Ejector cooling device

Abstract

To provide an ejector cooling device to which a hybrid type refrigeration cycle introducing a compressor for an ejector refrigeration cycle is applied, capable of avoiding the occurrence of cavitation in a pump during starting the device in a simple construction.SOLUTION: A control part C turns a compressor 7 on at starting the device and turns a pump 3 off, closes an on-off valve V2 for switching into a compression type mode to carry refrigerant from the compressor 7 via a switching mechanism 9 to a discharge port 1c of an ejector 1, finds a saturation temperature based on a pump pressure Pi, and starts the pump 3 when a pump temperature Ti is equal to or lower than a temperature subtracted a predetermined supercooling degree from the saturation temperature, to perform operation mode control.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ejector cooling device that uses a hybrid refrigeration cycle in which a compressor is introduced into an ejector refrigeration cycle and that can avoid the occurrence of pump cavitation at the time of startup of the device with a simple configuration. [Background technology]

[0002] An ejector cooling device such as that described in Patent Document 1 has already been provided. The ejector refrigeration cycle of this ejector cooling device can be driven only by a pump, so it can reduce power consumption compared to a compression refrigeration cycle using a compressor. However, if the temperature of the cooling water flowing through the condenser is high, the back pressure of the ejector increases, which can significantly reduce the refrigeration capacity and device efficiency.

[0003] For this reason, Patent Document 2 proposes an ejector cooling device incorporating a compressor. One of these proposes connecting the compressor and ejector in series, and using the ejector to reduce the compressor's discharge pressure, thereby reducing the power consumption of the compressor. Another proposes arranging the compressor and ejector in parallel.

[0004] Patent Document 3 also describes an ejector cooling device that has means for avoiding pump cavitation by installing a pump at the bottom, ensuring a liquid level head of the refrigerant in the condenser and storage tank, and operating to recover refrigerant into the storage tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-190587 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-94814 [Patent Document 3] Japanese Patent Publication No. 2022-28593 Summary of the Invention [Problem to be solved by the invention]

[0006] In an ejector cooling system equipped with a compressor, when the power is turned on at system startup, the pump and compressor start operating simultaneously, causing cavitation, in which the pump's suction pressure drops below the saturation pressure of the refrigerant. This cavitation must be avoided because it can cause equipment damage due to a sudden drop in flow rate or abnormal vibration. Furthermore, if there is not enough liquid refrigerant in the condenser at system startup, gas-phase refrigerant may be mixed in when the pump draws in the refrigerant, causing a similar problem.

[0007] The present invention has been made in view of the above, and aims to provide an ejector cooling device that uses a hybrid refrigeration cycle in which a compressor is introduced into an ejector refrigeration cycle and that can avoid the occurrence of pump cavitation when the device is started up, with a simple configuration. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides an ejector cooling device having a pump that pressurizes a refrigerant, a steam generator that heats the refrigerant with heat source water supplied from a heat source and generates an ejector-driven flow, an expansion valve that decompresses the refrigerant, an evaporator that cools a medium to be cooled with the refrigerant decompressed by the expansion valve, an ejector that sucks in the refrigerant evaporated by the evaporator with the ejector-driven flow of refrigerant from the steam generator, and a condenser that cools the refrigerant that has been sucked into the ejector and mixed with the ejector-driven flow, a compressor disposed between the evaporator and the evaporator to compress the refrigerant from the evaporator; a switching mechanism that switches at least between connection of the compressor to a suction inlet of the ejector and connection of the compressor to a discharge port of the ejector; an on-off valve connected in parallel to the compressor; a compressor pressure sensor that detects a compressor pressure that is a refrigerant pressure on the suction side of the compressor; a back pressure sensor that detects a back pressure that is a refrigerant pressure on the discharge side of the ejector; a pump temperature sensor that detects a pump temperature that is a refrigerant temperature on the suction side of the pump; a control unit that performs operation mode control to switch to an ejector mode in which, when a pressure ratio of a back pressure to the compressor pressure is less than a first threshold, the compressor is turned off and the on-off valve is opened to cause the refrigerant from the evaporator to flow to the suction inlet of the ejector via the switching mechanism; when the pressure ratio is equal to or greater than the first threshold and less than a second threshold, the control unit switches to a parallel hybrid mode in which the compressor is turned on and the on-off valve is opened to cause the refrigerant from the compressor to flow to the discharge port of the ejector via the switching mechanism; and when the pressure ratio is equal to or greater than the second threshold, the control unit switches to a series hybrid mode in which the compressor is turned on and the on-off valve is closed to cause the refrigerant from the compressor to flow to the suction inlet of the ejector via the switching mechanism, and when the pressure ratio is equal to or greater than the second threshold, the control unit turns on the compressor and turns off the pump at the time of startup of the device, and switches to a compression mode in which the on-off valve is closed to cause the refrigerant from the compressor to flow to the discharge port of the ejector via the switching mechanism; calculates a saturation temperature based on the pump pressure; and calculates a saturation temperature based on the pump pressure when the pump temperature is reduced by a predetermined degree of subcooling from the saturation temperature,When the temperature is equal to or lower than the subtracted temperature, the pump is started and the operation mode control is performed.

