Refrigeration equipment

Abstract

To set a volume ratio of an outdoor heat exchanger and an indoor heat exchanger to a volume ratio suitable for an HFO-based refrigerant, to suppress excess and deficiency of a refrigerant.SOLUTION: When a refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant, both an indoor heat exchanger 41 and an outdoor heat exchanger 23 are cross-fin heat exchangers or laminated heat exchangers, and the outdoor heat exchanger 23 has a single row configuration, a volume ratio S [%] of the outdoor heat exchanger 23 to the indoor heat exchanger 41 satisfies the following relation: 100≤S≤1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02, where ρ [kg / m^3] represents the average density of saturated gas at a condensation temperature of 45°C.SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to a refrigeration device using an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant.

Background Art

[0002] In an air conditioner that operates one indoor unit with one outdoor unit, generally, as described in the background art of Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-077983), the volume of the outdoor heat exchanger is set larger than that of the indoor heat exchanger. The larger the volume difference between the outdoor heat exchanger and the indoor heat exchanger, the more likely refrigerant shortage or refrigerant excess occurs during cooling operation and heating operation, resulting in a decrease in COP. In the above air conditioner, since the volume of the outdoor heat exchanger is larger than that of the indoor heat exchanger, if the refrigerant amount in the system is optimally adjusted during cooling operation, the refrigerant becomes surplus during heating operation. On the other hand, if the refrigerant amount in the system is optimally adjusted during heating operation, the refrigerant becomes insufficient during cooling operation.

Summary of the Invention

Problems to be Solved by the Invention

[0003] On the other hand, as the refrigerant adopted in air conditioners, the shift is being made from the mainstream R410A to R32 with a smaller global warming potential. In the future, HFO-based refrigerants with an even smaller global warming potential are expected.

[0004] However, in the case of HFO-based refrigerants, since the refrigerant density in the condenser, particularly the gas density, is larger than that of R32, the excess or shortage of the refrigerant becomes more prominent. Therefore, there is a problem of setting the volume ratio of the outdoor heat exchanger and the indoor heat exchanger to a volume ratio suitable for HFO-based refrigerants and suppressing the excess or shortage of the refrigerant.

Means for Solving the Problems

[0005] The refrigeration system relating to the first aspect is a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. Both the indoor and outdoor heat exchangers are cross-fin type heat exchangers or stacked type heat exchangers. Furthermore, if the outdoor heat exchanger is configured in a single row, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is, 100≦S≦1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02, ρ[kg / m^3]: Average density of saturated liquid gas at a condensation temperature of 45°C. The relationship satisfies the given equation.

[0006] In this refrigeration system, the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is set to a value that satisfies the above relationship, thereby suppressing excess or deficiency of refrigerant during cooling and heating operations.

[0007] The refrigeration system relating to the second aspect is a system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism, and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. Both the indoor and outdoor heat exchangers are cross-fin type heat exchangers or stacked type heat exchangers. Furthermore, if the outdoor heat exchanger has a two-row configuration, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is: 130≦S≦1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03, ρ[kg / m^3]: Average density of saturated liquid gas at a condensation temperature of 45°C. The relationship satisfies the given equation.

[0008] In this refrigeration system, the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is set to a value that satisfies the above relationship, thereby suppressing excess or deficiency of refrigerant during cooling and heating operations.

[0009] The refrigeration system relating to the third aspect is a system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism, and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The indoor heat exchanger is a cross-fin type heat exchanger, and the outdoor heat exchanger is a stacked type heat exchanger. Furthermore, if the outdoor heat exchanger has a single-row configuration, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is, 100×α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2427E+02)×α α: When a cross-fin type heat exchanger and a stacked type heat exchanger have the same heat exchange performance, the volume ratio of the stacked heat exchanger to the cross-fin type heat exchanger. ρ[kg / m^3]: Average density of saturated liquid gas at a condensation temperature of 45°C. The relationship satisfies the given equation.

[0010] In this refrigeration system, the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is set to a value that satisfies the above relationship, thereby suppressing excess or deficiency of refrigerant during cooling and heating operations.

[0011] The refrigeration system relating to the fourth aspect is a system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism, and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The indoor heat exchanger is a cross-fin type heat exchanger, and the outdoor heat exchanger is a stacked type heat exchanger. Furthermore, if the outdoor heat exchanger has a two-row configuration, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is: 130×α≦S≦(1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03)×α α: When a cross-fin type heat exchanger and a stacked type heat exchanger have the same heat exchange performance, the volume ratio of the stacked heat exchanger to the cross-fin type heat exchanger. ρ[kg / m^3]: Average density of saturated liquid gas at a condensation temperature of 45°C. The relationship satisfies the given equation.

[0012] In this refrigeration system, the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is set to a value that satisfies the above relationship, thereby suppressing excess or deficiency of refrigerant during cooling and heating operations.

[0013] The refrigeration system relating to the fifth aspect is a system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant, the indoor heat exchanger is a stacked heat exchanger, and the outdoor heat exchanger is a cross-fin type heat exchanger. Furthermore, when the outdoor heat exchanger is configured in a single row, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is, 100 / α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02) / α α: When a cross-fin type heat exchanger and a stacked type heat exchanger have the same heat exchange performance, the volume ratio of the stacked heat exchanger to the cross-fin type heat exchanger. ρ[kg / m^3]: Average density of saturated liquid gas at a condensation temperature of 45°C. The relationship satisfies the given equation.

[0014] In this refrigeration system, the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is set to a value that satisfies the above relationship, thereby suppressing excess or deficiency of refrigerant during cooling and heating operations.

[0015] The refrigeration system relating to the sixth aspect is a system in which, during cooling operation, the refrigerant flows in the order of compressor, outdoor heat exchanger, expansion mechanism, and indoor heat exchanger, and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, wherein the refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The indoor heat exchanger is a stacked heat exchanger, and the outdoor heat exchanger is a cross-fin type heat exchanger. Furthermore, if the outdoor heat exchanger has a two-row configuration, the volume ratio S[%] of the outdoor heat exchanger to the indoor heat exchanger is, 130 / α ≤ S ≤ (1.3483E-03×ρ^2 - 2.1115E+00×ρ + 1.0996E+03) / α α: When the cross-fin type heat exchanger and the laminated type heat exchanger have the same heat exchange performance, the volume ratio of the laminated type heat exchanger to the cross-fin type heat exchanger, ρ [kg / m^3]: The average density of the saturated liquid gas at a condensation temperature of 45°C, satisfies the relational expression of.

