Heat pump, hot water generator, and method of operating a heat pump

Abstract

To provide a heat pump that can reliably start up the refrigerant compressor. [Solution] The heat pumps 2, 3, and 5 each have a refrigerant compressor 52 that sucks in refrigerant and discharges compressed refrigerant, a refrigerant circulation unit 5 that circulates the refrigerant, a first discharge-side water circulation unit 3 that circulates discharge-side water that exchanges heat with the refrigerant discharged from the refrigerant compressor 52, and a control unit C. The first discharge-side water circulation unit 3 has a first discharge-side water line 31 through which discharge-side water can flow, a discharge-side bypass line 33 that branches off from the first discharge-side water line 31 and merges with the first discharge-side water line 31 so that discharge-side water flowing into and out of the condenser 55 short-circuits the first discharge-side water line 31, and a discharge-side flow adjustment unit 34 that adjusts the flow direction of the discharge-side water. The control unit C performs startup operation control, and in startup operation control, controls the operation of the discharge-side flow adjustment unit 34 so that discharge-side water flows through the discharge-side bypass line 33 immediately after the refrigerant compressor 52 is started.

Description

Technical Field

[0001] The present invention relates to a heat pump, a hot water generating device, and an operating method of a heat pump.

Background Art

[0002] Patent Document 1 discloses a heat pump including a compressor, a condenser, an expansion valve, and an evaporator, and having a circulation flow path filled with a refrigerant. When a start command is given, the heat pump checks whether start conditions such as pressure conditions and temperature conditions are satisfied, and when the start conditions are satisfied, it starts the compressor to start operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration disclosed in Patent Document 1 above, in order to stably operate the refrigerant compressor, it is necessary to satisfy predetermined start conditions.

[0005] An object of the present invention is to provide a heat pump, a hot water generating device, and an operating method of a heat pump that can stably operate a refrigerant compressor.

Means for Solving the Problems

[0006] One aspect of the present invention includes a refrigerant compressor that draws in and compresses a refrigerant and discharges the compressed refrigerant, a refrigerant circulation unit for circulating the refrigerant, a first discharge-side water circulation unit for circulating discharge-side water that exchanges heat with the refrigerant discharged from the refrigerant compressor, and a control unit, wherein the refrigerant circulation unit includes a refrigerant line through which the refrigerant can flow, an oil separator for separating oil from the refrigerant discharged from the refrigerant compressor, an oil supply line for supplying the oil separated by the oil separator to the refrigerant compressor, a condenser for heating the discharge-side water by exchanging heat between the refrigerant and the discharge-side water after it has been compressed by the refrigerant compressor, and the refrigerant after heat exchange in the condenser The present invention provides a heat pump further comprising an expansion valve for expansion and cooling, wherein the first discharge-side water circulation unit comprises a first discharge-side water line through which the discharge-side water can flow, a discharge-side bypass line that branches off from the first discharge-side water line and merges with the first discharge-side water line so that the discharge-side water flowing into and out of the condenser short-circuits the first discharge-side water line, and a discharge-side flow adjustment unit that adjusts the flow direction of the discharge-side water, wherein the control unit performs startup operation control, and in the startup operation control, the control unit controls the operation of the discharge-side flow adjustment unit so that the discharge-side water flows through the discharge-side bypass line immediately after the refrigerant compressor is started.

[0007] According to the above configuration, by circulating water (discharge water) through a discharge bypass line provided to short-circuit the first discharge water line, the amount of discharge water that exchanges heat with the refrigerant in the condenser (the water whose temperature is raised) can be reduced compared to the case where the discharge bypass line is not circulated. As a result, the temperature of the discharge water can be raised more quickly, and the pressure difference between the discharge pressure and suction pressure of the refrigerant compressor can be secured more quickly. This allows the refrigerant compressor to operate stably.

[0008] The system further includes a first suction water circulation unit that circulates suction water which exchanges heat with the refrigerant drawn in by the refrigerant compressor, and the refrigerant circulation unit further includes an evaporator that cools the suction water by evaporating the refrigerant through heat exchange between the refrigerant and the suction water, and the first suction water circulation unit includes a first suction water line through which the suction water can flow, a suction bypass line that branches off from the first suction water line and merges with the first suction water line so that the suction water flowing into and out of the evaporator short-circuits the first suction water line, and a suction flow adjustment unit that adjusts the direction of flow of the suction water, and the control unit may, in the startup operation control, further control the operation of the suction flow adjustment unit to keep the suction water flowing through the suction bypass line.