[0009] In addition, in the above invention, the present invention is characterized in that the control unit repeats a process of increasing the rotation speed of the compressor by a predetermined value when the pump temperature is not equal to or lower than a temperature obtained by subtracting a predetermined degree of subcooling from the saturation temperature.

[0010] In addition, the present invention is characterized in that, in the above invention, a heat source water temperature sensor is provided for detecting the temperature of the heat source water supplied to the steam generator, and when the temperature of the heat source water is below a predetermined threshold temperature, the control unit switches to the compression mode and performs the operation mode control. [Effects of the Invention]

[0011] According to the present invention, it is possible to avoid the occurrence of cavitation in a pump at the time of starting up an ejector cooling device that employs a hybrid refrigeration cycle in which a compressor is introduced into an ejector refrigeration cycle, with a simple configuration. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram showing the configuration of an ejector cooling device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a graph showing changes in operation mode efficiency and refrigeration capacity with respect to the pressure ratio (Pd / Ps). [Figure 3] FIG. 3 is a diagram showing the switching states of the compressor, pump, and on-off valves in accordance with the operation modes. [Figure 4] FIG. 4 is a diagram showing the flow of the refrigerant in the operation mode. [Figure 5] FIG. 5 is a flowchart showing the operation mode processing procedure performed by the control unit. [Figure 6] FIG. 6 is an overall flowchart showing the operation control process of the ejector cooling device shown in FIG. [Figure 7]FIG. 7 is a detailed flowchart showing the startup operation mode process of the ejector cooling device shown in FIG. [Figure 8] FIG. 8 is a diagram illustrating the state change in which the refrigerant that can be sucked by the pump becomes liquid through the startup operation mode process, enabling the pump to start. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] <Overall structure> Fig. 1 is a circuit diagram showing the configuration of an ejector cooling device according to an embodiment of the present invention. The ejector cooling device illustrated here recovers waste heat from waste hot water, such as factory wastewater or used cooling water, as heat source water to produce chilled water by cooling a medium to be cooled, and is an ejector refrigeration cycle to which a compression refrigeration cycle using a compressor 7 is applied. The medium to be cooled may be water, oil, air, or other refrigerants. In particular, this embodiment illustrates an ejector cooling device that produces chilled water from the cooled water using waste heat recovered from the waste hot water.

[0015] The ejector cooling device has a circulation path that sequentially connects an ejector 1, a condenser 2, a pump 3, and a steam generator 4. In addition, in the ejector cooling device, a part of the refrigerant circulating in the circulation path is supplied to the ejector 1 at a branch point P1 between the condenser 2 and the pump 3 as a suction fluid.

[0016] The refrigerant branched from branch point P1 is supplied to the ejector 1 side via an expansion valve 5 and an evaporator 6. Downstream of the evaporator 6, a compressor 7 and a check valve 8 are connected in parallel from branch point P2 and connected to a switching mechanism 9. The refrigerant discharged from the compressor 7 is connected to a suction inlet 1b or a discharge port 1c of the ejector 1 by the switching mechanism 9. Refrigerant supplied from the steam generator 4 is input as a driving flow into a driving inlet 1a of the ejector 1, and the driving flow causes refrigerant to be drawn in as a suction flow from the suction inlet 1b and discharged from the discharge port 1c.

[0017] The pump 3 circulates and supplies the refrigerant in the circulation path. The pump 3 is, for example, a liquid-phase variable displacement pump, and pressurizes the refrigerant and supplies it to the ejector 1. The pump 3 is driven at a rotation speed according to a drive signal given from a control unit C, which will be described later. The steam generator 4 evaporates the refrigerant supplied from the pump 3 by exchanging heat with heat source water, such as waste hot water, supplied to the steam generator 4 from a heat supply source 20.

