JP7760909B2 - Air conditioners and heat exchangers - Google Patents

Description

The technology disclosed herein relates to air conditioners and heat exchangers.

Air conditioners that adjust the amount of refrigerant circulating through the refrigerant circuit depending on the operating state of air conditioning are known (Patent Document 1). Such air conditioners are provided with a receiver tank in the refrigerant circuit. The receiver tank stores liquid refrigerant condensed in the condenser, absorbing fluctuations in the amount of liquid refrigerant required by the evaporator in response to changes in operating state, and appropriately adjusting the amount of refrigerant circulating through the refrigerant circuit.

JP 2015-87065 A

However, this type of air conditioner requires the refrigerant circuit to be filled with a larger amount of refrigerant to take into account the amount of refrigerant stored in the receiver tank, which poses the problem of increasing the total amount of refrigerant filled into the refrigerant circuit.

The disclosed technology was developed in light of these issues, and aims to provide an air conditioner and heat exchanger that can adjust the amount of refrigerant circulating through the refrigerant circuit in response to changes in operating conditions, and that reduces the amount of refrigerant charged into the refrigerant circuit.

An air conditioner according to one aspect of the present disclosure includes a heat exchanger that is provided in a path connecting a compressor and an expansion valve, and exchanges heat between outside air and a refrigerant, and a refrigerant reservoir that is provided in a region of the path that is steadily filled with gas-phase refrigerant when the heat exchanger functions as a condenser, and that accumulates liquid-phase refrigerant when the heat exchanger functions as an evaporator , the heat exchanger has a plurality of flat heat transfer tubes that are arranged in the region through which the outside air flows, and a plurality of flow paths through which the refrigerant flows are formed inside each of the plurality of flat heat transfer tubes, and the heat exchanger further has a header that has an internal space formed therein and is connected to one end of the plurality of flow paths that is connected to the compressor, the refrigerant reservoir is provided in the header, and the refrigerant reservoir is calculated by using an internal tube volume V1, a refrigerant liquid density ρ1, an internal tube volume V2, and a refrigerant liquid density ρ2 in the refrigerant reservoir by the equation:
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2
the internal pipe volume V1 indicates the volume of the subcooling path of the path that is filled with liquid-phase refrigerant when the heat exchanger functions as a condenser, the refrigerant liquid density ρ1 indicates the liquid density of the refrigerant that fills the subcooling path when the heat exchanger functions as a condenser, the internal pipe volume V2 indicates the volume of the refrigerant reservoir, and the refrigerant liquid density ρ2 indicates the liquid density of the refrigerant that fills the refrigerant reservoir when the heat exchanger functions as an evaporator .

The disclosed air conditioner and heat exchanger can adjust the amount of refrigerant circulating through the refrigerant circuit and reduce the amount of refrigerant charged into the refrigerant circuit.

FIG. 1 is a circuit diagram showing an air conditioner according to a first embodiment. FIG. 2 is a front view showing the outdoor heat exchanger of the air conditioner of the first embodiment. FIG. 3 is a block diagram showing the air conditioner of the first embodiment. FIG. 4 is a front view showing an outdoor heat exchanger of an air conditioner according to a second embodiment.

An air conditioner according to an embodiment disclosed in this application will be described in detail below with reference to the drawings. Note that the following description does not limit the technology of this disclosure. Furthermore, in the following description, identical components will be assigned the same reference numerals, and duplicate explanations will be omitted.

[Air conditioner]
FIG. 1 is a circuit diagram showing an air conditioner 1 of a first embodiment. The air conditioner 1 includes a water circuit 2 and a refrigerant circuit 3. The water circuit 2 has a flow path formed therein through which a heat medium (water in the following description) circulates, and includes an indoor heat exchanger 5, an intermediate heat exchanger 6, and a pump 7. The indoor heat exchanger 5 is connected to the pump 7, and to the intermediate heat exchanger 6. The intermediate heat exchanger 6 is connected to the pump 7. The pump 7 supplies water supplied from the intermediate heat exchanger 6 to the indoor heat exchanger 5. The heat medium circulating through the water circuit 2 may be a fluid other than water, such as antifreeze.

The refrigerant circuit 3 has a flow path through which the refrigerant circulates, and includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 14, an expansion valve 15, a suction pipe 16, and a discharge pipe 17. The compressor 11 compresses low-pressure gas-phase refrigerant supplied from the suction pipe 16 and discharges the high-pressure gas-phase refrigerant generated by the compression of the low-pressure gas-phase refrigerant to the discharge pipe 17. The four-way valve 12 has a first connection port 121, a second connection port 122, a third connection port 123, and a fourth connection port 124. The first connection port 121 is connected to the compressor 11 via the suction pipe 16. The second connection port 122 is connected to the compressor 11 via the discharge pipe 17. The third connection port 123 is connected to the outdoor heat exchanger 14. The fourth connection port 124 is connected to the intermediate heat exchanger 6. The four-way valve 12 can be switched between heating mode and cooling mode. When switched to heating mode, the four-way valve 12 connects the second connection port 122 to the fourth connection port 124 and the third connection port 123 to the first connection port 121. When switched to cooling mode, the four-way valve 12 connects the second connection port 122 to the third connection port 123 and the fourth connection port 124 to the first connection port 121.

The outdoor heat exchanger 14 is connected to the expansion valve 15. The intermediate heat exchanger 6 is connected to the expansion valve 15. By configuring the refrigerant circuit 3 in this manner, a first path 21 and a second path 22 are formed in the refrigerant circuit 3. The first path 21 is a flow path that connects the expansion valve 15 and the four-way valve 12 via the outdoor heat exchanger 14. That is, the outdoor heat exchanger 14 is located midway through the first path 21. The second path 22 is a flow path that connects the expansion valve 15 and the four-way valve 12 via the intermediate heat exchanger 6. That is, the intermediate heat exchanger 6 is located midway through the second path 22. When the four-way valve 12 is switched to the cooling mode, the discharge pipe 17 is connected to the first path 21 via the four-way valve 12, and the suction pipe 16 is connected to the second path 22 via the four-way valve 12. When the four-way valve 12 is switched to the heating mode, the discharge pipe 17 is connected to the second path 22 via the four-way valve 12, and the suction pipe 16 is connected to the first path 21 via the four-way valve 12.

