omitted here. The heat exchanger 11 of FIG. 13 has six paths. The refrigerant flows substantially horizontally through the heat exchanger 11. The six paths are arranged vertically. The liquid side flow path RC and the gas side flow path GC of each path each include multiple stages of flat multi-hole tubes 63, as shown in FIG. 7.

(5-2) Setting of the first and second paths With respect to the outdoor unit 2 of the air conditioner 1 shown in Fig. 10, the controller 23 performs control to perform defrosting by the reverse cycle defrosting already described. In other words, the controller 23 performs control to perform defrosting operation by increasing the ratio of gas components in the refrigerant flowing through the heat exchanger 11 by the refrigeration cycle. The lowest path is more likely to lose heat to the bottom frame 42 and is more likely to form a large amount of frost, so it takes longer to defrost than the highest path when the flow rate is not adjusted in defrosting operation. In addition, in the case of reverse cycle defrosting, liquid refrigerant accumulates in the lowest path, which impairs the flow of the refrigerant, resulting in a significant increase in the time required for defrosting.

Therefore, in the heat exchanger 11 of Figures 12 and 13, for example, only the top path is set as the first path PA1 (see Figures 4 and 7), and only the bottom path is set as the second path PA2 (see Figures 4 and 7). By setting the bottom path as the second path PA2, the effect of shortening the defrosting time is significantly manifested. Thus, in the case of reverse cycle defrosting, it is preferable to set the first path PA1 so that it is located higher in the direction of gravity than the second path PA2.

However, the number of paths set as the first path PA1 is not limited to the topmost path. For example, two paths, the topmost path and the path one path below the topmost path, may be set as the first path PA1. The number of paths set as the first path PA1 may be three or more. The paths set as the first path PA1 do not have to include the topmost path. Furthermore, all paths other than those set as the second path PA2 may be set as the first path PA1.

The number of paths set in the second path PA2 is not limited to the bottommost path. For example, two paths, the bottommost path and the path one step above the bottommost path, may be set in the second path PA2. The number of paths set in the second path PA2 may be three or more. The paths set in the second path PA2 do not have to include the bottommost path.

(5-3) Setting of the flow rate adjustment mechanism When a plurality of first paths PA1 are provided, each first path PA1 is provided with a first valve 111. The first temperature sensor 121 may be provided in any one of the plurality of first paths PA1, or may be provided in each first path PA1.

When a first temperature sensor 121 is provided in any of the multiple first paths PA1, when the measurement value of one of the first temperature sensors 121 exceeds the first set temperature Td1 (Yes in step S1), all first valves 111 provided in all first paths PA1 are closed (step S2).

When the first temperature sensor 121 is provided on all of the first paths PA1, the first valve 111 of the first path PA1 to which the first temperature sensor 121 is provided is closed each time the measurement value of each first temperature sensor 121 exceeds the first set temperature Td1. If the top path and the second path from the top are first paths PA1, for example, when the first temperature sensor 121 of the top first path PA1 exceeds the first set temperature Td1, only the top first valve 111 is closed. Then, after a while, when the first temperature sensor 121 of the second first path PA1 exceeds the first set temperature Td1, the second first valve 111 is closed. When the first temperature sensor 121 is provided on each of the multiple first paths PA1 in this way, the first valve 111 of each path can be closed with a time lag.

For example, when the first valve 111 is provided in each of the two first paths PA1A and PA1B shown in FIG. 14 and FIG. 15, and the first temperature sensor 121 is provided in each of them, the operation shown in FIG. 16 and FIG. 17 can be performed. Here, a case will be described in which the heat exchanger 11 has a configuration in which the frost melts and disappears in the first path PA1A before that in the first path PA1B in reverse cycle defrosting. In FIG. 14, the solid arrows indicate the flow of the refrigerant from the second refrigerant distribution pipe 76 through the header collecting pipe 70 toward the flat multi-hole pipe 63 of the second row 11B. The dashed arrows indicate the flow of the refrigerant from the flat multi-hole pipe 63 of the second row 11B through the connecting header 90 toward the flat multi-hole pipe 63 of the first row 11A. The solid arrows indicate the flow of the refrigerant from the flat multi-hole pipe 63 of the first row 11A through the header collecting pipe 80 toward the first refrigerant distribution pipe 72.

At the start of defrosting, the flow rate of the refrigerant in the first path PA1A shown by a solid line in FIG. 17, the flow rate of the refrigerant in the first path PA1B shown by a two-dot chain line, and the flow rate of the refrigerant in the second path PA2 shown by a dashed dot line are adjusted to be substantially the same, for example. However, the flow rates of the refrigerant in the first path PA1A, PA1B and the second path PA2 do not have to be the same at the start of defrosting. For example, the flow rate of the refrigerant in the second path PA2 may be set to be greater than the flow rate of the refrigerant in the first paths PA1A, PA1B.

When the defrost operation is started, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1A with the stored first set temperature Td1 (step S11). When the frost on the first path PA1A melts and disappears, the measurement value of the first temperature sensor 121 of the first path PA1A becomes greater than the first set temperature Td1. When the measurement value of the first temperature sensor 121 of the first path PA1A is equal to or lower than the first set temperature Td1 (No in step S11), the controller 23 keeps the first valve 111 of the first path PA1A open. Because the first valve 111 of the first path PA1A remains open, the flow rates of the refrigerant in the first path PA1A, first path PA1B, and second path PA2 do not change from the time when the defrost operation started, as shown in FIG. 17.

When the measured value of the first temperature sensor 121 of the first path PA1A becomes greater than the first set temperature Td1 (Yes in step S11), the controller 23 closes the first valve 111 of the first path PA1A (step S12). Here, the case where the first valve 111 is an on-off valve is described. When the first valve 111 of the first path PA1A is closed, the refrigerant does not flow through the first path PA1 (the flow rate of the refrigerant becomes 0). Before and after the opening and closing of the first valve 111 during defrost operation, the controller 23 does not change the rotation speed of the compressor 8, the outdoor expansion valve 12, and the indoor expansion valves 31a and 31b, so the amount of refrigerant flowing into the heat exchanger 11 is substantially constant. Since the refrigerant flowing into the heat exchanger 11 is divided into the first path PA1A, PA1B and the second path PA2, closing the first valve 111 of the first path PA1A causes the refrigerant flowing through the first path PA1A to flow into the first path PA1B and the second path PA2. Since the refrigerant flowing through the first path PA1A flows into the first path PA1B and the second path PA2 by closing the first valve 111 of the first path PA1A, the flow rate of the refrigerant flowing through the first path PA1B and the second path PA2 increases. Here, an example is described in which the amount of refrigerant flowing into the heat exchanger 11 during defrost operation is substantially constant, but the amount of refrigerant flowing into the heat exchanger 11 may be configured to change during defrost operation.