[0016] In this refrigeration device, by setting the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger to a value that satisfies the above relational expression, the excess or deficiency of the refrigerant amount in the cooling operation and the heating operation is suppressed.

[0017] The refrigeration device according to the seventh aspect is a refrigeration device according to any one of the second, fourth, and sixth aspects, and a high-pressure receiver is provided between the outdoor heat exchanger and the expansion mechanism. The volume of the outdoor heat exchanger includes the volume of the high-pressure receiver.

[0018] The refrigeration device according to the eighth aspect is a refrigeration device according to any one of the first to seventh aspects, and 476.1 < ρ.

[0019] The refrigeration device according to the ninth aspect is a refrigeration device according to any one of the first to eighth aspects, and the HFO refrigerant is any one of R1132(E), R1123, R1234yf, and R1234ze.

Brief Description of the Drawings

[0020] [Figure 1] Schematic configuration diagram of an air conditioner as a refrigeration device according to an embodiment of the present disclosure. [Figure 2] Schematic front view of a cross-fin type heat exchanger. [Figure 3] External perspective view of a laminated type heat exchanger. [Figure 4] List of target models for setting the upper limit value of the volume ratio. [Figure 5A]A table showing the relationship between the average liquid gas density of HFO-based refrigerants and the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger, when the outdoor heat exchanger is a single-row heat exchanger. [Figure 5B] This graph shows the relationship between the average liquid gas density of an HFO-based refrigerant and the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger, when the outdoor heat exchanger is a single-row heat exchanger. [Figure 6A] This table shows the relationship between the average liquid gas density of the HFO-based refrigerant and the upper limit of the volume ratio of the outdoor heat exchanger to the indoor heat exchanger, when the outdoor heat exchanger is a two-row heat exchanger. [Figure 6B] This graph shows the relationship between the average liquid gas density of the HFO-based refrigerant and the upper limit of the volume ratio of the outdoor heat exchanger to the indoor heat exchanger, when the outdoor heat exchanger is a two-row heat exchanger. [Figure 7] A schematic diagram of an air conditioning system as a refrigeration device according to a modified example of the present disclosure. [Modes for carrying out the invention]

[0021] <First Embodiment> (1) Configuration of the air conditioning system 1 Figure 1 is a schematic diagram of an air conditioning system 1 according to one embodiment of the present disclosure. In Figure 1, the air conditioning system 1 is a refrigeration system that performs cooling and heating operations using a vapor compression type refrigeration cycle.

[0022] The refrigerant circuit 10 of the air conditioning system 1 is configured such that the outdoor unit 2 and the indoor unit 4 are connected via a liquid refrigerant connecting pipe 5 and a gaseous refrigerant connecting pipe 6.

[0023] The refrigerant sealed in the refrigerant circuit 10 is either an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The HFO refrigerant is one of the following: R1132(E), R1123, R1234yf, or R1234ze.

[0024] (1-1) Indoor unit 4 The indoor unit 4 is installed indoors and constitutes part of the refrigerant circuit 10. The indoor unit 4 includes an indoor heat exchanger 41, an indoor fan 42, and an indoor control unit 44.

[0025] (1-1-1) Indoor heat exchanger 41 During cooling operation, the indoor heat exchanger 41 functions as a refrigerant evaporator to cool the indoor air. During heating operation, the indoor heat exchanger 41 functions as a refrigerant radiator to heat the indoor air. During cooling operation, the refrigerant inlet side of the indoor heat exchanger 41 is connected to the liquid refrigerant connecting pipe 5, and the refrigerant outlet side is connected to the gaseous refrigerant connecting pipe 6.

[0026] As the indoor heat exchanger 41, a cross-fin type heat exchanger or a stacked type heat exchanger will be used. The cross-fin type heat exchanger and the stacked type heat exchanger will be explained in "(3) Selection of indoor heat exchanger 41 and outdoor heat exchanger 23".

[0027] (1-1-2) Indoor fan 42 The indoor fan 42 draws indoor air into the indoor unit 4, exchanges heat with the refrigerant in the indoor heat exchanger 41, and then supplies that air to the room. Centrifugal fans, multi-blade fans, etc., can be used as the indoor fan 42. The indoor fan 42 is driven by an indoor fan motor 43. (1-1-3) Indoor control unit 44 The indoor control unit 44 controls the operation of each component that makes up the indoor unit 4. The indoor control unit 44 has a microcomputer and memory for controlling the indoor unit 4.

[0028] The indoor control unit 44 transmits and receives control signals, etc., with a remote controller (not shown). The indoor control unit 44 also transmits and receives control signals, etc., with the outdoor control unit 38 of the outdoor unit 2 via the transmission line 8a.

[0029] (1-2) Outdoor unit 2 The outdoor unit 2 is installed outdoors and constitutes part of the refrigerant circuit 10. The outdoor unit 2 includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, an expansion valve 26, a liquid-side shut-off valve 27, and a gas-side shut-off valve 28.

[0030] (1-2-1) Compressor 21 The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle. The compressor 21 rotates a positive displacement compression element (not shown), such as a rotary or scroll type, using a compressor motor 21a.

[0031] The compressor 21 has an intake pipe 31 connected to its intake side and a discharge pipe 32 connected to its discharge side. The intake pipe 31 is a refrigerant pipe that connects the intake side of the compressor 21 to the four-way switching valve 22. The discharge pipe 32 is a refrigerant pipe that connects the discharge side of the compressor 21 to the four-way switching valve 22.

[0032] An accumulator 29 is connected to the suction pipe 31. The accumulator 29 separates the incoming refrigerant into liquid refrigerant and gaseous refrigerant, and flows only the gaseous refrigerant to the suction side of the compressor 21.

[0033] (1-2-2) Four-way switching valve 22 The four-way switching valve 22 switches the direction of refrigerant flow in the refrigerant circuit 10. During cooling operation, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as a refrigerant heat radiator and the indoor heat exchanger 41 to function as a refrigerant evaporator.

[0034] During cooling operation, the four-way diverter valve 22 connects the discharge pipe 32 of the compressor 21 to the first gas refrigerant pipe 33 of the outdoor heat exchanger 23 (see the solid line of the four-way diverter valve 22 in Figure 1), and further connects the suction pipe 31 of the compressor 21 to the second gas refrigerant pipe 34 (see the solid line of the four-way diverter valve 22 in Figure 1).

