REFRIGERATION CYCLE DEVICE

Abstract

 A refrigeration cycle apparatus is obtained which allows high accurate estimation of the composition of a refrigerant even when the detection accuracy of a used sensor is the same as that in an existing one.
If an error equivalent to that for a first inlet temperature sensor 12 is observed in an outlet temperature TO that is a temperature detected by a first outlet temperature sensor 13, a constant-temperature line in a superheated gas state is sufficiently inclined as compared to a constant-temperature line in a two-phase gas-liquid refrigerant, and an enthalpy error δhTO caused with the error is sufficiently smaller than that in the case of a temperature sensor 103 in a related art example.

Description

Technical Field

[0001] The present invention relates to a refrigeration cycle apparatus using a non-azeotropic refrigerant mixture, and particularly relates to a refrigeration cycle apparatus which accurately estimates the composition of a refrigerant circulating through a refrigeration cycle and efficiently operates with high reliability.

Background Art

[0002] In an existing refrigeration cycle apparatus that uses a non-azeotropic refrigerant mixture, the composition of the circulating refrigerant changes. In particular, in a large-size refrigeration cycle apparatus, a change in the composition of the circulating refrigerant is noticeable. When the composition of the circulating refrigerant changes, the condensing temperature or the evaporating temperature is different even at the same pressure, and superheat or subcooling is different even at the same temperature and the same pressure at an outlet of a heat exchanger. Thus, it becomes hard to make an operating state of the refrigeration cycle apparatus into a desired state. In particular, in a refrigeration cycle apparatus that includes a plurality of load-side heat exchangers, it is possible to adjust a load in accordance with the number of operating heat exchangers by controlling a high pressure or a low pressure to be constant, and it is important to control, to desired values, the condensing temperature and the evaporating temperature that are determined by pressure and the composition of the circulating refrigerant. Thus, due to an inappropriate refrigerant saturation temperature at the heat exchanger, a desired ability is not exerted, or appropriate subcooling is not provided before the refrigerant flows into an expansion valve, the refrigerant comes into a two-phase gas-liquid state, and generation of refrigerant sound or an unstable phenomenon occurs. In addition, appropriate superheat is not provided before the refrigerant is sucked into a compressor, a liquid refrigerant flows into the compressor, and the compressor is damaged; or an appropriate refrigeration cycle is not formed, and the operating efficiency decreases. Thus, means for detecting a refrigerant composition is required in order to ensure an appropriate ability, high efficiency, and high reliability.

[0003] Moreover, it is known that a refrigeration cycle apparatus that includes a refrigerant storage container (receiver) at a high-pressure side has a smaller fluctuation range of the composition of a circulating refrigerant than that of a refrigeration cycle apparatus that includes a refrigerant storage container (accumulator) at a low-pressure side. However, when refrigerant leak occurs at a refrigeration cycle, the fluctuation range of the composition is increased immediately regardless of whether the pressure of the refrigerant storage container is low or high. Therefore, means for detecting the composition of the circulating refrigerant is required in order to operate in a desired cycle state and in order to detect refrigerant leak.

[0004] As a refrigerating and air-conditioning apparatus that is an existing refrigeration cycle apparatus which estimates a refrigerant composition, there is a refrigerating and air-conditioning apparatus in which a bypass is provided between an outlet pipe of a compressor and an inlet pipe of the compressor, the outlet pipe of the compressor, a high-pressure side path of high and low pressure heat exchangers, a pressure reducing device, a low-pressure side path of the high and low pressure heat exchangers, and the inlet pipe of the compressor are sequentially connected in this order, the temperature at an inlet of the pressure reducing device, the temperature at an outlet of the pressure reducing device, and the pressure at the outlet of the pressure reducing device are detected, a refrigerant composition is estimated by composition detection means on the basis of the detected information (see, for example, Patent Literature 1).

Citation List

Patent Literature

[0005] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 8-75280 (pages 5 and 6, Fig. 6)

Summary of Invention

Technical Problem

[0006] In the refrigerating and air-conditioning apparatus as described above, a refrigerant state is obtained on the basis of the temperatures and the pressures before and after the pressure reducing device, and the composition of the refrigerant is estimated, therefore the refrigerating and air-conditioning apparatus is influenced by the measurement errors of a temperature sensor for detecting the temperature of the refrigerant and a pressure sensor for detecting the pressure of the refrigerant. In particular, when a non-azeotropic refrigerant mixture is in a two-phase gas-liquid state, a unique temperature glide occurs, and thus the temperature and the pressure of the refrigerant that is in a two-phase gas-liquid state where the pressure is low at the outlet of the pressure reducing device are significantly influenced. Therefore, the poor detection accuracy of the temperature sensor or the pressure sensor particularly, influences on enthalpy calculation in a two-phase gas-liquid state with a temperature glide, leading to a problem that the detection accuracy of the refrigerant composition is deteriorated.

[0007] The present invention has been made in order to solve the above-described problems, and an object of the present invention is to obtain a refrigeration cycle apparatus which allows high accurate estimation of the composition of a refrigerant even when the detection accuracy of a used sensor is the same as that in an existing one.

Solution to Problem

[0008] A refrigeration cycle apparatus according to the present invention is a refrigeration cycle apparatus in which a compressor, a condenser, an expansion device, and an evaporator are sequentially connected via refrigerant pipes to form a refrigeration cycle and in which a non-azeotropic refrigerant mixture circulates as a refrigerant circulating through the refrigeration cycle. The refrigeration cycle apparatus includes: a detection path which bypasses the refrigerant from a high-pressure side that is an outlet side of the condenser to a low-pressure side that is a suction side of the compressor and on which a pressure reducing device and a heating device are provided from the high-pressure side toward the low-pressure side; and a controller which controls an operation of the refrigeration cycle. The heating device turns the refrigerant at an outlet side thereof into a superheated gas state. The controller calculates an enthalpy at an inlet side of the pressure reducing device on the detection path, calculates an enthalpy at the outlet side of the heating device on the detection path, calculates an enthalpy difference of the refrigerant between the outlet side and an inlet side of the heating device, calculates an enthalpy at an outlet side of the pressure reducing device on the basis of the enthalpy difference and the enthalpy at the outlet side of the heating device, and estimates a circulation composition that is a composition of the refrigerant circulating through the refrigeration cycle, on the basis of the calculated enthalpy at the inlet side of the pressure reducing device and the calculated enthalpy at the outlet side of the pressure reducing device.

Advantageous Effects of Invention

[0009] According to the present invention, an enthalpy at the outlet side of the pressure reducing device on the basis of which the composition of the circulating refrigerant is estimated is derived by using the temperature of the refrigerant at the outlet side of the heating device. Thus, a temperature error is low, it is possible to improve the accuracy of estimating the circulation composition of the refrigerant, and it is possible to improve the operating efficiency of the refrigeration cycle of the refrigeration cycle apparatus.

Brief Description of Drawings

[0010] 

[Fig. 1] Fig. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a flowchart illustrating an operation of estimating the composition of a non-azeotropic refrigerant mixture in the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 is a flowchart of a process of calculating an enthalpy difference Δh between an outlet side and an inlet side of a heating device 9 in the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 is a diagram illustrating a change in a state of a refrigerant in a detection path 7 in the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention.