When the first valve 111 of the first path PA1A is closed, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1B with the stored first set temperature Td1 (step S13). The first set temperature Td1 used in step S11 and the first set temperature Td1 used in step S13 may be the same or different (for example, the first set temperature Td1 in step S11 < the first set temperature Td1 in step S13). When the frost on the first path PA1B melts and disappears, the measurement value of the first temperature sensor 121 of the first path PA1B becomes larger than the first set temperature Td1. When the measurement value of the first temperature sensor 121 of the first path PA1B is equal to or lower than the first set temperature Td1 (No in step S13), the controller 23 keeps the first valve 111 of the first path PA1B open. Because the first valve 111 of the first path PA1B remains open, when no refrigerant flows through the first path PA1A, the flow rate of the refrigerant through the first path PA1B and the flow rate of the refrigerant through the second path PA2 are the same as when no refrigerant flows through the first path PA1A.

When the measured value of the first temperature sensor 121 of the first path PA1B becomes greater than the first set temperature Td1 (Yes in step S13), the controller 23 closes the first valve 111 of the first path PA1B (step S14). When the first valve 111 of the first path PA1B is closed, the refrigerant does not flow through the first path PA1B (the flow rate of the refrigerant becomes 0). By closing the first valves 111 of the first path PA1A and the first path PA1B, the refrigerant that flowed through the first path PA1A and PA1B flows through the first path PA1B and the second path PA2. The refrigerant that flows into the heat exchanger 11, which is substantially constant and was divided into the first path PA1A, PA1B and the second path PA2, flows only through the second path PA2 by closing the first valves 111 of the first paths PA1A and PA1B, and the flow rate of the refrigerant flowing through the second path PA2 is further increased.

After the first valves 111 of the first paths PA1A and PA1B are closed, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2 with the stored second set temperature Td2 (step S15). The second set temperature Td2 may be the same as the first set temperature Td1, or may be different. When the frost on the second path PA2 melts away, the measurement value of the second temperature sensor 122 becomes greater than the second set temperature Td2.

When the measurement value of the second temperature sensor 122 is equal to or lower than the second set temperature Td2 (No in step S15), the controller 23 continues the defrost operation with the first valves 111 of the first paths PA1A and PA1B closed. When the measurement value of the second temperature sensor 122 becomes greater than the second set temperature Td2 (Yes in step S15), the controller 23 ends the defrost operation.

(5-4) Flow rate adjustment during cooling operation and heating operation When the first valve 111 is an electric valve and has an adjustable opening degree, the controller 23 may be configured to control the opening degree of the first valve 111 during cooling operation and heating operation. For example, an adjustment of the opening degree of the first valve 111 that corrects the unevenness of the refrigerant flow rate between the paths is considered in advance by an experiment or simulation using an actual device. Based on the result of the consideration, the controller 23 stores in advance the opening degree of the first valve 111 that makes the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other than before adjustment during cooling operation and heating operation. Then, during cooling operation and heating operation, the controller 23 adjusts the opening degree of the first valve 111 to match the stored opening degree in order to make the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other.

Second Embodiment
(6) Overall Configuration The air conditioner 1 of the first embodiment is configured such that no valve is provided in the second path PA2. In contrast to the air conditioner 1 of the first embodiment, the air conditioner 1 of the second embodiment (see FIG. 1) is provided with a second valve 112 in the second path PA2 shown in FIGS. 18 and 19. In other words, as shown in FIGS. 18 and 19, the flow rate adjustment mechanism 100 of the second embodiment includes a second valve 112 provided in the first refrigerant distribution pipe 72, which is the outlet of the liquid refrigerant in the second path PA2. The second valve 112 is, for example, an electric valve whose opening degree can be adjusted. The configuration of the air conditioner 1 other than the second valve 112 can be the same in the first embodiment and the second embodiment. Here, a description of the parts of the air conditioner 1 of the second embodiment other than the second valve 112 will be omitted.

(7) Flow Control in Defrost Operation The operation of flow control in defrost operation will be described with reference to the flow chart shown in Fig. 20. The first valve 111 may be provided in a plurality of first paths PA1, or may be provided in only one first path PA1. The first valve 111 may be an electrically operated valve capable of adjusting the opening degree, or may be an on-off valve capable of only opening and closing. In the following description, a case will be described in which the first valve 111 is an electrically operated valve capable of adjusting the opening degree and is provided in two paths, the first path PA1A and the first path PA1B.

At the start of defrosting, the flow rate of the refrigerant in the first path PA1A shown by a solid line in FIG. 21, the flow rate of the refrigerant in the first path PA1B shown by a two-dot chain line, and the flow rate of the refrigerant in the second path PA2 shown by a one-dot chain line are adjusted to be substantially the same, for example. However, the flow rates of the refrigerant in the first path PA1A, PA1B and the second path PA2 do not have to be the same at the start of defrosting, and for example, the flow rate of the refrigerant in the second path PA2 may be set to be greater than the flow rates of the refrigerant in the first path PA1A and PA1B. Also, the flow rates of the refrigerant in the first path PA1A, PA1B do not have to be the same at the start of defrosting, and for example, the flow rate of the refrigerant in the first path PA1B may be set to be greater than the flow rate of the refrigerant in the first path PA1A.

When the defrost operation is started, the controller 23 compares the measured value received from the first temperature sensor 121 of the first path PA1A with the stored first set temperature Td1 (step S21). When the measured value of the first temperature sensor 121 of the first path PA1A is equal to or lower than the first set temperature Td1 (No in step S21), the controller 23 does not adjust the opening degree of the first valve 111 of the first path PA1A. Since the opening degree of the first valve 111 of the first path PA1A is not adjusted, as shown in FIG. 21, the flow rate of the refrigerant in the first path PA1A, the first path PA1B, and the second path PA2 does not change from the start of the defrost operation. Here, a case is described in which the opening degrees of the first valve 111 of the first path PA1A and the first path PA1B and the second valve 112 of the second path PA2 are not changed, but for example, the opening degrees of the two first valves 111 and the second valve 112 may be gradually changed over time. For example, the controller 23 may adjust the opening of the second valve 112 so that it gradually increases immediately after the defrost operation starts.

