JP7660334B2 - Refrigeration Cycle Equipment - Google Patents

Description

A refrigeration cycle device in which a heat source unit and a utilization unit are connected via a refrigerant connection pipe to form a refrigerant circuit, and carbon dioxide is used as the refrigerant sealed in the refrigerant circuit.

Conventionally, there are air conditioners (refrigeration cycle devices) in which a heat source unit and a utilization unit are connected via a refrigerant connection pipe to form a refrigerant circuit. As shown in Patent Document 1 (International Publication No. 2011/099063), one such refrigeration cycle device uses carbon dioxide as the refrigerant sealed in the refrigerant circuit.

When using carbon dioxide as the refrigerant sealed in the refrigerant circuit, adverse effects on the human body (oxygen deficiency, etc.) must be considered. Specifically, safety measures must be taken according to the concentration level of carbon dioxide in the indoor space when the refrigerant leaks from the refrigerant circuit. This tendency is particularly pronounced in refrigeration cycle devices with multiple utilization units, such as multi-air conditioners for buildings, where a large amount of refrigerant is sealed in the refrigerant circuit, and if refrigerant leaks from one of the utilization units, there is a risk that all of the refrigerant sealed in the refrigerant circuit will leak into the indoor space corresponding to the utilization unit where the refrigerant leak occurred.

For this reason, when using carbon dioxide as the refrigerant to be sealed in the refrigerant circuit, it is preferable to reduce the amount of refrigerant to be sealed in the refrigerant circuit.

The refrigeration cycle device according to the first aspect is a refrigeration cycle device in which a heat source unit and a utilization unit are connected via a gas refrigerant connection pipe and a liquid refrigerant connection pipe to form a refrigerant circuit, in which the refrigerant sealed in the refrigerant circuit is carbon dioxide, the gas refrigerant connection pipe is a pipe having an inner diameter of 6.2 mm or less, and/or the liquid refrigerant connection pipe is a pipe having an inner diameter of 3.6 mm or less.

As a result, because pipes with inner diameters not previously used as gas refrigerant connection pipes and/or liquid refrigerant connection pipes are used, the volume of the gas refrigerant connection pipes and/or liquid refrigerant connection pipes can be reduced, and the amount of refrigerant sealed in the refrigerant circuit can be reduced.

The refrigeration cycle device according to the second aspect is the refrigeration cycle device according to the first aspect, in which a copper pipe (1/2H quality) with a nominal diameter of less than 1/4 inch is used as a liquid refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 8.0 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as liquid refrigerant connection pipes are used here, which allows for an increase in the size of copper pipes that can be used as liquid refrigerant connection pipes, contributing to the optimization of liquid refrigerant connection pipes.

The refrigeration cycle device according to the third aspect is the refrigeration cycle device according to the first aspect, in which a copper pipe (1/2H quality) with a nominal diameter of 1.5/8 inches is used as a liquid refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 8.0 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as liquid refrigerant connection pipes are used here, which allows for an increase in the size of copper pipes that can be used as liquid refrigerant connection pipes, contributing to the optimization of liquid refrigerant connection pipes.

The refrigeration cycle device according to the fourth aspect is a refrigeration cycle device according to any one of the first to third aspects, in which a copper pipe (1/2H quality) with a nominal diameter larger than 1/4 inch and smaller than 3/8 inch is used as a gas refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 4.5 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as gas refrigerant connecting pipes are used here, which increases the size of copper pipes that can be used as gas refrigerant connecting pipes and contributes to optimizing gas refrigerant connecting pipes.

The refrigeration cycle device according to the fifth aspect is a refrigeration cycle device according to any one of the first to third aspects, in which a copper pipe (1/2H quality) with a nominal diameter of 2.5/8 inches is used as a gas refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 4.5 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as gas refrigerant connecting pipes are used here, which increases the size of copper pipes that can be used as gas refrigerant connecting pipes and contributes to optimizing gas refrigerant connecting pipes.

The refrigeration cycle device according to the sixth aspect is the refrigeration cycle device according to the first aspect, in which a copper pipe (with quality O) with a nominal diameter of less than 1/4 inch is used as a liquid refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 3.6 kW or less is connected.

As a result, by using copper pipes with nominal diameters that have not previously been used as liquid refrigerant connection pipes, it is possible to increase the size of copper pipes that can be used as liquid refrigerant connection pipes, contributing to the optimization of liquid refrigerant connection pipes.

The refrigeration cycle device according to the seventh aspect is the refrigeration cycle device according to the first aspect, in which a copper pipe (with quality O) with a nominal diameter of 1.5/8 inches is used as a liquid refrigerant connection pipe to which a utilization unit with a rated refrigeration capacity of 3.6 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as liquid refrigerant connection pipes are used here, which allows for an increase in the size of copper pipes that can be used as liquid refrigerant connection pipes, contributing to the optimization of liquid refrigerant connection pipes.

The refrigeration cycle device according to the eighth aspect is a refrigeration cycle device according to any one of the first, sixth and seventh aspects, in which a copper pipe (with quality O) having a nominal diameter larger than 1/4 inch and smaller than 3/8 inch is used as a gas refrigerant connection pipe to which a utilization unit having a rated refrigeration capacity of 2.8 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as gas refrigerant connecting pipes are used here, which increases the size of copper pipes that can be used as gas refrigerant connecting pipes and contributes to optimizing gas refrigerant connecting pipes.

The refrigeration cycle device according to the ninth aspect is a refrigeration cycle device according to any one of the first, sixth and seventh aspects, in which a copper pipe (with quality O) having a nominal diameter of 2.5/8 inches is used as a gas refrigerant connection pipe to which a utilization unit having a rated refrigeration capacity of 2.8 kW or less is connected.

As a result, copper pipes with nominal diameters that have not previously been used as gas refrigerant connecting pipes are used here, which increases the size of copper pipes that can be used as gas refrigerant connecting pipes and contributes to optimizing gas refrigerant connecting pipes.

The refrigeration cycle device according to the tenth aspect is a refrigeration cycle device according to any one of the first to ninth aspects, in which the gas refrigerant communication pipe and the liquid refrigerant communication pipe are covered on their outer surfaces with a heat insulating material and are bundled together to form a pair of refrigerant communication pipes.

Here, paired refrigerant connection pipes can be used to connect the heat source unit and utilization unit on-site, improving ease of installation.

The refrigeration cycle device according to the eleventh aspect is a refrigeration cycle device according to any one of the first to tenth aspects, in which when a pipe with a nominal diameter of 1.5/8 inches is used as a liquid refrigerant communication pipe with a nominal diameter of less than 1/4 inch, the pipe end has a different diameter section that is expanded to a nominal diameter of 1/4 inch.

When the liquid refrigerant connection pipe is long or branches, pipe fittings such as socket pipes and branch pipes are required to connect the pipes. However, the pipe fittings that have been used so far are compatible with pipes with nominal diameters in 1/8 inch increments, but are not compatible with pipes with nominal diameters in 0.5/8 inch increments.

Therefore, here, the end of the pipe with a nominal diameter of 1.5/8 inches used as the liquid refrigerant connection pipe has a different diameter section that is enlarged to a nominal diameter of 1/4 inch (= 2/8 inch).