[Fig. 5] Fig. 5 is a diagram illustrating influence of detection accuracy of each sensor of the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention on enthalpy.

[Fig. 6] Fig. 6 is a refrigerant circuit diagram of a refrigeration cycle apparatus 1a according to Embodiment 2 of the present invention.

[Fig. 7] Fig. 7 is a flowchart of a process of calculating an enthalpy difference Δh between an outlet side and an inlet side of a low-pressure side path of a refrigerant heat exchanger 22 in the refrigeration cycle apparatus 1 a according to Embodiment 2 of the present invention.

[Fig. 8] Fig. 8 is a refrigerant circuit diagram of a refrigeration cycle apparatus 101 as a related art example configured on the basis of the contents of the related art (Patent Literature 1).

[Fig. 9] Fig. 9 is a diagram illustrating a change in a state of a refrigerant in a detection path 102 in the refrigeration cycle apparatus 101.

[Fig. 10] Fig. 10 is a diagram illustrating influence of detection accuracy of each sensor of the refrigeration cycle apparatus 101 on enthalpy.

Description of Embodiments

Embodiment 1

(Configuration of refrigeration cycle apparatus 1)

[0011] Fig. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention.

[0012] As shown in Fig. 1, in the refrigeration cycle apparatus 1 according to the embodiment, a refrigerant circuit is formed in order of a compressor 2, a condenser 3, an expansion device 4, an evaporator 5, an accumulator 6, and again the compressor 2 via refrigerant pipes. In addition, in the refrigeration cycle apparatus 1, a detection path 7 is provided so as to branch from a high-pressure side refrigerant pipe connecting the condenser 3 to the expansion device 4, to bypass a refrigerant to a low-pressure side refrigerant pipe connecting the accumulator 6 to the compressor 2. A portion branching from the high-pressure side refrigerant pipe connecting the condenser 3 to the expansion device 4 to the detection path 7 is referred to as a connection portion 41, and a portion connecting the detection path 7 to the low-pressure side refrigerant pipe connecting the accumulator 6 to the compressor 2 is referred to as a connection portion 42. On the detection path 7, a pressure reducing device 8 and a heating device 9 are provided from the high-pressure side toward the low-pressure side, respectively. For example, a non-azeotropic refrigerant mixture including R32 which is a low-boiling-point component and HFO1234yf which is a high-boiling-point component (for example, a filled composition of R32 is 54 wt% and a filled composition of HFO1234yf is 46 wt%, whereby global warming potential (GWP) is 300 and the environmental load is reduced) is used as a non-azeotropic refrigerant mixture circulating through the refrigerant circuit configured as described above.

[0013] In addition, the refrigeration cycle apparatus 1 includes a high-pressure sensor 10 which detects the pressure of the refrigerant at a discharge side of the compressor 2, a low-pressure sensor 11 which detects the pressure of the refrigerant at a suction side of the compressor 2, a first inlet temperature sensor 12 which detects the temperature of the refrigerant at an inlet side of the detection path 7, and a first outlet temperature sensor 13 which detects the temperature of the refrigerant at an outlet side of the detection path 7. Furthermore, the refrigeration cycle apparatus 1 includes a controller 31 and receives detection information from each sensor described above.

[0014] The compressor 2 sucks a low-temperature and low-pressure gas refrigerant, compresses the gas refrigerant, and discharges the gas refrigerant as a high-temperature and high-pressure refrigerant to the condenser 3 side.

[0015] The condenser 3 performs heat exchange between the high-temperature and high-pressure refrigerant discharged from the compressor 2 and air sent from a fan (not shown) or the like to condense the refrigerant into a liquid refrigerant.

[0016] The expansion device 4 reduces the pressure of the high-pressure liquid refrigerant having flowed out of the condenser 3 to turn the liquid refrigerant into a low-pressure two-phase gas-liquid refrigerant.

[0017] The evaporator 5 performs heat exchange between the low-pressure two-phase gas-liquid refrigerant resulting from the pressure reduction by the expansion device 4 and air sent from a fan (not shown) or the like to evaporate the two-phase gas-liquid refrigerant into a gas refrigerant.

[0018] The accumulator 6 stores therein an excess non-azeotropic refrigerant mixture generated depending on an operation condition or a load condition of the refrigeration cycle apparatus 1, among the refrigerant having flowed out of the evaporator 5. Specifically, the accumulator 6 separates the non-azeotropic refrigerant mixture into a liquid refrigerant in which the high-boiling-point component is contained in a large amount and a gas refrigerant in which the low-boiling-point component is contained in a large amount, and stores therein the liquid-phase refrigerant in which the high-boiling-point component is contained in a large amount. Thus, when the liquid refrigerant is present within the accumulator 6, the composition of the refrigerant circulating through the refrigeration cycle shows a tendency that the low-boiling-point component is increased in amount. In addition, when the liquid refrigerant in which the high-boiling-point component is contained in a large amount leaks from a lower portion of the accumulator 6, the composition of the refrigerant circulating through the refrigeration cycle shows a tendency that the low-boiling-point component is increased in amount. Furthermore, when the refrigerant leaks from a refrigerant pipe through which a liquid single-phase refrigerant circulates, an amount of the low-boiling-point component that gasifies and leaks is larger. Thus, the composition of the refrigerant circulating through the refrigeration cycle shows a tendency that the high-boiling-point component is increased in amount.

[0019] As described above, the detection path 7 is a path which bypasses the refrigerant from the connection portion 41 on the high-pressure side refrigerant pipe to the connection portion 42 on the low-pressure side refrigerant pipe.

[0020] Of the high-pressure liquid refrigerant having flowed out of the condenser 3,The pressure reducing device 8 reduces the pressure of the liquid refrigerant branched at the connection portion 41 to the detection path 7, to turn the liquid refrigerant into a low-pressure two-phase gas-liquid refrigerant.

[0021] The heating device 9 is composed of an electric heater or the like and heats and evaporates the low-pressure two-phase gas-liquid refrigerant resulting from the pressure reduction by the pressure reducing device 8.

[0022] As described above, the high-pressure sensor 10 detects the pressure of the refrigerant at the discharge side of the compressor 2.

[0023] It should be noted that as shown in Fig. 1, the high-pressure sensor 10 is provided on the refrigerant pipe between the discharge side of the compressor 2 and an inlet side of the condenser 3, but suffices to be provided at any position from the discharge side of the compressor 2 to an inlet side of the expansion device 4.

[0024]  As described above, the low-pressure sensor 11 detects the pressure of the refrigerant at the suction side of the compressor 2.

[0025] It should be noted that as shown in Fig. 1, the low-pressure sensor 11 is provided on the refrigerant pipe between an outlet side of the accumulator 6 and the suction side of the compressor 2, but suffices to be provided at any position from an outlet side of the expansion device 4 to the suction side of the compressor 2.

[0026] As described above, the first inlet temperature sensor 12 detects the temperature of the refrigerant at the inlet side of the detection path 7.

[0027] It should be noted that the position at which the first inlet temperature sensor 12 is provided may be any position in a closed region defined by the condenser 3, the expansion device 4, and the pressure reducing device 8.

[0028] As described above, the first outlet temperature sensor 13 detects the temperature of the refrigerant at the outlet side of the detection path 7.