[0035] Furthermore, the four-way switching valve 22 switches to a heating cycle state during heating operation in which the outdoor heat exchanger 23 functions as a refrigerant evaporator and the indoor heat exchanger 41 functions as a refrigerant radiator.

[0036] During heating operation, the four-way switching valve 22 connects the discharge pipe 32 of the compressor 21 to the second gas refrigerant pipe 34 (see the dashed line on the four-way switching valve 22 in Figure 1), and further connects the suction pipe 31 of the compressor 21 to the first gas refrigerant pipe 33 of the outdoor heat exchanger 23 (see the dashed line on the four-way switching valve 22 in Figure 1).

[0037] Here, the first gas refrigerant pipe 33 is a refrigerant pipe that connects the four-way switching valve 22 to the refrigerant inlet of the outdoor heat exchanger 23 during cooling operation. The second gas refrigerant pipe 34 is a refrigerant pipe that connects the four-way switching valve 22 to the gas-side shut-off valve 28.

[0038] (1-2-3) Outdoor heat exchanger 23 The outdoor heat exchanger 23 functions as a refrigerant radiator during cooling operation. During heating operation, the outdoor heat exchanger 23 functions as a refrigerant evaporator. One end of a liquid refrigerant pipe 35 is connected to the refrigerant outlet of the outdoor heat exchanger 23 during cooling operation. The other end of the liquid refrigerant pipe 35 is connected to an expansion valve 26.

[0039] As the outdoor heat exchanger 23, a cross-fin type heat exchanger or a stacked type heat exchanger will be used. The cross-fin type heat exchanger and the stacked type heat exchanger will be explained in "(3) Selection of indoor heat exchanger 41 and outdoor heat exchanger 23".

[0040] (1-2-4) Expansion valve 26 The expansion valve 26 is an electrically operated expansion valve. During cooling operation, the expansion valve 26 reduces the pressure of the high-pressure refrigerant supplied from the outdoor heat exchanger 23 to a low pressure. During heating operation, the expansion valve 26 reduces the pressure of the high-pressure refrigerant supplied from the indoor heat exchanger 41 to a low pressure.

[0041] (1-2-5) Liquid side shut-off valve 27 and gas side shut-off valve 28 The liquid-side shut-off valve 27 is connected to the liquid refrigerant connecting pipe 5. The gas-side shut-off valve 28 is connected to the gas refrigerant connecting pipe 6. The liquid-side shut-off valve 27 is located downstream of the expansion valve 26 in the refrigerant circulation direction during cooling operation. The gas-side shut-off valve 28 is located upstream of the four-way switching valve 22 in the refrigerant circulation direction during cooling operation.

[0042] (1-2-6) Outdoor fan 36 The outdoor unit 2 includes an outdoor fan 36. The outdoor fan 36 draws in outdoor air into the outdoor unit 2, exchanges heat with the refrigerant in the outdoor heat exchanger 23, and then discharges the air to the outside. A propeller fan or the like is used as the outdoor fan 36. The outdoor fan 36 is driven by an outdoor fan motor 37.

[0043] (1-2-7) Outdoor control unit 38 The outdoor control unit 38 controls the operation of each component of the outdoor unit 2. The outdoor control unit 38 has a microcomputer and memory for controlling the outdoor unit 2.

[0044] The outdoor control unit 38 transmits and receives control signals and the like via the transmission line 8a to and from the indoor control unit 44 of the indoor unit 4.

[0045] (1-3) Refrigerant connecting pipes 5, 6 The refrigerant connecting pipes 5 and 6 are refrigerant pipes that are installed on-site when the air conditioning system 1 is installed in a building or other location. The refrigerant connecting pipes 5 and 6 are of appropriate length and diameter depending on the installation location and installation conditions such as the combination of the outdoor unit 2 and the indoor unit 4.

[0046] (2) Basic operation of air conditioning system 1 Next, the basic operation of the air conditioning system 1 will be explained using Figure 1. The air conditioning system 1 can perform both cooling and heating operations as its basic functions.

[0047] (2-1) Cooling operation During cooling operation, the four-way switching valve 22 is switched to the cooling cycle state (the state shown by the solid line in Figure 1). In the refrigerant circuit 10, the low-pressure gaseous refrigerant of the refrigeration cycle is drawn into the compressor 21, compressed, and then discharged.

[0048] The high-pressure gaseous refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23 via the four-way switching valve 22.

[0049] The high-pressure gaseous refrigerant sent to the outdoor heat exchanger 23, which functions as a heat exchanger, exchanges heat with the outdoor air supplied by the outdoor fan 36 and dissipates heat, becoming a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is then sent to the expansion valve 26.

[0050] The high-pressure liquid refrigerant sent to the expansion valve 26 is reduced in pressure by the expansion valve 26 to the low pressure of the refrigeration cycle, becoming a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant reduced in pressure by the expansion valve 26 is sent to the indoor heat exchanger 41 via the liquid side shut-off valve 27 and the liquid refrigerant connecting pipe 5.

[0051] The low-pressure, two-phase gas-liquid refrigerant sent to the indoor heat exchanger 41 evaporates through heat exchange with the indoor air supplied by the indoor fan 42. This cools the indoor air, and the cooled air is then supplied to the room to provide cooling.

[0052] The low-pressure gaseous refrigerant evaporated in the indoor heat exchanger 41 is drawn back into the compressor 21 via the gas refrigerant connecting pipe 6, the gas-side shut-off valve 28, and the four-way switching valve 22.

[0053] (2-2) Heating operation During heating operation, the four-way switching valve 22 is switched to the heating cycle state (the state shown by the dashed line in Figure 1). In the refrigerant circuit 10, the low-pressure gaseous refrigerant of the refrigeration cycle is drawn into the compressor 21, compressed, and then discharged.

[0054] The high-pressure gaseous refrigerant discharged from the compressor 21 is sent to the indoor heat exchanger 41 via the four-way switching valve 22, the gas-side shut-off valve 28, and the gaseous refrigerant connecting pipe 6.

[0055] The high-pressure gaseous refrigerant sent to the indoor heat exchanger 41 exchanges heat with the indoor air supplied by the indoor fan 42 in the indoor heat exchanger 41, releasing heat and becoming a high-pressure liquid refrigerant. As a result, the indoor air is heated, and then this heated air is supplied to the room to provide heating.

[0056] The high-pressure liquid refrigerant that has been heated by the indoor heat exchanger 41 is sent to the expansion valve 26 via the liquid refrigerant connecting pipe 5 and the liquid side shut-off valve 27.