When the measured value of the first temperature sensor 121 of the first path PA1A becomes greater than the first set temperature Td1 (Yes in step S21), the controller 23 reduces the opening of the first valve 111 of the first path PA1A and increases the opening of the second path PA2 (step S22). FIG. 21 shows a case where the flow rate of the refrigerant is adjusted so that the flow rate of the refrigerant is equal to the flow rate of the refrigerant that is decreased by decreasing the opening of the first valve 111 of the first path PA1A and the flow rate of the refrigerant that is increased by increasing the opening of the second valve 112 of the second path PA2. However, the method of adjusting the opening of the first valve 111 of the first path PA1A and the second valve 112 of the second path PA2 is not limited to this. Here, the case where the amount of refrigerant flowing into the heat exchanger 11 during defrost operation is substantially constant is described as an example, but the amount of refrigerant flowing into the heat exchanger 11 may be configured to change during defrost operation.

After determining that defrosting of the first path PA1A is completed, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1B with the stored first set temperature Td1 (step S23). When the measurement value of the first temperature sensor 121 of the first path PA1B is equal to or lower than the first set temperature Td1 (No in step S23), the controller 23 does not change the opening degree of the first valve 111 of the first path PA1B and maintains it as it is. Because the opening degree of the first valve 111 of the first path PA1B does not change, the flow rate of the refrigerant in the first path PA1B and the flow rate of the refrigerant in the second path PA2 are the same as when the opening degree of the first valve 111 of the first path PA1A is changed to be smaller.

When the measurement value of the first temperature sensor 121 of the first path PA1B becomes greater than the first set temperature Td1 (Yes in step S23), the controller 23 reduces the opening of the first valve 111 of the first path PA1B and further increases the opening of the second valve 112 of the second path PA2 (step S24). By such control by the controller 23, the flow rate of the refrigerant in the first path PA1B decreases and the flow rate of the refrigerant in the second path PA2 further increases.

After determining that defrosting of the first paths PA1A and PA1B is complete, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2 with the stored second set temperature Td2 (step S25). When the measurement value of the second temperature sensor 122 is equal to or lower than the second set temperature Td2 (No in step S25), the controller 23 maintains the opening of the first valve 111 of the first paths PA1A and PA1B and the second valve 112 of the second path PA2 to continue the defrost operation. When the measurement value of the second temperature sensor 122 becomes greater than the second set temperature Td2 (Yes in step S25), the controller 23 ends the defrost operation.

(8) Application to a Specific Air Conditioner The setting of the first path PA1 and the second path PA2 for the heat exchanger 11 (see FIGS. 12 and 13) of the outdoor unit 2 shown in FIGS. 10 and 11 can be performed in the second embodiment in the same manner as in the first embodiment.

In addition, the flow rate adjustment mechanism can be set in the second embodiment in the same way as in the first embodiment, except that in the second embodiment, a second valve 112 is provided in the second path PA2.

Furthermore, during cooling operation and heating operation, the controller 23 may be configured to control the opening of the first valve 111 and the second valve 112. For example, an adjustment of the opening of the first valve 111 and the second valve 112 to correct uneven refrigerant flow rates between the paths is considered in advance by experiments or simulations using an actual device. Based on the results of the consideration, the controller 23 stores in advance the opening of the first valve 111 and the second valve 112 such that the refrigerant flow rates of the multiple paths of the heat exchanger 11 become closer to each other during cooling operation and heating operation compared to before adjustment. Then, during cooling operation and heating operation, the controller 23 adjusts the opening of the first valve 111 and the second valve 112 to match the stored opening in order to make the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other.

Third Embodiment
(9) Overall Configuration The air conditioner 1 of the first embodiment is configured such that no valve is provided in the second path PA2. The air conditioner 1 of the second embodiment is configured such that valves are provided in both the first path PA1 and the second path PA2. In contrast to the air conditioners 1 of the first and second embodiments, the air conditioner 1 of the third embodiment (see FIG. 1) is provided with a second valve 112 in the second path PA2 as shown in FIGS. 22 and 23, but is not provided with a first valve in the first paths PA1A and PA1B. In other words, as shown in FIGS. 22 and 23, the flow rate adjustment mechanism 100 of the third embodiment includes a second valve 112 provided in the first refrigerant distribution pipe 72, which is the outlet of the liquid refrigerant in the second path PA2, but does not include a first valve 111. The second valve 112 is, for example, an electric valve whose opening degree can be adjusted. The configuration of the air conditioner 1 other than the first valve 111 and the second valve 112 can be the same in the first, second and third embodiments. Here, a description of the parts of the air conditioner 1 of the third embodiment other than the first valve 111 and the second valve 112 will be omitted.

(10) Flow Control in Defrost Operation The operation of flow control in defrost operation will be described with reference to the flow chart shown in Fig. 24. At the start of defrost, the refrigerant flow rate of the first path PA1A shown by the solid line in Fig. 25, the refrigerant flow rate of the first path PA1B shown by the two-dot chain line, and the refrigerant flow rate of the second path PA2 shown by the one-dot chain line are adjusted to be substantially the same, for example. However, the refrigerant flow rates of the first path PA1A, PA1B, and the second path PA2 do not have to be the same at the start of defrost, and for example, the refrigerant flow rate of the second path PA2 may be set to be greater than the refrigerant flow rates of the first paths PA1A and PA1B.

When the defrost operation is started, the controller 23 compares the measured value received from the first temperature sensor 121 of the first path PA1A with the stored first set temperature Td1 (step S31). When the measured value of the first temperature sensor 121 of the first path PA1A is equal to or lower than the first set temperature Td1 (No in step S31), the controller 23 does not adjust the opening degree of the second valve 112 of the second path PA2. Since the opening degree of the second valve 112 of the second path PA2 is not adjusted, the flow rate of the refrigerant of the first path PA1A shown by the solid line in FIG. 25, the flow rate of the refrigerant of the first path PA1B shown by the two-dot chain line, and the flow rate of the refrigerant of the second path PA2 shown by the one-dot chain line do not change from the time when the defrost operation is started.

When the measurement value of the first temperature sensor 121 of the first path PA1A becomes greater than the first set temperature Td1 (Yes in step S31), the controller 23 increases the opening of the second valve 112 of the second path PA2 (step S32). By increasing the opening of the second valve 112, the flow rate of the refrigerant in the second path PA2 increases and the flow rates of the refrigerant in the first paths PA1A and PA1B decrease.

After determining that defrosting of the first path PA1A is complete, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1B with the stored first set temperature Td1 (step S33). When the measurement value of the first temperature sensor 121 of the first path PA1B is equal to or lower than the first set temperature Td1 (No in step S33), the controller 23 does not change the opening degree of the second valve 112 of the second path PA2 and maintains it as it is. Because the opening degree of the second valve 112 of the second path PA2 does not change, the flow rates of the refrigerant in the first paths PA1A and PA1B and the flow rate of the refrigerant in the second path PA2 are the same as when the opening degree of the second valve 112 of the second path PA2 is changed to be larger.