As a result, even when using a pipe with a nominal diameter of 1.5/8 inches as a liquid refrigerant connection pipe with a nominal diameter of less than 1/4 inch, it is possible to use pipe fittings that are compatible with pipes with nominal diameters in 1/8 inch increments that have been used traditionally, eliminating the need to prepare pipe fittings that are compatible with pipes with nominal diameters in 0.5/8 inch increments, improving ease of installation.

The refrigeration cycle device according to the twelfth aspect is a refrigeration cycle device according to any one of the first to eleventh aspects, in which, when a pipe with a nominal diameter of 2.5/8 inches is used as a gas refrigerant communication pipe with a nominal diameter larger than 1/4 inch and less than 3/8 inch, the pipe end has a different diameter section that is expanded to a nominal diameter of 3/8 inch.

When the gas refrigerant communication pipe is long or branches, pipe fittings such as socket pipes and branch pipes are required to connect the pipes. However, the pipe fittings that have been used so far are compatible with pipes with nominal diameters in 1/8 inch increments, but are not compatible with pipes with nominal diameters in 0.5/8 inch increments.

Here, the end of a pipe with a nominal diameter of 2.5/8 inches used as a gas refrigerant connection pipe has a different diameter section that is enlarged to a nominal diameter of 3/8 inches.

As a result, even when a 2.5/8 inch nominal diameter pipe is used as a gas refrigerant connection pipe with a nominal diameter greater than 1/4 inch and less than 3/8 inch, conventional pipe fittings compatible with pipes with nominal diameters in 1/8 inch increments can be used, eliminating the need to prepare pipe fittings compatible with pipes with nominal diameters in 0.5/8 inch increments, improving ease of installation.

1 is a schematic configuration diagram of an air conditioner as a refrigeration cycle apparatus according to an embodiment of the present disclosure. 1 is a table showing the relationship between the rated refrigeration capacity and the pipe diameter of the refrigerant communication pipe when R410A, R32, or carbon dioxide is used as the refrigerant. FIG. 2 is an explanatory diagram of a refrigerant communication pipe constituting the refrigeration cycle apparatus of FIG. 1 (parts constituting a heat source unit and a utilization unit are not shown). 1 is a table showing the relationship between the rated refrigeration capacity and the pipe diameter of the refrigerant connection pipe when the quality of the copper pipe is ½H or O. FIG. 2 is a diagram showing the main parts of a pair of refrigerant communication pipes. FIG. 4 is a diagram showing a pipe end portion of a refrigerant communication pipe.

The refrigeration cycle device is explained below with reference to the drawings.

(1) Composition <Overall>
FIG. 1 is a schematic configuration diagram of an air conditioner 1 as a refrigeration cycle apparatus according to one embodiment of the present disclosure.

The air conditioner 1 is a device capable of cooling or heating the interior of a building or the like by a vapor compression refrigeration cycle. The air conditioner 1 mainly has a heat source unit 2, utilization units 4a and 4b, and a gas refrigerant connection pipe 5 and a liquid refrigerant connection pipe 6 that connect the heat source unit 2 and the utilization units 4a and 4b. That is, the vapor compression refrigerant circuit 7 of the air conditioner 1 is configured by connecting the heat source unit 2 and the utilization units 4a and 4b via the gas refrigerant connection pipe 5 and the liquid refrigerant connection pipe 6. Carbon dioxide is sealed in the refrigerant circuit 7 as a refrigerant. When carbon dioxide is used as the refrigerant, the refrigerant may become supercritical (a state in which the gas state and the liquid state cannot be distinguished) during the refrigeration cycle, but the names of the parts that make up the refrigerant circuit 7, including the refrigerant connection pipes 5 and 6, are named using the terms "gas" and "liquid" in the names of the parts, as in the case of using a refrigerant that does not become supercritical during the refrigeration cycle (R410A, R32, etc.).

<Usage unit>
The utilization units 4a and 4b are installed indoors or the like and constitute a part of the refrigerant circuit 7. The utilization unit 4a mainly has a utilization side expansion mechanism 41a and a utilization heat exchanger 42a. The utilization unit 4b mainly has a utilization side expansion mechanism 41b and a utilization heat exchanger 42b. Here, since the utilization units 4a and 4b have the same configuration, only the configuration of the utilization unit 4a will be described here, and the configuration of the utilization unit 4b will be described with the subscript "b" instead of the subscript "a" indicating each part of the utilization unit 4a, and the description of each part will be omitted.

The user-side expansion mechanism 41a is a mechanism for reducing the pressure of the refrigerant, and an expansion valve is used here. One end of the user-side expansion mechanism 41a is connected to the user-side heat exchanger 42a, and the other end is connected to the liquid refrigerant connection pipe 6.

The utilization side heat exchanger 42a is a heat exchanger that functions as an evaporator or radiator of the refrigerant. One end of the utilization side heat exchanger 42a is connected to the utilization side expansion mechanism 41a, and the other end is connected to the gas refrigerant connection pipe 5.

The utilization unit 4a has a utilization side fan 43a for drawing air into the unit and supplying it to the room, thereby allowing heat exchange between the air and the refrigerant flowing through the utilization side heat exchanger 42a.

<Heat source unit>
The heat source unit 2 is installed outdoors or the like, and constitutes a part of the refrigerant circuit 7. The heat source unit 2 mainly includes a compressor 21, a switching mechanism 22, a heat source side heat exchanger 23, a heat source side expansion mechanism 25, a subcooling heat exchanger 26, a suction return pipe 27, a liquid side shutoff valve 29, a gas side shutoff valve 30, and an accumulator 31.

The compressor 21 is a device that compresses the refrigerant. In addition, an accumulator 31 that temporarily stores the refrigerant is provided on the suction side of the compressor 21.

The switching mechanism 22 is a mechanism for switching the direction of the refrigerant flow in the refrigerant circuit 7, and a four-way switching valve is used here. In order to make the heat source side heat exchanger 23 function as a refrigerant radiator and the user side heat exchangers 42a and 42b function as refrigerant evaporators during cooling operation, the switching mechanism 22 connects the discharge side of the compressor 21 to one end of the heat source side heat exchanger 23 and connects the suction side of the compressor 21 to the gas side stop valve 30 (see the solid line of the switching mechanism 22 in FIG. 1). In order to make the user side heat exchanger 42 function as a refrigerant radiator and the heat source side heat exchanger 23 function as a refrigerant evaporator during heating operation, the switching mechanism 22 connects the discharge side of the compressor 21 to the gas side stop valve 30 and connects the suction side of the compressor 21 to one end of the heat source side heat exchanger 23 (see the dashed line of the switching mechanism 22 in FIG. 1).

The heat source side heat exchanger 23 is a heat exchanger that functions as a radiator or evaporator of the refrigerant. One end of the heat source side heat exchanger 23 is connected to the switching mechanism 22, and the other end is connected to the heat source side expansion mechanism 25.

The heat source unit 2 has a heat source side fan 24 for drawing air into the unit and discharging it to the outside, thereby allowing heat exchange between the air and the refrigerant flowing through the heat source side heat exchanger 23.