[0057] The high-pressure liquid refrigerant sent to the expansion valve 26 is reduced in pressure by the expansion valve 26 to the low pressure of the refrigeration cycle, becoming a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant reduced in pressure by the expansion valve 26 is sent to the outdoor heat exchanger 23.

[0058] The low-pressure gaseous two-phase refrigerant sent to the outdoor heat exchanger 23 evaporates in the outdoor heat exchanger 23 through heat exchange with the outdoor air supplied from the outdoor fan 36, becoming a low-pressure gaseous refrigerant.

[0059] The low-pressure refrigerant evaporated in the outdoor heat exchanger 23 is drawn back into the compressor 21 through the four-way switching valve 22.

[0060] (3) Selection of heat exchanger This section provides an overview of the cross-fin type heat exchanger or stacked type heat exchanger used in the indoor heat exchanger 41 and the outdoor heat exchanger 23.

[0061] (3-1) Outline of a cross-fin type heat exchanger Figure 2 is a front view of a cross-fin type heat exchanger 51. In Figure 2, the cross-fin type heat exchanger 51 has heat transfer fins 512 and heat transfer tubes 511.

[0062] The heat transfer fins 512 are thin aluminum plates. Multiple through holes are formed in the heat transfer fins 512. The heat transfer tubes 511 consist of straight tubes 511a that are inserted into the through holes of the heat transfer fins 512, and U-shaped tubes 511b and 511c that connect the ends of adjacent straight tubes 511a.

[0063] The straight pipe 511a is expanded after being inserted into the through-hole of the heat transfer fin 512, thereby making it tightly fitted to the heat transfer fin 512. The straight pipe 511a and the first U-shaped pipe 511b are formed as a single unit. The second U-shaped pipe 511c is connected to the end of the straight pipe 511a by welding, brazing, or the like after the straight pipe 511a has been inserted into the through-hole of the heat transfer fin 512 and expanded.

[0064] (3-2) Overview of stacked heat exchangers Figure 3 is an external perspective view of the stacked heat exchanger 53. In Figure 3, the stacked heat exchanger 53 includes a plurality of flattened tubes 531 and a plurality of heat transfer fins 532.

[0065] (3-2-1) Flat tube 531 The flattened tube 531 is a multi-hole tube. The flattened tube 531 is made of aluminum or an aluminum alloy and has a flat surface 531a that serves as a heat transfer surface and multiple internal passages 531b through which the refrigerant flows.

[0066] The flattened pipes 531 are arranged in multiple layers, stacked on top of each other with gaps (ventilation spaces) between them, with their flat sections 531a facing upwards and downwards.

[0067] (3-2-2) Heat transfer fin 532 The heat transfer fins 532 are made of aluminum or an aluminum alloy. The heat transfer fins 532 are positioned in the ventilation space sandwiched between two adjacent flat pipes 531, and are in contact with the flat portion 531a of the flat pipes 531.

[0068] The heat transfer fin 532 has a notch 532c into which the flattened tube 531 is inserted. After the flattened tube 531 is inserted into the notch 532c of the heat transfer fin 532, the heat transfer fin 532 and the flattened tube 531a are joined by brazing or the like.

[0069] (3-2-3) Headers 533a, 533b The headers 533a and 533b are connected to both ends of the flattened pipes 531, which are arranged in multiple stages in the vertical direction. The headers 533a and 533b have the functions of supporting the flattened pipes 531, guiding the refrigerant into the internal flow path of the flattened pipes 531, and collecting the refrigerant that comes out of the internal flow path.

[0070] When the stacked heat exchanger 53 functions as a refrigerant evaporator, the refrigerant flows into the first header 533a. The refrigerant that flows into the first header 533a is distributed almost equally to each internal flow path 531b of the flattened tubes 531 in each stage and flows toward the second header 533b. The refrigerant flowing through each internal flow path of the flattened tubes 531 in each stage absorbs heat from the airflow flowing through the ventilation space via the heat transfer fins 532. The refrigerant that has flowed through each internal flow path of the flattened tubes 531 in each stage collects at the second header 533b and flows out from the second header 533b.

[0071] When the stacked heat exchanger 53 functions as a refrigerant radiator, the refrigerant flows into the second header 533b. The refrigerant that flows into the second header 533b is distributed almost equally to each internal flow path 531b of the flattened tubes 531 in each stage and flows toward the first header 533a. The refrigerant flowing through each internal flow path of the flattened tubes 531 in each stage dissipates heat to the airflow in the ventilation space via the heat transfer fins 532. The refrigerant that has flowed through each internal flow path of the flattened tubes 531 in each stage collects at the first header 533a and flows out from the first header 533a.

[0072] (4) Volume ratio S of the outdoor heat exchanger to the indoor heat exchanger (4-1) Influence of HFO-based refrigerants In the air conditioning system 1 according to this embodiment, one indoor unit 4 is operated by one outdoor unit 2.

[0073] In such air conditioning systems, the volume of the outdoor heat exchanger is generally larger than the volume of the indoor heat exchanger.

[0074] This is because the temperature difference between the ambient temperature and the evaporation or condensation temperature is set smaller for the outdoor heat exchanger. In particular, during heating operation, the difference between the evaporation temperature and the ambient temperature is kept very small for the outdoor heat exchanger to minimize frost formation.

[0075] Due to the circumstances described above, a volume difference arises between the indoor and outdoor heat exchangers. For example, in heating operation, where the indoor heat exchanger, which has a smaller volume than the outdoor heat exchanger, acts as the condenser, even if the amount of refrigerant is determined to prevent a shortage, in cooling operation, the refrigerant tends to be insufficient, and supercooling at the condenser outlet will not occur.

[0076] Therefore, generally, the appropriate amount of refrigerant is determined by considering the effects of excess or insufficient refrigerant.

[0077] However, if an HFO-based refrigerant is used instead of an HFC-based refrigerant in an air conditioning system (hereinafter referred to as an HFC unit), adjusting the refrigerant amount to achieve the same degree of subcooling as an HFC unit during cooling operation will result in an even greater refrigerant excess during heating operation. Conversely, adjusting the refrigerant amount to achieve the same degree of subcooling as an HFC unit during heating operation will result in an even greater refrigerant deficiency during cooling operation, especially under low-load conditions.

[0078] This is because HFO-based refrigerants have a higher average liquid gas density at high pressure, particularly a higher gas density, than HFC refrigerants. Furthermore, at the same degree of supercooling, the amount of refrigerant held in the heat exchanger increases.