The air conditioner 1 further includes an outdoor unit 24 and an indoor unit 25. The outdoor unit 24 is installed outdoors. Inside the outdoor unit 24, a compressor 11, a four-way valve 12, an outdoor heat exchanger 14, an expansion valve 15, an intermediate heat exchanger 6, and a pump 7 are arranged. The indoor unit 25 is installed in a room that is cooled or heated by the air conditioner 1. Inside the indoor unit 25, an indoor heat exchanger 5 is arranged.

2 is a front view showing the outdoor heat exchanger 14 of the air conditioner 1 of the first embodiment. The outdoor heat exchanger 14 includes an inlet/outlet header 31 (header), a folded header 32, multiple flat heat transfer tubes 33, multiple fins 34, a liquid reservoir 35 (refrigerant reservoir), and a header outlet pipe 36. The inlet/outlet header 31 is generally tubular. When the outdoor heat exchanger 14 is installed, the inlet/outlet header 31 is arranged along a straight line parallel to an up-down direction 39, which is generally parallel to the vertical direction. A lower space 37 and an upper space 38 are formed inside the inlet/outlet header 31. The lower space 37 is located at the bottom of the interior of the inlet/outlet header 31 and is isolated from the outside of the inlet/outlet header 31. The lower space 37 is connected to the expansion valve 15 via a refrigerant pipe 41. The upper space 38 is located above the lower space 37 and is isolated from the outside of the inlet/outlet header 31 and the lower space 37.

The header outlet pipe 36 is formed in a tubular shape, and a flow path is formed inside the header outlet pipe 36. The header outlet pipe 36 passes through the inflow/outflow header 31 and is fixed to the inflow/outflow header 31 so that the internal flow path is connected to the upper space 38. The upper space 38 is connected to the four-way valve 12 via the header outlet pipe 36.

The fold header 32 is formed in a tubular shape and is arranged along a straight line parallel to the vertical direction 39, and so that the end position of the inlet/outlet header 31 in the vertical direction 39 is the same as the end position of the fold header 32 in the vertical direction 39. An internal space 43 is formed inside the fold header 32, isolating it from the outside of the fold header 32.

Each of the flat heat transfer tubes 33 is formed in a linear band shape. Multiple flow paths are formed inside each of the flat heat transfer tubes 33. The flat heat transfer tubes 33 are arranged between the inlet/outlet header 31 and the turn-back header 32, and are stacked in the vertical direction 39 at predetermined intervals. The multiple straight lines along which the flat heat transfer tubes 33 extend are parallel to each other and perpendicular to the vertical direction 39.

The plurality of flat heat transfer tubes 33 include a plurality of first flat heat transfer tubes 44 and a plurality of second flat heat transfer tubes 45. One end of each of the plurality of first flat heat transfer tubes 44 is joined to the inlet/outlet header 31 so that the plurality of flow paths within the plurality of first flat heat transfer tubes 44 are connected to the lower space 37 of the inlet/outlet header 31. The other end of each of the plurality of first flat heat transfer tubes 44 is joined to the turn-around header 32 so that the plurality of flow paths within the plurality of first flat heat transfer tubes 44 are connected to the internal space of the turn-around header 32. The plurality of second flat heat transfer tubes 45 are arranged above the plurality of first flat heat transfer tubes 44. One end of each of the plurality of second flat heat transfer tubes 45 is joined to the turn-around header 32 so that the plurality of flow paths within the plurality of second flat heat transfer tubes 45 are connected to the internal space of the turn-around header 32. The other ends of the multiple second flat heat transfer tubes 45 are joined to the inflow/outflow header 31 so that the multiple flow paths inside the multiple second flat heat transfer tubes 45 are connected to the upper space 38 of the inflow/outflow header 31.

Each of the multiple fins 34 is formed in a flat plate shape. The multiple fins 34 are arranged so as to respectively extend along multiple planes that are perpendicular to the multiple straight lines along which the multiple flat heat transfer tubes 33 extend. The multiple fins 34 are respectively joined to and fixed to the multiple flat heat transfer tubes 33 so that the multiple fins 34 are thermally connected to the multiple flat heat transfer tubes 33.

A refrigerant storage space 46 is formed inside the liquid reservoir 35. The liquid reservoir 35 is positioned so that the refrigerant storage space 46 is connected to the lower part of the upper space 38 of the inflow/outflow header 31, and is fixed to the inflow/outflow header 31. During cooling operation, the liquid reservoir 35 is located upstream of the refrigerant flow relative to the multiple second flat heat transfer tubes 45 through which the refrigerant exchanges heat with the air. The liquid reservoir 35 may be provided with a heat insulating material (not shown). By providing a heat insulating material, the refrigerant storage space 46 can be insulated from the outside of the liquid reservoir 35 to prevent the refrigerant stored in the refrigerant storage space 46 from exchanging heat with the outside air.

The outdoor unit 24 is equipped with an outdoor fan (not shown). The outdoor fan blows outside air so that it flows through the gaps between the multiple fins 34 and the gaps between the multiple flat heat transfer tubes 33. The direction in which the outside air flows due to the outdoor fan is perpendicular to the up-down direction 39 and perpendicular to the multiple straight lines along which the multiple flat heat transfer tubes 33 respectively extend; that is, it is generally parallel to the multiple planes along which the multiple fins 34 respectively extend.

Figure 3 is a block diagram showing the air conditioner 1 of Example 1. The air conditioner 1 further includes a control device 51. The control device 51 is a computer and includes a storage device 52 and a CPU (Central Processing Unit) 53 (not shown). The storage device 52 stores computer programs installed in the control device 51 and stores information used by the CPU 53. The CPU 53 processes information and controls the storage device 52 by executing the computer programs installed in the control device 51.

The control device 51 controls the compressor 11, four-way valve 12, and expansion valve 15. The computer program installed in the control device 51 includes multiple computer programs that cause the control device 51 to perform multiple functions. The control device 51 has four-way valve switching means 54, rotation speed control means 55, and opening control means 56 as its multiple functions.

The four-way valve switching means 54 controls the four-way valve 12 so that it switches to cooling mode when the air conditioner 1 is in cooling operation. The four-way valve switching means 54 controls the four-way valve 12 so that it switches to heating mode when the air conditioner 1 is in heating operation. The rotation speed control means 55 calculates the rotation speed based on the temperature difference between the set temperature set by the user and the room temperature, and controls the compressor 11 so that the rotation speed of the compressor 11 is equal to the calculated rotation speed.