The heat source side expansion mechanism 25 is a mechanism for reducing the pressure of the refrigerant, and an expansion valve is used here. One end of the heat source side expansion mechanism 25 is connected to the heat source side heat exchanger 23, and the other end is connected to the subcooling heat exchanger 26.

The subcooling heat exchanger 26 is a heat exchanger that further cools the refrigerant that has released heat in the heat source side heat exchanger 23. One end of the subcooling heat exchanger 26 is connected to the heat source side expansion mechanism 25, and the other end is connected to the liquid side shutoff valve 29. The refrigerant circuit 7 is provided with an intake return pipe 27 that reduces the pressure of a portion of the refrigerant that flows from the other end of the heat source side heat exchanger 23 through the heat source side expansion mechanism 25 and the subcooling heat exchanger 26 to the liquid side shutoff valve 29 and then returns it to the intake side of the compressor 21. Here, the intake return pipe 27 is provided in the refrigerant circuit 7 so that a portion of the refrigerant that flows between the heat source side expansion mechanism 25 and the subcooling heat exchanger 26 is branched from the refrigerant circuit 7 and returned to the intake side of the compressor 21 (more specifically, between the switching mechanism 22 and the accumulator 31). The intake return pipe 27 is provided with an intake return expansion mechanism 28 for reducing the pressure of the refrigerant. Here, an expansion valve is used as the intake return expansion mechanism 28. As a result, part of the refrigerant cooled in the heat source side heat exchanger 23 is bypassed to the suction side of the compressor 21 through the suction return pipe 27, and the remainder is cooled in the heat source side heat exchanger 26 by the refrigerant flowing through the suction return pipe 27.

The liquid-side shutoff valve 28 is a valve to which the liquid refrigerant communication pipe 6 is connected for exchanging refrigerant between the heat source unit 2 and the utilization units 4a and 4b, and is connected to the subcooling heat exchanger 26.

The gas side shutoff valve 30 is a valve to which the gas refrigerant communication pipe 5 for exchanging refrigerant between the heat source unit 2 and the utilization units 4a, 4b is connected, and is connected to the switching mechanism 22.

<Refrigerant connection pipe>
The refrigerant connection pipes 5, 6 are refrigerant pipes that connect the heat source unit 2 and the utilization units 4a, 4b on-site when the air conditioning apparatus 1 is constructed.

The gas refrigerant communication pipe 5 is a refrigerant pipe through which refrigerant flows from the end of the evaporation process to the start of the compression process, or from the end of the compression process to the start of the heat dissipation process, when described using the compression process, heat dissipation process, and evaporation process of the refrigeration cycle. Here, the gas refrigerant communication pipe 5 connects the gas side shutoff valve 30 of the heat source unit 2 to the other end of the utilization side heat exchangers 42a, 42b of the utilization units 4a, 4b. The gas refrigerant communication pipe 5 mainly includes a gas refrigerant communication branch pipe 52a connected to the utilization unit 4a, a gas refrigerant communication branch pipe 52b connected to the utilization unit 4b, and a gas refrigerant communication main pipe 51 that connects the junction of the gas refrigerant communication branch pipes 52a, 52b to the heat source unit 2.

The liquid refrigerant communication pipe 6 is a refrigerant pipe through which refrigerant flows from the end of the heat radiation process to the start of the evaporation process, when explained using the compression process, heat dissipation process, expansion process, and evaporation process of the refrigeration cycle. Here, the liquid refrigerant communication pipe 6 connects between the liquid side shutoff valve 29 of the heat source unit 2 and the utilization side expansion mechanisms 41a, 41b of the utilization units 4a, 4b. The liquid refrigerant communication pipe 6 mainly includes a liquid refrigerant communication branch pipe 62a connected to the utilization unit 4a, a liquid refrigerant communication branch pipe 62b connected to the utilization unit 4b, and a liquid refrigerant communication main pipe 61 that connects between the junction of the liquid refrigerant communication branch pipes 62a, 62b and the heat source unit 2.

(2) Operation Next, the operation of the air conditioner 1 will be described with reference to Fig. 1. Note that the operation of the air conditioner 1, such as cooling operation and heating operation, described below, is performed by a control unit (not shown) configured by communication connections between control boards and remote controls provided in the utilization units 4a and 4b and the heat source unit 2.

<Cooling operation>
During cooling operation, the switching mechanism 22 is in the state shown by the solid line in Figure 1, i.e., the discharge side of the compressor 21 is connected to the heat source side heat exchanger 23 and the suction side of the compressor 21 is connected to the gas side shut-off valve 30.

In this state of the refrigerant circuit 7, the low-pressure refrigerant in the refrigeration cycle is sucked into the compressor 21, compressed to the high pressure of the refrigeration cycle, and then discharged from the compressor 21. The high-pressure refrigerant discharged from the compressor 21 is sent to the heat source side heat exchanger 23 via the switching mechanism 22, and dissipates heat by exchanging heat with the outdoor air supplied by the heat source side fan 24. The high-pressure refrigerant that has dissipated heat in the heat source side heat exchanger 23 flows into the subcooling heat exchanger 26 via the heat source side expansion mechanism 25, and is cooled by exchanging heat with the refrigerant flowing through the suction return pipe 27. At this time, a portion of the high-pressure refrigerant that has dissipated heat in the heat source side heat exchanger 23 is branched off to the suction return pipe 27 and depressurized by the suction return expansion mechanism 28. The refrigerant decompressed in the suction return expansion mechanism 28 is heated in the subcooling heat exchanger 26 by heat exchange with the high-pressure refrigerant flowing through the refrigerant circuit 7, and then returned to the suction side of the compressor 21 (here, between the switching mechanism 22 and the accumulator 31).

The high-pressure refrigerant cooled in the subcooling heat exchanger 26 is then sent to the utilization units 4a, 4b via the liquid-side shutoff valve 29 and the liquid refrigerant connection pipe 6. The high-pressure refrigerant sent to the utilization units 4a, 4b is decompressed by the utilization side expansion mechanisms 41a, 41b to become a low-pressure gas-liquid two-phase refrigerant. The refrigerant decompressed in the utilization side expansion mechanisms 41a, 41b is sent to the utilization side heat exchangers 42a, 42b, where it exchanges heat with indoor air supplied by the utilization side fans 43a, 43b to evaporate. At this time, the indoor air is cooled by exchanging heat with the refrigerant in the utilization side heat exchangers 42a, 42b and sent to the room, thereby cooling the room.

The low-pressure refrigerant evaporated in the user-side heat exchangers 42a and 42b is sent to the heat source unit 2 via the gas refrigerant connection pipe 5. The low-pressure refrigerant sent to the heat source unit 2 is sucked back into the compressor 21 via the gas shutoff valve 30, the switching mechanism 22, and the accumulator 31 together with the refrigerant returned from the suction return pipe 27.

<Heating operation>
During heating operation, the switching mechanism 22 is in the state shown by the dashed line in Figure 1, i.e., the discharge side of the compressor 21 is connected to the gas side shut-off valve 30 and the suction side of the compressor 21 is connected to the heat source side heat exchanger 23.

