Ejector-type refrigeration cycle

Abstract

An ejector-type refrigeration cycle (10) comprises a compressor (11), a gas cooler (12), an ejector (14), a suction-side evaporator (16), and a target high-pressure-side pressure determining unit (20a). The compressor (11) compresses a refrigerant until the refrigerant reaches or exceeds a critical pressure, and discharges the refrigerant. The target high-pressure-side pressure determining unit (20a) determines a target high-pressure-side pressure (PHO), which is a target value for a high-pressure-side pressure (Ph), on the basis of a high-pressure-side temperature (Th), an intermediate-side pressure (Ps), and a low-pressure-side pressure (Tefin). In the ejector-type refrigeration cycle (10), the high-pressure-side pressure (Ph) is adjusted to approach the target high-pressure-side pressure (PHO).

Description

Ejector-type refrigeration cycle Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2024-203400 filed on November 21, 2024, the contents of which are incorporated herein by reference.

[0002] This disclosure relates to an ejector-type refrigeration cycle in which the pressure of the high-pressure refrigerant is equal to or higher than the critical pressure of the refrigerant.

[0003] Conventionally, Patent Document 1 discloses a so-called transcritical refrigeration cycle in which the pressure of the high-pressure refrigerant is equal to or higher than the critical pressure of the refrigerant. Further, Patent Document 1 describes that by bringing the high-pressure side pressure of the refrigerant at the outlet side of the radiator closer to the target high-pressure side pressure determined based on the high-pressure side temperature of the refrigerant at the outlet side of the radiator, the coefficient of performance (COP) of the transcritical refrigeration cycle approaches a maximum value.

[0004] Also, Patent Document 2 discloses an ejector-type refrigeration cycle including an ejector. In this type of ejector-type refrigeration cycle, the suction pressure of the suction refrigerant sucked into the compressor can be increased by the pressure boosting action of the ejector. Thereby, in the ejector-type refrigeration cycle, the power consumption of the compressor can be reduced, and the improvement of the COP can be aimed at more than that of a normal refrigeration cycle.

[0005] Japanese Patent No. 2931668 Japanese Patent No. 3322263

[0006] Therefore, as a means for further improving the COP of an ejector-type refrigeration cycle in which the pressure of the high-pressure refrigerant is equal to or higher than the critical pressure of the refrigerant, similar to Patent Document 1, it is conceivable to bring the high-pressure side pressure closer to the target high-pressure side pressure determined based on the high-pressure side temperature. However, in an ejector-type refrigeration cycle, even if the high-pressure side pressure is brought closer to the target high-pressure side pressure determined only based on the high-pressure side temperature, there is a possibility that the COP cannot be sufficiently improved.

[0007] The reason for this is that in an ejector-type refrigeration cycle, even if the high-pressure side pressure is brought close to the target high-pressure side pressure determined solely based on the high-pressure side temperature, the ejector may not exhibit adequate pressure boosting capabilities.

[0008] The present disclosure aims to provide an ejector-type refrigeration cycle in which the pressure of the high-pressure side refrigerant is equal to or greater than the critical pressure of the refrigerant, and which is capable of sufficiently improving the COP.

[0009] An ejector-type refrigeration cycle according to one aspect of the present disclosure comprises a compression unit, a heat dissipation unit, a suction-side evaporation unit, an ejector, and a target high-pressure-side pressure determination unit.

[0010] The compression section compresses the refrigerant to a critical pressure or higher and then discharges it. The heat dissipation section dissipates heat from the refrigerant discharged from the compression section. The suction-side evaporation section evaporates the refrigerant.

[0011] The ejector has a nozzle section, a suction port, and a pressurizing section. The nozzle section depressurizes and ejects the refrigerant that has flowed out from the heat dissipation section. The suction port draws in the refrigerant that has flowed out from the suction-side evaporation section due to the action of the refrigerant injected from the nozzle section. The pressurizing section increases the pressure of the refrigerant mixture, which is the injected refrigerant and the refrigerant drawn in from the suction port.

[0012] The target high-pressure side pressure determination unit determines the target high-pressure side pressure based on the high-pressure side temperature, intermediate side pressure, and low-pressure side pressure. The high-pressure side pressure is then adjusted to approach the target high-pressure side pressure.

[0013] The high-pressure side temperature is defined as a physical quantity correlated with the temperature of the refrigerant at the outlet side of the heat dissipation section. The high-pressure side pressure is defined as a physical quantity correlated with the pressure of the refrigerant at the outlet side of the heat exchanger. The intermediate side pressure is defined as a physical quantity correlated with the pressure of the refrigerant at the outlet side of the booster section. The low-pressure side pressure is defined as a physical quantity correlated with the pressure of the refrigerant at the suction port.

[0014] According to this, the target high-pressure side pressure determination unit determines the target high-pressure side pressure based not only on the high-pressure side temperature, but also on the intermediate side pressure and the low-pressure side pressure. Therefore, the target high-pressure side pressure determination unit can determine the target high-pressure side pressure so that the ejector can exert an appropriate pressure boosting capacity. As a result, the COP of the ejector-type refrigeration cycle, where the pressure of the high-pressure side refrigerant is equal to or greater than the critical pressure of the refrigerant, can be sufficiently improved.

[0015] The above-mentioned objectives and other objectives, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. A schematic overall configuration diagram of the ejector-type refrigeration cycle of the first embodiment. A Mollier diagram showing the change in the state of the refrigerant in the ejector-type refrigeration cycle of the first embodiment. A graph showing the relationship between the COP ratio, high-pressure side pressure, and suction pressure in the ejector-type refrigeration cycle of the first embodiment. A graph showing the relationship between the high-pressure side pressure, high-pressure side temperature, and pressure increase amount at which the COP of the ejector-type refrigeration cycle of the first embodiment is maximized. A graph showing the relationship between the high-pressure side pressure, high-pressure side temperature, and pressure increase ratio at which the COP of the ejector-type refrigeration cycle of the first embodiment is maximized. A schematic overall configuration diagram showing the flow of the refrigerant in the normal mode of the ejector-type refrigeration cycle of the second embodiment. A schematic overall configuration diagram showing the flow of the refrigerant in the low-load mode of the ejector-type refrigeration cycle of the second embodiment. A schematic overall configuration diagram of the ejector-type refrigeration cycle of the third embodiment. A Mollier diagram showing the change in the state of the refrigerant in the ejector-type refrigeration cycle of the third embodiment. This graph shows the relationship between the high-pressure side pressure, high-pressure side temperature, and flow rate ratio at which the COP of the ejector-type refrigeration cycle of the third embodiment is maximized.

[0016] Several embodiments for implementing this disclosure are described below with reference to the drawings. In each embodiment, parts corresponding to matters described in a prior embodiment are denoted by the same reference numerals, and redundant descriptions may be omitted. If only a part of the configuration is described in each embodiment, other parts of the configuration can be applied to other embodiments described in advance. Not only are combinations of parts that are explicitly shown to be combinable in each embodiment possible, but embodiments can also be partially combined even if not explicitly shown, as long as there are no particular problems with the combination.

[0017] (First Embodiment) A first embodiment of the ejector-type refrigeration cycle according to the present disclosure will be described with reference to Figures 1 to 3. In this embodiment, the ejector-type refrigeration cycle 10 shown in the overall configuration diagram of Figure 1 is applied to a vehicle air conditioning system 1. The vehicle air conditioning system 1 provides air conditioning to the vehicle interior, which is the space to be air-conditioned. The ejector-type refrigeration cycle 10 cools the air that is blown into the vehicle interior in the vehicle air conditioning system 1.

[0018] In the ejector-type refrigeration cycle 10, carbon dioxide (i.e., R744) is used as the refrigerant. The ejector-type refrigeration cycle 10 constitutes a supercritical refrigeration cycle in which the pressure of the high-pressure refrigerant from the discharge port of the compressor 11, which is the compression section, to the inlet of the high-pressure side expansion valve 13a, which is the pressure reduction section, is equal to or greater than the critical pressure of the refrigerant.