The opening control means 56 controls the opening of the expansion valve 15 so that the discharge temperature of the refrigerant discharged from the compressor 11 is equal to the target discharge temperature calculated based on the rotation speed of the compressor 11, etc. Furthermore, when the outdoor heat exchanger 14 functions as an evaporator and the superheat of the intake refrigerant supplied to the compressor 11 is greater than a predetermined threshold, the opening control means 56 controls the opening of the expansion valve 15 to increase so that the superheat of the intake refrigerant becomes less than the threshold. When the superheat of the intake refrigerant is high, the refrigerant passing through the refrigerant storage space 46 at the outlet of the outdoor heat exchanger 14 may become superheated (gas-phase state). The threshold is set taking into account the temperature change of the refrigerant along the path from the outdoor heat exchanger 14 to the compressor 11, so that the refrigerant does not become superheated and remains in a gas-liquid two-phase state at the outlet of the outdoor heat exchanger 14.

The operations performed by the air conditioner 1 include cooling operation and heating operation.
[Cooling operation]
When the air conditioner 1 performs cooling operation, the four-way valve 12 is controlled by the control device 51 and switched to cooling mode. The control device 51 calculates the rotation speed based on the temperature difference with the room temperature and controls the compressor 11 to compress the low-pressure gas-phase refrigerant supplied via the suction pipe 16. The low-pressure gas-phase refrigerant changes state to high-pressure gas-phase refrigerant by being compressed by the compressor 11. The compressor 11 discharges the high-pressure gas-phase refrigerant to the discharge pipe 17. By switching to the cooling mode, the four-way valve 12 supplies the high-pressure gas-phase refrigerant discharged to the discharge pipe 17 to the outdoor heat exchanger 14.

The high-pressure gas-phase refrigerant supplied from the four-way valve 12 to the outdoor heat exchanger 14 is supplied to the upper space 38 of the inlet/outlet header 31 via the header outlet pipe 36. At this time, the upper space 38 of the inlet/outlet header 31 is filled with high-pressure gas-phase refrigerant in a steady state when the air conditioner 1 is performing cooling operation.

The high-pressure gas-phase refrigerant supplied to the upper space 38 flows through the multiple flow paths of the multiple second flat heat transfer tubes 45, descends through the internal space 43 of the return header 32, and flows through the multiple flow paths of the multiple first flat heat transfer tubes 44. In the outdoor heat exchanger 14, the high-pressure gas-phase refrigerant flows through the multiple flow paths of the multiple first flat heat transfer tubes 44 and the multiple flow paths of the multiple second flat heat transfer tubes 45, thereby exchanging heat between the high-pressure gas-phase refrigerant and the outside air, cooling the high-pressure gas-phase refrigerant, and heating the outside air. As the high-pressure gas-phase refrigerant is cooled, it changes state to a supercooled high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant, which has changed state from the high-pressure gas-phase refrigerant, is supplied to the lower space 37 of the inlet/outlet header 31. The outdoor heat exchanger 14 supplies the high-pressure liquid-phase refrigerant supplied to the lower space 37 to the expansion valve 15 via the refrigerant piping 41. In other words, the outdoor heat exchanger 14 functions as a condenser when the air conditioner 1 is in cooling operation. Therefore, the lower space 37 of the inlet/outlet header 31 and the flow path formed inside the refrigerant piping 41 are filled with high-pressure liquid-phase refrigerant when the air conditioner 1 is in cooling operation.

The control device 51 calculates the target discharge temperature based on the rotation speed of the compressor 11, etc., and adjusts the opening of the expansion valve 15 so that the discharge temperature of the refrigerant discharged from the compressor 11 is equal to the target discharge temperature. By adjusting the opening of the expansion valve 15, the flow rate of refrigerant flowing from the outdoor heat exchanger 14 to the intermediate heat exchanger 6 is adjusted, and the high-pressure liquid-phase refrigerant supplied from the outdoor heat exchanger 14 is depressurized. By being depressurized, the high-pressure liquid-phase refrigerant changes to low-pressure gas-liquid two-phase refrigerant with a high humidity level. The low-pressure gas-liquid two-phase refrigerant flowing out of the expansion valve 15 is supplied to the intermediate heat exchanger 6.

During cooling operation, the intermediate heat exchanger 6 exchanges heat between the low-pressure gas-liquid two-phase refrigerant flowing out of the expansion valve 15 and the water circulating through the water circuit 2, thereby cooling the water and heating the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated by the intermediate heat exchanger 6 and converted into low-pressure gas-phase refrigerant. In other words, the intermediate heat exchanger 6 functions as an evaporator when the air conditioner 1 performs cooling operation. The low-pressure gas-phase refrigerant flowing out of the intermediate heat exchanger 6 is supplied to the four-way valve 12. The low-pressure gas-phase refrigerant supplied to the four-way valve 12 is supplied to the compressor 11 via the suction pipe 16 because the four-way valve 12 is switched to cooling mode.

The pump 7 circulates water through the water circuit 2. As a result, water cooled by the intermediate heat exchanger 6 is supplied to the indoor heat exchanger 5. The indoor heat exchanger 5 exchanges heat between the water supplied from the pump 7 and the air in the room where the indoor unit 25 is installed, thereby heating the water and cooling the air in the room. The heated water is circulated through the water circuit 2 and supplied to the intermediate heat exchanger 6. The indoor unit 25 cools the room by the indoor heat exchanger 5 cooling the air in the room.

[Heating operation]
When the air conditioner 1 performs a heating operation, the four-way valve 12 is controlled by the control device 51 and switched to the heating mode. The control device 51 calculates the rotation speed based on the temperature difference between a set temperature set by a user and the room temperature, and controls the compressor 11 to compress the low-pressure gas-phase refrigerant supplied via the suction pipe 16. The low-pressure gas-phase refrigerant changes state to high-pressure gas-phase refrigerant by being compressed by the compressor 11. The compressor 11 discharges the high-pressure gas-phase refrigerant to the discharge pipe 17. The high-pressure gas-phase refrigerant supplied to the four-way valve 12 is supplied to the intermediate heat exchanger 6 because the four-way valve 12 is switched to the heating mode.