In this state of the refrigerant circuit 7, the low-pressure refrigerant in the refrigeration cycle is sucked into the compressor 21, compressed to the high pressure of the refrigeration cycle, and then discharged from the compressor 21. The high-pressure refrigerant discharged from the compressor 21 is sent to the utilization units 4a and 4b via the switching mechanism 22, the gas-side shutoff valve 30, and the gas refrigerant connection pipe 5.

The high-pressure refrigerant sent to the utilization units 4a, 4b then exchanges heat with indoor air supplied by utilization fans 43a, 43b in utilization side heat exchangers 42a, 42b, releasing heat. At this time, the indoor air is heated by heat exchange with the refrigerant in the utilization side heat exchangers 42a, 42b and sent to the room, thereby heating the room. The high-pressure refrigerant that has released heat in the utilization side heat exchangers 42a, 42b is depressurized by utilization side expansion mechanisms 41a, 41b.

The refrigerant decompressed in the utilization side expansion mechanisms 41a and 41b is sent to the heat source unit 2 via the liquid refrigerant connection pipe 6. The refrigerant sent to the heat source unit 2 is sent to the heat source side expansion mechanism 25 via the liquid side shutoff valve 29 and the subcooling heat exchanger 26. At this time, the suction return expansion mechanism 28 is closed, so the refrigerant is not branched to the suction return pipe 27. The refrigerant sent to the heat source side expansion mechanism 25 is further decompressed by the heat source side expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant. The refrigerant decompressed in the heat source side expansion mechanism 25 is sent to the heat source side heat exchanger 23, where it exchanges heat with the outdoor air supplied by the heat source side fan 24 and evaporates. The low-pressure refrigerant evaporated in the heat source side heat exchanger 23 is sucked back into the compressor 21 via the switching mechanism 22 and the accumulator 31.

(3) Selection of Pipe Diameter of Refrigerant Communication Pipe In the air conditioner 1, refrigerant communication pipes 5, 6 having various pipe diameters and lengths are used depending on the refrigeration capacity of the air conditioner 1, the conditions of the installation location, and the like.

As shown in FIG. 2, the pipe diameters of the refrigerant connection pipes 5, 6 are selected according to the rated refrigeration capacity of the utilization units 4a, 4b connected to the heat source unit 2. Here, "rated refrigeration capacity" means, for example, when the refrigeration cycle device is an air conditioning device 1, a value equivalent to the "rated cooling capacity" or "nominal capacity" of the utilization units 4a, 4b or the heat source unit 2 described in the product catalog or instruction manual.

The values of the pipe diameters of the refrigerant communication pipes 5 and 6 shown in FIG. 2 indicate the pipe diameters of the refrigerant communication pipes 5 and 6 (i.e., the refrigerant communication branch pipes 52a, 52b, 62a, 62b and the refrigerant communication mother pipes 51 and 61) excluding pipe joints such as the socket pipes 53a, 63a and the branch pipes 54a, 64a for connecting the pipes shown in FIG. 3. In addition, the values of the pipe diameters are shown here when copper pipes (with a quality of 1/2H) such as phosphorus-deoxidized copper seamless copper pipes are used as the pipe material for the refrigerant communication pipes 5 and 6. Here, "quality" means, for example, the type of tempering of copper pipes specified in JIS H 3300, and "quality of 1/2H" indicates the degree of tensile strength obtained by the processing hardening treatment performed during manufacturing. In addition, here, the case where carbon dioxide is used as the refrigerant sealed in the refrigerant circuit 7, and the case where R410A, which has been used frequently in the past, and R32, which has recently begun to be used, are used as comparative examples. In addition, in FIG. 2, the nominal diameter and the inside diameter are shown as the values of the pipe diameter. Here, when carbon dioxide is used, the value of the inside diameter is shown when the design pressure of the refrigerant communication pipes 5 and 6 is set to 12.3 MPa, taking into account the high pressure in the refrigeration cycle. However, when carbon dioxide is used, the design pressure of the refrigerant communication pipes 5 and 6 may be set to a somewhat higher pressure, such as 13.7 MPa, in which case the pipe wall thickness may increase, resulting in an inside diameter smaller than that shown in FIG. 2.

According to FIG. 2, a copper pipe with a nominal diameter of less than 1/4 inch (outer diameter of 6.35 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a and 4b with a rated refrigeration capacity of 8.0 kW or less are connected. Specifically, a copper pipe with a nominal diameter of 1.5/8 inch (outer diameter of 4.76 mm) is used as the liquid refrigerant connection pipe 6 with a nominal diameter of less than 1/4 inch. Here, since a copper pipe with a nominal diameter of 1.5/8 inch has an inner diameter of 3.6 mm, this means that a pipe with an inner diameter of 3.6 mm or less is used as the liquid refrigerant connection pipe 6. Note that "a liquid refrigerant connection pipe 6 to which a utilization unit with a rated refrigeration capacity of 8.0 kW or less is connected" does not only mean a liquid refrigerant connection pipe 6 to which only one utilization unit with a rated refrigeration capacity of 8.0 kW or less is connected. In the case where the liquid refrigerant connection pipe 6 branches out and multiple utilization units 4a, 4b are connected to the liquid refrigerant connection pipe 6 as in the configuration in Figure 3, it also means the branched portions (liquid refrigerant connection branch pipes 62a, 62b) of the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of 8.0 kW or less are connected, and the junction portion (liquid refrigerant connection main pipe 61) of the liquid refrigerant connection pipe 6 where the total rated refrigeration capacity of the multiple utilization units 4a, 4b is 8.0 kW or less. In addition, "using copper pipes with a nominal diameter of less than 1/4 inch (1.5/8 inches) (inner diameter of 3.6 mm or less) as the liquid refrigerant connection pipe 6" does not only mean using only copper pipes with a nominal diameter of less than 1/4 inch (1.5/8 inches) (inner diameter of 3.6 mm or less), but also includes using copper pipes with a nominal diameter of less than 1/4 inch (1.5/8 inches) (inner diameter of 3.6 mm or less) and copper pipes with a nominal diameter of 1/4 inch or more (greater than 1.5/8 inches) (inner diameter greater than 3.6 mm).

Also, according to FIG. 2, a copper pipe with a nominal diameter of 1/4 inch (outer diameter 6.35 mm, inner diameter 5.0 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 8.0 kW and less than 16.0 kW are connected.

Also, according to FIG. 2, a copper pipe with a nominal diameter greater than 1/4 inch (outer diameter 6.35 mm) and less than 3/8 inch (outer diameter 9.52 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of greater than 16.0 kW and less than 28.0 kW are connected. Specifically, a copper pipe with a nominal diameter of 2.5/8 inch (outer diameter 7.94 mm, inner diameter 6.2 mm) is used as the liquid refrigerant connection pipe 6 with a nominal diameter greater than 1/4 inch and less than 3/8 inch.