[0079] As described above, when using HFO-based refrigerants in air conditioning systems, the difference in the volume ratio between the indoor and outdoor heat exchangers, and the difference in the average density of the liquid gas at high pressure, make it more likely for the amount of refrigerant to be excessive or insufficient compared to conventional systems.

[0080] (4-2) Target Models Here, when using an HFO-based refrigerant in an air conditioning system, an upper limit is set for the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41 in order to avoid incorrect design of the volume ratio S.

[0081] Figure 4 is a list of models for which the upper limit of the volume ratio S is set. In Figure 4, the models are first broadly classified into two types: one in which the outdoor heat exchanger 23 is a single-row heat exchanger, and another in which the outdoor heat exchanger 23 is a double-row heat exchanger.

[0082] (4-2-1) Types A1, B1, C1 Next, assuming that the outdoor heat exchanger 23 is a single-row heat exchanger, the combinations of heat exchanger types for the indoor heat exchanger 41 and the outdoor heat exchanger 23 were divided into three types: Type A1, Type B1, and Type C1.

[0083] Type A1 has both the indoor heat exchanger 41 and the outdoor heat exchanger 23 as either cross-fin type or stacked type. Type B1 has the indoor heat exchanger 41 as cross-fin type and the outdoor heat exchanger 23 as stacked type. Type C1 has the indoor heat exchanger 41 as stacked type and the outdoor heat exchanger 23 as cross-fin type.

[0084] (4-2-2) Types A2, B2, C2 Next, assuming that the outdoor heat exchanger 23 is a two-row heat exchanger, the combinations of heat exchanger types for the indoor heat exchanger 41 and the outdoor heat exchanger 23 were divided into three types: Type A2, Type B2, and Type C2.

[0085] Type A2 has both the indoor heat exchanger 41 and the outdoor heat exchanger 23 as either cross-fin type or stacked type. Type B2 has the indoor heat exchanger 41 as cross-fin type and the outdoor heat exchanger 23 as stacked type. Type C2 has the indoor heat exchanger 41 as stacked type and the outdoor heat exchanger 23 as cross-fin type.

[0086] (4-3) Upper limit of volume ratio S for types A1, B1, and C1 In order to determine the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41 in a refrigerant circuit using an HFO-based refrigerant, the volume ratio of the outdoor heat exchanger to the indoor heat exchanger in a refrigerant circuit using a conventional refrigerant, HFC-32 (hereinafter referred to as R32), which will serve as a comparative standard, will be explained.

[0087] (4-3-1) Type A1 As a prerequisite, both the indoor heat exchanger 41 and the outdoor heat exchanger 23 are of the cross-fin type or stacked type, and the outdoor heat exchanger 23 is a single-row heat exchanger, the indoor heat exchanger 41 is a double-row heat exchanger, and the operating mode is heating operation.

[0088] Here, the heat exchange capacity Qc of the indoor heat exchanger 41 and the heat exchange capacity Qe of the outdoor heat exchanger 23 during heating operation can be roughly expressed by the following equations.

[0089] Qc = K × Ac × △Tc Qe = K × Ae × △Te K: Heat transmission coefficient (based on front area) Ac: Front surface area of ​​indoor heat exchanger 41 Ae: Front surface area of ​​outdoor heat exchanger 23 △Tc: Difference between condensation temperature and standard indoor heating temperature △Te: Difference between standard outdoor heating temperature and evaporation temperature Here, if the condensation temperature is approximately 43°C and the standard indoor heating temperature is 20°C, then △Tc = 23. Also, if the standard outdoor heating temperature is 6°C and the evaporation temperature is approximately 0°C, then △Te = 6.

[0090] therefore, Qc = K × Ac × 2³···[1] Qe = K × Ae × 6 ····[2] That is the case.

[0091] When the coefficient of performance (COP) during heating operation is set to 5, Qc / Qe ≈ 5 / 4 ····[3] That is the case.

[0092] From equations [1], [2] and [3], Ac / Ae ≈ 1 / 3.

[0093] This represents the upper limit of the volume ratio S.

[0094] Therefore, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger in a refrigerant circuit using R32 is 300%.

[0095] HFO-based refrigerants have a higher average liquid gas density ρ in the condensation zone than R32. Here, the average liquid gas density ρ is defined as the average value of the saturated liquid density and saturated gas density at a temperature of 45°C.

[0096] If the average liquid gas density of R32 is ρR32 and the average liquid gas density of HFO-based refrigerants is ρHFO, then the required volume of the outdoor heat exchanger 23 will be [ρR32 / ρHFO] times the volume of the outdoor heat exchanger using R32.

[0097] Therefore, the upper limit of the volume ratio S corresponding to each HFO-based refrigerant can be calculated from the average liquid gas density of several types of HFO-based refrigerants.

[0098] Figure 5A is a table showing the relationship between the average liquid gas density ρ of an HFO-based refrigerant and the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41, when the outdoor heat exchanger 23 is a single-row heat exchanger. In Figure 5A, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze were selected as HFO-based refrigerants to be compared with the average liquid gas density of the HFC-based refrigerant R32, and the average liquid gas density, ρR32 / ρHFO, and upper limit of the volume ratio S for each refrigerant were calculated and listed.

[0099] Both mixed refrigerant A and mixed refrigerant B are mixed refrigerants of R1132(E), R1123, and R1234yf, but there are differences in their three-component composition diagrams. However, details are not described in this application.

[0100] (4-3-2) Type B1 As a prerequisite, the indoor heat exchanger 41 is of the cross-fin type, the outdoor heat exchanger 23 is of the stacked type, the outdoor heat exchanger 23 is a single-row heat exchanger, and the indoor heat exchanger 41 is a double-row heat exchanger, and the operating mode is heating operation.

[0101] As explained in Type A1, in a refrigerant circuit using R32, when both the indoor and outdoor heat exchangers are of the cross-fin type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger was 300%.

[0102] Generally, the volume ratio α of a laminated heat exchanger to a cross-fin heat exchanger is (where α < 1; preferably α = 0.6). Therefore, in a refrigerant circuit using R32, if the indoor heat exchanger is of the cross-fin type and the outdoor heat exchanger is of the laminated type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is 300 × α%.

[0103] Therefore, by multiplying 300 × α% by [ρR32 / ρHFO], the upper limit of the volume ratio S corresponding to HFO-based refrigerants can be calculated.