The intermediate heat exchanger 6 exchanges heat between the high-pressure gas phase refrigerant supplied from the four-way valve 12 and the water circulating through the water circuit 2, thereby heating the water and cooling the high-pressure gas phase refrigerant. The high-pressure gas phase refrigerant is cooled by the intermediate heat exchanger 6 and changes into a supercooled high-pressure liquid phase refrigerant. The high-pressure liquid phase refrigerant flowing out of the intermediate heat exchanger 6 is supplied to the expansion valve 15.

The control device 51 calculates a target discharge temperature based on the rotation speed of the compressor 11, etc., and controls the expansion valve 15 so that the discharge temperature of the refrigerant discharged from the compressor 11 is equal to the target discharge temperature. The control device 51 further adjusts the opening of the expansion valve 15 so that the superheat of the suction refrigerant supplied to the compressor 11 is less than a predetermined threshold value when the superheat of the suction refrigerant is greater than a predetermined threshold value. By adjusting the opening of the expansion valve 15, the flow rate of refrigerant flowing from the intermediate heat exchanger 6 to the outdoor heat exchanger 14 is adjusted, and the high-pressure liquid-phase refrigerant supplied from the intermediate heat exchanger 6 is depressurized. By reducing the pressure, the high-pressure liquid-phase refrigerant changes into low-pressure two-phase gas-liquid refrigerant with a high humidity level. The low-pressure two-phase gas-liquid refrigerant flowing out of the expansion valve 15 is supplied to the outdoor heat exchanger 14.

The low-pressure gas-liquid two-phase refrigerant supplied from the expansion valve 15 to the outdoor heat exchanger 14 is supplied to the lower space 37 of the inlet/outlet header 31. The low-pressure gas-liquid two-phase refrigerant supplied to the lower space 37 flows through the multiple flow paths of the multiple first flat heat transfer tubes 44, and then flows through the multiple flow paths of the multiple second flat heat transfer tubes 45 via the internal space 43 of the folded header 32. The outdoor heat exchanger 14 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and outside air by flowing through the multiple flow paths of the multiple first flat heat transfer tubes 44 and the multiple flow paths of the multiple second flat heat transfer tubes 45, heating the low-pressure gas-liquid two-phase refrigerant and cooling the outside air. By adjusting the opening of the expansion valve 15 to be larger when the superheat degree of the low-pressure gas-phase refrigerant supplied to the compressor 11 is greater than a threshold value, the low-pressure gas-liquid two-phase refrigerant supplied to the outdoor heat exchanger 14 is kept in a state where the refrigerant does not become superheated at the outlet of the outdoor heat exchanger 14. As a result, the low-pressure gas-liquid two-phase refrigerant is heated and changes state to a low-pressure gas-liquid two-phase refrigerant that has a lower wetness than the low-pressure gas-liquid two-phase refrigerant supplied to the outdoor heat exchanger 14.

Low-pressure gas-liquid two-phase refrigerant with low humidity is supplied to the upper space 38 of the inlet/outlet header 31. The low-pressure gas-liquid two-phase refrigerant supplied to the upper space 38 flows toward the header outlet pipe 36 connected to the top. However, the liquid-phase refrigerant, which is significantly affected by gravity, has a reduced flow rate in the upper space 38, causing it to separate into low-pressure gas-phase refrigerant and liquid-phase refrigerant in the upper space 38. The outdoor heat exchanger 14 supplies the low-pressure gas-phase refrigerant separated in the upper space 38 to the four-way valve 12 via the header outlet pipe 36. In other words, the outdoor heat exchanger 14 functions as an evaporator when the air conditioner 1 performs heating operation.

By switching the four-way valve 12 to heating mode, the low-pressure gas phase refrigerant supplied from the outdoor heat exchanger 14 is supplied to the suction pipe 16, and the low-pressure gas phase refrigerant is supplied to the compressor 11 via the suction pipe 16. The liquid phase refrigerant separated in the upper space 38 flows down the upper space 38 and is stored in the lower part of the upper space 38. It is then supplied from the upper space 38 to the refrigerant storage space 46 in the liquid reservoir 35 and is stored in the refrigerant storage space 46.

The pump 7 circulates water through the water circuit 2. As a result, water heated by the intermediate heat exchanger 6 is supplied to the indoor heat exchanger 5. The indoor heat exchanger 5 cools the water and heats the indoor air by exchanging heat between the water supplied from the pump 7 and the air in the room where the indoor unit 25 is installed. The cooled water is circulated through the water circuit 2 and supplied to the intermediate heat exchanger 6. The indoor unit 25 heats the room by the indoor heat exchanger 5 heating the air in the room.

When the air conditioner 1 is in cooling operation, liquid-phase refrigerant flows through the outdoor heat exchanger 14, which has a large internal pipe volume, which tends to result in a shortage of refrigerant circulating through the refrigerant circuit 3. When the air conditioner 1 is in heating operation, liquid-phase refrigerant flows through the intermediate heat exchanger 6, which has a relatively small internal pipe volume, which tends to result in an excess of refrigerant circulating through the refrigerant circuit 3.

The air conditioner of the comparative example omits the liquid reservoir 35 of the air conditioner 1 of the first embodiment, and instead provides a receiver tank between the intermediate heat exchanger 6 and the expansion valve 15. In the air conditioner of the comparative example, liquid refrigerant flows into the receiver tank during heating operation, and the liquid refrigerant is stored in the receiver tank, preventing an excess of refrigerant circulating through the refrigerant circuit 3. In the air conditioner of the comparative example, two-phase gas-liquid refrigerant flows into the receiver tank during cooling operation, and the liquid refrigerant stored in the receiver tank during heating operation is replaced with two-phase gas-liquid refrigerant with lower density, increasing the amount of refrigerant circulating through the refrigerant circuit 3 and preventing a shortage of refrigerant in the refrigerant circuit 3. However, in the air conditioner of the comparative example, two-phase gas-liquid refrigerant flows into the receiver tank during cooling operation, which can cause too much liquid refrigerant to be stored in the receiver tank, preventing the amount of refrigerant in the refrigerant circuit 3 from being increased and preventing a shortage of refrigerant circulating through the refrigerant circuit 3.