According to FIG. 2, a copper pipe with a nominal diameter larger than 1/4 inch (outer diameter 6.35 mm) and smaller than 3/8 inch (outer diameter 9.52 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a and 4b with a rated refrigeration capacity of 4.5 kW or less are connected. Specifically, a copper pipe with a nominal diameter of 2.5/8 inch (outer diameter 7.94 mm) is used as the gas refrigerant connection pipe 5 with a nominal diameter larger than 1/4 inch and smaller than 3/8 inch. Here, since a copper pipe with a nominal diameter of 2.5/8 inch has an inner diameter of 6.2 mm or less, this means that a pipe with an inner diameter of 6.2 mm or less is used as the gas refrigerant connection pipe 5. Note that the "gas refrigerant connection pipe 5 to which a utilization unit with a rated refrigeration capacity of 4.5 kW or less is connected" does not only mean a gas refrigerant connection pipe 6 to which only one utilization unit with a rated refrigeration capacity of 4.5 kW or less is connected. When the gas refrigerant communication pipe 5 branches and a plurality of utilization units 4a, 4b are connected to the gas refrigerant communication pipe 5 as in the configuration in FIG. 3 , it also means the branched portions (gas refrigerant communication branch pipes 52a, 52b) of the gas refrigerant communication pipe 5 to which the utilization units 4a, 4b having a rated refrigeration capacity of 4.5 kW or less are connected, and the junction portion (gas refrigerant communication mother pipe 51) of the gas refrigerant communication pipe 5 where the total rated refrigeration capacity of the plurality of utilization units 4a, 4b is 4.5 kW or less. In addition, "using copper pipes with a nominal diameter of more than 1/4 inch and less than 3/8 inch (2.5/8 inch) (inner diameter 6.2 mm or less) as the gas refrigerant connection pipe 5" does not only mean using only copper pipes with a nominal diameter of more than 1/4 inch and less than 3/8 inch (2.5/8 inch) (inner diameter 6.2 mm or less), but also includes the use of copper pipes with a nominal diameter of more than 1/4 inch and less than 3/8 inch (2.5/8 inch) (inner diameter 6.2 mm or less) and copper pipes with a nominal diameter of 3/8 inch or more (greater than 2.5/8 inch) (inner diameter greater than 6.2 mm).

Also, according to FIG. 2, a copper pipe with a nominal diameter of 3/8 inch (outer diameter 9.52 mm, inner diameter 7.4 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 4.5 kW and less than 8.0 kW are connected.

Also, according to FIG. 2, a copper pipe with a nominal diameter of 1/2 inch (outer diameter 12.70 mm, inner diameter 9.9 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 8.0 kW and less than or equal to 16.0 kW are connected.

Also, according to FIG. 2, a copper pipe with a nominal diameter of 5/8 inch (outer diameter 15.88 mm, inner diameter 12.3 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 16.0 kW and less than 28.0 kW are connected.

Also, according to Figure 2, when carbon dioxide is used, the refrigerant connection pipes 5 and 6 are selected to have a smaller pipe diameter than when conventional refrigerants such as R410A or R32 are used at the same rated refrigeration capacity.

Then, by using the table of pipe diameters of the refrigerant connection pipes 5 and 6 shown in Figure 2, the pipe diameters of the refrigerant connection pipes 5 and 6 can be selected as follows.

For example, if the rated refrigeration capacity of both utilization units 4a and 4b is 2.8 kW, then the gas refrigerant communication branch pipes 52a and 52b are made of copper pipes with a nominal diameter of 2.5/8 inches, and the liquid refrigerant communication branch pipes 62a and 62b are made of copper pipes with a nominal diameter of 1.5/8 inches. After utilization units 4a and 4b are joined, the total rated refrigeration capacity becomes 5.6 kW, so the gas refrigerant communication main pipe 51 is made of copper pipes with a nominal diameter of 3/8 inches, and the liquid refrigerant communication main pipe 61 is made of copper pipes with a nominal diameter of 1.5/8 inches.

For example, if the rated refrigeration capacity of both utilization units 4a and 4b is 11.2 kW, then the gas refrigerant communication branch pipes 52a and 52b are made of copper pipes with a nominal diameter of 1/2 inch, and the liquid refrigerant communication branch pipes 62a and 62b are made of copper pipes with a nominal diameter of 1/4 inch. After utilization units 4a and 4b are joined, the total rated refrigeration capacity becomes 22.4 kW, so the gas refrigerant communication main pipe 51 is made of copper pipes with a nominal diameter of 5/8 inch, and the liquid refrigerant communication main pipe 61 is made of copper pipes with a nominal diameter of 2.5/8 inch.

For example, if the rated refrigeration capacity of utilization unit 4a is 2.2 kW and the rated refrigeration capacity of utilization unit 4b is 9.0 kW, a copper pipe with a nominal diameter of 2.5/8 inches is used for the gas refrigerant communication branch pipe 52a, a copper pipe with a nominal diameter of 1/2 inches is used for the gas refrigerant communication branch pipe 52b, a copper pipe with a nominal diameter of 1.5/8 inches is used for the liquid refrigerant communication branch pipe 62a, and a copper pipe with a nominal diameter of 1/4 inches is used for the liquid refrigerant communication branch pipe 62b. After utilization units 4a and 4b are joined, the total rated refrigeration capacity becomes 11.2 kW, so a copper pipe with a nominal diameter of 1/2 inches is used for the gas refrigerant communication main pipe 51, and a copper pipe with a nominal diameter of 1/4 inches is used for the liquid refrigerant communication main pipe 61.

(4) Features Next, the features of the air conditioning apparatus 1 will be described.

<A>
Here, in the air conditioning apparatus 1 (refrigeration cycle apparatus) in which the heat source unit 2 and the utilization units 4a, 4b are connected via a gas refrigerant connection pipe 5 and a liquid refrigerant connection pipe 6 to form a refrigerant circuit 7, as described above, carbon dioxide is used as the refrigerant sealed in the refrigerant circuit 7, and a pipe having an inner diameter of 6.2 mm or less is used as the gas refrigerant connection pipe 5 and/or a pipe having an inner diameter of 3.6 mm or less is used as the liquid refrigerant connection pipe 6 (see FIG. 2 ).

Here, carbon dioxide, which has a higher refrigeration capacity per unit volume than conventional refrigerants (R410A, R32, etc.), is used as the refrigerant, so the flow rate of the refrigerant circulating through the refrigerant circuit 7 (refrigerant circulation amount) can be reduced. For this reason, here, pipes with smaller inner diameters than those used for conventional refrigerants can be used as the refrigerant connection pipes 5, 6 while ensuring that the flow resistance of the refrigerant flowing through the refrigerant connection pipes 5, 6 is not excessively large.

Specifically, in conventional refrigerants, taking into account the flow path resistance, a pipe with an inner diameter smaller than 11.1 mm is not used as a gas refrigerant connection pipe, and a pipe with an inner diameter smaller than 4.7 mm is not used as a liquid refrigerant connection pipe (see Figure 2). In contrast, here, as described above, a pipe with an inner diameter too small to be used as a gas refrigerant connection pipe with conventional refrigerants (a pipe with an inner diameter of 6.2 mm or less) is used as the gas refrigerant connection pipe 5, and/or a pipe with an inner diameter too small to be used as a liquid refrigerant connection pipe with conventional refrigerants (a pipe with an inner diameter of 3.6 mm or less) is used as the liquid refrigerant connection pipe 6.

As a result, the volume of the gas refrigerant connection tube 5 and/or the liquid refrigerant connection tube 6 can be reduced, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced.