[0018] The condenser 2 condenses the refrigerant by exchanging heat between the gas-phase refrigerant discharged from the ejector 1 and the cooling water supplied to the condenser 2 and dissipating heat. The expansion valve 5 expands and reduces the pressure of the refrigerant that passes through the condenser 2 and is branched off and supplied via branch point P1. The evaporator 6 evaporates the refrigerant and produces chilled water by exchanging heat between the liquid-phase refrigerant that has passed through the expansion valve 5 and the cooled water that is supplied to the evaporator 6. Note that an electronic expansion valve is preferred as the expansion valve 5, but other types of expansion valves, such as a manual expansion valve, a constant pressure expansion valve, or a temperature expansion valve, may be selected as appropriate depending on the application and configuration. The compressor 7 may be any device that can compress the refrigerant.

[0019] The switching mechanism 9 has a first pipe connecting the compressor 7 and the discharge port 1c of the ejector 1, a second pipe connecting the check valve 8 and the suction inlet 1b of the ejector 1, and a connecting pipe connecting a connection point 9a of the first pipe and a connection point 9b of the second pipe. An on-off valve V1 is provided between the connection point 9a and the discharge port 1c of the ejector 1, and an on-off valve V2 is provided in the connecting pipe.

[0020] In this embodiment, the compressor 7, check valve 8, and switching mechanism 9 can switch between four operation modes: ejector mode, parallel hybrid mode, series hybrid mode, and compression mode (see FIGS. 3 and 4). In the ejector mode, the compressor 7 is off, the pump 3 is on, the on-off valve V1 is closed, and the on-off valve V2 is closed, resulting in an ejector refrigeration cycle using only the ejector 1. In this ejector mode, the compressor 7 is stopped, so the system can be driven with low power consumption, but cannot be driven under high back pressure.

[0021] In the parallel hybrid mode, the compressor 7 is on, the pump 3 is on, the on-off valve V1 is open, and the on-off valve V2 is closed. In this mode, the refrigerant from the evaporator 6 is branched into a refrigerant drawn into the compressor 7 and a refrigerant drawn into the suction inlet 1b of the ejector 1 through the check valve 8. The refrigerant compressed by the compressor 7 and the refrigerant compressed by the ejector 1 join together upstream of the condenser 2 and are sent to the condenser 2. A radiator such as an internal heat exchanger may be provided upstream of the condenser 2. This parallel hybrid mode is effective under medium back pressure conditions because the compressor 7 can compensate for the reduced refrigeration capacity of the ejector 1.

[0022] In the series hybrid mode, the compressor 7 is on, the pump 3 is on, the on-off valve V1 is closed, and the on-off valve V2 is open. In this mode, the refrigerant from the evaporator 6 is drawn into the compressor 7 and then into the suction inlet 1b of the ejector 1. In this series hybrid mode, the ejector 1 can lower the discharge pressure of the compressor 7, thereby reducing the power consumption of the compressor 7 and achieving a higher efficiency (COP) than conventional compression refrigeration cycles. The series hybrid mode is effective under conditions of medium to high back pressure.

[0023] In the compression mode, the compressor 7 is on, the pump 3 is off, the on-off valve V1 is open, and the on-off valve V2 is closed. This mode is not an ejector refrigeration cycle, but a general compression refrigeration cycle. The compression mode is the least efficient, but it can be operated even without heat source water such as exhaust heat. In other words, even if the heat source of the heat source water supplied from the heat supply source 20 is not available, the ejector cooling device can be operated stably without stopping.

[0024] The compressor pressure sensor S1 detects the compressor pressure Ps, which is the refrigerant pressure on the suction side of the compressor 7. The back pressure sensor S2 detects the back pressure Pd, which is the refrigerant pressure on the discharge side of the ejector 1. The heat source water temperature sensor S3 detects the heat source water temperature Tw of the heat source water supplied to the steam generator 4. The pump temperature sensor S4 detects the pump temperature Ti, which is the refrigerant temperature on the suction side (suction side) of the pump 3. The pump pressure sensor S5 detects the pump pressure Pi, which is the refrigerant pressure on the suction side (suction side) of the pump 3.