[0019] The refrigerant in the ejector-type refrigeration cycle 10 is mixed with refrigeration oil for lubricating the compressor 11. The refrigeration oil can be an oil containing PAG (i.e., polyalkylene glycol) or POE (i.e., polyol ester) which are compatible with the liquid-phase refrigerant. A portion of the refrigeration oil circulates in the ejector-type refrigeration cycle 10 together with the refrigerant.

[0020] The compressor 11 is a compression unit in the ejector-type refrigeration cycle 10 that draws in refrigerant, compresses it to a critical pressure or higher, and then discharges it. The compressor 11 is an electric compressor that rotates a fixed-capacity compression mechanism with a fixed discharge capacity using an electric motor. The rotational speed (i.e., refrigerant discharge capacity) of the compressor 11 is controlled by a control signal output from the control device 20, which will be described later.

[0021] The refrigerant inlet side of the gas cooler 12 is connected to the discharge port of the compressor 11. The gas cooler 12 is a heat exchanger that exchanges heat between the discharged refrigerant discharged from the compressor 11 and the outside air blown in by the cooling fan 12a. The gas cooler 12 is also a heat dissipation unit that releases the heat contained in the high-pressure refrigerant to the outside air.

[0022] The inlet side of the high-pressure side expansion valve 13a is connected to the refrigerant outlet of the gas cooler 12. The high-pressure side expansion valve 13a is a pressure reducing unit that reduces the pressure of the refrigerant flowing out of the gas cooler 12. The high-pressure side expansion valve 13a is a nozzle-side flow rate adjustment unit that adjusts the refrigerant flow rate (in this embodiment, the refrigerant flow rate is the mass flow rate) flowing into the nozzle portion 14a of the ejector 14. The high-pressure side expansion valve 13a can adjust the pressure of the high-pressure side refrigerant by changing the throttle opening.

[0023] The high-pressure side expansion valve 13a is an electrically operated variable throttling mechanism having a valve body that changes the throttling opening and an electric actuator (specifically, a stepping motor or a brushless DC motor) as a drive unit that displaces the valve body. The operation of the high-pressure side expansion valve 13a is controlled by a control signal output from the control device 20.

[0024] The outlet of the high-pressure side expansion valve 13a is connected to the inlet side of the nozzle portion 14a of the ejector 14. The ejector 14 depressurizes the refrigerant that has flowed out of the high-pressure side expansion valve 13a. The ejector 14 is a refrigerant transport unit that sucks in and transports the refrigerant that has flowed out of the suction side evaporator 16. Furthermore, the ejector 14 is a refrigerant pressurization unit that increases the pressure of the refrigerant that has flowed into the interior.

[0025] The ejector 14 has a nozzle portion 14a and a body portion 14b. The nozzle portion 14a is formed of a substantially cylindrical metal member (made of stainless steel alloy in this embodiment) that tapers in the direction of refrigerant flow. The nozzle portion 14a reduces the pressure of the refrigerant in an isentropically controlled manner in a refrigerant passage formed inside, accelerates it to supersonic speed, and then ejects it. A so-called Laval nozzle or a tapered nozzle can be used as the nozzle portion 14a.

[0026] The body portion 14b is formed from a substantially cylindrical member made of metal (in this embodiment, an aluminum alloy). The body portion 14b is a fixing member that supports and fixes the nozzle portion 14a, and also forms the outer shell of the ejector 14. Specifically, the nozzle portion 14a is fixed by press-fitting so that it is housed inside one end of the body portion 14b in the longitudinal direction. The body portion 14b may also be made of resin.

[0027] Viewed from the outer periphery of the body portion 14b, a suction port 14c is formed in the portion corresponding to the outer periphery of the nozzle portion 14a, penetrating from the inside to the outside and communicating with the refrigerant injection port of the nozzle portion 14a. The suction port 14c is a through-hole that draws the refrigerant that has flowed out of the suction-side evaporator 16 into the interior of the ejector 14 due to the suction action of the refrigerant injected from the nozzle portion 14a.

[0028] A suction passage and a diffuser section 14d are formed inside the body section 14b. The suction passage is a refrigerant passage that guides the refrigerant drawn in from the suction port 14c to the refrigerant injection port side of the nozzle section 14a. The diffuser section 14d is a pressurizing section that increases the pressure of the refrigerant mixture of the injected refrigerant and the drawn refrigerant.

[0029] More specifically, the diffuser section 14d is a refrigerant passage arranged to be continuous with the outlet of the suction passage. The diffuser section 14d is formed in a frustoconical shape, with the passage cross-sectional area expanding toward the downstream side of the refrigerant flow. In the diffuser section 14d, the kinetic energy of the mixed refrigerant is converted into pressure energy by the action of the shock wave generated by the injected refrigerant and the expansion of the passage cross-sectional area.

[0030] The outlet of the diffuser section 14d is connected to the inlet side of the accumulator 15. The accumulator 15 is a low-pressure gas-liquid separation section that separates the gas-liquid phase of the refrigerant flowing out from the ejector 14. The accumulator 15 is a liquid storage section that stores a portion of the separated liquid-phase refrigerant as excess refrigerant in the cycle. In a supercritical refrigeration cycle using carbon dioxide as a refrigerant, the refrigerant pressure in the cycle tends to become high. For this reason, it is desirable that the liquid storage section be arranged to store low-pressure refrigerant, such as the intake refrigerant.

[0031] The liquid phase refrigerant outlet, which primarily discharges liquid phase refrigerant from the accumulator 15, is connected to the inlet side of the low-pressure side expansion valve 13b. The gas phase refrigerant outlet, which discharges gas phase refrigerant from the accumulator 15, is connected to the suction port side of the compressor 11.

[0032] The low-pressure side expansion valve 13b reduces the pressure of the refrigerant that has flowed out from the liquid phase refrigerant outlet of the accumulator 15. The low-pressure side expansion valve 13b is an evaporator-side flow rate adjustment unit that adjusts the flow rate of refrigerant flowing into the suction side evaporator 16. The basic configuration of the low-pressure side expansion valve 13b is the same as that of the high-pressure side expansion valve 13a.

[0033] The suction-side evaporator 16 is a heat exchange unit that exchanges heat between the low-pressure refrigerant, which has been depressurized by the low-pressure-side expansion valve 13b, and the air blown into the vehicle interior from the interior blower 16a. The suction-side evaporator 16 is a suction-side evaporation unit that cools the air by evaporating the low-pressure refrigerant and exerting an endothermic effect.

[0034] The indoor blower 16a is an electric blower whose rotational speed (i.e., blowing capacity) is controlled by a control voltage output from the control device 20. The refrigerant outlet of the suction-side evaporator 16 is connected to the suction port 14c side of the ejector 14.

[0035] Next, the electrical control unit of the ejector-type refrigeration cycle 10 will be described. The control unit 20 consists of a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits. Based on the air conditioning control program stored in the ROM, the control unit 20 performs various calculations and processes and controls the operation of various controlled devices 11, 12a, 13a, 13b, 16a, etc. connected to the output side.

[0036] Multiple sensors for air conditioning control, such as an internal temperature sensor, an external temperature sensor, a solar radiation sensor, a discharge temperature sensor 21a, a gas cooler outlet refrigerant sensor 21b, an intake pressure sensor 21c, an intake refrigerant sensor 21d, and an evaporator temperature sensor 21f, are connected to the input side of the control device 20. Detection signals from these sensors are input to the control device 20.

[0037] More specifically, the interior temperature sensor (not shown) is an interior temperature detection unit that detects the temperature inside the vehicle (i.e., the interior temperature) Tr. The exterior temperature sensor (not shown) is an exterior temperature detection unit that detects the temperature outside the vehicle (i.e., the exterior temperature) Tam. The solar radiation sensor (not shown) is a solar radiation detection unit that detects the amount of solar radiation As inside the vehicle.

[0038] The discharge temperature sensor 21a is a discharge pressure detection unit that detects the discharge temperature Td, which is the temperature of the discharged refrigerant discharged from the compressor 11. The gas cooler outlet refrigerant sensor 21b is a heat dissipation outlet refrigerant detection unit that detects the high-pressure side pressure Ph, which is the pressure of the refrigerant on the outlet side of the gas cooler 12, and the high-pressure side temperature Th, which is the temperature of the refrigerant on the outlet side of the gas cooler 12. The suction pressure sensor 21c is an suction pressure detection unit that detects the suction pressure Ps, which is the pressure of the suction refrigerant drawn into the compressor 11.