[0104] Figure 5A shows the upper limit of the volume ratio S in type B1 for each refrigerant, including mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze. The calculations are performed using α = 0.6.

[0105] (4-3-3) Type C1 As a prerequisite, the indoor heat exchanger 41 is of the stacked type, the outdoor heat exchanger 23 is of the cross-fin type, the outdoor heat exchanger 23 is a single-row heat exchanger, and the indoor heat exchanger 41 is a double-row heat exchanger, and the operating mode is heating operation.

[0106] As explained in Type A1, in a refrigerant circuit using R32, when both the indoor and outdoor heat exchangers are of the cross-fin type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger was 300%.

[0107] Generally, the volume ratio α of a laminated heat exchanger to a cross-fin heat exchanger (where α < 1; preferably α = 0.6) is used. Therefore, in a refrigerant circuit using R32, if the indoor heat exchanger is laminated and the outdoor heat exchanger is cross-fin, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is 300 / α%.

[0108] Therefore, by multiplying 300 / α% by [ρR32 / ρHFO], the upper limit of the volume ratio S corresponding to HFO-based refrigerants can be calculated.

[0109] Figure 5A shows the upper limit of the volume ratio S in type C1 for each refrigerant, including mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze. The calculations are performed using α = 0.6.

[0110] Figure 5B is a graph showing the relationship between the average liquid gas density ρ of the HFO-based refrigerant and the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41, when the outdoor heat exchanger 23 is a single-row heat exchanger. In Figure 5B, the horizontal axis of the graph represents the average liquid gas density [kg / m³]. 3 This shows the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41.

[0111] Curve SA1 is a curve obtained by plotting the upper limit of the volume ratio S for R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type A1. Curve SA1 is represented as "1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02", and its relationship with the volume ratio S is: 100≦S≦1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02, This is the result.

[0112] Similarly, curve SB1 is a curve obtained by plotting the upper limit of the volume ratio S of R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type B1.

[0113] Since the curve SB1 is represented as "(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2427E+02)×α", the relationship with the volume ratio S is: 100×α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2427E+02)×α This is the result.

[0114] Similarly, curve SC1 is a curve obtained by plotting the upper limit of the volume ratio S for R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type C1.

[0115] Since the curve SC1 is represented as "(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02) / α", the relationship with the volume ratio S is: 100 / α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02) / α This is the result.

[0116] (4-4) Upper limit of volume ratio S for types A2, B2, and C2 (4-4-1) Type A2 As a prerequisite, both the indoor heat exchanger 41 and the outdoor heat exchanger 23 are of the cross-fin type or stacked type, and the outdoor heat exchanger 23 is a two-row heat exchanger, the indoor heat exchanger 41 is a three-row heat exchanger, and the operating mode is heating operation.

[0117] In this case, the front surface area Ae of the outdoor heat exchanger is twice as large, and the front surface area Ac of the indoor heat exchanger is 1.5 times larger compared to type A1. Since "Ac / Ae ≈ 1 / 3" in type A1, in type A2, Ac / Ae ≈ (1 / 3) × (1.5 / 2) = 1 / 4.

[0118] Therefore, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger in a refrigerant circuit using R32 is 400%.

[0119] HFO-based refrigerants have a higher average liquid gas density ρ in the condensation zone than R32. Here, the average liquid gas density ρ is defined as the average value of the saturated liquid density and saturated gas density at a temperature of 45°C.

[0120] If the average liquid gas density of R32 is ρR32 and the average liquid gas density of HFO-based refrigerants is ρHFO, then the required volume of the outdoor heat exchanger will be [ρR32 / ρHFO] times the volume of the outdoor heat exchanger using R32.

[0121] Therefore, the upper limit of the volume ratio S corresponding to each HFO-based refrigerant can be calculated from the average liquid gas density of several types of HFO-based refrigerants.

[0122] Figure 6A is a table showing the relationship between the average liquid gas density ρ of an HFO-based refrigerant and the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41, when the outdoor heat exchanger 23 is a two-row heat exchanger. In Figure 6A, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze were selected as HFO-based refrigerants to be compared with the average liquid gas density of the HFC-based refrigerant R32, and the average liquid gas density, ρR32 / ρHFO, and upper limit of the volume ratio S for each refrigerant were calculated and listed.

[0123] Both mixed refrigerant A and mixed refrigerant B are mixed refrigerants of R1132(E), R1123, and R1234yf, but there are differences in their three-component composition diagrams. However, details are not described in this application.

[0124] (4-4-2) Type B2 As a prerequisite, the indoor heat exchanger 41 is of the cross-fin type, the outdoor heat exchanger 23 is of the stacked type, the outdoor heat exchanger 23 is a two-row heat exchanger, the indoor heat exchanger 41 is a three-row heat exchanger, and the operating mode is heating operation.

[0125] As explained in Type A2, in a refrigerant circuit using R32, when both the indoor and outdoor heat exchangers are of the cross-fin type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger was 400%.

[0126] Generally, the volume ratio α of a laminated heat exchanger to a cross-fin heat exchanger is (where α < 1; preferably α = 0.6). Therefore, in a refrigerant circuit using R32, if the indoor heat exchanger is of the cross-fin type and the outdoor heat exchanger is of the laminated type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is 400 × α%.

[0127] Therefore, by multiplying 400 × α% by [ρR32 / ρHFO], the upper limit of the volume ratio S corresponding to HFO-based refrigerants can be calculated.

[0128] Figure 6A shows the upper limit of the volume ratio S in type B1 for each refrigerant, including mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze. The calculations are performed using α = 0.6.

[0129] (4-4-3) Type C2 As a prerequisite, the indoor heat exchanger 41 is of the stacked type, the outdoor heat exchanger 23 is of the cross-fin type, the outdoor heat exchanger 23 is a two-row heat exchanger, and the indoor heat exchanger 41 is a three-row heat exchanger, and the operating mode is heating operation.

[0130] As explained in Type A2, in a refrigerant circuit using R32, when both the indoor and outdoor heat exchangers are of the cross-fin type, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger was 400%.

[0131] Generally, the volume ratio α of a laminated heat exchanger to a cross-fin heat exchanger is (where α < 1; preferably α = 0.6). Therefore, in a refrigerant circuit using R32, if the indoor heat exchanger is laminated and the outdoor heat exchanger is cross-fin, the upper limit of the volume ratio S of the outdoor heat exchanger to the indoor heat exchanger is 400 / α%.

[0132] Therefore, by multiplying 400 / α% by [ρR32 / ρHFO], the upper limit of the volume ratio S corresponding to HFO-based refrigerants can be calculated.