[0025] The control unit C detects the pressure and temperature of the refrigerant, the temperature of the heat-source water, and the like, and controls the pump 3, expansion valve 5, compressor 7, switching mechanism 9, and the like. The control unit C detects, among other things, the compressor pressure Ps, back pressure Pd, and heat-source water temperature Tw, and controls the switching of the operation mode. When controlling the switching of the operation mode, the control unit C uses the pressure ratio (Pd / Ps) of the back pressure Pd to the compressor pressure Ps. The control unit C also turns on the compressor 7 and turns off the pump 3, closes the on-off valve connecting the compressor 7 in parallel, and switches to a compression mode in which the refrigerant from the compressor 7 flows to the discharge port of the ejector. The control unit C calculates the saturation temperature Tis based on the pump pressure Pi, and starts the pump 3 when the pump temperature Ti is equal to or lower than the temperature obtained by subtracting a predetermined degree of subcooling ΔTsc from the saturation temperature Tis.

[0026] <Efficiency and refrigeration capacity for each operating mode> FIG. 2 shows the change in operation mode efficiency and refrigeration capacity with respect to the pressure ratio (Pd / Ps). As shown in FIG. 2, in a low back pressure region E1 where the pressure ratio (Pd / Ps) is less than the first threshold R12, the efficiency and refrigeration capacity of the ejector mode are high, as indicated by the curve M1. Also, in a medium back pressure region E2 where the pressure ratio (Pd / Ps) is equal to or greater than the first threshold R12 but less than the second threshold R23, the efficiency and refrigeration capacity of the parallel hybrid mode are high, as indicated by the curve M2. Furthermore, in a high back pressure region E3 where the pressure ratio (Pd / Ps) is equal to or greater than the second threshold R23, the efficiency and refrigeration capacity of the series hybrid mode and the compression mode are high, as indicated by the curves M3 and M4. Therefore, when the pressure ratio (Pd / Ps) is in the region E1, the control unit C switches to the ejector mode. When the pressure ratio (Pd / Ps) is in the region E2, the control unit C switches to the parallel hybrid mode. When the pressure ratio (Pd / Ps) is in the region E3, the control unit C switches to the series hybrid mode. The switching control of the compressor 7, the pump 3, the on-off valve V1, and the on-off valve V2 and the flow of the refrigerant for each operation mode are as shown in FIGS. 3 and 4, as described above.

[0027] <Operation mode processing> Fig. 5 is a flowchart showing the operation mode processing procedure by the control unit C. As shown in Fig. 5, the control unit C first measures the heat-source water temperature Tw, the compressor pressure Ps, and the back pressure Pd (step S101). Then, it determines whether the heat-source water temperature Tw is less than a predetermined threshold temperature Tth (step S102). If the heat-source water temperature Tw is less than the predetermined threshold temperature Tth (step S102: Yes), it switches the operation mode to the compression mode (step S103) and ends this processing.

[0028] On the other hand, if the heat source water temperature Tw is not less than the predetermined threshold temperature Tth (step S102: No), it is further determined whether the pressure ratio (Pd / Ps) is less than the first threshold R12 (step S104). If the pressure ratio (Pd / Ps) is less than the first threshold R12 (step S104: Yes), the operation mode is switched to the ejector mode (step S105), and this process ends.

[0029] If the pressure ratio (Pd / Ps) is not less than the first threshold value R12 (step S104: No), it is further determined whether the pressure ratio (Pd / Ps) is less than the second threshold value R23 (step S106). If the pressure ratio (Pd / Ps) is less than the second threshold value R23 (step S106: Yes), the operation mode is switched to the parallel hybrid mode (step S107), and this process ends.

[0030] On the other hand, if the pressure ratio (Pd / Ps) is not less than the second threshold value R23 (step S106: No), the operation mode is switched to the series hybrid mode (step S108), and this process ends.

[0031] Conventionally, in a refrigeration cycle using a series hybrid system, the compressor 7 cannot operate in the medium back pressure region, resulting in a decrease in efficiency and refrigeration capacity. However, in this embodiment, by switching to the parallel hybrid mode in this medium back pressure region, the decrease in efficiency and refrigeration capacity can be suppressed.

[0032] Furthermore, in the conventional parallel hybrid refrigeration cycle, efficiency and refrigeration capacity decrease in the high back pressure region. However, in the present embodiment, by switching to the series hybrid mode in this high back pressure region, the decrease in efficiency and refrigeration capacity can be suppressed.

[0033] <Startup operation mode processing> Fig. 6 is an overall flowchart showing the operation control process of the ejector cooling device shown in Fig. 1. As shown in Fig. 6, when the ejector cooling device is started up, it first performs a startup operation mode process (step S201), and then performs the above-mentioned operation mode process (step S202). The startup operation mode process is a process in which the compressor 7 is started up before the pump 3 when the device is started up, thereby preventing cavitation from occurring in the pump 3.