[0039] The suction refrigerant sensor 21d is a suction temperature detection unit that detects the suction-side pressure Psuc, which is the pressure of the refrigerant on the suction port side being drawn into the suction port 14c of the ejector 14, and the suction-side temperature Tsuc, which is the temperature of the refrigerant on the suction port side. The evaporator temperature sensor 21f is an evaporator temperature detection unit that detects the evaporator temperature Tefin, which is the temperature of the suction-side evaporator 16. Specifically, the evaporator temperature sensor 21f in this embodiment detects the heat exchange fin temperature of the suction-side evaporator 16.

[0040] Furthermore, an operation panel (not shown), located near the instrument panel at the front of the vehicle interior, is connected to the input side of the control device 20 by wire or wireless connection. The control device 20 receives operation signals from various operation switches provided on the operation panel. The various operation switches provided on the operation panel include an air conditioning activation switch for requesting the activation of the vehicle interior air conditioning, and a vehicle interior temperature setting switch for setting the vehicle interior temperature.

[0041] The control device 20 is formed by integrating control units that control the operations of various controlled devices connected to the output side. Among the control device 20, the configurations (specifically, hardware and software) that control the operations of the various controlled devices constitute the control units of the various controlled devices. For example, the configuration that controls the refrigerant discharge capacity of the compressor 11 constitutes the discharge capacity control unit. Also, the configuration that determines the target high-pressure-side pressure PHO, which is the target value of the high-pressure-side pressure Ph, constitutes the target high-pressure-side pressure determination unit 20a.

[0042] In the overall configuration diagrams such as FIG. 1, power lines or signal lines connecting the control device 20 and various controlled devices are illustrated, but for the sake of clarity of illustration, the illustration of the signal lines connecting the control device 20 and various sensors is omitted.

[0043] Next, the operation of the ejector type refrigeration cycle 10 of the present embodiment in the above configuration will be described. When the air conditioning operation switch on the operation panel is turned on (ON), the control device 20 controls the operations of various controlled devices.

[0044] Specifically, the control device 20 controls the refrigerant discharge capacity of the compressor 11 so that the evaporator temperature Tefin detected by the evaporator temperature sensor 21f approaches the target evaporation temperature TEO. The target evaporation temperature TEO is determined by referring to a control map stored in the control device 20 in advance based on the target blow-out temperature TAO. In the control map, it is determined to increase the target evaporation temperature TEO as the target blow-out temperature TAO increases.

[0045] The target blow-out temperature TAO is the target temperature of the air blown into the vehicle interior. In the control device 20, every predetermined control cycle, the interior air temperature Tr detected by the interior air temperature sensor, the outside air temperature Tam detected by the outside air temperature sensor, the solar radiation amount As detected by the solar radiation sensor, and the set temperature Tset set by the occupant using the vehicle interior temperature setting switch are read. Then, the target blow-out temperature TAO is calculated using the read detection signals and operation signals.

[0046] Further, the control device 20 controls the throttle opening degree of the high-pressure side expansion valve 13a so that the high-pressure side pressure Ph detected by the gas cooler outlet refrigerant sensor 21b approaches the target high-pressure side pressure PHO determined by the target high-pressure side pressure determination unit 20a.

[0047] In the target high-pressure side pressure determination unit 20a, every predetermined control cycle, the high-pressure side temperature Th detected by the gas cooler outlet refrigerant sensor 21b, the suction pressure Ps detected by the suction pressure sensor 21c, and the evaporator temperature Tefin detected by the evaporator temperature sensor 21f are read. Then, based on the read detection values, the target high-pressure side pressure PHO is determined by referring to a control map stored in advance.

[0048] In the control map, the target high-pressure side pressure PHO is determined so that the COP of the ejector type refrigeration cycle 10 approaches the maximum value. Here, in a normal transcritical refrigeration cycle without an ejector, the target high-pressure side pressure determined so that the COP approaches the maximum value based only on the high-pressure side temperature Th is defined as the normal target high-pressure side pressure PHO n.

[0049] In the control map of the present embodiment, the target high-pressure side pressure PHO is determined to be a value lower than the normal target high-pressure side pressure PHO n. Further, as the pressure boost amount ΔPej of the ejector 14 increases, the target high-pressure side pressure PHO is determined to decrease. The pressure boost amount ΔPej of the ejector 14 is the middle-low pressure difference obtained by subtracting the low-pressure side pressure from the intermediate side pressure.

[0050] The intermediate side pressure is a physical quantity correlated with the pressure of the refrigerant at the outlet side of the diffuser portion 14d of the ejector 14. In the present embodiment, the suction pressure Ps is used as the intermediate side pressure. The low-pressure side pressure is a physical quantity correlated with the pressure of the refrigerant at the suction port 14c of the ejector 14. In the present embodiment, the saturation pressure of the refrigerant at the evaporator temperature Tefin is used as the low-pressure side pressure.

[0051] Furthermore, the control device 20 controls the throttle opening of the low-pressure side expansion valve 13b so that the superheating degree of the refrigerant at the suction port 14c of the ejector 14 approaches the reference superheating degree (0°C in this embodiment). The control device 20 detects the superheating degree of the refrigerant at the suction port 14c of the ejector 14 from the suction side pressure Psuc and suction side temperature Tsuc detected by the suction refrigerant sensor 21d. The control device 20 also appropriately controls the operation of other controlled devices.

[0052] Therefore, in the ejector-type refrigeration cycle 10, as shown in the Mollier diagram in Figure 2, the high-pressure refrigerant (point a2 in Figure 2), which has been pressurized above the critical pressure by the compressor 11, flows into the gas cooler 12. The high-pressure refrigerant that flows into the gas cooler 12 exchanges heat with the outside air blown in by the cooling fan 12a, thereby lowering the enthalpy (from point a2 to point b2 in Figure 2).

[0053] The refrigerant flowing out of the gas cooler 12 flows into the high-pressure side expansion valve 13a and is depressurized (from point b2 to point c2 in Figure 2). As a result, the high-pressure side pressure Ph approaches the target high-pressure side pressure PHO. The refrigerant flowing out of the high-pressure side expansion valve 13a flows into the nozzle section 14a of the ejector 14. The refrigerant flowing into the nozzle section 14a is isentropically depressurized and injected (from point c2 to point d2 in Figure 2).

[0054] In the ejector 14, the refrigerant injected from the nozzle 14a causes the refrigerant that has flowed out of the suction-side evaporator 16 to be drawn in through the suction port 14c. As a result, the refrigerant, which has been depressurized by the low-pressure-side expansion valve 13b, flows into the suction-side evaporator 16.

[0055] The injected refrigerant and the suctioned refrigerant drawn in through the suction port 14c flow into the diffuser section 14d (from point d2 to point e2, and from point j2 to point e2 in Figure 2). In the diffuser section 14d, the kinetic energy of the mixed refrigerant (injected and suctioned) is converted into pressure energy due to the action of the shock wave generated by the injected refrigerant and the expansion of the passage cross-sectional area. As a result, the pressure of the mixed refrigerant increases (from point e2 to point f2 in Figure 2).

[0056] The refrigerant flowing out from the diffuser section 14d flows into the accumulator 15 and undergoes gas-liquid separation (from point f2 to point g2, and from point f2 to point h2 in Figure 2). The refrigerant flowing out from the liquid phase refrigerant outlet of the accumulator 15 (point h2 in Figure 2) flows into the low-pressure side expansion valve 13b and is depressurized (from point h2 to point i2 in Figure 2). As a result, the superheat level of the refrigerant at the suction port 14c of the ejector 14 approaches the reference superheat level (0°C in this embodiment).

[0057] The refrigerant, depressurized by the low-pressure expansion valve 13b, flows into the suction-side evaporator 16. The refrigerant flowing into the suction-side evaporator 16 absorbs heat from the air blown by the interior blower 16a and evaporates (from point i2 to point j2 in Figure 2). This cools the air blown into the vehicle interior. The refrigerant that flows out from the gas phase refrigerant outlet of the accumulator 15 is drawn into the compressor 11 and compressed again until it reaches a pressure above critical pressure (from point g2 to point a2 in Figure 2).