[0133] Figure 6A shows the upper limit of the volume ratio S in type C1 for each refrigerant, including mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234ze. The calculations are performed using α = 0.6.

[0134] Figure 6B is a graph showing the relationship between the average liquid gas density ρ of the HFO-based refrigerant and the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41, when the outdoor heat exchanger 23 is a two-row heat exchanger. In Figure 6B, the horizontal axis of the graph represents the average liquid gas density ρ [kg / m³]. 3 This shows the upper limit of the volume ratio S of the outdoor heat exchanger 23 to the indoor heat exchanger 41.

[0135] Curve SA2 is a curve obtained by plotting the upper limit of the volume ratio S for R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type A2. Curve SA2 is represented as "1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03", and its relationship with the volume ratio S is: 130≦S≦1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03, This is the result.

[0136] Similarly, curve SB2 is a curve obtained by plotting the upper limit of the volume ratio S for R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type B2.

[0137] Since the curve SB1 is represented by (1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03)×α, the relationship with the volume ratio S is: 130×α≦S≦(1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03)×α, This is the result.

[0138] Similarly, curve SC2 is a curve obtained by plotting the upper limit of the volume ratio S for R32, mixed refrigerant A, mixed refrigerant B, R1123, R1234yf, and R1234z in type C2.

[0139] Since the curve SC1 is represented by (1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03) / α, the relationship with the volume ratio S is: 130 / α≦S≦(1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03) / α This is the result.

[0140] (5) Characteristics (5-1) In a refrigeration system using HFO refrigerant or a mixed refrigerant containing HFO refrigerant, when the outdoor heat exchanger 23 is a single-row heat exchanger, the indoor heat exchanger 41 is a double-row heat exchanger, the operating mode is heating operation, and both the indoor heat exchanger 41 and the outdoor heat exchanger 23 are of the cross-fin type or stacked type, a model is designated as Type A1, a model where the indoor heat exchanger 41 is of the cross-fin type and the outdoor heat exchanger 23 is of the stacked type is designated as Type B1, and a model where the indoor heat exchanger 41 is of the stacked type and the outdoor heat exchanger 23 is of the cross-fin type is designated as Type C1, The relationship between the average liquid gas density ρ and the volume ratio S in type A1 is: 100≦S≦1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02, The relationship between the average liquid gas density ρ and the volume ratio S in type B1 is: 100×α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2427E+02)×α The relationship between the average liquid-gas density ρ and the volume ratio S in type C1 is: 100 / α≦S≦(1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02) / α This is the result.

[0141] However, α is the volume ratio of the laminated heat exchanger to the cross-fin heat exchanger when the cross-fin heat exchanger and the laminated heat exchanger have the same heat exchange performance, and ρ [kg / m^3] is the average density of saturated liquid gas at a condensation temperature of 45°C.

[0142] (5-2) In a refrigeration system through which HFO refrigerant or a mixed refrigerant containing HFO refrigerant flows, if the outdoor heat exchanger 23 is a two-row heat exchanger, the indoor heat exchanger 41 is a three-row heat exchanger, the operating mode is heating operation, and the model in which both the indoor heat exchanger 41 and the outdoor heat exchanger 23 are cross-fin type or stacked type is designated as Type A2, the model in which the indoor heat exchanger 41 is cross-fin type and the outdoor heat exchanger 23 is stacked type is designated as Type B2, and the model in which the indoor heat exchanger 41 is stacked type and the outdoor heat exchanger 23 is cross-fin type is designated as Type C2, The relationship between the average liquid gas density ρ and the volume ratio S in type A2 is: 130≦S≦1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03, The relationship between the average liquid gas density ρ and the volume ratio S in type B2 is: 130×α≦S≦(1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03)×α, The relationship between the average liquid gas density ρ and the volume ratio S in type C2 is: 130 / α≦S≦(1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03) / α This is the result.

[0143] However, α is the volume ratio of the laminated heat exchanger to the cross-fin heat exchanger when the cross-fin heat exchanger and the laminated heat exchanger have the same heat exchange performance, and ρ [kg / m^3] is the average density of saturated liquid gas at a condensation temperature of 45°C.

[0144] (5-3) 476.1 < ρ.

[0145] (5-4) HFO refrigerants are one of the following: R1132(E), R1123, R1234yf, and R1234ze.

[0146] (6) Variant Figure 7 is a schematic diagram of an air conditioning system as a refrigeration system according to a modified example of the present disclosure. In Figure 7, the differences from the embodiment described in Figure 1 are that it includes a receiver 24 connected between the outdoor heat exchanger 23 and the expansion valve 26 of the refrigerant circuit 10, a bypass pipe 30 connecting the receiver 24 and the suction pipe 31, and a flow control valve 25 connected in the middle of the bypass pipe 30. Other than the above, it is the same as the embodiment described in Figure 1, so the explanation is omitted.

[0147] The receiver 24 is a container capable of storing excess refrigerant. Generally, in the refrigerant circuit of an air conditioning system, the optimal amount of refrigerant for cooling operation differs from the optimal amount of refrigerant for heating operation. Therefore, the appropriate volume of the outdoor heat exchanger, which functions as a condenser during cooling operation, differs from the appropriate volume of the indoor heat exchanger, which functions as a condenser during heating operation.

[0148] Normally, the volume of the outdoor heat exchanger is larger than that of the indoor heat exchanger, and any refrigerant that cannot be contained in the indoor heat exchanger during heating operation is temporarily stored in the accumulator 29 or the like. Any excess liquid refrigerant that cannot be contained in the accumulator 29 is stored in the receiver 24.

[0149] During heating operation, the refrigerant just before entering the receiver 24 contains gaseous components generated when passing through the expansion valve 26. After entering the receiver 24, it is separated into liquid refrigerant and gaseous refrigerant, with the liquid refrigerant stored in the lower part and the gaseous refrigerant in the upper part.

[0150] The gaseous refrigerant separated by the receiver 24 flows through the bypass pipe 30 to the suction pipe 31. The liquid refrigerant separated by the receiver 24 flows to the outdoor heat exchanger 23. A flow control valve 25 is connected to the bypass pipe 30. In this modified example, the flow control valve 25 is an electrically operated expansion valve.