[0009] According to the above configuration, by circulating water (suction water) through a suction bypass line provided to short-circuit the first suction water line, the amount of water that exchanges heat with the refrigerant (is cooled) in the evaporator can be reduced compared to the case where the suction bypass line is not used. As a result, the temperature of the suction water can be lowered more quickly, and the pressure difference between the discharge pressure and suction pressure of the refrigerant compressor can be secured more quickly. This allows the refrigerant compressor to operate stably.

[0010] The refrigerant circulation unit further includes an intake pressure sensor for measuring the pressure of the refrigerant drawn into the refrigerant compressor and a discharge pressure sensor for measuring the pressure of the refrigerant discharged from the refrigerant compressor. The control unit stops the startup operation control and starts normal operation control when the pressure difference between the discharge pressure measured by the discharge pressure sensor and the suction pressure measured by the intake pressure sensor exceeds a predetermined value. In the normal operation control, the operation of the discharge flow adjustment unit is controlled to reduce the discharge water flowing through the discharge bypass line compared to that during the startup operation control.

[0011] With the above configuration, when the pressure difference exceeds a predetermined value and sufficient oil is supplied to the refrigerant compressor, normal operation control is initiated, and the destination of the discharge water flowing through the discharge bypass line decreases compared to the start-up operation control (it switches to the first discharge water line). This allows the refrigerant compressor to operate stably. In addition, the amount of discharge water circulating in the first discharge water circulation section increases, making it possible to stably secure relatively high-temperature discharge water.

[0012] The first discharge-side water circulation unit further includes a discharge-side temperature sensor for measuring the temperature of the discharge-side water flowing into the condenser, and the first suction-side water circulation unit further includes a suction-side temperature sensor for measuring the temperature of the suction-side water flowing into the evaporator. The control unit stops the startup operation control and starts normal operation control when the discharge-side temperature measured by the discharge-side temperature sensor becomes equal to or above a predetermined first threshold temperature, and the suction-side temperature measured by the suction-side temperature sensor becomes equal to or below a predetermined second threshold temperature. In the normal operation control, the control unit may reduce the amount of discharge-side water flowing through the discharge-side bypass line compared to the startup operation control by controlling the operation of the discharge-side flow adjustment unit, and also reduce the amount of suction-side water flowing through the suction-side bypass line compared to the startup operation control by controlling the operation of the suction-side flow adjustment unit.

[0013] With the above configuration, when the temperature of the discharge water is above the first threshold temperature and the temperature of the suction water is below the second threshold temperature, the pressure difference becomes above a predetermined pressure, ensuring sufficient lubrication to the refrigerant compressor. This allows the refrigerant compressor to operate stably.

[0014] Another aspect of the present invention provides a hot water generating device comprising: the heat pump described above; a suction tank for storing the suction water; a heat recovery unit for recovering heat using the suction water; a second suction water circulation unit communicating with the first suction water line via the suction tank and having a second suction water line through which the suction water flows; a discharge tank for storing the discharge water; and a second discharge water circulation unit communicating with the first discharge water line via the discharge tank and having a second discharge water line through which the discharge water flows.

[0015] With the above configuration, since the refrigerant compressor is equipped with a heat pump that can operate stably, the hot water generator can also operate stably.

[0016] The control unit may, in the normal operation control, allow the outflow of suction water from the first suction water line to the suction tank and the inflow of suction water from the suction tank, and may also allow the inflow of discharge water from the first discharge water line to the discharge tank and the outflow of discharge water from the discharge tank.

[0017] With the above configuration, the water stored in the discharge tank (discharge water) can be circulated to the first discharge water circulation unit, thereby increasing the amount of discharge water that exchanges heat with the refrigerant and enabling stable heat exchange with the refrigerant. In addition, the amount of suction water used for heat recovery from the heat recovery unit can be increased, enabling stable heat recovery from the heat recovery unit.

[0018] The discharge-side bypass line branches off from the downstream discharge-side section of the first discharge-side water line through which the discharge-side water flows from the condenser to the discharge-side tank, and merges with the upstream discharge-side section of the first discharge-side water line through which the discharge-side water flows from the discharge-side tank to the condenser. The discharge-side flow adjustment section includes a discharge-side three-way solenoid valve located at the branching point from the downstream discharge-side section, and a discharge-side solenoid valve located upstream of the discharge-side merging point of the discharge-side bypass line in the upstream discharge-side section. The control unit may, in the startup operation control, control the discharge-side three-way solenoid valve to allow flow to the discharge-side bypass line and prevent the inflow of the discharge-side water into the discharge-side tank, and control the discharge-side solenoid valve to prevent the outflow of the discharge-side water from the discharge-side tank.