[0029] It should be noted that the position at which the first outlet temperature sensor 13 is provided may be any position between the heating device 9 and the connection portion 42.

[0030] When each sensor is provided at a position in the limited range as described above, it is possible to commonalize each sensor with a sensor used for another purpose, leading to cost reduction.

[0031] The controller 31 receives information detected by the high-pressure sensor 10, the low-pressure sensor 11, the first inlet temperature sensor 12, and the first outlet temperature sensor 13, estimates the composition of the refrigerant of the non-azeotropic refrigerant mixture circulating through the refrigeration cycle on the basis of this information, and controls the entirety of the refrigeration cycle apparatus 1. A process of estimating the composition of the refrigerant by the controller 31 will be described in detail later.

[0032] It should be noted that the high-pressure sensor 10, the low-pressure sensor 11, the first inlet temperature sensor 12, and the first outlet temperature sensor 13 correspond to "high-pressure detection means," "low-pressure detection means," "first inlet temperature detection means," and "first outlet temperature detection means," respectively, in the present invention.

(Refrigerant circulating operation in refrigeration cycle)

[0033] Next, a refrigerant circulating operation in the refrigeration cycle apparatus 1 according to the embodiment will be described with reference to Fig. 1.

[0034] The high-temperature and high-pressure gas refrigerant compressed and discharged from the compressor 2 flows into the condenser 3. The gas refrigerant having flowed into the condenser 3 is subjected to heat exchange with air sent from the fan or the like, to be condensed into a liquid refrigerant, and flows out of the condenser 3. The liquid refrigerant having flowed out of the condenser 3 is separated at the connection portion 41 into a refrigerant flowing toward the expansion device 4 and a refrigerant flowing toward the detection path 7.

[0035] The liquid refrigerant flowing toward the expansion device 4 is reduced in pressure by the expansion device 4 into a low-temperature and low-pressure two-phase gas-liquid refrigerant, and flows into the evaporator 5. The two-phase gas-liquid refrigerant having flowed into the evaporator 5 is subjected to heat exchange with air sent from the fan or the like, to be evaporated into a low-temperature and low-pressure refrigerant, and flows out of the evaporator 5. The refrigerant having flowed out of the evaporator 5 flows into the accumulator 6 and is separated into a liquid refrigerant and a gas refrigerant, and the gas refrigerant flows out of the accumulator 6. The gas refrigerant having flowed out of the accumulator 6 joins, at the connection portion 42, the refrigerant having flowed through the detection path 7, and is sucked into the compressor 2 and compressed again.

[0036] Meanwhile, the liquid refrigerant branched at the connection portion 41 to the detection path 7 is reduced in pressure by the pressure reducing device 8 into a low-temperature and low-pressure two-phase gas-liquid refrigerant, and flows into the heating device 9. The two-phase gas-liquid refrigerant having flowed into the heating device 9 is heated and evaporated into a low-temperature and low-pressure gas refrigerant, and flows out of the heating device 9. The gas refrigerant having flowed out of the heating device 9 joins, at the connection portion 42, the gas refrigerant having flowed out of the accumulator 6, and is sucked into the compressor 2 and compressed again.

[0037] A state of the refrigeration cycle greatly changes depending on a load and an operating state of the refrigeration cycle apparatus 1, and design values such as the capacities of the condenser 3 and the evaporator 5, the refrigerant charging amount, and the capacity of the heating device 9 are designed such that under major operation conditions, the refrigerant state becomes a supercooled liquid state (subcooling) at the connection portion 41 which is at the high-pressure side of the detection path 7, and becomes a superheated gas state (superheat) at an outlet portion of the low-pressure side of the detection path 7.

(Operation of estimating composition of circulating refrigerant)

[0038] Fig. 2 is a flowchart illustrating an operation of estimating the composition of the non-azeotropic refrigerant mixture in the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention, and Fig. 3 is a flowchart of a process of calculating an enthalpy difference Δh between an outlet side and an inlet side of the heating device 9 in the refrigeration cycle apparatus 1. Hereinafter, the operation of estimating the composition of the refrigerant will be described with reference to Figs. 2 and 3.

[0039]  When the refrigeration cycle of the refrigeration cycle apparatus 1 operates, the controller 31 starts the following operation of estimating the composition of the non-azeotropic refrigerant mixture, under a predetermined condition.

(S1)

[0040] First, the controller 31 determines whether a given period of time has elapsed from the start of the operation of estimating the composition of the refrigerant. When the controller 31 detects that the given period of time has elapsed, the controller 31 proceeds to step S2.

[0041] It should be noted that delaying timing at which another control process is performed by the controller 31 from the timing at which it is detected by the controller 31 that the given period of time has elapsed alleviates a processing load on the controller 31 and stabilizes the controllability of the controller 31. However, the operation of estimating the composition of the refrigerant is reflected by various controls, and thus the given period of time is desirably a short period such as 10 sec or 20 sec.

(S2)

[0042] The controller 31 receives a high-pressure pressure Pd detected by the high-pressure sensor 10, a low-pressure pressure Ps detected by the low-pressure sensor 11, an inlet temperature TI detected by the first inlet temperature sensor 12, and an outlet temperature TO detected by the first outlet temperature sensor 13. Then, the controller 31 proceeds to step S3.

(S3)

[0043] The controller 31 grasps a flow rate characteristic by deriving a flow rate coefficient k of the pressure reducing device 8. For example, when the flow rate coefficient k of the pressure reducing device 8 is a fixed value, the flow rate coefficient k is stored in an internal memory or the like of the controller 31, and the controller 31 derives the flow rate coefficient k by obtaining the flow rate coefficient k stored in the internal memory. On the other hand, when the flow rate characteristic of the pressure reducing device 8 changes, a correlation between an opening degree of the pressure reducing device 8 and the flow rate coefficient k is stored in the internal memory, and the controller 31 derives the flow rate coefficient k from the opening degree of the pressure reducing device 8 during operation of the refrigeration cycle apparatus 1 on the basis of the correlation. Then, the controller 31 proceeds to step S4.

(S4)

[0044] First, the controller 31 provisionally determines an assumed value αtmp as the composition of the low-boiling-point component. For example, the controller 31 may determine the composition of the low-boiling-point component in charging the non-azeotropic refrigerant mixture into the refrigeration cycle apparatus 1, as the assumed value αtmp. Then, the controller 31 proceeds to step S5.

(S5)

[0045] The controller 31 calculates an inlet enthalpy hl that is an enthalpy at the inlet side of the detection path 7, on the basis of the high-pressure pressure Pd, the inlet temperature TI, and the assumed value αtmp with the following formula (1). Then, the controller 31 proceeds to step S6.

[0046] [Math. 1]

(S6)

[0047] The controller 31 calculates an outlet enthalpy hO that is an enthalpy at the outlet side of the detection path 7, on the basis of the low-pressure pressure Ps, the outlet temperature TO, and the assumed value αtmp with the following formula (2). Then, the controller 31 proceeds to step S7.

[0048] [Math. 2]

(S7)

[0049] Then, the controller 31 calculates an enthalpy difference Δh between the outlet side and the inlet side of the heating device 9 by the following procedure of steps S21 to S24.