When the air conditioner 1 is operating in heating mode, high-density liquid-phase refrigerant accumulates in the liquid reservoir 35, preventing an excess of refrigerant from circulating through the refrigerant circuit 3. When the air conditioner 1 is operating in cooling mode, the liquid reservoir 35 is filled with gas-phase refrigerant, and the liquid-phase refrigerant accumulated in the liquid reservoir 35 during heating mode is replaced with low-density gas-phase refrigerant, increasing the amount of refrigerant circulating through the refrigerant circuit 3 and preventing a shortage of refrigerant in the refrigerant circuit 3. In other words, because the air conditioner 1 does not accumulate liquid-phase refrigerant in the liquid reservoir 35 during cooling mode, it can more reliably increase the amount of refrigerant circulating through the refrigerant circuit 3 during cooling mode compared to the comparative air conditioner, thereby more reliably preventing a shortage of refrigerant from circulating through the refrigerant circuit 3 during cooling mode. Furthermore, because the air conditioner 1 does not store liquid-phase refrigerant in the liquid reservoir 35 during cooling operation, there is no need to charge excess refrigerant into the refrigerant circuit 3 in anticipation of a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation, and the amount of refrigerant charged into the refrigerant circuit 3 can be reduced.

The intermediate heat exchanger 6 exchanges heat between the refrigerant and water, which is a heat medium. Because water has a higher thermal conductivity than air, the internal volume of the tubes of the intermediate heat exchanger 6 through which the refrigerant flows may be relatively small. For this reason, the intermediate heat exchanger 6 is configured so that the internal volume of the tubes of the tubes through which the refrigerant flows is relatively small. In contrast, the outdoor heat exchanger 14 exchanges heat between the refrigerant and outside air, which is a gas. Because air has a lower thermal conductivity than water, the heat transfer area of the tubes through which the refrigerant flows in the outdoor heat exchanger 14 is made relatively large. To increase the heat transfer area of the tubes through which the refrigerant flows while suppressing an increase in flow resistance, the outdoor heat exchanger 14 is configured so that the internal volume of the tubes of the tubes through which the refrigerant flows in the outdoor heat exchanger 14 is larger than the internal volume of the tubes of the tubes through which the refrigerant flows in the intermediate heat exchanger 6. The internal volume of the first path 21 is larger than the internal volume of the second path 22 because the internal volume of the refrigerant flow path of the outdoor heat exchanger 14 is larger than the internal volume of the refrigerant flow path of the intermediate heat exchanger 6.

The first path 21 includes a subcooling path. The subcooling path is a region of the first path 21 that is filled with liquid-phase refrigerant when the outdoor heat exchanger 14 functions as a condenser. That is, the subcooling path includes the lower space 37 of the inlet/outlet header 31 and a flow path formed inside the refrigerant piping 41. The liquid reservoir 35 is formed so that the following equation (1) is satisfied using the internal volume V1, the refrigerant liquid density ρ1, the internal volume V2, and the refrigerant liquid density ρ2: 0.8≦(ρ2·V2)/(ρ1·V1)≦1.2... (1) Here, the internal volume V1 indicates the volume of the subcooling path. The refrigerant liquid density ρ1 indicates the liquid density of the refrigerant that fills the subcooling path when the outdoor heat exchanger 14 functions as a condenser. The internal volume V2 indicates the volume of the liquid reservoir 35, which is the volume of the refrigerant storage space 46 in the liquid reservoir 35. The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant filled in the refrigerant storage space 46 of the liquid reservoir 35 when the outdoor heat exchanger 14 functions as an evaporator. In the air conditioner 1, a liquid-phase refrigerant with a high density accumulates in the subcooling path during cooling operation, which tends to result in a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation. On the other hand, the liquid-phase refrigerant that accumulated in the subcooling path during cooling operation circulates through the refrigerant circuit 3 during heating operation, which tends to result in an excess of refrigerant circulating through the refrigerant circuit 3 during heating operation. In the air conditioner 1, a liquid-phase refrigerant with a high density accumulates in the liquid reservoir 35 during heating operation, which prevents an excess of refrigerant circulating through the refrigerant circuit 3 during heating operation. On the other hand, the liquid-phase refrigerant that accumulated in the liquid reservoir 35 during heating operation circulates through the refrigerant circuit 3 during cooling operation, which prevents a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation. In other words, when roughly the same amount of refrigerant is stored in the liquid reservoir 35 during heating operation as the amount of refrigerant that accumulates in the subcooling path during cooling operation, the refrigerant circulates appropriately through the refrigerant circuit 3 so that there is neither an excess nor a deficiency of refrigerant, whether cooling operation or heating operation is being performed. Therefore, by configuring the liquid reservoir 35 and the subcooling path so that equation (1) is satisfied, the air conditioner 1 can adjust the amount of refrigerant circulating through the refrigerant circuit 3 to an appropriate amount whether cooling operation or heating operation is being performed.

[Effects of the air conditioner 1 according to the first embodiment]
The air conditioner 1 of the first embodiment includes an outdoor heat exchanger 14 and a liquid reservoir 35. The outdoor heat exchanger 14 is provided in the first path 21 connecting the compressor 11 and the expansion valve 15 and exchanges heat between outdoor air and the refrigerant. The liquid reservoir 35 is provided in a region of the first path 21 that is filled with gas-phase refrigerant during steady operation when the outdoor heat exchanger 14 functions as a condenser. The liquid reservoir 35 is provided in a region of the first path 21 that is filled with liquid-phase refrigerant during steady operation when the outdoor heat exchanger 14 functions as an evaporator. The liquid reservoir 35 accumulates liquid-phase refrigerant when the outdoor heat exchanger 14 functions as an evaporator. Note that steady operation refers to operation excluding a state in which the state of the refrigerant discharged from the compressor 11 is unstable, such as immediately after the compressor is started.