When the measurement value of the first temperature sensor 121 of the first path PA1B becomes greater than the first set temperature Td1 (Yes in step S33), the controller 23 further increases the opening of the second valve 112 of the second path PA2 (step S34). This control by the controller 23 reduces the flow rate of the refrigerant in the first paths PA1A and PA1B, and further increases the flow rate of the refrigerant in the second path PA2.

After determining that defrosting of the first paths PA1A and PA1B is complete, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2 with the stored second set temperature Td2 (step S35). When the measurement value of the second temperature sensor 122 is equal to or lower than the second set temperature Td2 (No in step S35), the controller 23 maintains the opening of the first valve 111 of the first paths PA1A and PA1B and the second valve 112 of the second path PA2 to continue the defrost operation. When the measurement value of the second temperature sensor 122 becomes greater than the second set temperature Td2 (Yes in step S35), the controller 23 ends the defrost operation.

(11) Specific Application to Air Conditioners (11-1) Setting of First Path and Second Path The setting of the first path PA1 and the second path PA2 for the heat exchanger 11 (see FIGS. 12 and 13) of the outdoor unit 2 shown in FIGS. 10 and 11 can be performed in the third embodiment in the same manner as in the first embodiment.

(11-2) Setting of the flow rate adjustment mechanism In the above description of the third embodiment, a case where two first paths PA1 are provided, such as first paths PA1A and PA1B, is described. The number of first paths PA1 may be one, or may be three or more. A first temperature sensor 121 is provided for each first path PA1.

When only one first path PA1 is provided, the opening degree of the second valve 112 of the second path PA2 is increased when the measurement value of one first temperature sensor 121 exceeds the first set temperature Td1. In such a configuration, if multiple second paths PA2 are set, the opening degrees of the multiple second paths PA2 can be increased. When increasing the opening degrees of the multiple second paths PA2, the degree of increase in the opening degree may be different for each second path PA2, or may be the same.

When multiple first paths PA1 and multiple second paths PA2 are provided, each first path PA1 is provided with a first temperature sensor 121, and each second path PA2 is provided with a second valve 112. When multiple second paths PA2 are provided, at least one second temperature sensor 122 is provided to detect the end of the overall defrost operation. When only one second temperature sensor 122 is provided, the second temperature sensor 122 detects the end of the overall defrost operation. When multiple second temperature sensors 122 are provided, the controller 23 may be configured to determine that the overall defrost operation is to be terminated when all the second temperature sensors 122 exceed the second set temperature Td2. Alternatively, the completion of the overall defrost operation may be determined by one of the multiple second temperature sensors 122, and the completion of the defrost operation of each second path PA2 may be determined by the remaining second temperature sensors 122.

(12) Flow Control in Defrost Operation (12-1) In the Case Where the Flow Rate of the Second Pass is Increasing with the Progress of Defrosting FIG. 26 illustrates a heat exchanger 11 having two first passes PA1A, PA1B and two second passes PA2A, PA2B. The second pass PA2A is provided below the second pass PA2B. For example, the second pass PA2A is the lowest pass, and the second pass PA2B is the pass one step above the lowest pass. The first passes PA1A, PA1B are each provided with a first temperature sensor 121, but are not provided with a first valve 111. The second passes PA2A, PA2B are each provided with a second temperature sensor 122 and a second valve 112. Note that, although a two-row heat exchanger 11 is described here as an example, a single-row heat exchanger 11 can be set to a similar pass configuration.

The heat exchanger 11 shown in FIG. 26 can be operated as shown in FIG. 27 and FIG. 28, for example. Here, we will explain a case where the heat exchanger 11 has a configuration in which, in reverse cycle defrosting, the frost melts and disappears on the first path PA1A before the frost melts and disappears on the first path PA1B, and the frost melts and disappears on the second path PA2B before the frost melts and disappears on the second path PA2A.

When the defrost operation is started, for example, the controller 23 adjusts the opening of the second valve 112 so that the refrigerant flow rates of the first paths PA1A, PA1B and the second paths PA2A, PA2B are substantially the same. However, it is not necessary to adjust the refrigerant flow rates of all paths to be the same, and the refrigerant flow rates of the second paths PA2A, PA2B may be set to be greater than the refrigerant flow rates of the first paths PA1A, PA1B from the start of the defrost operation. When the defrost operation is started, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1A with the stored first set temperature Td1 (step S41). When the measurement value of the first temperature sensor 121 of the first path PA1A is equal to or lower than the first set temperature Td1 (No in step S41), the frost on the first paths PA1A and PA1B and the second paths PA2A and PA2B has not melted, so the controller 23 does not change the opening degree of any of the second valves 112.

When the measurement value of the first temperature sensor 121 of the first path PA1A becomes greater than the first set temperature Td1 (Yes in step S41), the controller 23 increases the opening of the second valve 112 of the second path PA2A, PA2B (step S42). When the opening of the second valve 112 of the second path PA2A, PA2B increases, the flow rate of the refrigerant flowing through the second path PA2A, PA2B increases and the flow rate of the refrigerant flowing through the first path PA1A, PA1B decreases.

After determining that the defrost of the first path PA1A is complete, the controller 23 compares the measurement value received from the first temperature sensor 121 of the first path PA1B with the stored first set temperature Td1 (step S43). When the measurement value of the first temperature sensor 121 of the first path PA1B is equal to or lower than the first set temperature Td1 (No in step S43), the controller 23 maintains the opening degree of the second valve 112 after determining that the defrost of the first path PA1A is complete. When the measurement value of the first temperature sensor 121 of the first path PA1B is greater than the first set temperature Td1 (Yes in step S43), the controller 23 further increases the opening degree of the second valve 112 of the second paths PA2A and PA2B (step S44). When the opening of the second valve 112 of the second paths PA2A and PA2B becomes larger, the flow rate of the refrigerant flowing through the second paths PA2A and PA2B increases further and the flow rate of the refrigerant flowing through the first paths PA1A and PA1B decreases further.