(S21)

[0050] The controller 31 calculates a density pi of the refrigerant at the inlet side of the detection path 7 on the basis of the high-pressure pressure Pd, the inlet temperature TI, and the assumed value αtmp with the following formula (3). Then, the controller 31 proceeds to step S22.

[0051] [Math. 3]

(S22)

[0052] In addition, the controller 31 calculates a pressure difference ΔP of the refrigerant between before and after the pressure reducing device 8 on the basis of the high-pressure pressure Pd and the low-pressure pressure Ps with the following formula (4). Then, the controller 31 proceeds to step S23.

[0053] [Math. 4]

(S23)

[0054] In addition, the controller 31 calculates a refrigerant flow rate Gdet in the detection path 7 on the basis of the flow rate coefficient k, the density pi, and the pressure difference ΔP with the following formula (5). Then, the controller 31 proceeds to step S24.

[0055] [Math. 5]

(S24)

[0056] Here, the output of the heating device 9 is denoted by Q, and the controller 31 calculates the enthalpy difference Δh on the basis of the output Q and the refrigerant flow rate Gdet with the following formula (6).

[0057] [Math. 6]


(Q: output of the heating device 9)

[0058] The following formula (7) is derived from the formulas (3) to (6). Then, the controller 31 proceeds to step S8.

[0059] [Math. 7]

(S8)

[0060] Here, the pressure reducing device 8 causes pressure reduction change based on isenthalpic change, thus an enthalpy at the inlet side of the pressure reducing device 8 and an enthalpy at the outlet side of the pressure reducing device 8 should be the same, and the inlet enthalpy hl at the inlet side of the detection path 7 (the inlet side of the pressure reducing device 8) should be the enthalpy at the outlet side of the pressure reducing device 8 (it is referred to as enthalpy h*). Therefore, the controller 31 calculates the enthalpy h* with the following formula (8).

[0061] [Math. 8]

[0062] Next, the controller 31 compares the inlet enthalpy hl at the inlet side of the detection path 7 which is calculated with formula (1) to the enthalpy h* at the outlet side of the pressure reducing device 8 which is calculated with formula (8), and calculates the difference therebetween. Then, the controller 31 determines whether the difference is equal to or less than a predetermined specified value δ. As a result of the determination, when the difference is equal to or less than the specified value δ, the controller 31 proceeds to step S10, and when the difference is greater than the specified value δ, the controller 31 proceeds to step S9.

(S9)

[0063] The controller 31 determines that the assumed value αtmp which is assumed in step S4 and is the composition of the low-boiling-point component is not an appropriate composition, and, for example, adds or subtracts a predetermined correction value which is based on the difference between the inlet enthalpy hl and the enthalpy h* in step S8 described above to or from the assumed value αtmp to newly determine an assumed value αtmp again. Then, the controller 31 returns to step S5.

(S10)

[0064] The controller 31 determines that the assumed value αtmp which is assumed in step S4 and is the composition of the low-boiling-point component is an appropriate composition, and estimates the assumed value αtmp as a circulation composition α that is the composition of the low-boiling-point component. This is the end of the operation of estimating the composition of the non-azeotropic refrigerant mixture in the refrigeration cycle apparatus 1.

[0065] It should be noted that Figs. 2 and 3 described above illustrate the operation of estimating the composition of the low-boiling-point component of the non-azeotropic refrigerant mixture, but the present invention is not limited to this and the composition of the high-boiling-point component may be estimated.

[0066] In addition, the controller 31 performs all the calculations shown in formulas (1) to (8) described above, but the present invention is not limited to the single controller performing the calculations, and a plurality of controllers or calculators distribute and process the calculation based on each formula described above.

(Operation of calculating composition of refrigerant and its accuracy in related art)

[0067] Fig. 8 is a refrigerant circuit diagram of a refrigeration cycle apparatus 101 as a related art example configured on the basis of the contents of the related art (Patent Literature 1). Hereinafter, the difference from the configuration of the refrigeration cycle apparatus 1 according to the embodiment shown in Fig. 1 will be described with reference to Fig. 8.

[0068] As shown in Fig. 8, the refrigeration cycle apparatus 101 has a detection path 102 which branches from a high-pressure side refrigerant pipe connecting the condenser 3 to the expansion device 4, to bypass the refrigerant to a low-pressure side refrigerant pipe connecting the accumulator 6 to the compressor 2, and which corresponds to the detection path 7 in the refrigeration cycle apparatus 1. In addition, the refrigeration cycle apparatus 101 includes a temperature sensor 103 which detects the temperature of the refrigerant between the pressure reducing device 8 and the heating device 9, instead of the first outlet temperature sensor 13 in the refrigeration cycle apparatus 1. The refrigeration cycle apparatus 101 includes a controller 104 instead of the controller 31 in the refrigeration cycle apparatus 1. The controller 104 receives information detected by the high-pressure sensor 10, the low-pressure sensor 11, the first inlet temperature sensor 12, and the temperature sensor 103, and determines the composition of the refrigerant of the non-azeotropic refrigerant mixture circulating through the refrigeration cycle, on the basis of this information.

[0069] On the basis of the configuration of the existing refrigerant circuit shown in Fig. 8 as described above, the controller 104 of the refrigeration cycle apparatus 101 first receives a high-pressure pressure Pd detected by the high-pressure sensor 10, a low-pressure pressure Ps detected by the low-pressure sensor 11, an inlet temperature TI detected by the first inlet temperature sensor 12, and a temperature T* at the outlet side of the pressure reducing device 8 which is detected by the temperature sensor 103. Next, the controller 104 calculates an enthalpy at the outlet side of the pressure reducing device 8 on the basis of the low-pressure pressure Ps and the temperature T* at the outlet side of the pressure reducing device 8, and calculates an enthalpy at the inlet side of the pressure reducing device 8 on the basis of the high-pressure pressure Pd and the inlet temperature TI. Then, the controller 104 calculates a circulation composition value of the refrigerant that causes the calculated enthalpy at the outlet side of the pressure reducing device 8 to agree with the calculated enthalpy at the inlet side of the pressure reducing device 8.

[0070] Fig. 9 is a diagram illustrating a change in a state of the refrigerant in the detection path 102 in the refrigeration cycle apparatus 101, and Fig. 10 is a diagram illustrating influence of detection accuracy of each sensor of the refrigeration cycle apparatus 101 on enthalpy.

[0071] As shown in Fig. 9, the refrigerant at the inlet side of the detection path 102 is a supercooled liquid, and the refrigerant at the outlet side of the detection path 102 is a superheated gas. The refrigerant between the pressure reducing device 8 and the heating device 9 between which the temperature sensor 103 is provided is a two-phase gas-liquid refrigerant. Here, it is a characteristic of the non-azeotropic refrigerant mixture that, of a constant-temperature line shown in Fig. 10, a portion in a two-phase gas-liquid state is nearly horizontal but has a gradient that is not zero.

[0072] As shown in Fig. 10, even if an error is observed in the inlet temperature TI which is a temperature detected by the first inlet temperature sensor 12, since the constant-temperature line in a supercooled liquid state is nearly vertical, an enthalpy error δhTI caused with the error is small. Similarly, even if an error is observed in the high-pressure pressure Pd which is a pressure detected by the high-pressure sensor 10, an enthalpy error δhPd caused with the error δPd is also fairly small.