[0151] On the other hand, if the indoor heat exchanger 41 is of the cross-fin type and the outdoor heat exchanger 23 is of the stacked type, the volume of the outdoor heat exchanger 23 becomes smaller than the volume of the indoor heat exchanger, and excess refrigerant (excess refrigerant) is generated that cannot be contained by the outdoor heat exchanger 23 during cooling operation, and the amount of excess refrigerant exceeds the amount that can be stored in the accumulator 29, etc.

[0152] In such cases, the receiver 24 stores any excess liquid refrigerant that cannot be contained in the outdoor heat exchanger 23 during cooling operation.

[0153] In this modified example, a receiver 24 is provided between the outdoor heat exchanger 23 and the expansion valve 26, so the volume of the outdoor heat exchanger 23 includes the volume of the receiver 24.

[0154] (7) Definitions of terms The volume of a heat exchanger refers to the internal volume that can be filled with refrigerant, from the refrigerant inlet to the refrigerant outlet of the heat exchanger itself.

[0155] As shown in the modified example above, if there is a receiver 24 for storing refrigerant, the volume of the outdoor heat exchanger 23 refers to the internal volume that can be filled with refrigerant from the refrigerant inlet of the outdoor heat exchanger 23 itself to the refrigerant outlet of the receiver 24 itself.

[0156] While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims. [Industrial applicability]

[0157] This disclosure is broadly applicable to refrigeration equipment (e.g., low-temperature equipment) capable of performing both cooling and heating operations. [Explanation of symbols]

[0158] 1. Air conditioning system (refrigeration system) 21 Compressor 23 Outdoor heat exchanger 24 Receiver (High-voltage receiver) 26. Expansion valve (expansion mechanism) 41 Indoor heat exchanger [Prior art documents] [Patent Documents]

[0159] [Patent Document 1] Japanese Patent Publication No. 2012-077983

Claims

1. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The expansion mechanism consists of a single expansion valve that reduces the pressure of the refrigerant flowing from the outdoor heat exchanger to the indoor heat exchanger during the cooling operation, and reduces the pressure of the refrigerant flowing from the indoor heat exchanger to the outdoor heat exchanger during the heating operation. If both the indoor heat exchanger and the outdoor heat exchanger are cross-fin type heat exchangers or stacked type heat exchangers, and the outdoor heat exchanger has a single row configuration and the indoor heat exchanger has a double row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 100≦S≦1.0112E-03×ρ^2-1.5836E+00×ρ+8.2472E+02, ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

2. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The expansion mechanism consists of a single expansion valve that reduces the pressure of the refrigerant flowing from the outdoor heat exchanger to the indoor heat exchanger during the cooling operation, and reduces the pressure of the refrigerant flowing from the indoor heat exchanger to the outdoor heat exchanger during the heating operation. If both the indoor heat exchanger and the outdoor heat exchanger are cross-fin type heat exchangers or stacked type heat exchangers, and the outdoor heat exchanger has a two-row configuration and the indoor heat exchanger has a three-row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 130≦S≦1.3483E-03×ρ^2-2.1115E+00×ρ+1.0996E+03, ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

3. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The expansion mechanism consists of a single expansion valve that reduces the pressure of the refrigerant flowing from the outdoor heat exchanger to the indoor heat exchanger during the cooling operation, and reduces the pressure of the refrigerant flowing from the indoor heat exchanger to the outdoor heat exchanger during the heating operation. If the indoor heat exchanger is a cross-fin type heat exchanger, the outdoor heat exchanger is a stacked type heat exchanger, and the outdoor heat exchanger has a single row configuration, and the indoor heat exchanger has a double row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 100×α≦S≦(1.0112E−03×ρ^2−1.5836E+00×ρ+8.2427E+02)×α α: The volume ratio of a laminated heat exchanger to a cross-fin heat exchanger when a cross-fin heat exchanger and a laminated heat exchanger have the same heat exchange performance. ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

4. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. The expansion mechanism consists of a single expansion valve that reduces the pressure of the refrigerant flowing from the outdoor heat exchanger to the indoor heat exchanger during the cooling operation, and reduces the pressure of the refrigerant flowing from the indoor heat exchanger to the outdoor heat exchanger during the heating operation. If the indoor heat exchanger is a cross-fin type heat exchanger, the outdoor heat exchanger is a stacked type heat exchanger, and the outdoor heat exchanger has a two-row configuration, and the indoor heat exchanger has a three-row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 130×α≦S≦(1.3483E−03×ρ^2−2.1115E+00×ρ+1.0996E+03)×α α: The volume ratio of a laminated heat exchanger to a cross-fin heat exchanger when a cross-fin heat exchanger and a laminated heat exchanger have the same heat exchange performance. ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

5. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. If the indoor heat exchanger is a stacked heat exchanger, the outdoor heat exchanger is a cross-fin type heat exchanger, and the outdoor heat exchanger has a single row configuration, and the indoor heat exchanger has a double row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 100 / α≦S≦(1.0112E−03×ρ^2−1.5836E+00×ρ+8.2472E+02) / α α: The volume ratio of a laminated heat exchanger to a cross-fin heat exchanger when the cross-fin heat exchanger and the laminated heat exchanger have the same heat exchange performance, where α = 0.

6. ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

6. In a refrigeration system in which, during cooling operation, the refrigerant flows in the order of compressor (21), outdoor heat exchanger (23), expansion mechanism (26), and indoor heat exchanger (41), and during heating operation, the refrigerant flows in the order of compressor, indoor heat exchanger, expansion mechanism, and outdoor heat exchanger, The refrigerant is an HFO refrigerant or a mixed refrigerant containing an HFO refrigerant. If the indoor heat exchanger is a stacked heat exchanger, the outdoor heat exchanger is a cross-fin type heat exchanger, and the outdoor heat exchanger has a two-row configuration, and the indoor heat exchanger has a three-row configuration, The volume ratio S [%] of the outdoor heat exchanger to the indoor heat exchanger is, 130 / α≦S≦(1.3483E−03×ρ^2−2.1115E+00×ρ+1.0996E+03) / α α: The volume ratio of a laminated heat exchanger to a cross-fin heat exchanger when the cross-fin heat exchanger and the laminated heat exchanger have the same heat exchange performance, where α = 0.

6. ρ [kg / m³]: Average density of saturated liquid gas at a condensation temperature of 45°C. Satisfying the relationship, Refrigeration equipment.

7. 476.1 < ρ That is, A refrigeration apparatus according to any one of claims 1 to 6.

8. The HFO refrigerant is one of the following: R1132(E), R1123, R1234yf, or R1234ze. A refrigeration apparatus according to any one of claims 1 to 7.

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