After determining the completion of defrosting of the first path PA1B, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2B with the stored second set temperature Td2 (step S45). When the measurement value of the second temperature sensor 122 of the second path PA2B is equal to or lower than the second set temperature Td2 (No in step S43), the controller 23 maintains the opening degree of the second valve 112 after the determination of the completion of defrosting of the first path PA1B. When the measurement value of the second temperature sensor 122 of the second path PA2B is greater than the second set temperature Td2 (Yes in step S45), the controller 23 reduces the opening degree of the second valve 112 of the second path PA2B (step S46). When the opening degree of the second valve 112 of the second path PA2B is reduced, the flow rate of the refrigerant flowing through the second path PA2B decreases, and the flow rate of the refrigerant flowing through the second path PA2A and the first paths PA1A and PA1B increases.

Then, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2A with the stored second set temperature Td2 (step S47). When the measurement value of the second temperature sensor 122 of the second path PA2A is equal to or lower than the second set temperature Td2 (No in step S47), the controller 23 maintains the opening degree of the two second valves 112 after reducing the opening degree of the second valve 112 of the second path PA2B. When the measurement value of the second temperature sensor 122 of the second path PA2A becomes greater than the second set temperature Td2 (Yes in step S47), the controller 23 ends the defrost operation.

(12-2) When the flow rate of the second path is decreased as defrosting progresses At the start of defrosting, the flow rate of the refrigerant in the second paths PA2A and PA2B shown by the dashed dotted line is set to be greater than the flow rate of the refrigerant in the first path PA1A shown by the solid line in Figure 30 and the flow rate of the refrigerant in the first path PA1B shown by the dashed dotted line.

As shown in Fig. 29, when the defrost operation is started, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2 with the stored second set temperature Td2 (step S51 ). When the measurement value of the second temperature sensor 122 of the second path PA2A is equal to or lower than the second set temperature Td2 (No in step S51 ), the controller 23 does not adjust the aperture of the second valve 112 of the second path PA2. Since the aperture of the second valve 112 of the second path PA2 is not adjusted, the flow rate of the refrigerant in the first path PA1A shown by the solid line in Fig. 30 , the flow rate of the refrigerant in the first path PA1B shown by the two-dot chain line, and the flow rate of the refrigerant in the second path PA2 shown by the one-dot chain line do not change from the start of the defrost operation.

When the measurement value of the second temperature sensor 122 of the second path PA2B becomes greater than the second set temperature Td2 (Yes in step S51), the controller 23 reduces the opening of the second valve 112 of the second path PA2B and increases the opening of the second valve 112 of the second path PA2A (step S52). By reducing the opening of the second valve 112, the flow rate of the refrigerant in the second path PA2B decreases and the flow rates of the refrigerant in the first paths PA1A, PA1B and second path PA2A increase.

After determining that defrosting of the second path PA2B is completed, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2A with the stored second set temperature Td2 (step S53). When the measurement value of the second temperature sensor 122 of the second path PA2A is equal to or lower than the second set temperature Td2 (No in step S53), the controller 23 does not change the opening degree of the second valve 112 of the second paths PA2A and PA2B and maintains it as it is. Since the opening degree of the second valve 112 of the second paths PA2A and PA2B does not change, the flow rate of the refrigerant in the first paths PA1A and PA1B and the second paths PA2A and PA2B is the same as when the opening degree of the second valve 112 was changed in step S52.

When the measurement value of the second temperature sensor 122 of the second path PA2A becomes greater than the second set temperature Td2 (Yes in step S53), the controller 23 reduces the opening of the second valve 112 of the second path PA2A (step S54). This control by the controller 23 increases the flow rate of the refrigerant in the first paths PA1A and PA1B and decreases the flow rate of the refrigerant in the second path PA2A. At this time, for example, the opening of the second valve 112 of the second path PA2B is adjusted so as to cause almost no change in the flow rate of the refrigerant in the second path PA2B.

After determining that defrosting of the second paths PA2A and PA2B is complete, the controller 23 compares the measurement values received from the first temperature sensors 121 of the first paths PA1A and PA1B with the stored first set temperature Td1 (step S55). When the measurement value of any of the first temperature sensors 121 is equal to or lower than the first set temperature Td1 (No in step S55), the controller 23 maintains the opening of the second valves 112 of the second paths PA2A and PA2B to continue the defrost operation. When the measurement values of all the first temperature sensors 121 become greater than the first set temperature Td1 (Yes in step S55), the controller 23 ends the defrost operation.

(12-3) Flow rate adjustment during cooling operation and heating operation The controller 23 may be configured to control the opening degree of the first valve 111 and the second valve 112 during cooling operation and heating operation. For example, an adjustment of the opening degree of the first valve 111 and the second valve 112 to correct uneven refrigerant flow rates occurring between the paths is considered in advance by an experiment or simulation using an actual machine. Based on the result of the consideration, the controller 23 stores in advance the opening degree of the first valve 111 and the second valve 112 such that the refrigerant flow rates of the multiple paths of the heat exchanger 11 become closer to each other compared to before adjustment during cooling operation and heating operation. Then, during cooling operation and heating operation, the controller 23 adjusts the opening degree of the first valve 111 and the second valve 112 to match the stored opening degree in order to make the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other.

Fourth Embodiment
(13) Overall Configuration The air conditioners 1 of the first to third embodiments use the first temperature sensor 121 or the second temperature sensor 122 to determine the completion of the defrost operation of each path and the completion of the defrost operation of the entire heat exchanger 11. In the fourth embodiment, the completion of the defrost operation of each path is determined based on the elapsed time from the start of defrost. In the air conditioner 1 of the fourth embodiment, the operation time of the defrost operation is counted by the timer 23a shown in Fig. 3.

(14) Application to specific air conditioners For example, as shown in Fig. 31, the air conditioner 1 of the fourth embodiment is provided with a second temperature sensor 122 in the second refrigerant distribution pipe 76 of the second path PA2A. However, no temperature sensor is provided in the first paths PA1A, PA1B and the second path PA2B of the fourth embodiment. The heat exchanger 11 shown in Fig. 31 is provided with a first valve 111 or a second valve 112 in each second refrigerant distribution pipe 76.

The heat exchanger 11 having the configuration shown in FIG. 31 can be operated as shown in FIG. 32 and FIG. 33, for example. Here, a case will be described in which the heat exchanger 11 has a configuration in which, in reverse cycle defrost, frost melts and disappears in the order of first path PA1A, first path PA1B, second path PA2B, and second path PA2A. Also, it is assumed that the first set time TM1 < second set time TM2 < third set time TM3.