[0073] Meanwhile, if an error equivalent to that for the first inlet temperature sensor 12 is observed in the temperature T* at the outlet side of the pressure reducing device 8 which is a temperature detected by the temperature sensor 103, since the constant-temperature line in a two-phase gas-liquid state is nearly horizontal as described above, an enthalpy error δhT* caused with the error is large as compared to the error δhtl and the error δhPd. Similarly, if an error equivalent to that for the high-pressure sensor 10 is observed in the low-pressure pressure Ps which is a pressure detected by the low-pressure sensor 11, an enthalpy error δhPs caused with the error δPs is large as compared to the error δhTI and the error δhPd.

[0074] As described above, the influence of the errors of the detection values of the first inlet temperature sensor 12 and the high-pressure sensor 10 on enthalpy error is fairly small, but the influence of the detection values of the temperature sensor 103 and the low-pressure sensor 11 on enthalpy error is significant, and the precision of the composition value of the refrigerant calculated with the errors is poor.

(Accuracy of operation for estimating composition of refrigerant in Embodiment)

[0075] Fig. 4 is a diagram illustrating a change in a state of the refrigerant in the detection path 7 in the refrigeration cycle apparatus 1 according to Embodiment 1 of the present invention, and Fig. 5 is a diagram illustrating influence of detection accuracy of each sensor of the refrigeration cycle apparatus 1 on enthalpy.

[0076] As shown in Fig. 4, the refrigerant at the inlet side of the detection path 7 is a supercooled liquid, and the refrigerant at the outlet side of the detection path 7 is a superheated gas. The refrigerant between the pressure reducing device 8 and the heating device 9 is a two-phase gas-liquid refrigerant. Here, as described above with reference to Fig. 10, it is a characteristic of the non-azeotropic refrigerant mixture that, of a constant-temperature line shown in Fig. 5, a portion in a two-phase gas-liquid state is nearly horizontal but has a gradient that is not zero.

[0077] As shown in Fig. 5, an enthalpy error δhTI and error δhPd caused with errors of the detection values of the first inlet temperature sensor 12 and the high-pressure sensor 10 are small as described above with reference to Fig. 10.

[0078] It should be noted that the influence of the detection value of the high-pressure sensor 10 itself on enthalpy is sufficiently smaller than the influence of the detection value of the first inlet temperature sensor 12 itself on enthalpy. Thus, it is possible to estimate the circulation composition α only with the inlet temperature TI detected by the first inlet temperature sensor 12, without using the high-pressure pressure Pd detected by the high-pressure sensor 10. Therefore, it is possible to reduce the arguments in formulas (1) and (3), reducing the processing load on the controller 31 and reducing the storage capacity of the controller 31.

[0079] Furthermore, if an error equivalent to that for the first inlet temperature sensor 12 is observed in the outlet temperature TO which is a temperature detected by the first outlet temperature sensor 13, the constant-temperature line in a superheated gas state is sufficiently inclined as compared to the constant-temperature line in the two-phase gas-liquid refrigerant, and an enthalpy error δhTO caused with the error is sufficiently smaller than that in the case of the temperature sensor 103 in the related art example. Similarly, if an error equivalent to that for the high-pressure sensor 10 is observed in the low-pressure pressure Ps which is a pressure detected by the low-pressure sensor 11, an enthalpy error δhPs caused with the error δPs is sufficiently smaller than that in the case of the low-pressure sensor 11 in the related art example.

[0080] Therefore, in the configuration of the refrigeration cycle apparatus 1 according to the embodiment shown in Fig. 1, the influence of the detection errors of each temperature sensor and each pressure sensor on enthalpy is suppressed, and thus it is possible to improve the accuracy of estimating the circulation composition α of the refrigerant.

[0081] For example, in the case where the average condensing temperature is 50 degrees C, the saturated gas evaporating temperature is 0 degrees C, subcooling at the inlet side of the detection path 7 is 5 degrees C, and superheat at the outlet side of the detection path 7 is 5 degrees C, when the refrigerant composition of R32 is fixed at 54 [wt%], the refrigerant composition of HFO1234yf is fixed at 46 [wt%], and the detection accuracy of each pressure sensor and each temperature sensor is the same between the embodiment and the related art example, variation of the enthalpy at the outlet side of the pressure reducing device 8 in the embodiment is about 1/4 of that in the related art example. The variation of the enthalpy deteriorates the accuracy of estimating the circulation composition of the refrigerant, and the accuracy in the embodiment is about 1/2 of that in the related art example.

[0082] In addition, the detection path 7 in the refrigeration cycle apparatus 1 according to the embodiment bypasses from the high-pressure side to the low-pressure side in the refrigeration cycle, and thus causes decrease of the ability of the refrigeration cycle apparatus 1. Furthermore, power is consumed by the heating device 9, and thus it is conceived that the efficiency of the refrigeration cycle apparatus 1 further falls. However, the advantages provided by improvement of the operating efficiency by estimating the circulation composition of the refrigerant with high accuracy and appropriately operating the refrigeration cycle as in the embodiment is much greater than the above disadvantages. In particular, in a large-size refrigeration cycle apparatus, estimating the circulation composition of the refrigerant with high accuracy is even more advantageous. In addition, in the embodiment, the detection path 7 including only the pressure reducing device 8 and the heating device 9 which is an electric heater or the like is used in order to estimate the circulation composition of the refrigerant, and the configuration is simple and size reduction thereof is possible.

(Advantageous effects of Embodiment 1)

[0083] By the configuration and the operation described above, it is possible to suppress the influence of the detection errors of each temperature sensor and each pressure sensor on enthalpy. Thus, the accuracy of estimating the circulation composition α of the refrigerant is improved, and it is possible to improve the operating efficiency of the refrigeration cycle of the refrigeration cycle apparatus 1.

[0084] In addition, the detection path 7 including only the pressure reducing device 8 and the heating device 9 which is an electric heater or the like is used as a means for estimating the circulation composition of the refrigerant, the configuration is simple, and size reduction thereof is possible.

[0085] It should be noted that the non-azeotropic refrigerant mixture of R32 and HFO1234yf is used as the refrigerant in the embodiment, but the present invention is not limited to this, and a non-azeotropic refrigerant mixture of another low-boiling-point refrigerant and another high-boiling-point refrigerant may be used. For example, a hydrofluoroolefin-based refrigerant having double bonds may be used, a low flammable refrigerant may be used, or a flammable HC-based refrigerant may be used.

[0086] In addition, the non-azeotropic refrigerant mixture used in the embodiment contains two components as described above, but may contain three or more components. In this case, representation with the composition of one low-boiling-point component is possible.

Embodiment 2

[0087] Regarding a refrigeration cycle apparatus 1a according to the embodiment, the difference from the configuration and the operation of the refrigeration cycle apparatus 1 according to Embodiment 1 will be mainly described.

(Configuration of refrigeration cycle apparatus 1 a)

[0088] Fig. 6 is a refrigerant circuit diagram of the refrigeration cycle apparatus 1 a according to Embodiment 2 of the present invention.