[0034] 7 is a detailed flowchart showing the startup operation mode process of the ejector cooling device shown in FIG. 1. As shown in FIG. 7, first, the control unit C starts a liquid pump for feeding cooling water to the condenser 2 (step S301). Note that a cooling fan may be started instead of the cooling water. Thereafter, the control unit C starts a liquid pump for feeding the medium to be cooled to the evaporator 6 (step S302). Note that instead of feeding the liquid of the medium to be cooled, a blower fan may be started to blow cool air using air as the medium to be cooled.

[0035] Thereafter, the on-off valve V1 is opened and the on-off valve V2 is closed (step S303), and the compressor 7 is started (step S304). That is, the compressor 7 is operated in the compression mode. The control unit C then acquires the pump temperature Ti and the pump pressure Pi, and calculates the saturation temperature Tis for the pump pressure Pi using the approximation equation for the saturated vapor pressure curve shown in FIG. 8 or the like (step S305).

[0036] Thereafter, it is determined whether the pump temperature Ti is equal to or lower than the temperature obtained by subtracting a predetermined degree of subcooling ΔTsc from the saturation temperature Tis (Ti≦Tis−ΔTsc) (step S306). If the pump temperature Ti is not equal to or lower than the temperature obtained by subtracting the predetermined degree of subcooling ΔTsc from the saturation temperature Tis (step S306: No), the rotation speed f of the compressor 7 is increased by an incremental rotation speed Δf (step S307), and the process proceeds to step S304, where the operation of the compressor 7 continues. On the other hand, if the pump temperature Ti is equal to or lower than the temperature obtained by subtracting the predetermined degree of subcooling ΔTsc from the saturation temperature Tis (step S306: Yes), the start of the pump 3 is permitted, and the process proceeds to the operation mode processing of step S202.

[0037] 8 is a diagram illustrating the state change in which the refrigerant that can be sucked by the pump 3 becomes liquid phase through the startup operation mode process, enabling the start of the pump 3. As shown in Fig. 8, when the determination process in step S306 determines that the pump temperature Ti is equal to or lower than the temperature obtained by subtracting a predetermined degree of subcooling ΔTsc from the saturation temperature Tis (Ti≦Tis−ΔTsc), the refrigerant on the suction side of the pump 3 becomes liquid phase, thereby preventing cavitation in the pump 3. The predetermined degree of subcooling ΔTsc is a margin for reliably determining whether the refrigerant is in liquid phase in response to state changes, etc.

[0038] In this embodiment, in a hybrid ejector cooling device using a pump 3 and a compressor 7, when the device is started, the compressor 7 is started before the pump 3, thereby recovering liquid refrigerant or increasing the compressor discharge pressure and raising the pump suction pressure above the saturated vapor pressure, thereby preventing cavitation from occurring in the pump 3. As a result, the pump is protected and stable start-up of the ejector cooling device is achieved.

[0039] In addition, in this embodiment, there is no need to install a pump at the bottom, ensure a liquid level head of the refrigerant in the condenser or storage tank, or perform refrigerant recovery operation in the storage tank, so the simple configuration can avoid cavitation of the pump when the device is started up.

[0040] Furthermore, in this embodiment, in the ejector cooling device incorporating a compressor, it is possible to switch to an operation mode with high efficiency and high refrigeration capacity over the entire range of the pressure ratio (Pd / Ps), and when a hybrid refrigeration cycle in which a compressor is introduced into an ejector refrigeration cycle is applied, it is possible to suppress the occurrence of a decrease in refrigeration capacity and device efficiency.

[0041] The first threshold value R12, the second threshold value R23, and the predetermined threshold temperature Tth are determined in advance by conducting a performance test on the ejector cooling device in advance, etc. The first threshold value R12 is, for example, the point at which the efficiency of the ejector 1 alone decreases due to an increase in back pressure, and the second threshold value R23 is, for example, the point at which the compressor 7 cannot operate due to a decrease in back pressure.

[0042] Furthermore, instead of the pressure ratio (Pd / Ps), the pressure difference (Pd-Ps) may be used as a parameter. Moreover, instead of the compressor pressure Ps, the pressure between the compressor 7 and the suction inlet 1b may be used. Moreover, instead of the compressor pressure Ps, the temperature on the inlet side of the evaporator 6, i.e., after expansion by the expansion valve 5, may be indirectly used, and instead of the back pressure Pd, the temperature after condensation by the condenser 2 or the temperature of the cooling water may be indirectly used. Furthermore, instead of the heat-source water temperature Tw, the flow rate of the heat-source water may be used.