At the time when the defrost operation is started, for example, the controller 23 adjusts the opening degree of the second valve 112 so that the refrigerant flow rate of the first path PA1A, PA1B and the second path PA2A, PA2B are substantially the same. However, it is not necessary to adjust the refrigerant flow rate of all paths to be the same, and the refrigerant flow rate of the second path PA2A, PA2B may be set to be greater than the refrigerant flow rate of the first path PA1A, PA1B from the start of the defrost operation. When the defrost operation is started, the controller 23 compares the count of the timer 23a with the stored first set time TM1 (step S61). When the count of the timer 23a is equal to or less than the first set time TM1 (No in step S61), the frost of the first path PA1A, PA1B and the second path PA2A, PA2B has not melted, so the controller 23 does not change the opening degree of any of the first valves 111 and the second valve 112.

When the count of the timer 23a becomes greater than the first set time TM1 (Yes in step S61), the controller 23 determines that the defrosting of the first path PA1A is completed. The controller 23, which has determined that the defrosting of the first path PA1A is completed, reduces the opening of the first valve 111 of the first path PA1A and increases the opening of the second valve 112 of the second paths PA2A and PA2B (step S62). When the opening of the first valve 111 of the first path PA1A is reduced and the opening of the second valve 112 of the second paths PA2A and PA2B is increased, the flow rate of the refrigerant flowing through the second paths PA2A and PA2B increases and the flow rate of the refrigerant flowing through the first path PA1A decreases. Here, a case where the flow rate of the refrigerant flowing through the first path PA1B does not change is exemplified, but in order to terminate the defrosting earlier, the flow rate of the refrigerant through the first path PA1B may be increased or decreased.

After determining that the defrost of the first path PA1A is complete, the controller 23 compares the count of the timer 23a with the stored second set time TM2 (step S63). When the count of the timer 23a is equal to or less than the second set time TM2 (No in step S63), the controller 23 maintains the opening of the first valve 111 and the second valve 112 after determining that the defrost of the first path PA1A is complete. When the count of the timer 23a is greater than the second set time TM2 (Yes in step S63), the controller 23 determines that the defrost of the first path PA1B is complete. The controller 23, having determined that the defrost of the first path PA1B is complete, reduces the opening of the first valve 111 of the first path PA1B and further increases the opening of the second valves 112 of the second paths PA2A and PA2B (step S64). When the opening of the first valve 111 of the first path PA1B decreases and the opening of the second valve 112 of the second paths PA2A and PA2B increases further, the flow rate of the refrigerant flowing through the first path PA1B decreases and the flow rate of the refrigerant flowing through the second paths PA2A and PA2B increases further. Here, an example is given in which the flow rate of the refrigerant flowing through the first path PA1A does not change, but in order to terminate defrosting earlier, the flow rate of the refrigerant through the first path PA1A may be increased or decreased.

After determining that the first path PA1B is in defrost operation, the controller 23 compares the count of the timer 23a with the stored third set time TM3 (step S65). When the count of the timer 23a is equal to or less than the third set time TM3 (No in step S63), the controller 23 maintains the opening of the first valve 111 and the second valve 112 after the defrost completion determination of the first path PA1B. When the count of the timer 23a is greater than the third set time TM3 (Yes in step S65), the controller 23 determines that the defrost of the second path PA2B is completed. The controller 23, having determined that the defrost of the second path PA2B is completed, reduces the opening of the second valve 112 of the second path PA2B (step S66). When the opening of the second valve 112 of the second path PA2B is reduced, the flow rate of the refrigerant flowing through the second path PA2B is reduced. Here, we have taken an example in which the flow rate of the refrigerant flowing through the first paths PA1A and PA1B does not change, but in order to end defrosting earlier, the flow rate of the refrigerant through the first paths PA1A and PA1B may be increased or decreased.

Then, the controller 23 compares the measurement value received from the second temperature sensor 122 of the second path PA2A with the stored second set temperature Td2 (step S67). When the measurement of the second temperature sensor 122 of the second path PA2A is equal to or lower than the second set temperature Td2 (No in step S67), the controller 23 maintains the opening of the first valve 111 and the second valve 112 after reducing the opening of the second valve 112 of the second path PA2B. When the measurement of the second temperature sensor 122 of the second path PA2A is greater than the second set temperature Td2 (Yes in step S67), the controller 23 ends the defrost operation.

The controller 23 may be configured to control the opening of the first valve 111 and the second valve 112 during cooling operation and heating operation. For example, an adjustment of the opening of the first valve 111 and the second valve 112 to correct uneven refrigerant flow rates between the paths is considered in advance by experiments or simulations using an actual device. Based on the results of the consideration, the controller 23 stores the opening of the first valve 111 and the second valve 112 in advance, which makes the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other than before adjustment during cooling operation and heating operation. Then, during cooling operation and heating operation, the controller 23 adjusts the opening of the first valve 111 and the second valve 112 to match the stored opening in order to make the refrigerant flow rates of the multiple paths of the heat exchanger 11 closer to each other.

(15) Modifications (15-1) Modification A
In addition to the air conditioner 1 described above, the refrigeration cycle apparatus of the present disclosure includes, for example, a heat pump chiller, a heat pump water heater, a refrigerator, and a cooling device that cools the interior of a refrigerator.

(15-2) Modification B
In the first to fourth embodiments, the heat exchanger 11 has been described as having the flat multi-hole tube 63. However, the configuration of the heat exchanger 11 is not limited to having the flat multi-hole tube 63. For example, the heat exchanger 11 may be a so-called fin-tube type heat exchanger that is configured with a plurality of cylindrical heat transfer tubes and heat transfer fins.

(15-3) Modification C
In the air conditioner 1 of the first embodiment, the case where the flow rate adjustment mechanism 100 includes the first valve 111 has been described. However, the flow rate adjustment mechanism 100 may be configured with a device other than a valve. For example, a flow rate adjustment mechanism may be used that provides multiple flow paths with different flow path resistances and adjusts the flow rate by changing the flow path resistance by switching the flow paths. In addition, the flow rate adjustment mechanism may be a device that changes the ratio of the flow rate for each path when the flow is divided into each path in the header collecting pipe 80.

(15-4) Modification D
In the first to third embodiments, the controller 23 determines the timing to change the flow rate of the refrigerant flowing through the path using the first temperature sensor 121 or the second temperature sensor 122. However, the device used to determine the timing to change the flow rate of the refrigerant flowing through the path is not limited to a temperature sensor. For example, the controller 23 may be configured to determine the timing to change the flow rate of the refrigerant flowing through the path based on the result of measuring the pressure of the refrigerant using a pressure sensor.

(15-5) Modification E
In the description of the fourth embodiment, the second temperature sensor 122 of the second path PA2A is used to determine the completion of the overall defrost operation, but the count of the timer 23a may also be used.