[0089] As shown in Fig. 6, in the refrigeration cycle apparatus 1a according to the embodiment, a refrigerant circuit is formed in order of a compressor 2, a condenser 3, a refrigerant heat exchanger 22, an expansion device 4, an evaporator 5, an accumulator 6, and again the compressor 2 via refrigerant pipes, whereby a refrigeration cycle is formed. In addition, a detection path 7 is provided so as to branch from a high-pressure side refrigerant pipe connecting the refrigerant heat exchanger 22 to the expansion device 4, to bypass a refrigerant to a low-pressure side refrigerant pipe connecting the accumulator 6 to the compressor 2. A portion branching from the high-pressure side refrigerant pipe connecting the refrigerant heat exchanger 22 to the expansion device 4 to the detection path 7 is referred to as a connection portion 41 a. On the detection path 7, a pressure reducing device 21 and the refrigerant heat exchanger 22 are provided from the high-pressure side toward the low-pressure side, respectively.

[0090] In addition, similarly to Embodiment 1, the refrigeration cycle apparatus 1 a includes a high-pressure sensor 10, a low-pressure sensor 11, a first inlet temperature sensor 12, and a first outlet temperature sensor 13, and also includes a second inlet temperature sensor 23 which detects the temperature of the refrigerant at an inlet side of a high-pressure side path of the refrigerant heat exchanger 22, a third inlet temperature sensor 24 which detects the temperature of the refrigerant at a suction side of the compressor 2, and a second outlet temperature sensor 25 which detects the temperature of the refrigerant at a discharge side of the compressor 2.

[0091] Of the liquid refrigerant having flowed from the later-described high-pressure side path of the refrigerant heat exchanger 22, the pressure reducing device 21 reduces the pressure of the liquid refrigerant branched at the connection portion 41 a to the detection path 7, to turn the liquid refrigerant into a low-pressure two-phase gas-liquid refrigerant.

[0092] The refrigerant heat exchanger 22 has the high-pressure side path which causes the refrigerant to flow from the condenser 3 to the expansion device 4 and a low-pressure side path which causes the refrigerant to flow from the pressure reducing device 21 toward an outlet of the detection path 7, and performs heat exchange between the refrigerant in the high-pressure side path and the refrigerant in the low-pressure side path. For the refrigerant in the low-pressure side path, the refrigerant heat exchanger 22 is regarded as a heating device for heating with the refrigerant in the high-pressure side. On the other hand, for the refrigerant in the high-pressure side, the refrigerant heat exchanger 22 is regarded as a cooler for cooling with the refrigerant in the low-pressure side.

[0093] The controller 31 receives information detected by the high-pressure sensor 10, the low-pressure sensor 11, the first inlet temperature sensor 12, the first outlet temperature sensor 13 the second inlet temperature sensor 23, the third inlet temperature sensor 24, and the second outlet temperature sensor 25, and estimates the composition of the refrigerant of the non-azeotropic refrigerant mixture circulating through the refrigeration cycle on the basis of these information. A process of estimating the composition of the refrigerant by the controller 31 will be described in detail later.

[0094] It should be noted that the second inlet temperature sensor 23, the third inlet temperature sensor 24, and the second outlet temperature sensor 25 correspond to "second inlet temperature detection means," "third inlet temperature detection means," and "second outlet temperature detection means," respectively, in the present invention.

(Refrigerant circulating operation in refrigeration cycle)

[0095] Next, a refrigerant circulating operation in the refrigeration cycle apparatus 1 a according to the embodiment will be described with reference to Fig. 6.

[0096] A high-temperature and high-pressure gas refrigerant compressed and discharged from the compressor 2 flows into the condenser 3. The gas refrigerant having flowed into the condenser 3 is subjected to heat exchange with air sent from a fan or the like, to be condensed into a liquid refrigerant, and flows out of the condenser 3. The liquid refrigerant having flowed out of the condenser 3 flows into the high-pressure side path of the refrigerant heat exchanger 22, and heat is removed therefrom by the refrigerant flowing through the low-pressure side path in the refrigerant heat exchanger 22, so that the liquid refrigerant is cooled. The liquid refrigerant having flowed out of the high-pressure side path of the refrigerant heat exchanger 22 is separated at the connection portion 41 a into a refrigerant flowing toward the expansion device 4 and a refrigerant flowing through the detection path 7.

[0097] The liquid refrigerant flowing toward the expansion device 4 is reduced in pressure by the expansion device 4 into a low-temperature and low-pressure two-phase gas-liquid refrigerant, and flows into the evaporator 5. The two-phase gas-liquid refrigerant having flowed into the evaporator 5 is subjected to heat exchange with air sent from a fan or the like, to be evaporated into a low-temperature and low-pressure refrigerant, and flows out of the evaporator 5. The refrigerant having flowed out of the evaporator 5 flows into the accumulator 6 and is separated into a liquid refrigerant and a gas refrigerant, and the gas refrigerant flows out of the accumulator 6. The gas refrigerant having flowed out of the accumulator 6 joins, at the connection portion 42, the refrigerant having flowed through the detection path 7, and is sucked into the compressor 2 and compressed again.

[0098] Meanwhile, the liquid refrigerant branched at the connection portion 41 a to the detection path 7 is reduced in pressure by the pressure reducing device 21 into a low-temperature and low-pressure two-phase gas-liquid refrigerant, and flows into the low-pressure side path of the refrigerant heat exchanger 22. The two-phase gas-liquid refrigerant having flowed into the low-pressure side path of the refrigerant heat exchanger 22 is heated and evaporated into a low-temperature and low-pressure gas refrigerant by the refrigerant flowing through the high-pressure side path in the refrigerant heat exchanger 22, and flows out of the low-pressure side path. The gas refrigerant having flowed out of the low-pressure side path of the refrigerant heat exchanger 22 joins, at the connection portion 42, the gas refrigerant having flowed out of the accumulator 6, and is sucked into the compressor 2 and compressed again.

[0099] A state of the refrigeration cycle greatly changes depending on a load and an operating state of the refrigeration cycle apparatus 1 a, and design values such as the capacities of the condenser 3 and the evaporator 5, the refrigerant charging amount, and the capacity of the refrigerant heat exchanger 22 are set such that under major operation conditions, the refrigerant state becomes a supercooling (subcooling) state between the condenser 3 and the high-pressure side path of the refrigerant heat exchanger 22, becomes a supercooling state (subcooling) at the connection portion 41 a at the high-pressure side of the detection path 7, and becomes a superheated gas state (superheat) at an outlet portion of the low-pressure side of the detection path 7.

(Operation of estimating composition of circulating refrigerant)

[0100] Fig. 7 is a flowchart of a process of calculating an enthalpy difference Δh between an outlet side and an inlet side of the low-pressure side path of the refrigerant heat exchanger 22 in the refrigeration cycle apparatus 1 a according to Embodiment 2 of the present invention. Hereinafter, an operation of estimating the composition of the refrigerant will be described with reference to Figs. 2 and 7.

[0101] The operation of estimating the composition of the non-azeotropic refrigerant mixture in the refrigeration cycle apparatus 1a according to the embodiment is similar to the flowchart shown in Fig. 2, but the type of information detected by each temperature sensor and each pressure sensor in step S2 and the method of calculating the enthalpy difference Δh in step S7 are different. In the embodiment, the enthalpy difference Δh represents the enthalpy difference between the outlet side and the inlet side of the low-pressure side path of the refrigerant heat exchanger 22.