In the air conditioner 1 of Example 1, when the outdoor heat exchanger 14 functions as an evaporator, liquid-phase refrigerant accumulates in the liquid reservoir 35. Furthermore, when the outdoor heat exchanger 14 functions as a condenser, the liquid reservoir 35 is filled with gas-phase refrigerant. That is, in the air conditioner 1 of Example 1, liquid-phase refrigerant does not accumulate in the liquid reservoir 35 during cooling operation, making it possible to increase the amount of refrigerant circulating through the refrigerant circuit 3 during cooling operation and preventing a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation. Furthermore, because liquid-phase refrigerant does not accumulate in the liquid reservoir 35 during cooling operation, the air conditioner 1 of Example 1 does not need to charge excess refrigerant into the refrigerant circuit 3 in anticipation of a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation, and the amount of refrigerant charged into the refrigerant circuit 3 can be reduced.

The outdoor heat exchanger 14 of the air conditioner 1 of Example 1 also includes a plurality of flat heat transfer tubes 33 arranged in an area where outdoor air flows. A plurality of flow paths through which refrigerant flows are formed inside each of the plurality of flat heat transfer tubes 33. Therefore, the internal volume of the tube of the outdoor heat exchanger 14 is relatively small. Because the internal volume of the tube of the outdoor heat exchanger 14 is small, the air conditioner 1 of Example 1 can reduce the internal volume of the tube of the refrigerant circuit 3, thereby reducing the amount of refrigerant circulating through the refrigerant circuit 3. Because the amount of refrigerant circulating through the refrigerant circuit 3 is small, the air conditioner 1 of Example 1 can reduce the volume of the liquid reservoir 35, thereby reducing the amount of refrigerant filled into the refrigerant circuit 3.

Furthermore, the liquid reservoir 35 of the air conditioner 1 of the first embodiment satisfies formula (1) using the pipe volume V1, the refrigerant liquid density ρ1, the pipe volume V2, and the refrigerant liquid density ρ2.
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2…(1)
Here, the internal pipe volume V1 indicates the volume of the subcooling path in the first path 21 that is filled with liquid-phase refrigerant when the outdoor heat exchanger 14 functions as a condenser. The refrigerant liquid density ρ1 indicates the liquid density of the refrigerant that fills the subcooling path when the outdoor heat exchanger 14 functions as a condenser. The internal pipe volume V2 indicates the volume of the liquid reservoir 35. The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant that fills the liquid reservoir 35 when the outdoor heat exchanger 14 functions as an evaporator. In the air conditioner 1, liquid-phase refrigerant with a high density accumulates in the subcooling path during cooling operation, which tends to result in a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation. However, the liquid-phase refrigerant that accumulated in the subcooling path during cooling operation circulates through the refrigerant circuit 3 during heating operation, which tends to result in an excess of refrigerant circulating through the refrigerant circuit 3 during heating operation. In the air conditioner 1 of Example 1, a liquid-phase refrigerant with a high density is stored in the liquid reservoir 35 during heating operation, thereby preventing an excess of refrigerant circulating through the refrigerant circuit 3 during heating operation. Furthermore, the liquid-phase refrigerant stored in the liquid reservoir 35 during heating operation circulates through the refrigerant circuit 3 during cooling operation, thereby preventing a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation. In other words, when approximately the same amount of refrigerant as that stored in the subcooling path during cooling operation is stored in the liquid reservoir 35 during heating operation, the refrigerant is appropriately circulated through the refrigerant circuit 3 so that there is neither an excess nor a shortage of refrigerant, whether the cooling operation or the heating operation is being performed. Therefore, in the air conditioner 1 of Example 1, the liquid reservoir 35 and the subcooling path are configured to satisfy equation (1), so that the amount of refrigerant circulating through the refrigerant circuit 3 can be adjusted to an appropriate amount whether the cooling operation or the heating operation is being performed.

The air conditioner 1 of Example 1 also includes a control device 51 that controls the expansion valve 15 when the outdoor heat exchanger 14 functions as an evaporator, so that the refrigerant at the outlet of the outdoor heat exchanger 14 flowing from the outdoor heat exchanger 14 to the compressor 11 does not completely evaporate. The control device 51 of the air conditioner 1 of Example 1 also controls the expansion valve 15 to reduce the degree of intake superheat when the outdoor heat exchanger 14 functions as an evaporator and the degree of intake superheat of the refrigerant flowing from the outdoor heat exchanger 14 to the compressor 11 is greater than a threshold value. The air conditioner 1 of Example 1 can more reliably store liquid-phase refrigerant in the liquid reservoir 35 during heating operation, and more reliably prevent an excess of refrigerant circulating through the refrigerant circuit 3 during heating operation.

The air conditioner 1 of Example 1 also includes an indoor heat exchanger 5 and an intermediate heat exchanger 6. The indoor heat exchanger 5 exchanges heat between the water circulating between the indoor unit 25 and the outdoor unit 24 and the indoor air. The intermediate heat exchanger 6 exchanges heat between the refrigerant and water. A heat exchanger that exchanges heat between a refrigerant and water has a smaller internal volume than a heat exchanger that exchanges heat between a refrigerant and air. Therefore, the internal volume of the pipe through which the refrigerant flows in the outdoor heat exchanger 14 is larger than the internal volume of the pipe through which the refrigerant flows in the intermediate heat exchanger 6. In other words, the difference in the amount of refrigerant required for cooling operation and heating operation becomes significant, and the benefits of the present invention are significant. Alternatively, the water circuit 2 may be omitted, and the intermediate heat exchanger 6 in the refrigerant circuit 3 may be replaced with the indoor heat exchanger 5, allowing the refrigerant to directly exchange heat with the air in the indoor heat exchanger 5.

Incidentally, the liquid reservoir 35 and the subcooling path of the air conditioner 1 of the first embodiment described above are formed so as to satisfy formula (1), but formula (1) does not necessarily have to be satisfied. Even if formula (1) is not satisfied, the air conditioner 1 of the first embodiment can adjust the amount of refrigerant circulating through the refrigerant circuit 3 and reduce the amount of refrigerant charged into the refrigerant circuit 3 by storing or not storing liquid-phase refrigerant in the liquid reservoir 35. Note that the liquid reservoir 35 may be formed so as to satisfy formula (2).
0.9≦(ρ2・V2)/(ρ1・V1)≦1.1…(2)
When approximately the same amount of refrigerant as that accumulated in the subcooling path during cooling operation is stored in the liquid reservoir 35 during heating operation, refrigerant circulates appropriately through the refrigerant circuit 3 without excess or deficiency, whether cooling operation or heating operation is being performed. Therefore, when equation (2) is satisfied, the air conditioner 1 can adjust the amount of refrigerant circulating through the refrigerant circuit 3 to a more appropriate amount than when equation (2) is not satisfied. Furthermore, when the value of (ρ2·V2)/(ρ1·V1) is 1.0, the air conditioner 1 can adjust the amount of refrigerant circulating through the refrigerant circuit 3 to a more appropriate amount than when the value of (ρ2·V2)/(ρ1·V1) is different from 1.0.