(15-6) Modification F
10 and 11 show the heat exchanger 11 that is U-shaped in plan view. However, the shape of the heat exchanger in plan view is not limited to U-shaped, and may be other shapes, for example, I-shaped or L-shaped. Also, the heat exchanger 11 has been described as being configured to turn the refrigerant around at the end (connection header 90), but the heat exchanger may not be configured to turn the refrigerant around and may be configured to flow in from one end of the heat exchanger and out from the other end.

(15-7) Modification G
In the first to fourth embodiments, the flow rate adjustment mechanism 100 adjusts the refrigerant flow rates of the first paths PA1, PA1A, PA1B and the second paths PA2, PA2A, PA2B during the defrost operation to reduce the refrigerant flow rate of the first paths PA1, PA1A, PA1B and increase the refrigerant flow rate of the second paths PA2, PA2A, PA2B. However, at the time of entering the defrost operation, the flow rate adjustment mechanism 100 may adjust the refrigerant flow rates of the first paths PA1, PA1A, PA1B and the second paths PA2, PA2A, PA2B to reduce the refrigerant flow rate of the first paths PA1, PA1A, PA1B and increase the refrigerant flow rate of the second paths PA2, PA2A, PA2B. In this case, the flow rate adjustment mechanism 100 increases the flow rate resistance of the first paths PA1, PA1A, PA1B and decreases the flow rate resistance of the second paths PA2, PA2A, PA2B compared to during the heating operation before the defrost operation starts. This means that the controller 23 controls the flow rates of the refrigerant in the first paths PA1, PA1A, PA1B and increases the flow rates of the refrigerant in the second paths PA2, PA2A, PA2B from the start to the end of the defrost operation.

(15-8) Modification H
In the first to fourth embodiments, a case has been described in which frost easily forms below the heat exchanger 11, heat easily escapes, or the refrigerant does not easily flow during defrost operation, so that the time required to defrost the lower path of the heat exchanger 11 is longer than that required to defrost the upper path. However, the technology disclosed herein can also be applied to a heat exchanger in which the time required to defrost the upper path is longer than that required to defrost the lower path.

For example, when the multiple paths include a first path and a second path that requires a greater amount of heat for defrosting than the first path during defrost operation, the controller may be configured to adjust the flow rates of the refrigerant in the first path and the second path during defrost operation using a flow rate adjustment mechanism to reduce the flow rate of the refrigerant in the first path and increase the flow rate of the refrigerant in the second path.

For example, if the multiple paths include a first path and a second path in which the refrigerant flow rate is reduced more than in the first path during defrost operation, the controller may be configured to adjust the refrigerant flow rates in the first and second paths using a flow rate adjustment mechanism during defrost operation to reduce the refrigerant flow rate in the first path and increase the refrigerant flow rate in the second path.

(16) Features (16-1)
A refrigeration cycle device such as an air conditioner 1 includes a heat exchanger 11 having a plurality of paths for dividing a refrigerant that performs a refrigeration cycle. The heat exchanger 11 includes first paths PA1, PA1A, PA1B and second paths PA2, PA2A, PA2B as paths. The air conditioner 1 includes a first valve 111 and a second valve 112 as a flow rate adjustment mechanism 100 that adjusts the flow rate of the refrigerant that flows through the plurality of paths. The plurality of paths of the heat exchanger 11 include the first paths PA1, PA1A, PA1B, and the second paths PA2, PA2A, PA2B that require a longer time for defrosting than the first paths PA1, PA1A, PA1B when the flow rate is not adjusted in the defrost operation. In the defrost operation, the controller 23 adjusts the flow rate of the refrigerant in the first paths PA1, PA1A, PA1B and the second paths PA2, PA2A, PA2B by the flow rate adjustment mechanism 100 (first valve 111, second valve 112). In the defrost operation, the controller 23 performs control to reduce the flow rate of the refrigerant in the first paths PA1, PA1A, PA1B and increase the flow rate of the refrigerant in the second paths PA2, PA2A, PA2B. By such control, in a refrigeration cycle device such as the air conditioner 1, the flow rate adjustment mechanism 100 (first valve 111, second valve 112) adjusts the refrigerant flow rate in the first paths PA1, PA1A, PA1B and the second paths PA2, PA2A, PA2B in the defrost operation, thereby making it possible to increase the flow rate of the refrigerant flowing in the second paths PA2, PA2A, PA2B. As a result, the time required for defrosting the first paths PA1, PA1A, PA1B can be made closer to the time required for defrosting the second paths PA2, PA2A, PA2B, the overall time required for defrost operation can be shortened, and the overall time required for defrost operation can be shortened.

(16-2)
A refrigeration cycle device such as the air conditioner 1 includes, for example, a first temperature sensor 121 that measures the temperature of the refrigerant flowing through the first paths PA1, PA1A, and PA1B. The controller 23 determines the completion of defrosting from the measurement result of the first temperature sensor 121, and controls the flow rate adjustment mechanism 100 (the first valve 111 and the second valve 112) to increase the flow rate of the refrigerant through the second paths PA2, PA2A, and PA2B when it is determined that the defrosting of the first paths PA1, PA1A, and PA1B is completed. By such control, in a refrigeration cycle device such as the air conditioner 1, the first temperature sensor 121 can determine an appropriate timing for the control of the controller 23, and a configuration for determining an appropriate timing for the control of the controller can be realized with a simple configuration.

In addition, a refrigeration cycle device such as the air conditioner 1 is provided with a second temperature sensor 122 that measures the temperature of the refrigerant flowing through the second paths PA2, PA2A, and PA2B. The controller 23 may be configured to determine the completion of defrosting from the measurement result of the second temperature sensor 122, and to control the flow rate adjustment mechanism 100 (first valve 111, second valve 112) to reduce the flow rate of the refrigerant through the second paths PA2, PA2A, and PA2B when it is determined that the defrosting of the second paths PA2, PA2A, and PA2B is completed. With this type of control, in a refrigeration cycle device such as the air conditioner 1, the second temperature sensor 122 can determine the appropriate timing for the control of the controller 23, and a configuration for determining the appropriate timing for the control of the controller can be realized with a simple configuration.

(16-3)
A refrigeration cycle device such as the air conditioner 1 includes, for example, a timer 23a that counts the operation time of the defrost operation. The controller 23 controls the flow rate adjustment mechanism 100 (the first valve 111 and the second valve 112) so as to reduce the flow rate of the refrigerant flowing through the first paths PA1, PA1A, and PA1B or to increase the flow rate of the refrigerant flowing through the second paths PA2, PA2A, and PA2B during the defrost operation in accordance with the operation time of the defrost operation. The timer 23a can determine an appropriate timing for the control of the controller 23, and the configuration for determining the appropriate timing for the control of the controller 23 can be realized with a simple configuration.