[0058] The ejector-type refrigeration cycle 10 of this embodiment operates as described above and can cool the air blown into the vehicle cabin.

[0059] Furthermore, in the ejector-type refrigeration cycle 10, the pressure-boosting action of the ejector 14 allows the suction pressure Ps to be raised above the refrigerant evaporation pressure in the suction-side evaporator 16. Therefore, the ejector-type refrigeration cycle 10 can reduce the power consumption of the compressor 11 and improve the COP compared to a normal refrigeration cycle where the suction pressure Ps and the refrigerant evaporation pressure in the evaporation section are equal.

[0060] Furthermore, in the ejector-type refrigeration cycle 10 of this embodiment, the target high-pressure side pressure determination unit 20a determines the target high-pressure side pressure PHO based not only on the high-pressure side temperature Th, but also on the suction pressure Ps and the evaporator temperature Tefin. This makes it possible to determine the target high-pressure side pressure PHO in a way that sufficiently improves the COP of the ejector-type refrigeration cycle 10.

[0061] More specifically, the inventors investigated the relationship between the suction pressure Ps and the high-pressure side pressure Ph at which the COP is actually maximum, under the condition that the refrigerant evaporation pressure in the suction-side evaporator 16 is kept constant in an ejector-type refrigeration cycle 10. As a result, as shown in Figure 3, it was confirmed that the high-pressure side pressure Ph at which the COP is maximum decreases as the suction pressure Ps increases.

[0062] Therefore, in the ejector-type refrigeration cycle 10, even if the high-pressure side pressure Ph is brought close to the normal target high-pressure side pressure PHOn, which is determined solely based on the high-pressure side temperature Th, it may not be possible to sufficiently improve the COP. Here, the COP ratio on the vertical axis of Figure 3 is the ratio to the maximum COP that the cycle under each condition can achieve. Also, the suction pressure Ps1 in Figure 3 is lower than the suction pressure Ps2.

[0063] Therefore, the inventors investigated the parameters necessary to bring the COP of the ejector-type refrigeration cycle 10 closer to its maximum value. First, the COP of the ejector-type refrigeration cycle 10 can be defined by the following formula F1. Also, the ejector efficiency ηeje, which is the energy conversion efficiency of the ejector 14, can be defined by the following formula F2.

[0064]

[0065]

[0066] G is the discharge flow rate of the discharged refrigerant discharged from the compressor 11. Ge is the flow rate of the refrigerant flowing into the suction-side evaporator 16. Δleva is the difference in specific enthalpy of the suction-side evaporator, obtained by subtracting the specific enthalpy of the inlet-side refrigerant from the specific enthalpy of the outlet-side refrigerant, as shown in Figure 2.

[0067] Δlnoz is the nozzle specific enthalpy difference obtained by subtracting the specific enthalpy of the refrigerant at the injection port from the specific enthalpy of the refrigerant at the inlet of the nozzle portion 14a of the ejector 14. Δlc is the compressor specific enthalpy difference obtained by subtracting the specific enthalpy of the suction refrigerant from the specific enthalpy of the discharge refrigerant. Δldif is the booster specific enthalpy difference obtained by subtracting the specific enthalpy of the inlet refrigerant from the specific enthalpy of the inlet refrigerant of the diffuser portion 14d.

[0068] As is clear from equation F1, in order to improve the COP of the ejector-type refrigeration cycle 10, means of reducing the compressor specific enthalpy difference Δlc and increasing the suction-side evaporator flow rate Ge can be considered. And in order to reduce the compressor specific enthalpy difference Δlc, means of increasing the booster specific enthalpy difference Δldif can be considered.

[0069] However, as can be understood from equation F2, when the ejector 14 is exhibiting a predetermined ejector efficiency ηeje, increasing the relative enthalpy difference Δldif of the booster section will decrease the flow rate Ge of the suction-side evaporator. Similarly, increasing the flow rate Ge of the suction-side evaporator will decrease the relative enthalpy difference Δldif of the booster section.

[0070] Therefore, in order to reliably and sufficiently improve the COP of the ejector-type refrigeration cycle 10, it is necessary to adjust the relative enthalpy difference Δldif of the booster section to an appropriate value. In other words, it is necessary to ensure that the ejector 14 exhibits appropriate boosting capacity.

[0071] Therefore, the inventors focused on the pressure boost amount ΔPej of the ejector 14 as a parameter correlated with the pressure boosting capacity of the ejector 14. They then investigated the relationship between the pressure boost amount ΔPej and the high-pressure side pressure Ph at which COP reaches its maximum value. As a result, as shown in Figure 4, it was confirmed that, regardless of the high-pressure side temperature Th, the high-pressure side pressure Ph at which COP reaches its maximum value decreases as the pressure boost amount ΔPej increases.

[0072] Here, Figure 4 shows the results of an investigation under the condition that the refrigerant evaporation pressure in the suction-side evaporator 16 is kept constant. Also, the pressure increase ΔPej1 in Figure 4 is smaller than the pressure increase ΔPej2.

[0073] Based on the above, the target high-pressure side pressure determination unit 20a of this embodiment determines that the target high-pressure side pressure PHO is lowered in a range lower than the normal target high-pressure side pressure PHOn as the pressure increase amount ΔPej increases.

[0074] According to this, the target high-pressure side pressure PHO can be determined so that the ejector 14 exhibits appropriate pressure boosting capability. In other words, the target high-pressure side pressure PHO can be determined so as to sufficiently improve the COP of the ejector-type refrigeration cycle 10. As a result, the COP of the ejector-type refrigeration cycle 10 can be sufficiently improved.

[0075] Furthermore, the ejector-type refrigeration cycle 10 of this embodiment is equipped with a high-pressure side expansion valve 13a as a pressure reduction section. Therefore, the high-pressure side pressure Ph can be brought closer to the target high-pressure side pressure PHO without requiring a complex cycle configuration.

[0076] In this embodiment, an example was described in which the target high-pressure side pressure determination unit 20a determines to decrease the target high-pressure side pressure PHO as the pressure increase amount ΔPej of the ejector 14 increases. However, the method of determining the target high-pressure side pressure PHO is not limited to this. A modified example of the method of determining the target high-pressure side pressure PHO will be described below.

[0077] For example, the boost ratio Pp of the ejector 14, defined by the following formula F3, can be used as a parameter correlated with the boosting effect of the ejector 14.

[0078]

[0079] ΔPh is the high-low pressure difference obtained by subtracting the low-pressure side pressure from the high-pressure side pressure, as shown in Figure 2. In other words, the boost ratio Pp is the ratio of the boost amount ΔPej to the high-low pressure difference ΔPh. The boost ratio Pp correlates with the ejector efficiency ηeje and is a parameter that can be used as a surrogate indicator of the ejector efficiency ηeje.

[0080] According to the inventors' tests and studies, as shown in Figure 5, it was confirmed that, regardless of the high-pressure side temperature Th, the high-pressure side pressure Ph at which COP is maximized decreases as the boost ratio Pp increases. Furthermore, it was confirmed that when the boost ratio Pp reaches the reference boost ratio KPp, the high-pressure side pressure Ph at which COP is maximized becomes the lowest value. The reference boost ratio KPp may be the theoretical maximum boost ratio determined from the dimensional specifications of the ejector 14.

[0081] Here, Figure 5 shows the results of an investigation under the condition that the refrigerant evaporation pressure in the suction-side evaporator 16 is kept constant. Also, the pressure boost ratio Pp1 in Figure 5 is smaller than the pressure boost ratio Pp2.

[0082] Therefore, the same effect can be obtained even if the target high-pressure side pressure determination unit 20a determines the target high-pressure side pressure PHO to decrease as the boost ratio Pp increases, within a range lower than the normal target high-pressure side pressure PHOn. Furthermore, the same effect can be obtained even if the target high-pressure side pressure PHO is determined so that the boost ratio Pp approaches the reference boost ratio KPp. In other words, the COP of the ejector-type refrigeration cycle 10 can be sufficiently improved.