(S2)

[0102] The controller 31 receives a high-pressure pressure Pd detected by the high-pressure sensor 10, a low-pressure pressure Ps detected by the low-pressure sensor 11, an inlet temperature TI detected by the first inlet temperature sensor 12, an outlet temperature TO detected by the first outlet temperature sensor 13, an high-pressure side inlet temperature TI2 that is the temperature of the refrigerant at the inlet side of the high-pressure side path of the refrigerant heat exchanger 22 which is detected by the second inlet temperature sensor 23, a temperature Ts at the compressor inlet which is detected by the third inlet temperature sensor 24, a temperature Td at the compressor outlet which is detected by the second outlet temperature sensor 25.

(S7)

[0103] The controller 31 calculates the enthalpy difference Δh between the outlet side and the inlet side of the low-pressure side path of the refrigerant heat exchanger 22 by the following procedure of steps S31 to S36.

(S31 )

[0104] The controller 31 calculates a density pi of the refrigerant at the inlet side of the detection path 7 on the basis of the high-pressure pressure Pd, the inlet temperature TI, and an assumed value αtmp with formula (3). Then, the controller 31 proceeds to step S32.

(S32)

[0105] In addition, the controller 31 calculates a pressure difference ΔP of the refrigerant between before and after the pressure reducing device 21 on the basis of the high-pressure pressure Pd and the low-pressure pressure Ps with formula (4). Then, the controller 31 proceeds to step S33.

(S33)

[0106] In addition, the controller 31 calculates a refrigerant flow rate Gdet in the detection path 7 on the basis of a flow rate coefficient k, the density pi, and the pressure difference ΔP with formula (5). Here, the flow rate coefficient k is derived in step S3 of Fig. 2. Then, the controller 31 proceeds to step S34.

(S34)

[0107] In addition, the controller 31 calculates a compressor flow rate Gmain that is a flow rate of the refrigerant flowing through the compressor 2, on the basis of the high-pressure pressure Pd, the low-pressure pressure Ps, the temperature Td at the compressor outlet, the temperature Ts at the compressor inlet, the assumed value αtmp, and a rotation speed N of the compressor 2 with the following formula (9). The rotation speed N is controlled by the controller 31 instructing the compressor 2, and thus is grasped by the controller 31 even without specific detection means. Moreover, a function f in the following formula (9) is a function of the high-pressure pressure Pd, the low-pressure pressure Ps, the temperature Td at the compressor outlet, the temperature Ts at the compressor inlet, the assumed value αtmp, and the rotation speed N, and the unit characteristics of the compressor 2 may be grasped in advance, and tabled and stored in an internal memory or the like within the controller 31.

[0108] [Math. 9]

[0109] It should be noted that when the refrigerant at the suction side of the compressor 2 is in a two-phase gas-liquid state, it is possible to estimate a state at the suction side of the compressor 2 on the basis of the low-pressure pressure Ps and the temperature Ts at the compressor inlet, but temperature change in the two-phase gas-liquid state greatly changes the refrigerant physical properties. Thus, it is possible to estimate a state at the suction side of the compressor 2 with high accuracy on the basis of the characteristics of the compressor 2 and a state at the discharge side of the compressor 2 which is estimated on the basis of the high-pressure pressure Pd and the temperature Td at the compressor outlet.

[0110] In addition, when the refrigerant at the suction side of the compressor 2 is a superheated gas, it is possible to estimate a state at the suction side of the compressor 2 on the basis of the low-pressure pressure Ps and the temperature Ts at the compressor inlet, and thus there is no problem even when the second outlet temperature sensor 25 which detects the temperature Td at the compressor outlet is not provided.

[0111] Then, the controller 31 proceeds to step S35.

(S35)

[0112] In addition, the controller 31 calculates a high-pressure side enthalpy hl2 that is an enthalpy at the inlet side of the high-pressure side path of the refrigerant heat exchanger 22, on the basis of the high-pressure pressure Pd, the high-pressure side inlet temperature TI2, and the assumed value αtmp with the following formula (10). Then, the controller 31 proceeds to step S36.

[0113] [Math. 10]

(S36)

[0114] Then, the controller 31 calculates the enthalpy difference Δh on the basis of the high-pressure side enthalpy hl2, an inlet enthalpy hl, the compressor flow rate Gmain, and the refrigerant flow rate Gdet with the following formula (11) that is based on a relationship formula of a heat exchange amount between the high-pressure side path and the low-pressure side path of the refrigerant heat exchanger 22.

[0115] [Math. 11]

[0116] Then, the controller 31 proceeds to step S8.

(Accuracy of operation of estimating composition of refrigerant in embodiment)

[0117] Even if an error is observed in each detection value of the first inlet temperature sensor 12, the second inlet temperature sensor 23, and the high-pressure sensor 10, since a constant-temperature line in a supercooling state is nearly vertical, an enthalpy error caused with the error is smaller than that in the case where the temperature and the pressure of the refrigerant in a two-phase gas-liquid state are detected.

[0118]  It should be noted that the influence of the detection value of the high-pressure sensor 10 itself on enthalpy is sufficiently smaller than the influence of the detection value of the second inlet temperature sensor 23 itself on enthalpy. Thus, it is possible to estimate the circulation composition α only with the high-pressure side inlet temperature TI2 detected by the second inlet temperature sensor 23, without using the high-pressure pressure Pd detected by the high-pressure sensor 10. Therefore, the arguments in formula (10) are reduced, ensuring the reduction of the processing load on the controller 31 and reduction of the storage capacity of the controller 31.

[0119] Furthermore, even if an error is observed in each detection value of the first outlet temperature sensor 13, the low-pressure sensor 11, the third inlet temperature sensor 24, and the second outlet temperature sensor 25, a constant-temperature line in a superheated gas state is sufficiently inclined as compared to the constant-temperature line in the two-phase gas-liquid refrigerant, and an enthalpy error caused with the error is sufficiently smaller than that in the case where the temperature and the pressure of the refrigerant in the two-phase gas-liquid state are detected.

[0120] Therefore, in the configuration of the refrigeration cycle apparatus 1 a according to the embodiment shown in Fig. 6, it is possible to suppress the influence of the detection errors of each temperature sensor and each pressure sensor on enthalpy, and thus it is possible to improve accuracy of estimating the circulation composition α of the refrigerant.

(Advantageous effects of Embodiment 2)

[0121] By the configuration and operation described above, it is possible to suppress the influence of the detection errors of each temperature sensor and each pressure sensor on enthalpy. Thus, it is possible to improve the accuracy of estimating the circulation composition α of the refrigerant, and further, it is possible to improve the operating efficiency of the refrigeration cycle of the refrigeration cycle apparatus 1 a.