(16-4)
In the air conditioner 1, the controller 23 controls the defrost operation by increasing the ratio of gas components in the refrigerant flowing through the heat exchanger 11 by the refrigeration cycle. The above-mentioned air conditioner 1 performs such an operation in the reverse cycle defrost operation controlled by the controller 23. In the heat exchanger 11 shown in Figs. 12 and 13, the first paths PA1, PA1A, PA1B are located higher in the direction of gravity than the second paths PA2, PA2A, PA2B. In such a heat exchanger 11, the flow of the refrigerant is poor in the lower flow path in the direction of gravity where a large amount of liquid components with a large mass flows, making it difficult for the frost to melt. However, by increasing the flow rate of the lower second paths PA2, PA2A, PA2B, the amount of heat supplied to the second paths PA2, PA2A, PA2B can be increased, and the time of the defrost operation can be reliably shortened.

(16-5)
The heat exchanger 11 has a flat multi-hole tube 63 through which the first paths PA1, PA1A, and PA1B, which are the first flat multi-hole tubes, pass, and a flat multi-hole tube 63 through which the second paths PA2, PA2A, and PA2B, which are the second flat multi-hole tubes, pass. In the flat multi-hole tube 63 in which the flow passage cross-sectional area of each passage 63b is small, the flow rate varies greatly. However, if the flow rate of the second paths PA2, PA2A, and PA2B in which such second flat multi-hole tubes are arranged can be increased, the time required for defrosting the second paths PA2, PA2A, and PA2B can be significantly shortened, and the effect of shortening the defrost time becomes remarkable.

(16-6)
The flow rate adjustment mechanism 100 includes at least one of a first valve 111 arranged in the first paths PA1, PA1A, PA1B for adjusting the flow rate of the refrigerant flowing through the first paths PA1, PA1A, PA1B, and a second valve 112 arranged in the second paths PA2, PA2A, PA2B for adjusting the flow rate of the refrigerant flowing through the second paths PA2, PA2A, PA2B. The flow rate adjustment mechanism 100 is configured with at least one valve (the first valve 111, the second valve 112), and the flow rate adjustment mechanism 100 can be realized with a simple configuration.

(16-7)
When the flow rate adjustment mechanism 100 includes both the first valve 111 and the second valve 112, the controller 23 may be configured to adjust the first valve 111 and the second valve 112 in a direction that brings the flow rates through the first paths PA1, PA1A, PA1B and the second paths PA2, PA2A, PA2B closer to each other in cooling operation or heating operation. In the air conditioner 1 configured in this manner, it is possible to shorten the defrost operation time and improve the efficiency of the cooling operation or heating operation.

Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the present disclosure as set forth in the claims.

1. Air conditioner (example of refrigeration cycle device)
11 Heat exchanger 23 Controller 23a Timer 63 Flat multi-hole pipe 100 Flow rate adjustment mechanism 111 First valve 112 Second valve 121 First temperature sensor 122 Second temperature sensor PA1, PA1A, PA1B First path PA2, PA2A, PA2B Second path

JP 2011-247582 A

Claims (7)

A heat exchanger (11) having a plurality of paths for dividing a refrigerant for a refrigeration cycle;
A flow rate adjusting mechanism (100) that adjusts the flow rate of a refrigerant flowing through the multiple paths;
A second temperature sensor (122);
A controller (23);
Equipped with
the plurality of paths include a first path (PA1, PA1A, PA1B) and a second path (PA2, PA2A, PA2B) that requires a longer time for defrosting than the first path when a flow rate is not adjusted in a defrost operation,
The second temperature sensor measures a temperature of the refrigerant flowing through the second path,
The controller adjusts the flow rates of the refrigerant in the first path and the second path using the flow rate adjustment mechanism during the defrost operation, and sets the flow rate of the refrigerant in the second path to be greater than the flow rate of the first path by reducing the flow rate of the refrigerant in the first path and increasing the flow rate of the refrigerant in the second path while flowing refrigerant in both the first path and the second path at a start of the defrost operation, and when a measurement value of the second temperature sensor exceeds a second set temperature, controls to reduce the flow rate of the refrigerant in the second path and increase the flow rate of the refrigerant in the first path. A first temperature sensor (121) is provided for measuring the temperature of the refrigerant flowing through the first path,
The controller determines that defrosting is completed when the measurement value of the first temperature sensor exceeds a first set temperature, and performs control to terminate the defrost operation.
A refrigeration cycle device (1) as claimed in claim 1. The controller controls the ratio of a gas component of the refrigerant flowing through the heat exchanger to be higher than that of the heating operation by the refrigeration cycle so as to perform the defrost operation,
The first path is located above the second path in a direction of gravity.
A refrigeration cycle device (1) according to claim 1 or 2 . The heat exchanger has a first flat multi-hole tube (63) through which the first path passes and a second flat multi-hole tube (63) through which the second path passes.
A refrigeration cycle device (1) according to any one of claims 1 to 3 . The flow rate adjustment mechanism includes at least one of a first valve (111) arranged in the first path for adjusting a flow rate of the refrigerant flowing through the first path, and a second valve (112) arranged in the second path for adjusting a flow rate of the refrigerant flowing through the second path.
A refrigeration cycle device (1) according to any one of claims 1 to 4 . the flow rate adjusting mechanism includes both the first valve and the second valve,
the controller adjusts the first valve and the second valve in a direction in which the flow rates through the first path and the second path approach each other during a cooling operation or a heating operation.
A refrigeration cycle device (1) according to claim 5 . The second path includes a lowermost path (PA2A) and an upper path (PA2B) located above the lowermost path,
The flow rate adjustment mechanism includes a lowest stage valve ( 112 ) for adjusting the flow rate of the refrigerant flowing through the lowest stage path, and an upper valve ( 112 ) for adjusting the flow rate of the refrigerant flowing through the upper path,
the second temperature sensor includes a lowest stage temperature sensor that measures the temperature of the refrigerant flowing through the lowest stage path and an upper stage temperature sensor that measures the temperature of the refrigerant flowing through the upper stage path;
the controller, when the measurement value of the upper temperature sensor exceeds the second set temperature, reduces the opening degree of the upper valve and increases the opening degree of the bottom stage valve, and, when the measurement value of the bottom stage temperature sensor exceeds the second set temperature, performs control to reduce the opening degree of the bottom stage valve.
A refrigeration cycle device (1) as claimed in claim 1.

Images