[0083] (Second Embodiment) In this embodiment, an example of applying the ejector-type refrigeration cycle 10a according to the present disclosure to a vehicle air conditioning system will be described. In the ejector-type refrigeration cycle 10a, as shown in the overall configuration diagrams of Figures 6 and 7, an electric three-way valve 17, a bypass passage 18a, a merging section 19a, etc. are added to the ejector-type refrigeration cycle 10 described in the first embodiment.

[0084] The electric three-way valve 17 is a refrigerant circuit switching unit that switches between a refrigerant circuit connecting the outlet side of the high-pressure side expansion valve 13a and the inlet side of the nozzle portion 14a of the ejector 14, and a refrigerant circuit connecting the outlet side of the high-pressure side expansion valve 13a and the inlet side of the bypass passage 18a. The operation of the electric three-way valve 17 is controlled by a control voltage output from the control device 20.

[0085] The bypass passage 18a is a refrigerant passage that directs the refrigerant flowing out from the electric three-way valve 17 to the refrigerant inlet side of the suction-side evaporator 16, bypassing the nozzle portion 14a of the ejector 14. More specifically, the outlet of the bypass passage 18a is connected to one of the inlets of the confluence portion 19a, which is located in the refrigerant flow path from the outlet of the low-pressure-side expansion valve 13b to the refrigerant inlet of the suction-side evaporator 16.

[0086] The junction 19a is a three-way joint having three interconnected inlet and outlet connections. The outlet side of the low-pressure side expansion valve 13b is connected to another inlet of the junction 19a. The refrigerant inlet side of the suction side evaporator 16 is connected to the outlet of the junction 19a.

[0087] Furthermore, the low-pressure side expansion valve 13b in this embodiment has a fully closing function that closes the refrigerant passage by closing the throttle opening to a fully closed state. By exhibiting the fully closing function, the low-pressure side expansion valve 13b can switch the refrigerant circuit. Therefore, the low-pressure side expansion valve 13b also functions as a refrigerant circuit switching unit. The other configurations of the ejector-type refrigeration cycle 10a are the same as those of the ejector-type refrigeration cycle 10 described in the first embodiment.

[0088] Next, the operation of the ejector-type refrigeration cycle 10a of this embodiment in the above configuration will be described. When the air conditioning operation switch on the control panel is turned ON, the control device 20 controls the operation of various controlled devices. Furthermore, the control device 20 switches between normal mode and low-load mode according to the heat load of the ejector-type refrigeration cycle 10a. Details of each operating mode will be described below.

[0089] (a) Normal mode The normal mode is an operating mode selected when the heat load of the ejector-type refrigeration cycle 10a is equal to or greater than a predetermined reference load. In this embodiment, specifically, the normal mode is selected when the rotational speed of the compressor 11 is equal to or greater than a predetermined reference rotational speed.

[0090] In normal mode, the control device 20 controls the operation of the electric three-way valve 17 to connect the outlet side of the high-pressure expansion valve 13a to the inlet side of the nozzle portion 14a of the ejector 14. The operation of the other components is the same as in the first embodiment.

[0091] Therefore, in the normal mode ejector-type refrigeration cycle 10a, the refrigerant discharged from the compressor 11 circulates in the following order as shown by the thick solid line in the overall configuration diagram of Figure 6: gas cooler 12, high-pressure side expansion valve 13a, electric three-way valve 17, ejector 14, accumulator 15, and the suction port of the compressor 11. At the same time, the refrigerant that flows out from the liquid phase refrigerant outlet of the accumulator 15 flows to the low-pressure side expansion valve 13b, suction side evaporator 16, and the suction port 14c of the ejector 14.

[0092] In other words, in the ejector-type refrigeration cycle 10a in normal mode, the system switches to a first circuit that allows the refrigerant, which has been depressurized by the high-pressure side expansion valve 13a, to flow into the nozzle portion 14a of the ejector 14. In the ejector-type refrigeration cycle 10a in normal mode, the refrigerant flows in exactly the same order as in the first embodiment.

[0093] Therefore, in normal mode, the ejector-type refrigeration cycle 10a operates similarly to the ejector-type refrigeration cycle 10 of the first embodiment, and can cool the air blown into the vehicle cabin. Furthermore, similar to the first embodiment, the COP of the ejector-type refrigeration cycle 10a can be sufficiently improved.

[0094] (b) Low-load mode The low-load mode is an operating mode selected when the heat load of the ejector-type refrigeration cycle 10a is lower than a predetermined reference load. In this embodiment, specifically, the low-load mode is selected when the rotational speed of the compressor 11 is lower than the reference rotational speed.

[0095] In low-load mode, the control device 20 controls the operation of the electric three-way valve 17 to connect the outlet side of the high-pressure side expansion valve 13a to the inlet side of the bypass passage 18a. The control device 20 also closes the low-pressure side expansion valve 13b completely.

[0096] Therefore, in the ejector-type refrigeration cycle 10a in low-load mode, the refrigerant discharged from the compressor 11 circulates in the following order, as shown by the thick solid line in the overall configuration diagram of Figure 7: gas cooler 12, high-pressure side expansion valve 13a, electric three-way valve 17, suction side evaporator 16, ejector 14, accumulator 15, and the suction port of the compressor 11.

[0097] In other words, in the ejector-type refrigeration cycle 10a in low-load mode, the refrigerant, which has been depressurized by the high-pressure side expansion valve 13a, is switched to a second circuit that flows into the suction side evaporator 16 via the bypass passage 18a.

[0098] In low-load mode, refrigerant is not allowed to flow into the nozzle portion 14a of the ejector 14. Therefore, the ejector 14 does not exhibit its pressurizing ability. For this reason, the ejector 14 in this embodiment becomes simply a refrigerant passage. Consequently, in the ejector-type refrigeration cycle 10a in low-load mode, the refrigerant flows in substantially the same order as in a normal supercritical refrigeration cycle.

[0099] Furthermore, in low-load mode, the target high-pressure side pressure determination unit 20a determines the target high-pressure side pressure PHO based on the high-pressure side temperature Th by referring to a pre-stored control map. The control map determines the target high-pressure side pressure PHO so that the COP of the ejector-type refrigeration cycle 10 in low-load mode approaches its maximum value. Therefore, the target high-pressure side pressure PHO determined in low-load mode is the same value as the normal target high-pressure side pressure PHOn. The operation of other components is the same as in normal mode.

[0100] Therefore, in the low-load mode ejector-type refrigeration cycle 10a, a vapor compression type refrigeration cycle is configured in which the refrigerant is cooled by the gas cooler 12 and evaporated by the suction-side evaporator 16. As a result, the air blown into the vehicle interior is cooled by the suction-side evaporator 16.

[0101] In this case, under the operating conditions where low-load operation is selected, the rotational speed of the compressor 11 is lower than the reference rotational speed. Therefore, if the system switches to the first circuit, the flow rate of refrigerant flowing into the nozzle portion 14a of the ejector 14 will decrease, potentially resulting in insufficient refrigerant suction and refrigerant pressurization by the ejector 14. As a result, the air in the suction-side evaporator 16 may not be able to be sufficiently cooled.

[0102] In contrast, in the ejector-type refrigeration cycle 10a of this embodiment, during low-load mode, the system switches to a second circuit, which is a refrigerant circuit similar to that of a normal supercritical refrigeration cycle. Therefore, even in low-load mode, the air can be cooled by the suction-side evaporator 16. Furthermore, in low-load mode, the target high-pressure side pressure PHO is set to the same value as the normal target high-pressure side pressure PHOn, so the COP can be improved, as in the conventional technology.

[0103] (Third Embodiment) In this embodiment, an example of applying the ejector-type refrigeration cycle 10b according to the present disclosure to a vehicle air conditioning system will be described. In the ejector-type refrigeration cycle 10b, as shown in the overall configuration diagram of Figure 8, an outlet-side evaporator 16b, a suction-side passage 18b, a branch section 19b, etc. are added to the ejector-type refrigeration cycle 10 described in the first embodiment.

[0104] The branching section 19b branches the flow of refrigerant that has flowed out from the high-pressure side expansion valve 13a. The branching section 19b is a three-way joint with the same configuration as the merging section 19a described in the second embodiment. The inlet side of the nozzle section 14a of the ejector 14 is connected to one outlet of the branching section 19b. The inlet side of the suction side passage 18b is connected to the other outlet of the branching section 19b.