<B>
As described above, a copper pipe (classified as 1/2H) with a nominal diameter of less than 1/4 inch (outer diameter of 6.35 mm) is used as the liquid refrigerant communication pipe 6 with an inner diameter of 3.6 mm or less (see FIG. 2). Specifically, a copper pipe (classified as 1/2H) with a nominal diameter of 1.5/8 inch (outer diameter of 4.76 mm) is used (see FIG. 2).

Here, for conventional refrigerants (R410A, R32, etc.), copper pipes with a nominal diameter of less than 1/4 inch (here, 1.5/8 inch) are not used as liquid refrigerant connection pipes (see Figure 2). Also, conventionally used copper pipes for refrigerants have nominal diameters in increments of 1/8 inch, such as 1/4 (= 2/8) inch, 3/8 inch, 1/2 (= 4/8) inch, 5/8 inch, and 3/4 (= 6/8) inch, and nominal diameters in increments of 0.5/8 inch are not used. In other words, here, copper pipes (classified as 1/2H) with a nominal diameter of less than 1/4 inch (outer diameter of 6.35 mm) (here, 1.5/8 inch), which have an inner diameter of 3.6 mm or less and have not been used conventionally because their nominal diameter (outer diameter) is too small for use as liquid refrigerant connection pipes, are used as liquid refrigerant connection pipes 6 to which utilization units 4a and 4b with a rated refrigeration capacity of 8.0 kW or less are connected.

As a result, the volume of the liquid refrigerant connection pipe 6 can be reduced, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced. Moreover, because a copper pipe with a nominal diameter that has not been used as a liquid refrigerant connection pipe in the past is used, the size of the copper pipe that can be used as the liquid refrigerant connection pipe 6 can be increased, which contributes to optimizing the liquid refrigerant connection pipe 6.

＜C＞
As described above, the gas refrigerant communication pipe 5 having an inner diameter of 6.2 mm or less is made of a copper pipe (classified as 1/2H) having a nominal diameter of more than 1/4 inch (outer diameter of 6.35 mm) and less than 3/8 inch (outer diameter of 9.52 mm) (see FIG. 2). Specifically, a copper pipe (classified as 1/2H) having a nominal diameter of 2.5/8 inch (outer diameter of 7.94 mm) is used here (see FIG. 2).

Here, for conventional refrigerants (R410A, R32, etc.), copper pipes with a nominal diameter of less than 1/2 inch are not used as gas refrigerant connection pipes 5 (see Figure 2). Furthermore, conventionally used copper pipes for refrigerants have nominal diameters in 1/8 inch increments, such as 1/2 (= 4/8) inch, 5/8 inch, 3/4 (= 6/8) inch, 7/8 inch, and 1 (= 8/8) inch, and nominal diameters in 0.5/8 inch increments are not used. That is, here, the nominal diameter (outer diameter) is too small for conventional refrigerants to be used as a gas refrigerant connection pipe, and the copper pipe (classified as 1/2H) with a nominal diameter larger than 1/4 inch (outer diameter 6.35 mm) and less than 3/8 inch (outer diameter 9.52 mm) (here, 2.5/8 inch) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a and 4b with a rated refrigeration capacity of 4.5 kW or less are connected.

As a result, the volume of the gas refrigerant connection pipe 5 can be reduced, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced. Moreover, because a copper pipe with a nominal diameter that has not been used as a gas refrigerant connection pipe in the past is used here, the size of the copper pipe that can be used as the gas refrigerant connection pipe 5 can be increased, which contributes to optimizing the gas refrigerant connection pipe 5.

(5) Modification Example <A>
In the above embodiment, copper pipes (having a quality of 1/2H) such as phosphorus-deoxidized copper seamless copper pipes are used as the pipe material for the refrigerant connection pipes 5 and 6 (see FIG. 2). However, there are various qualities of copper pipes, and the qualities used as copper pipes for refrigerants include, in addition to "1/2H", "H" which has been subjected to work hardening treatment so that its tensile strength is higher than that of "1/2H", and "O" which has been annealed without being subjected to work hardening treatment during manufacturing (low tensile strength).

Here, as shown in Figure 4, copper pipes with a quality of O are used as the pipe material for the refrigerant connection pipes 5 and 6. Note that Figure 4 also shows a comparative example in which copper pipes with a quality of 1/2H are used.

According to FIG. 4, a copper pipe with a nominal diameter of less than 1/4 inch (outer diameter of 6.35 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a and 4b with a rated refrigeration capacity of 3.6 kW or less are connected. Specifically, a copper pipe with a nominal diameter of 1.5/8 inch (outer diameter of 4.7 mm) is used as the liquid refrigerant connection pipe 6 with a nominal diameter of less than 1/4 inch. Here, a copper pipe with a nominal diameter of 1.5/8 inch has an inner diameter of 2.8 mm, which means that a pipe with an inner diameter of 3.6 mm or less is used as the liquid refrigerant connection pipe 6, as in the case of a 1/2H quality.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 1/4 inch (outer diameter 6.35 mm, inner diameter 3.8 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 3.6 kW and less than 7.1 kW are connected.

Also, according to FIG. 4, a copper pipe with a nominal diameter greater than 1/4 inch (outer diameter 6.35 mm) and less than 3/8 inch (outer diameter 9.52 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of greater than 7.1 kW and less than 14.0 kW are connected. Specifically, a copper pipe with a nominal diameter of 2.5/8 inch (outer diameter 7.94 mm, inner diameter 4.8 mm) is used as the liquid refrigerant connection pipe 6 with a nominal diameter greater than 1/4 inch and less than 3/8 inch.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 3/8 inch (outer diameter 9.52 mm, inner diameter 5.8 mm) is used as the liquid refrigerant connection pipe 6 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 14.0 kW and less than 22.4 kW are connected.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 1/2 inch (outer diameter 12.70 mm, inner diameter 7.7 mm) is used as the liquid refrigerant connection pipe 6 to which utilization units 4a, 4b with a rated refrigeration capacity of greater than 22.4 kW and less than 28.0 kW are connected.

According to FIG. 4, a copper pipe with a nominal diameter larger than 1/4 inch (outer diameter 6.35 mm) and smaller than 3/8 inch (outer diameter 9.52 mm) is used as the gas refrigerant communication pipe 5 to which the utilization units 4a and 4b with a rated refrigeration capacity of 2.8 kW or less are connected. Specifically, a copper pipe with a nominal diameter of 2.5/8 inch (outer diameter 7.94 mm) is used as the gas refrigerant communication pipe 5 with a nominal diameter larger than 1/4 inch and smaller than 3/8 inch. Here, since a copper pipe with a nominal diameter of 2.5/8 inch has an inner diameter of 4.8 mm or less, this means that a pipe with an inner diameter of 6.2 mm or less is used as the gas refrigerant communication pipe 5, as in the case of a 1/2H quality.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 3/8 inch (outer diameter of 9.52 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 2.8 kW and less than 4.5 kW are connected. Here, a copper pipe with a nominal diameter of 3/8 inch has an inner diameter of 5.8 mm or less, which means that a pipe with an inner diameter of 6.2 mm or less is used as the gas refrigerant connection pipe 5, as in the case of a 1/2H quality.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 1/2 inch (outer diameter 12.70 mm, inner diameter 7.7 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 4.5 kW and less than 9.0 kW are connected.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 5/8 inch (outer diameter 15.88 mm, inner diameter 9.7 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 9.0 kW and less than 16.0 kW are connected.