In the air conditioner 1 of the first embodiment described above, the outdoor heat exchanger 14 is provided with a liquid reservoir 35 in which high-pressure liquid-phase refrigerant is stored when heating operation is performed. However, this may be replaced with a refrigerant reservoir other than the liquid reservoir 35. An example of a refrigerant reservoir is a refrigerant tank provided midway through the flow path connecting the outdoor heat exchanger 14 and the four-way valve 12. Even when such a refrigerant tank is provided, the air conditioner 1 can adjust the amount of refrigerant circulating through the refrigerant circuit 3 and reduce the amount of refrigerant filled into the refrigerant circuit 3.

As shown in Figure 4, the air conditioner of Example 2 replaces the outdoor heat exchanger 14 of the air conditioner 1 of Example 1 with another outdoor heat exchanger 61. Figure 4 is a front view showing the outdoor heat exchanger 61 of the air conditioner of Example 2. Like the outdoor heat exchanger 14 described above, the outdoor heat exchanger 61 includes an inlet/outlet header 31, a folded header 32, multiple flat heat transfer tubes 33, multiple fins 34, and a header outlet pipe 36, but does not include the liquid reservoir 35.

The header outlet pipe 36 penetrates the inlet/outlet header 31 and is fixed to the inlet/outlet header 31 so that the flow path inside the header outlet pipe 36 is connected to the top of the upper space 38. A refrigerant storage space 62 (refrigerant storage section) is also formed inside the inlet/outlet header 31. The refrigerant storage space 62 is a space below the portion of the upper space 38 of the inlet/outlet header 31 that is connected to the header outlet pipe 36. Therefore, the volume of the refrigerant storage space 62 changes when the inner diameter of the inlet/outlet header 31 changes, and also when the position where the header outlet pipe 36 of the inlet/outlet header 31 is joined changes. For example, the volume of the refrigerant storage space 62 increases as the inner diameter of the inlet/outlet header 31 increases, and increases as the position where the header outlet pipe 36 of the inlet/outlet header 31 is joined increases.

The air conditioner of Example 2 performs cooling operation and heating operation in the same manner as the air conditioner 1 of Example 1. The refrigerant storage space 62 is formed so that the formula (3) is satisfied using the internal volume V3 and the refrigerant liquid density ρ3.
0.8≦(ρ3・V3)/(ρ1・V1)≦1.2…(3)
Here, the internal pipe volume V3 indicates the volume of the refrigerant storage space 62. The refrigerant liquid density ρ3 indicates the density of the refrigerant that fills the refrigerant storage space 62 when the outdoor heat exchanger 61 functions as an evaporator. For example, the inner diameter of the inlet/outlet header 31 and the position where the header outlet pipe 36 of the inlet/outlet header 31 is joined are designed to satisfy equation (3).

The air conditioner of Example 2, like the air conditioner 1 of Example 1, can prevent an excess of refrigerant circulating through the refrigerant circuit 3 by accumulating liquid-phase refrigerant in the refrigerant storage space 62 when the outdoor heat exchanger 61 functions as an evaporator. Furthermore, the air conditioner of Example 2 can prevent a shortage of refrigerant circulating through the refrigerant circuit 3 by filling the refrigerant storage space 62 with gas-phase refrigerant when the outdoor heat exchanger 61 functions as a condenser. Furthermore, because liquid-phase refrigerant is not accumulated in the refrigerant storage space 62 during cooling operation, the air conditioner of Example 2 does not need to charge excess refrigerant into the refrigerant circuit 3 in anticipation of a shortage of refrigerant circulating through the refrigerant circuit 3 during cooling operation, and the amount of refrigerant charged into the refrigerant circuit 3 can be reduced. When approximately the same amount of refrigerant as that stored in the subcooling path during cooling operation is stored in the refrigerant storage space 62 during heating operation, refrigerant circulates appropriately through the refrigerant circuit 3 so that there is neither an excess nor a deficiency of refrigerant, whether cooling operation or heating operation is being performed. Therefore, by further satisfying equation (3), the air conditioner of Example 2, like the air conditioner 1 of Example 1, can adjust the amount of refrigerant circulating through the refrigerant circuit 3 to an appropriate amount whether cooling operation or heating operation is being performed.

Incidentally, the refrigerant storage space 62 and subcooling path of the air conditioner of Example 2 described above are configured to satisfy equation (3), but equation (3) does not necessarily have to be satisfied. Even if equation (3) is not satisfied, the air conditioner of Example 2 can adjust the amount of refrigerant circulating through the refrigerant circuit 3 and reduce the amount of refrigerant filled into the refrigerant circuit 3 by storing or not storing refrigerant in the refrigerant storage space 62.

Although the embodiments have been described above, the embodiments are not limited to the above content. Furthermore, the components described above include those that would be easily conceivable by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is known as equivalents. Furthermore, the components described above can be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the components can be made without departing from the spirit of the embodiments.

1: Air conditioner 2: Water circuit 3: Refrigerant circuit 5: Indoor heat exchanger 6: Intermediate heat exchanger 11: Compressor 12: Four-way valve 14: Outdoor heat exchanger 15: Expansion valve 21: First path 22: Second path 24: Outdoor unit 25: Indoor unit 31: Inflow/outflow header (header)
33: Multiple flat heat transfer tubes 35: Liquid reservoir 36: Header outlet pipe 38: Upper space 41: Refrigerant piping 46: Refrigerant storage space 51: Control device 61: Outdoor heat exchanger 62: Refrigerant storage space