[0105] The suction-side passage 18b is a refrigerant passage that guides the refrigerant flowing out from the other outlet of the branching section 19b (i.e., the other refrigerant branched at the branching section 19b) to the refrigerant inlet side of the suction-side evaporator 16, bypassing the nozzle section 14a of the ejector 14. The low-pressure-side expansion valve 13b in this embodiment is located in the suction-side passage 18b.

[0106] The low-pressure side expansion valve 13b reduces the pressure of the other refrigerant that has flowed out from the branch section 19b. The low-pressure side expansion valve 13b adjusts the flow rate of the refrigerant flowing into the suction side evaporator 16. For this reason, the low-pressure side expansion valve 13b in this embodiment also functions as a flow rate ratio adjustment unit that adjusts the flow rate ratio Fp (= Ge / G), which is the ratio of the suction side evaporator flow rate Ge to the discharge flow rate G.

[0107] The outlet-side evaporator 16b is a heat exchange unit that exchanges heat between the refrigerant discharged from the diffuser section 14d of the ejector 14 and the air blown into the vehicle interior from the interior blower 16a. The outlet-side evaporator 16b is an outlet-side evaporation unit that cools the air by evaporating the refrigerant and exerting an endothermic effect.

[0108] The inlet side of the accumulator 15 is connected to the refrigerant outlet of the outflow side evaporator 16b. In this embodiment, the liquid phase refrigerant outlet of the accumulator 15 has been eliminated.

[0109] In this embodiment, the suction-side evaporator 16 exchanges heat between the low-pressure refrigerant, which has been depressurized by the low-pressure-side expansion valve 13b, and the air that has been blown from the indoor blower 16a and passed through the outlet-side evaporator 16b. The suction-side evaporator 16 cools the air that has passed through the outlet-side evaporator 16b by evaporating the low-pressure refrigerant and exerting an endothermic effect. The other configurations of the ejector-type refrigeration cycle 10b are the same as those of the ejector-type refrigeration cycle 10 described in the first embodiment.

[0110] Next, the operation of the ejector-type refrigeration cycle 10b of this embodiment in the above configuration will be described. When the air conditioning operation switch on the control panel is turned on, the control device 20 controls the operation of various controlled devices.

[0111] Specifically, the control device 20 controls the throttle opening of the low-pressure side expansion valve 13b so that the flow rate ratio Fp approaches the target flow rate ratio FPO. The target flow rate ratio FPO is set so that the COP of the ejector-type refrigeration cycle 10b reaches its maximum value. The target flow rate ratio FPO is determined by referring to a control map pre-stored in the control device 20, based on the rotational speed of the thermal load (compressor 11 in this embodiment) of the ejector-type refrigeration cycle 10a.

[0112] Furthermore, the target high-pressure side pressure determination unit 20a determines that, within a range lower than the normal target high-pressure side pressure PHOn, the target high-pressure side pressure PHO will decrease as the pressure increase amount ΔPej increases, and the target high-pressure side pressure PHO will decrease as the flow rate ratio Fp decreases. The operation of the other components is the same as in the first embodiment.

[0113] Therefore, in the ejector-type refrigeration cycle 10b, the state of the refrigerant changes as shown in the Mollier diagram of Figure 9. Here, in Figure 9, the state of the refrigerant at the same points in the cycle configuration as in Figure 2, which was explained in the first embodiment, is shown with the same reference numerals (alphabetical letters), and only the subscripts (numbers) are changed to match the figure number.

[0114] The high-pressure refrigerant (point a9 in Figure 9), which has been pressurized above the critical pressure by the compressor 11, flows into the gas cooler 12. The high-pressure refrigerant that flows into the gas cooler 12 exchanges heat with the outside air blown in by the cooling fan 12a, lowering its enthalpy (from point a9 to point b9 in Figure 9).

[0115] The refrigerant flowing out of the gas cooler 12 flows into the high-pressure side expansion valve 13a and is depressurized (from point b9 to point c9 in Figure 9). As a result, the high-pressure side pressure Ph approaches the target high-pressure side pressure PHO. The flow of refrigerant flowing out of the high-pressure side expansion valve 13a is branched at the branching section 19b. The refrigerant flowing out from one outlet of the branching section 19b (i.e., one of the refrigerants branched at the branching section 19b) flows into the nozzle section 14a of the ejector 14.

[0116] The refrigerant flowing into the nozzle portion 14a of the ejector 14 is isentropically depressurized and ejected (from point c9 to point d9 in Figure 9). In the ejector 14, the refrigerant flowing out from the suction-side evaporator 16 is drawn in through the suction port 14c by the action of the ejected refrigerant. As a result, the refrigerant depressurized by the low-pressure-side expansion valve 13b flows into the suction-side evaporator 16.

[0117] The injected refrigerant and the suctioned refrigerant drawn in from the suction port 14c flow into the diffuser section 14d (from point d9 to point e9, and from point j9 to point e9 in Figure 9). In the diffuser section 14d, the pressure of the mixed refrigerant increases, similar to the first embodiment (from point e9 to point f9 in Figure 9).

[0118] The refrigerant flowing out from the diffuser section 14d flows into the outlet-side evaporator 16b. The refrigerant flowing into the outlet-side evaporator 16b absorbs heat from the air blown from the indoor fan 16a and evaporates (from point f9 to point g9 in Figure 9). This cools the air blown from the indoor fan 16a. The refrigerant flowing out from the outlet-side evaporator 16b flows into the accumulator 15 where it is separated into gas and liquid.

[0119] The other refrigerant branched off at branching point 19b flows into the low-pressure side expansion valve 13b and is depressurized (from point c9 to point i9 in Figure 9). The refrigerant depressurized at the low-pressure side expansion valve 13b flows into the suction side evaporator 16. The refrigerant flowing into the suction side evaporator 16 absorbs heat from the air passing through the outlet side evaporator 16b and evaporates (from point i9 to point j9 in Figure 9). As a result, the air that passes through the outlet side evaporator 16b and is blown into the vehicle interior is further cooled.

[0120] The refrigerant that flows out from the gas phase refrigerant outlet of the accumulator 15 is drawn into the compressor 11 and compressed again until it reaches a pressure above critical pressure (from point g9 to point a9 in Figure 9).

[0121] The ejector-type refrigeration cycle 10b of this embodiment operates as described above and can cool the air blown into the vehicle cabin. Furthermore, in the ejector-type refrigeration cycle 10b, similar to the first embodiment, the power consumption of the compressor 11 can be reduced by the pressure-boosting action of the ejector 14, thereby improving the COP.

[0122] In this case, in the ejector-type refrigeration cycle 10b, the refrigerant evaporation pressure in the outlet-side evaporator 16b becomes the pressure increased by the diffuser section 14d, and the refrigerant evaporation pressure in the suction-side evaporator 16 approaches the pressure of the refrigerant reduced by the nozzle section 14a. This ensures a temperature difference between the refrigerant evaporation temperature in the outlet-side evaporator 16b and the suction-side evaporator 16 and the air, allowing for efficient cooling of the air.

[0123] Furthermore, in the ejector-type refrigeration cycle 10b of this embodiment, the target high-pressure side pressure determination unit 20a determines the target high-pressure side pressure PHO based not only on the high-pressure side temperature Th, but also on the suction pressure Ps and the evaporator temperature Tefin, similar to the first embodiment. This makes it possible to determine the target high-pressure side pressure PHO in a way that sufficiently improves the COP of the ejector-type refrigeration cycle 10b.

[0124] More specifically, the COP of the ejector-type refrigeration cycle 10b in this embodiment can be defined by the following formulas F4 and F5.

[0125]

[0126]

[0127] Δleva2 is the difference in specific enthalpy of the outlet evaporator 16b, obtained by subtracting the specific enthalpy of the inlet refrigerant from the specific enthalpy of the outlet refrigerant, as shown in Figure 9.