Also, according to FIG. 4, a copper pipe with a nominal diameter of 3/4 inch (outer diameter 19.05 mm, inner diameter 11.7 mm) is used as the gas refrigerant connection pipe 5 to which the utilization units 4a, 4b with a rated refrigeration capacity of more than 16.0 kW and less than 28.0 kW are connected.

Also, according to Figure 4, when copper pipes of quality O are used, the inner diameter of the gas refrigerant connection pipes 5 and 6 is selected to be the same as when copper pipes of quality 1/2H are used at the same rated refrigeration capacity.

Then, by using the table of pipe diameters for the refrigerant connection pipes 5 and 6 shown in Figure 4, the pipe diameters for the refrigerant connection pipes 5 and 6 when using copper pipes with a quality of O can be selected as follows.

For example, if the rated refrigeration capacity of both utilization units 4a and 4b is 2.8 kW, then the gas refrigerant communication branch pipes 52a and 52b are copper pipes with a nominal diameter of 2.5/8 inches, and the liquid refrigerant communication branch pipes 62a and 62b are copper pipes with a nominal diameter of 1.5/8 inches. After utilization units 4a and 4b join together, the total rated refrigeration capacity becomes 5.6 kW, so the gas refrigerant communication main pipe 51 is copper pipes with a nominal diameter of 1/2 inches, and the liquid refrigerant communication main pipe 61 is copper pipes with a nominal diameter of 1/4 inches.

For example, if the rated refrigeration capacity of both utilization units 4a and 4b is 11.2 kW, then the gas refrigerant communication branch pipes 52a and 52b are made of copper pipes with a nominal diameter of 5/8 inches, and the liquid refrigerant communication branch pipes 62a and 62b are made of copper pipes with a nominal diameter of 2.5/8 inches. After utilization units 4a and 4b are joined, the total rated refrigeration capacity becomes 22.4 kW, so the gas refrigerant communication main pipe 51 is made of copper pipes with a nominal diameter of 3/4 inches, and the liquid refrigerant communication main pipe 61 is made of copper pipes with a nominal diameter of 3/8 inches.

For example, if the rated refrigeration capacity of utilization unit 4a is 2.2 kW and the rated refrigeration capacity of utilization unit 4b is 9.0 kW, then a copper pipe with a nominal diameter of 2.5/8 inches is used for the gas refrigerant communication branch pipe 52a, a copper pipe with a nominal diameter of 1/2 inches is used for the gas refrigerant communication branch pipe 52b, a copper pipe with a nominal diameter of 1.5/8 inches is used for the liquid refrigerant communication branch pipe 62a, and a copper pipe with a nominal diameter of 2.5/8 inches is used for the liquid refrigerant communication branch pipe 62b. After utilization units 4a and 4b are joined, the total rated refrigeration capacity becomes 11.2 kW, so a copper pipe with a nominal diameter of 5/8 inches is used for the gas refrigerant communication main pipe 51, and a copper pipe with a nominal diameter of 2.5/8 inches is used for the liquid refrigerant communication main pipe 61.

As described above, in the air conditioning device 1 (refrigeration cycle device) in which the heat source unit 2 and the utilization units 4a, 4b are connected via the gas refrigerant connection pipe 5 and the liquid refrigerant connection pipe 6 to form the refrigerant circuit 7, the refrigerant sealed in the refrigerant circuit 7 is carbon dioxide, and the gas refrigerant connection pipe 5 is a pipe with an inner diameter of 6.2 mm or less, and/or the liquid refrigerant connection pipe 6 is a pipe with an inner diameter of 3.6 mm or less (see Figure 4), just as in the case of using copper pipes with a quality of 1/2H.

As a result, the volume of the gas refrigerant connection tube 5 and/or the liquid refrigerant connection tube 6 can be reduced, as in the case of using copper pipes with a quality of 1/2H, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced.

As described above, a copper pipe (quality O) with a nominal diameter of less than 1/4 inch (outer diameter 6.35 mm) is used as the liquid refrigerant connection pipe 6 with an inner diameter of 3.6 mm or less, just as in the case of using copper pipes with a quality of 1/2H (see Figure 4). Specifically, a copper pipe (quality O) with a nominal diameter of 1.5/8 inch (outer diameter 4.76 mm) is used here (see Figure 4). However, unlike the case of using copper pipes with a quality of 1/2H, this copper pipe with this nominal diameter is used as the liquid refrigerant connection pipe 6 to which utilization units 4a, 4b with a rated refrigeration capacity of 3.6 kW or less are connected.

As a result, the volume of the liquid refrigerant connection pipe 6 can be reduced, as in the case of using copper pipes with a quality of 1/2H, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced. Moreover, because copper pipes with a nominal diameter that have not been used as liquid refrigerant connection pipes in the past are used here, the size of the copper pipes that can be used as the liquid refrigerant connection pipe 6 can be increased, contributing to the optimization of the liquid refrigerant connection pipe 6. In addition, because copper pipes with a quality of O are used as the liquid refrigerant connection pipe 6 here, they are easier to handle, such as by bending, compared to the case of using copper pipes with a quality of 1/2H, and the workability of connecting the heat source unit 2 and the utilization units 4a and 4b on site can be improved.

As described above, a copper pipe (quality O) with a nominal diameter larger than 1/4 inch (outer diameter 6.35 mm) and smaller than 3/8 inch (outer diameter 9.52 mm) is used as the gas refrigerant communication pipe 5 with an inner diameter of 6.2 mm or less, as in the case of using a copper pipe with a quality of 1/2H (see Figure 4). Specifically, a copper pipe (quality O) with a nominal diameter of 2.5/8 inch (outer diameter 7.94 mm) is used here (see Figure 4). However, unlike the case of using a copper pipe with a quality of 1/2H, this copper pipe with this nominal diameter is used as the gas refrigerant communication pipe 5 to which the utilization units 4a and 4b with a rated refrigeration capacity of 2.8 kW or less are connected.

As a result, the volume of the gas refrigerant connection pipe 5 can be reduced, as in the case of using copper pipes with a quality of 1/2H, and the amount of refrigerant sealed in the refrigerant circuit 7 can be reduced. Moreover, because copper pipes with a nominal diameter that have not been used as gas refrigerant connection pipes in the past are used here, the size of the copper pipes that can be used as the gas refrigerant connection pipe 5 can be increased, which contributes to optimizing the gas refrigerant connection pipe 5. In addition, because copper pipes with a quality of O are used as the gas refrigerant connection pipe 5 here, they are easier to handle, such as by bending, compared to the case of using copper pipes with a quality of 1/2H, and the workability of connecting the heat source unit 2 and the utilization units 4a, 4b on site can be improved.

<B>
In the above embodiment and modified examples, in order to improve ease of installation when connecting the heat source unit 2 and the utilization units 4a, 4b on site, the gas refrigerant connection pipe 5 and the liquid refrigerant connection pipe 6 may form a pair refrigerant connection pipe 8, as shown in FIG. 5 .