Claims (9)

a heat exchanger provided in a path connecting the compressor and the expansion valve to exchange heat between the outside air and the refrigerant;
a four-way valve that switches the direction in which the refrigerant flows through the path;
a refrigerant reservoir provided in a region of the path that is steadily filled with gas-phase refrigerant when the heat exchanger functions as a condenser , and that accumulates liquid-phase refrigerant when the heat exchanger functions as an evaporator;
the heat exchanger has a plurality of flat heat transfer tubes arranged in a region where the outside air flows,
A plurality of flow paths through which the refrigerant flows are formed inside each of the plurality of flat heat transfer tubes,
the heat exchanger further includes a header having an internal space formed therein, the internal space being connected to one end of the plurality of flow paths connected to the compressor,
the refrigerant reservoir is provided in the header,
The refrigerant storage portion is calculated by the following equation using the pipe internal volume V1, the refrigerant liquid density ρ1, the pipe internal volume V2, and the refrigerant liquid density ρ2:
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2
Fulfilling
the internal tube volume V1 represents the volume of a subcooling path among the paths that is filled with a liquid-phase refrigerant when the heat exchanger functions as a condenser,
the refrigerant liquid density ρ1 represents the liquid density of the refrigerant filled in the subcooling path when the heat exchanger functions as a condenser,
The pipe volume V2 indicates the volume of the refrigerant storage section,
The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant filled in the refrigerant reservoir when the heat exchanger functions as an evaporator.
Air conditioner. The air conditioner according to claim 1 , wherein a header outlet pipe in the path that connects the heat exchanger and the compressor is connected to a position in the internal space that satisfies the formula. The air conditioner according to claim 1 or 2 , wherein the inner diameter of the header is formed so as to satisfy the formula. The air conditioner according to any one of claims 1 to 3, further comprising a control device that controls the expansion valve when the heat exchanger functions as an evaporator so that evaporator outlet refrigerant of the refrigerant flowing from the heat exchanger to the compressor does not completely evaporate. The air conditioner according to claim 4, wherein when the heat exchanger functions as an evaporator and the degree of intake superheat of the intake refrigerant flowing from the heat exchanger to the compressor is greater than a threshold value, the control device controls the expansion valve so as to reduce the degree of intake superheat. an indoor heat exchanger that exchanges heat between another refrigerant circulating between the indoor unit and the outdoor unit and the indoor air;
The air conditioner according to any one of claims 1 to 5 , further comprising: an intermediate heat exchanger provided in another path connecting the compressor and the expansion valve, exchanging heat between the refrigerant and the other refrigerant. a heat exchanger that is provided in the middle of a path connecting the compressor and the expansion valve and exchanges heat between the outside air and the refrigerant;
a plurality of flat heat transfer tubes arranged in the region where the outside air flows, each of which has a plurality of flow paths formed therein through which the refrigerant flows;
a header having an internal space formed therein, the internal space being connected to one end of the plurality of flow paths connected to the compressor;
a refrigerant reservoir provided in the header ,
the refrigerant reservoir is provided between the plurality of flat heat transfer tubes and the compressor so that the inside of the refrigerant reservoir is filled with gas-phase refrigerant when the refrigerant is supplied from the compressor through the plurality of flow paths to the expansion valve, and so that liquid-phase refrigerant accumulates inside the refrigerant reservoir when the refrigerant is supplied from the expansion valve through the plurality of flow paths to the compressor ,
The refrigerant storage portion is calculated by the following equation using the pipe internal volume V1, the refrigerant liquid density ρ1, the pipe internal volume V2, and the refrigerant liquid density ρ2:
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2
Fulfilling
the internal tube volume V1 represents the volume of a subcooling path among the paths that is filled with a liquid-phase refrigerant when the heat exchanger functions as a condenser,
the refrigerant liquid density ρ1 represents the liquid density of the refrigerant filled in the subcooling path when the heat exchanger functions as a condenser,
The pipe volume V2 indicates the volume of the refrigerant storage section,
The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant filled in the refrigerant reservoir when the heat exchanger functions as an evaporator.
heat exchanger. a heat exchanger provided in a path connecting the compressor and the expansion valve to exchange heat between the outside air and the refrigerant;
a four-way valve that switches the direction in which the refrigerant flows through the path;
a refrigerant reservoir provided in a region of the path that is steadily filled with gas-phase refrigerant when the heat exchanger functions as a condenser, and that accumulates liquid-phase refrigerant when the heat exchanger functions as an evaporator;
The refrigerant storage portion is calculated by the following equation using the pipe internal volume V1, the refrigerant liquid density ρ1, the pipe internal volume V2, and the refrigerant liquid density ρ2:
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2
Fulfilling
the internal tube volume V1 represents the volume of a subcooling path among the paths that is filled with a liquid-phase refrigerant when the heat exchanger functions as a condenser,
the refrigerant liquid density ρ1 represents the liquid density of the refrigerant filled in the subcooling path when the heat exchanger functions as a condenser,
The pipe volume V2 indicates the volume of the refrigerant storage section,
The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant filled in the refrigerant reservoir when the heat exchanger functions as an evaporator.
Air conditioner. a heat exchanger that is provided in the path connecting the compressor and the expansion valve and exchanges heat between the outside air and the refrigerant;
a plurality of flat heat transfer tubes arranged in the region where the outside air flows, each of which has a plurality of flow paths formed therein through which the refrigerant flows;
a refrigerant reservoir,
the refrigerant reservoir is provided between the plurality of flat heat transfer tubes and the compressor so that the inside of the refrigerant reservoir is filled with gas-phase refrigerant when the refrigerant is supplied from the compressor through the plurality of flow paths to the expansion valve, and so that liquid-phase refrigerant accumulates inside the refrigerant reservoir when the refrigerant is supplied from the expansion valve through the plurality of flow paths to the compressor,
The refrigerant storage portion is calculated by the following equation using the pipe internal volume V1, the refrigerant liquid density ρ1, the pipe internal volume V2, and the refrigerant liquid density ρ2:
0.8≦(ρ2・V2)/(ρ1・V1)≦1.2
Fulfilling
the internal tube volume V1 represents the volume of a subcooling path among the paths that is filled with a liquid-phase refrigerant when the heat exchanger functions as a condenser,
the refrigerant liquid density ρ1 represents the liquid density of the refrigerant filled in the subcooling path when the heat exchanger functions as a condenser,
The pipe volume V2 indicates the volume of the refrigerant storage section,
The refrigerant liquid density ρ2 indicates the liquid density of the refrigerant filled in the refrigerant reservoir when the heat exchanger functions as an evaporator.
heat exchanger.