[0128] As is clear from equation F4, in order to improve the COP of the ejector-type refrigeration cycle 10, one possible method is to reduce the compressor specific enthalpy difference Δlc. And in order to reduce the compressor specific enthalpy difference Δlc, one possible method is to increase the booster specific enthalpy difference Δldif.

[0129] However, as can be understood from equation F5, when the compressor 11 is discharging a predetermined flow rate of refrigerant, increasing the nozzle-side flow rate Gnoz to increase the specific enthalpy difference Δldif in the booster section will decrease the suction-side evaporator flow rate Ge. Conversely, increasing the suction-side evaporator flow rate Ge will decrease the nozzle-side flow rate Gnoz, which in turn will decrease the specific enthalpy difference Δldif in the booster section.

[0130] Therefore, in order to reliably and sufficiently improve the COP of the ejector-type refrigeration cycle 10b, it is necessary to adjust the flow rate ratio Fp to an appropriate value. In this embodiment, the throttling opening of the low-pressure side expansion valve 13b is controlled so that the flow rate ratio Fp approaches the reference flow rate ratio KFP. The reference flow rate ratio KFP changes depending on the heat exchange capacity of the suction side evaporator 16, the heat exchange capacity of the outlet side evaporator 16b, etc., according to the operating conditions.

[0131] Furthermore, since the flow rate ratio Fp is a parameter that changes the COP of the ejector-type refrigeration cycle 10b, it is a parameter that correlates with the pressure boosting capacity of the ejector 14. Therefore, the inventors investigated the relationship between the flow rate ratio Fp and the high-pressure side pressure Ph at which the COP reaches its maximum value. As a result, as shown in Figure 10, it was confirmed that, regardless of the high-pressure side temperature Th, the high-pressure side pressure Ph at which the COP reaches its maximum value decreases as the flow rate ratio Fp decreases.

[0132] Here, Figure 10 shows the results of an investigation under the condition that the refrigerant evaporation pressure in the suction-side evaporator 16 is constant. Also, in Figure 10, the flow rate ratio Fp1 is greater than the flow rate ratio Fp2. The flow rate ratio Fp2 is greater than the flow rate ratio Fp3.

[0133] Therefore, in the target high-pressure side pressure determination unit 20a of this embodiment, the target high-pressure side pressure PHO is determined to decrease in a range lower than the normal target high-pressure side pressure PHOn as the pressure increase amount ΔPej increases, and also as the flow rate ratio Fp decreases.

[0134] According to this, the target high-pressure side pressure PHO can be determined so that the ejector 14 exhibits appropriate pressure boosting capability. In other words, the target high-pressure side pressure PHO can be determined so as to sufficiently improve the COP of the ejector-type refrigeration cycle 10b. As a result, the COP of the ejector-type refrigeration cycle 10b can be sufficiently improved.

[0135] Furthermore, the inventors have confirmed that in the ejector-type refrigeration cycle 10b, the same effect can be obtained by determining that the target high-pressure side pressure PHO is reduced as the pressure boosting ratio Pp increases, and also by determining that the target high-pressure side pressure PHO is reduced as the flow rate ratio Fp decreases.

[0136] This disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of this disclosure, as follows.

[0137] In the embodiments described above, an example of applying the ejector-type refrigeration cycle according to this disclosure to a vehicle air conditioning system was explained, but the application of the ejector-type refrigeration cycle according to this disclosure is not limited to this. For example, it may be applied to stationary air conditioning systems, refrigeration and freezing systems that cool air circulated into the storage area by a suction-side evaporation unit or an outlet-side evaporation unit, etc. The object to be cooled by the ejector-type refrigeration cycle may be domestic water or a cooling heat transfer medium that cools the object to be cooled.

[0138] Furthermore, the ejector-type refrigeration cycle described herein may also be applied to a heating device. When applied to a heating device, the refrigerant absorbs heat from the ambient air in the suction-side evaporation section or the outlet-side evaporation section, and the heat absorbed by the refrigerant from the ambient air is released to the object to be heated in the heat dissipation section. The object to be heated may be air, domestic water, or a heat transfer medium used to heat the object to be heated.

[0139] Furthermore, while the third embodiment describes an example of application to a vehicle air conditioning system in which both the suction-side evaporator 16 and the outlet-side evaporator 16b cool the same object to be cooled, air, it is not limited to this. The suction-side evaporator 16 and the outlet-side evaporator 16b may be configured to cool different objects, respectively.

[0140] The configuration of the ejector-type refrigeration cycle relating to this disclosure is not limited to the configuration disclosed in the embodiments described above.

[0141] Multiple cycle components may be integrated to the extent that the effects described in the above-described embodiments can be obtained. For example, in the ejector-type refrigeration cycle 10 of the first embodiment, the high-pressure side expansion valve 13a and the ejector 14 may be configured as a single unit. Specifically, a needle-shaped valve body may be placed in the refrigerant passage of the nozzle portion 14a, and by displacing the valve body, it may perform the same function as the high-pressure side expansion valve 13a.

[0142] In the first embodiment described above, an example was given in which a variable throttling mechanism was used as the low-pressure side expansion valve 13b, but the invention is not limited to this. For example, a fixed throttling mechanism such as an orifice or capillary tube may be used.

[0143] In the second embodiment described above, an example was given in which an electric three-way valve 17 was used, but a solenoid valve may also be used as long as the refrigerant circuit can be switched in a similar manner.

[0144] In the embodiment described above, the high-pressure side temperature Th is the temperature of the refrigerant on the outlet side of the gas cooler 12, but the embodiment is not limited to this. The temperature of the outlet portion of the gas cooler 12 itself may also be used as the high-pressure side temperature Th.

[0145] In the embodiment described above, the suction pressure Ps was used as the intermediate pressure, but the invention is not limited to this. If there is a differential pressure detection unit that detects the amount of pressure increase of the ejector 14, the value obtained by adding the amount of pressure increase of the ejector 14 to the suction pressure Psuc may be used as the intermediate pressure. Alternatively, the internal pressure of the accumulator 15 may be used as the intermediate pressure.

[0146] In the above-described embodiment, the saturation pressure of the refrigerant at the evaporator temperature Tefin was used as the low-pressure side pressure, but the invention is not limited to this. If there is a differential pressure detection unit that detects the amount of pressure increase of the ejector 14, the value obtained by subtracting the amount of pressure increase of the ejector 14 from the suction pressure Ps may be used as the low-pressure side pressure. Alternatively, the suction side pressure Psuc may be used as the low-pressure side pressure.

[0147] The group of control sensors connected to the input side of the control device 20 is not limited to the detection unit disclosed in the above-described embodiment. Various detection units may be added as needed.

[0148] An internal heat exchanger may be added to the ejector-type refrigeration cycle described in the above embodiment. The internal heat exchanger is a heat exchanger that uses the suction refrigerant drawn into the compressor 11 as a cooling source to reduce the enthalpy of the refrigerant flowing into the suction-side evaporator 16.