Here, the paired refrigerant connection pipes 8 have a structure in which the outer surfaces of the refrigerant connection pipes 5, 6 are covered with heat-insulating materials 9, 10 and both pipes 5, 6 are bundled together. Here, the refrigerant connection pipes 5, 6 are covered with heat-insulating materials 9, 10 of a two-layer structure, and the heat-insulating materials 9, 10 are tied together to bundle the refrigerant connection pipes 5, 6. Then, such paired refrigerant connection pipes 8 can be prepared for each rated refrigeration capacity. For example, if copper pipes with a quality of 1/2H are used as the refrigerant connection pipes 5, 6 according to the pipe diameter table in Figure 4, a paired refrigerant connection pipe 8 with a gas refrigerant connection pipe 5 of 2.5/8 inches and a liquid refrigerant connection pipe 6 of 1.5/8 inches is prepared for a rated refrigeration capacity of 2.2 to 4.5 kW. In addition, a pair of refrigerant connection pipes 8 with a gas refrigerant connection pipe 5 of 3/8 inches and a liquid refrigerant connection pipe 6 of 1.5/8 inches is prepared for a rated refrigeration capacity of 5.6 to 8.0 kW. In addition, a pair of refrigerant connection pipes 8 with a gas refrigerant connection pipe 5 of 1/2 inches and a liquid refrigerant connection pipe 6 of 1/4 inches is prepared for a rated refrigeration capacity of 9.0 to 16.0 kW. In addition, a pair of refrigerant connection pipes 8 with a gas refrigerant connection pipe 5 of 5/8 inches and a liquid refrigerant connection pipe 6 of 2.5/8 inches is prepared for a rated refrigeration capacity of 22.4 to 28.0 kW. Although details are not described, even when copper pipes with a quality of O are used as the refrigerant connection pipes 5 and 6, a pair of refrigerant connection pipes 8 similar to the case where copper pipes with a quality of 1/2H are used as the refrigerant connection pipes 5 and 6 (however, the applicable range of the rated refrigeration capacity is different) can be prepared.

As a result, when connecting the heat source unit 2 and the utilization units 4a, 4b on-site, the above-mentioned paired refrigerant connection pipes 8 can be used, improving workability. In particular, pipes with nominal diameters in 0.5/8-inch increments (here, 1.5/8 inches and 2.5/8 inches) that are not used with conventional refrigerants (R410A, R32, etc.) may be used, so preparing paired refrigerant connection pipes 8 that include pipes with such nominal diameters is extremely useful for improving workability.

＜C＞
In the above embodiment and modified examples, when the refrigerant communication pipes 5, 6 are long or branched, pipe joints such as socket pipes 53a, 63a and branch pipes 54a, 64a for connecting the pipes are required as shown in Fig. 3. However, such pipe joints that have been used conventionally are compatible with pipes with nominal diameters in 1/8 inch increments, but are not compatible with pipes with nominal diameters in 0.5/8 inch increments, such as pipes with nominal diameters of 1.5/8 inch and 2.5/8 inch (see Fig. 4).

Here, as shown in FIG. 6, the end of a pipe with a nominal diameter of 1.5/8 inches used as a liquid refrigerant connection pipe 6 with a nominal diameter of less than 1/4 inch has a different diameter section 6a enlarged to a nominal diameter of 1/4 inch (= 2/8 inch). Also, as shown in FIG. 6, the end of a pipe with a nominal diameter of 2.5/8 inches used as a gas refrigerant connection pipe 5 with a nominal diameter of greater than 1/4 inch and less than 3/8 inch and a liquid refrigerant connection pipe 6 has a different diameter section 5a, 6a enlarged to a nominal diameter of 3/8 inch.

As a result, even if a pipe with a nominal diameter of 1.5/8 inches is used as the liquid refrigerant communication pipe 6 with a nominal diameter of less than 1/4 inch, a pipe joint corresponding to a pipe with a nominal diameter of 1/8 inch that has been used conventionally can be used. That is, even if a pipe with a nominal diameter of 1.5/8 inches is used as the liquid refrigerant communication branch pipes 62a, 62b and the liquid refrigerant communication main pipe 61 in FIG. 3, a socket pipe 63a and a branch pipe 64a corresponding to a pipe with a nominal diameter of 1/4 inch can be used. Therefore, it is possible to avoid the need to prepare pipe joints corresponding to pipes with a nominal diameter of 0.5/8 inch, improving workability. Also, even if a pipe with a nominal diameter of 2.5/8 inches is used as the gas refrigerant communication pipe 5 and the liquid refrigerant communication pipe 6 with a nominal diameter of more than 1/4 inch and less than 3/8 inch, a pipe joint corresponding to a pipe with a nominal diameter of 1/8 inch that has been used conventionally can be used. That is, in FIG. 3, even if pipes with a nominal diameter of 2.5/8 inches are used as the refrigerant communication branch pipes 52a, 52b, 62a, 62b and the refrigerant communication main pipes 51, 61, the socket pipes 53a, 63a and the branch pipes 54a, 64a can be those corresponding to pipes with a nominal diameter of 3/8 inches. Therefore, it is possible to avoid the need to prepare pipe joints corresponding to pipes with nominal diameters in 0.5/8 inch increments, improving workability.

<D>
In the above embodiment and modified example, the air conditioner 1 capable of heating and cooling having two utilization units 4a and 4b has been described as an example of the refrigeration cycle apparatus, but the refrigeration cycle apparatus is not limited to this. For example, the refrigeration cycle apparatus may be an air conditioner dedicated to cooling, or may be an air conditioner having one utilization unit or three or more utilization units.

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.

This disclosure is widely applicable to refrigeration cycle devices in which a refrigerant circuit is formed by connecting a heat source unit and a utilization unit via a refrigerant connection pipe, and carbon dioxide is used as the refrigerant sealed in the refrigerant circuit.

1. Air conditioning equipment (refrigeration cycle equipment)
2 Heat source unit 4a, 4b Utilization unit 5 Gas refrigerant connection pipe 5a Different diameter section 6 Liquid refrigerant connection pipe 6a Different diameter section 7 Refrigerant circuit 8 Pair refrigerant connection pipe

International Publication No. 2011/099063

Claims (2)

A refrigeration cycle device in which a heat source unit (2) and utilization units (4a, 4b) are connected via a gas refrigerant connection pipe (5) and a liquid refrigerant connection pipe (6) to form a refrigerant circuit (7),
The refrigerant charged in the refrigerant circuit is carbon dioxide,
As the gas refrigerant communication pipe, a pipe having an inner diameter of 6.2 mm or less is used ,
The gas refrigerant connecting pipe to which the utilization unit having a rated refrigeration capacity of 4.5 kW or less is connected is made of copper pipe having a nominal diameter of 2.5/8 inches (1/2H quality).
Or,
The gas refrigerant connecting pipe to which the utilization unit having a rated refrigeration capacity of 2.8 kW or less is connected is made of copper pipe (quality O) having a nominal diameter of 2.5/8 inches.
Refrigeration cycle device (1). The gas refrigerant communication pipe and the liquid refrigerant communication pipe are covered on their outer surfaces with a heat insulating material, and the two pipes are bundled together to form a pair of refrigerant communication pipes (8).
The refrigeration cycle device according to claim 1.

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