[0122] In addition, since heat is exchanged between the refrigerants in the refrigerant heat exchanger 22, even when the refrigerant is bypassed by the detection path 7 from the high-pressure side to the low-pressure side, a highly efficient operation is made possible without reducing the ability of the refrigeration cycle apparatus 1 a. Reference Signs List

[0123] 1, 1 a refrigeration cycle apparatus 2 compressor 3 condenser 4 expansion device 5 evaporator 6 accumulator 7 detection path 8 pressure reducing device 9 heating device 10 high-pressure sensor 11 low-pressure sensor 12 first inlet temperature sensor 13 first outlet temperature sensor 21 pressure reducing device 22 refrigerant heat exchanger 23 second inlet temperature sensor 24 third inlet temperature sensor 25 second outlet temperature sensor 31 controller 41, 41 a, 42 connection portion 101 refrigeration cycle apparatus 102 detection path 103 temperature sensor 104 controller

Claims

1. A refrigeration cycle apparatus in which a compressor, a condenser, an expansion device, and an evaporator are sequentially connected via refrigerant pipes to form a refrigeration cycle and in which a non-azeotropic refrigerant mixture circulates as a refrigerant circulating through the refrigeration cycle, the refrigeration cycle apparatus comprising:

a detection path configured to bypass the refrigerant from a high-pressure side that is an outlet side of the condenser to a low-pressure side that is a suction side of the compressor and on which a pressure reducing device and a heating device are provided from the high-pressure side toward the low-pressure side; and

a controller configured to control an operation of the refrigeration cycle,

wherein the heating device turns the refrigerant at an outlet side thereof into a superheated gas state, and

wherein the controller

calculates an enthalpy at an inlet side of the pressure reducing device on the detection path,

calculates an enthalpy at the outlet side of the heating device on the detection path,

calculates an enthalpy difference of the refrigerant between the outlet side and an inlet side of the heating device,

calculates an enthalpy at an outlet side of the pressure reducing device on the basis of the enthalpy difference and the enthalpy at the outlet side of the heating device, and

estimates a circulation composition that is a composition of the refrigerant circulating through the refrigeration cycle, on the basis of the calculated enthalpy at the inlet side of the pressure reducing device and the calculated enthalpy at the outlet side of the pressure reducing device.

2. The refrigeration cycle apparatus of claim 1, further comprising:

high-pressure detection means for detecting a high-pressure pressure that is a pressure of the refrigerant at a discharge side of the compressor;

low-pressure detection means for detecting a low-pressure pressure that is a pressure of the refrigerant at the suction side of the compressor;

first inlet temperature detection means for detecting an inlet temperature that is a temperature of the refrigerant at the inlet side of the pressure reducing device, and

first outlet temperature detection means for detecting an outlet temperature that is a temperature of the refrigerant at the outlet side of the heating device,

wherein the controller calculates

an enthalpy at the inlet side of the pressure reducing device on the basis of the high-pressure pressure and the inlet temperature or on the basis of the inlet temperature,

an enthalpy at the outlet side of the heating device on the basis of the low-pressure pressure and the outlet temperature, and

an enthalpy difference of the refrigerant between the outlet side and the inlet side of the heating device on the basis of the high-pressure pressure, the low-pressure pressure, and the inlet temperature.

3. The refrigeration cycle apparatus of claim 2,
wherein the heating device is a heater,
wherein the controller calculates

a density of the refrigerant at the inlet side of the pressure reducing device on the basis of the high-pressure pressure and the inlet temperature, and

a flow rate of the refrigerant in the detection path on the basis of the density of the refrigerant, a pressure difference between the high-pressure pressure and the low-pressure pressure, and a flow rate characteristic of the pressure reducing device, and

the enthalpy difference on the basis of the flow rate of the refrigerant and an output of the heater.

4.  The refrigeration cycle apparatus of claim 1, further comprising:

high-pressure detection means for detecting a high-pressure pressure that is a pressure of the refrigerant at a discharge side of the compressor;

low-pressure detection means for detecting a low-pressure pressure that is a pressure of the refrigerant at the suction side of the compressor;

first inlet temperature detection means for detecting an inlet temperature that is a temperature of the refrigerant at the inlet side of the pressure reducing device; and

first outlet temperature detection means for detecting an outlet temperature that is a temperature of the refrigerant at the outlet side of the heating device,

wherein the heating device

includes a high-pressure side path through which the refrigerant flows from the condenser to the expansion device and a low-pressure side path through which the refrigerant flows from the pressure reducing device to an outlet side of the detection path, and

is a refrigerant heat exchanger that heats the refrigerant in the low-pressure side path with the refrigerant in the high-pressure side path, and turns the refrigerant at an outlet side of the high-pressure side path into a supercooled liquid state,

wherein the refrigeration cycle apparatus further comprises:

second inlet temperature detection means for detecting a high-pressure side inlet temperature that is a temperature of the refrigerant at an inlet side of the high-pressure side path;

third inlet temperature detection means for detecting a compressor inlet temperature that is a temperature of the refrigerant at the suction side of the compressor; and

second outlet temperature detection means for detecting a compressor outlet temperature that is a temperature of the refrigerant at the discharge side of the compressor,

wherein the enthalpy difference is an enthalpy difference of the refrigerant between an outlet side and an inlet side of the low-pressure side path of a cooling energy heat exchanger, and

wherein the controller calculates

an enthalpy at the inlet side of the pressure reducing device on the basis of the high-pressure pressure and the inlet temperature,

an enthalpy at the outlet side of the low-pressure side path of the cooling energy heat exchanger on the basis of the low-pressure pressure and the outlet temperature, and

calculates the enthalpy difference on the basis of the high-pressure pressure, the low-pressure pressure, the inlet temperature, the outlet temperature, the high-pressure side inlet temperature, the compressor inlet temperature, and the compressor outlet temperature.

5. The refrigeration cycle apparatus of claim 4, wherein the controller calculates
a density of the refrigerant at the inlet side of the pressure reducing device on the basis of the high-pressure pressure and the inlet temperature,
a flow rate of the refrigerant in the detection path on the basis of the density of the refrigerant, a pressure difference between the high-pressure pressure and the low-pressure pressure, and a flow rate characteristic of the pressure reducing device,
a compressor flow rate that is a flow rate of the refrigerant flowing through the compressor, on the basis of the high-pressure pressure, the low-pressure pressure, the compressor inlet temperature, the compressor outlet temperature, and a characteristic of the compressor,
a high-pressure side enthalpy that is an enthalpy at the inlet side of the high-pressure side path of the cooling energy heat exchanger on the basis of the high-pressure pressure and the high-pressure side inlet temperature or on the basis of the high-pressure side inlet temperature, and
the enthalpy difference on the basis of the flow rate of the refrigerant, the compressor flow rate, the high-pressure side enthalpy, and the enthalpy at the inlet side of the pressure reducing device.

6. The refrigeration cycle apparatus of claim 3 or 5, wherein the controller
determines an assumed value as the circulation composition of the refrigerant circulating through the refrigeration cycle, and
estimates the assumed value as the circulation composition when the controller determines that a difference between the enthalpy at the inlet side of the pressure reducing device and the enthalpy at the outlet side of the pressure reducing device is equal to or less than a predetermined value.

7. The refrigeration cycle apparatus of claim 6, wherein when the controller determines that the difference between the enthalpy at the inlet side of the pressure reducing device and the enthalpy at the outlet side of the pressure reducing device is greater than the predetermined value, the controller adds or subtracts a predetermined correction value corresponding to the difference and re-determines the assumed value.

8. The refrigeration cycle apparatus of any one of claims 1 to 7, wherein one component of low-boiling-point components of the non-azeotropic refrigerant mixture is R32.

9. The refrigeration cycle apparatus of any one of claims 1 to 7, wherein one component of high-boiling-point components of the non-azeotropic refrigerant mixture is a hydrofluoroolefin-based refrigerant or a flammable refrigerant.

Drawing