[0149] The features of the ejector-type refrigeration cycle disclosed herein are as follows: (Item 1) An ejector (14) having a compression section (11) that compresses and discharges a refrigerant to a critical pressure or higher, a heat dissipation section (12) that dissipates heat from the refrigerant discharged from the compression section, a suction-side evaporation section (16) that evaporates the refrigerant, a nozzle section (14a) that depressurizes and sprays the refrigerant that has flowed out from the heat dissipation section, a suction port (14c) that sucks in the refrigerant that has flowed out from the suction-side evaporation section due to the action of the sprayed refrigerant sprayed from the nozzle section, and a pressure boosting section (14d) that boosts the pressure of the mixed refrigerant of the sprayed refrigerant and the suctioned refrigerant sucked in from the suction port, when the temperature of the refrigerant at the outlet side of the heat dissipation section is defined as the high-pressure side temperature (Th), the pressure of the refrigerant at the outlet side of the heat dissipation section is defined as the high-pressure side pressure (Ph), the pressure of the refrigerant at the outlet side of the pressure boosting section is defined as the intermediate side pressure (Ps), and the pressure of the refrigerant at the suction port is defined as the low-pressure side pressure (Tefin), (Item 2) An ejector-type refrigeration cycle comprising: a target high-pressure side pressure determination unit (20a) that determines a target high-pressure side pressure (PHO) which is a target value of the high-pressure side pressure based on the high-pressure side temperature, the intermediate side pressure, and the low-pressure side pressure, wherein the high-pressure side pressure is adjusted to approach the target high-pressure side pressure. (Item 2) An ejector-type refrigeration cycle according to Item 1, comprising: a pressure reduction unit (13a) that reduces the pressure of the refrigerant flowing out from the heat dissipation unit and causes it to flow out to the inlet side of the nozzle unit, wherein the throttling opening of the pressure reduction unit is adjusted so that the high-pressure side pressure approaches the target high-pressure side pressure. (Item 3) An ejector-type refrigeration cycle according to Item 1 or 2, wherein the target high-pressure side pressure determination unit reduces the target high-pressure side pressure in accordance with an increase in the intermediate-low pressure difference (ΔPej) obtained by subtracting the low-pressure side pressure from the intermediate side pressure. (Item 4) The ejector-type refrigeration cycle according to Item 1 or 2, wherein the target high-pressure side pressure determination unit reduces the target high-pressure side pressure as the pressure increase ratio (Pp) of the intermediate-low pressure difference (ΔPej), obtained by subtracting the low-pressure side pressure from the intermediate-side pressure, with respect to the high-low pressure difference (ΔPh), obtained by subtracting the low-pressure side pressure from the high-pressure side pressure.(Item 5) The ejector-type refrigeration cycle according to Item 1 or 2, wherein the target high-pressure side pressure determination unit determines the target high-pressure side pressure such that the pressure boost ratio (Pp) of the intermediate-low pressure difference (ΔPej), obtained by subtracting the low-pressure side pressure from the intermediate-side pressure, with respect to the high-low pressure difference (ΔPh), obtained by subtracting the low-pressure side pressure from the high-pressure side pressure, approaches a predetermined reference pressure boost ratio (KPp). (Item 6) An ejector-type refrigeration cycle according to any one of items 1 to 5, comprising: a branching section (19b) that branches the flow of the refrigerant discharged from the heat dissipation section and discharges one of the branched portions of the refrigerant to the inlet side of the nozzle section; a suction-side passage (18b) that guides the other portion of the refrigerant branched at the branching section (19b) to the refrigerant inlet side of the suction-side evaporation section, bypassing the nozzle section; and an outlet-side evaporation section (16b) that evaporates the refrigerant discharged from the ejector, wherein the target high-pressure side pressure determination section reduces the target high-pressure side pressure as the flow rate ratio (Ge / G) of the refrigerant flowing from the branching section to the suction-side evaporation section (Ge) decreases with respect to the flow rate (G) of the refrigerant discharged from the compression section (Ge). (Item 7) An ejector-type refrigeration cycle according to any one of items 1 to 6, comprising: a bypass passage (18a) that guides the refrigerant flowing out from the heat dissipation section to the refrigerant inlet side of the suction-side evaporation section, bypassing the nozzle section; and a refrigerant circuit switching section (13b, 17) for switching between refrigerant circuits, wherein the refrigerant circuit switching section can switch between a first circuit that causes the refrigerant flowing out from the heat dissipation section to flow into the nozzle section and a second circuit that causes the refrigerant flowing out from the heat dissipation section to flow into the bypass passage; and the target high-pressure side pressure determination section determines the target high-pressure side pressure based on the high-pressure side temperature, the intermediate side pressure, and the low-pressure side pressure when the refrigerant circuit switching section is switched to the first circuit, and determines the target high-pressure side pressure based on the high-pressure side temperature when the refrigerant circuit switching section is switched to the second circuit.

[0150] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. An ejector (14) having: a compression section (11) that compresses and discharges a refrigerant to a critical pressure or higher; a heat dissipation section (12) that dissipates heat from the refrigerant discharged from the compression section; a suction-side evaporation section (16) that evaporates the refrigerant; a nozzle section (14a) that depressurizes and sprays the refrigerant that has flowed out of the heat dissipation section; a suction port (14c) that sucks in the refrigerant that has flowed out of the suction-side evaporation section due to the action of the sprayed refrigerant sprayed from the nozzle section; and a pressure boosting section (14d) that increases the pressure of the mixed refrigerant of the sprayed refrigerant and the suctioned refrigerant sucked in from the suction port; When the temperature of the refrigerant at the outlet side of the heat dissipation section is defined as the high-pressure side temperature (Th), the pressure of the refrigerant at the outlet side of the heat dissipation section is defined as the high-pressure side pressure (Ph), the pressure of the refrigerant at the outlet side of the pressure boosting section is defined as the intermediate side pressure (Ps), and the pressure of the refrigerant at the suction port is defined as the low-pressure side pressure (Tefin), An ejector-type refrigeration cycle comprising: a target high-pressure side pressure determination unit (20a) that determines a target high-pressure side pressure (PHO) which is a target value of the high-pressure side pressure based on the high-pressure side temperature, the intermediate side pressure, and the low-pressure side pressure, wherein the high-pressure side pressure is adjusted to approach the target high-pressure side pressure.

2. The ejector-type refrigeration cycle according to claim 1, further comprising a pressure reducing section (13a) that reduces the pressure of the refrigerant flowing out from the heat dissipation section and causes it to flow out towards the inlet side of the nozzle section, wherein the throttling opening of the pressure reducing section is adjusted so that the high-pressure side pressure approaches the target high-pressure side pressure.

3. The ejector-type refrigeration cycle according to claim 1, wherein the target high-pressure side pressure determination unit reduces the target high-pressure side pressure in accordance with an increase in the intermediate-low pressure difference (ΔPej) obtained by subtracting the low-pressure side pressure from the intermediate side pressure.

4. The ejector-type refrigeration cycle according to claim 1, wherein the target high-pressure side pressure determination unit reduces the target high-pressure side pressure as the pressure increase ratio (Pp) of the intermediate-low pressure difference (ΔPej), obtained by subtracting the low-pressure side pressure from the intermediate-side pressure, with respect to the high-low pressure difference (ΔPh), obtained by subtracting the low-pressure side pressure from the high-pressure side pressure.

5. The ejector-type refrigeration cycle according to claim 1, wherein the target high-pressure side pressure determination unit determines the target high-pressure side pressure such that the pressure boost ratio (Pp) of the intermediate-low pressure difference (ΔPej), obtained by subtracting the low-pressure side pressure from the intermediate-side pressure, with respect to the high-low pressure difference (ΔPh), obtained by subtracting the low-pressure side pressure from the high-pressure side pressure, approaches a predetermined reference pressure boost ratio (KPp).

6. The ejector-type refrigeration cycle according to claim 1, comprising: a branching section (19b) that branches the flow of the refrigerant discharged from the heat dissipation section and discharges one of the branched portions of the refrigerant to the inlet side of the nozzle section; a suction-side passage (18b) that guides the other portion of the refrigerant branched at the branching section (19b) to the refrigerant inlet side of the suction-side evaporation section, bypassing the nozzle section; and an outlet-side evaporation section (16b) that evaporates the refrigerant discharged from the ejector, wherein the target high-pressure side pressure determination section reduces the target high-pressure side pressure in accordance with a decrease in the flow rate ratio (Ge / G) of the refrigerant flowing from the branching section to the suction-side evaporation section to the flow rate (G) of the refrigerant discharged from the compression section to the evaporation section flow rate (Ge).

7. The ejector-type refrigeration cycle according to claim 1, comprising: a bypass passage (18a) that guides the refrigerant flowing out from the heat dissipation section to the refrigerant inlet side of the suction-side evaporation section, bypassing the nozzle section; and a refrigerant circuit switching section (13b, 17) for switching between refrigerant circuits, wherein the refrigerant circuit switching section can switch between a first circuit that causes the refrigerant flowing out from the heat dissipation section to flow into the nozzle section and a second circuit that causes the refrigerant flowing out from the heat dissipation section to flow into the bypass passage; and the target high-pressure side pressure determination section determines the target high-pressure side pressure based on the high-pressure side temperature, the intermediate side pressure, and the low-pressure side pressure when the refrigerant circuit switching section is switched to the first circuit, and determines the target high-pressure side pressure based on the high-pressure side temperature when the refrigerant circuit switching section is switched to the second circuit.

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