[0043] The check valve 8 may also be an on-off valve such as a solenoid valve controlled by the control unit C. From the standpoint of cost, the check valve 8 is preferable.

[0044] Note that the configurations illustrated in the above embodiments are merely functional schematics and are not necessarily physically configured as shown. In other words, the distribution and integration of each device and component is not limited to that illustrated, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various usage situations, etc. [Explanation of symbols]

[0045] 1 Ejector 1a Drive inlet 1b Suction inlet 1c outlet 2 Condenser 3. Pump 4 Steam Generator 5 Expansion valve 6. Evaporator 7 Compressor 8. Check valve 9 Switching mechanism 9a,9b connection points 20 Heat source C control section E1~E3 area M1~M4 curve P1, P2 branch point Pd back pressure Pi pump pressure Ps Compressor pressure R12 First Threshold R23 Second Threshold S1 Compressor Pressure Sensor S2 Back Pressure Sensor S3 Heat source water temperature sensor S4 Pump Temperature Sensor S5 Pump Pressure Sensor Ti Pump Temperature Tis saturation temperature Tth Predetermined threshold temperature Tw Heat source water temperature V1, V2 shut-off valve ΔTsc Specified degree of supercooling

Claims

1. An ejector cooling device comprising: a pump that pressurizes a refrigerant; a steam generator that heats the refrigerant with heat source water supplied from a heat source and generates an ejector-driven flow; an expansion valve that decompresses the refrigerant; an evaporator that cools a medium to be cooled with the refrigerant decompressed by the expansion valve; an ejector that sucks in the refrigerant evaporated by the evaporator with the ejector-driven flow of refrigerant from the steam generator; and a condenser that cools the refrigerant that has been sucked into the ejector and mixed with the ejector-driven flow, a compressor disposed between the evaporator and the ejector to compress the refrigerant from the evaporator; a switching mechanism that switches at least between connection of the compressor to a suction inlet of the ejector and connection of the compressor to a discharge port of the ejector; an on-off valve connected in parallel to the compressor; a compressor pressure sensor for detecting a compressor pressure, which is a refrigerant pressure on the suction side of the compressor; a back pressure sensor for detecting a back pressure, which is a refrigerant pressure on a discharge side of the ejector; a pump temperature sensor for detecting a pump temperature, which is the temperature of the refrigerant on the suction side of the pump; a pump pressure sensor for detecting a pump pressure, which is a refrigerant pressure on the suction side of the pump; a control unit that performs operation mode control to switch to an ejector mode in which, when a pressure ratio of a back pressure to the compressor pressure is less than a first threshold, the compressor is turned off and the on-off valve is opened to cause the refrigerant from the evaporator to flow to the suction inlet of the ejector via the switching mechanism; when the pressure ratio is equal to or greater than the first threshold and less than a second threshold, the operation mode is switched to a parallel hybrid mode in which, when the pressure ratio is equal to or greater than the first threshold and less than a second threshold, the compressor is turned on and the on-off valve is opened to cause the refrigerant from the compressor to flow to the discharge port of the ejector via the switching mechanism; and when the pressure ratio is equal to or greater than the second threshold, the operation mode is switched to a series hybrid mode in which, when the pressure ratio is equal to or greater than the second threshold, the compressor is turned on and the on-off valve is closed to cause the refrigerant from the compressor to flow to the suction inlet of the ejector via the switching mechanism; Equipped with the control unit, when starting up the device, turns on the compressor and turns off the pump, closes the on-off valve, and switches to a compression mode in which the refrigerant from the compressor flows to the discharge port of the ejector via the switching mechanism, calculates a saturation temperature based on the pump pressure, and starts the pump when the pump temperature is equal to or lower than a temperature obtained by subtracting a predetermined degree of subcooling from the saturation temperature.

2. 2. The ejector cooling device according to claim 1, wherein the control unit repeats a process of increasing the rotation speed of the compressor by a predetermined value when the pump temperature is not equal to or lower than a temperature obtained by subtracting a predetermined degree of subcooling from the saturation temperature.

3. a heat source water temperature sensor for detecting the temperature of the heat source water supplied to the steam generator; 3. The ejector cooling device according to claim 1, wherein the control unit performs the operation mode control by switching to the compression mode when the temperature of the heat-source water is lower than a predetermined threshold temperature.

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