[0019] With the above configuration, the destination of the discharge water can be switched between the discharge bypass line and the first discharge water line using a simple configuration such as a three-way solenoid valve and a solenoid valve.

[0020] The suction-side bypass line branches off from the downstream suction-side section of the first suction-side water line through which the suction-side water flows from the evaporator to the suction-side tank, and merges with the upstream suction-side section of the first suction-side water line through which the suction-side water flows from the suction-side tank to the evaporator. The suction-side flow adjustment section includes a suction-side three-way solenoid valve positioned at the branching point from the downstream suction-side section, and a suction-side solenoid valve positioned upstream of the suction-side merging point of the suction-side bypass line in the upstream suction-side section. The control unit may, in the startup operation control, control the suction-side three-way solenoid valve to allow flow to the suction-side bypass line and prevent flow to the suction-side tank, and control the suction-side solenoid valve to prevent the outflow of the suction-side water from the suction-side tank.

[0021] With the above configuration, the flow destination of the suction water can be switched between the suction bypass line and the first suction water line using a simple configuration such as a three-way solenoid valve and a solenoid valve.

[0022] Another aspect of the present invention has a refrigerant compressor that sucks in and discharges compressed refrigerant, a refrigerant circulation unit that circulates the refrigerant, and a first discharge-side water circulation unit that circulates discharge-side water that exchanges heat with the refrigerant discharged from the refrigerant compressor, and a control unit. A method for operating a heat pump, wherein the refrigerant circulation unit includes a refrigerant line through which the refrigerant can flow, an oil separator that separates oil from the refrigerant discharged from the refrigerant compressor, and an oil supply line that supplies the oil separated by the oil separator to the refrigerant compressor. A condenser that condenses the refrigerant by exchanging heat between the refrigerant after being compressed by the refrigerant compressor and the discharge-side water, and heats the discharge-side water, and an expansion valve that expands and cools the refrigerant after heat exchange in the condenser. The first discharge-side water circulation unit further includes a first discharge-side water line through which the discharge-side water can flow, and a discharge-side bypass line that branches from the first discharge-side water line and merges into the first discharge-side water line so that the discharge-side water flowing into and out of the condenser short-circuits the first discharge-side water line, and a discharge-side flow adjustment unit that adjusts the flow direction of the discharge-side water. By controlling the operation of the discharge-side flow adjustment unit, the control unit causes the discharge-side water to flow through the discharge-side bypass line immediately after the refrigerant compressor is started, and provides a method for operating a heat pump.

[0023] According to the above method, by circulating water (discharge-side water) through a discharge-side bypass line provided so as to short-circuit the first discharge-side water line, the amount of discharge-side water (the object whose temperature is to be increased) that exchanges heat with the refrigerant in the condenser can be reduced compared to the case where the discharge-side bypass line is not circulated. As a result, the temperature of the discharge-side water can be increased earlier, and the pressure difference between the discharge-side pressure and the suction-side pressure of the refrigerant compressor can be ensured earlier. Thereby, the refrigerant compressor can be stably operated.

Effects of the Invention

[0024] According to the present invention, it is possible to provide a heat pump, a hot water generation device, and a method for operating a heat pump that can stably operate a refrigerant compressor.

Brief Description of the Drawings

[0025] [Figure 1] Schematic configuration diagram of the hot water generation system according to the first embodiment. [Figure 2] Flowchart showing the operation process executed by the control unit according to the first embodiment. [Figure 3A] Diagram showing the discharge side bypass route according to the first embodiment. [Figure 3B] Diagram showing the suction side bypass route according to the first embodiment. [Figure 4A] Diagram showing the discharge side normal route according to the first embodiment. [Figure 4B] Diagram showing the suction side normal route according to the first embodiment. [Figure 5] Graph showing the relationship between pressure difference and time according to the first embodiment. [Figure 6] Diagram showing the refrigerant circulation section according to the comparative example. [Figure 7] Schematic configuration diagram of the hot water generation system according to the second embodiment. [Figure 8] Flowchart showing the operation process executed by the control unit according to the second embodiment. [Figure 9] Graph showing the relationship between pressure difference, temperature and time according to the embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0026] Hereinafter, embodiments will be described with reference to the drawings. The same or corresponding elements are denoted by the same reference numerals throughout the drawings, and redundant detailed descriptions are omitted.

[0027] (First Embodiment) As shown in FIG. 1, a hot water generation system S (an example of a hot water generation device) includes a compressor unit A, a heat recovery unit B, and a controller C (an example of a control unit). The hot water generation system S supplies the compressed gas compressed by the compressor unit A to the demand destination, and provides hot water to the demand destination using the heat generated during compression.

[0028] (Compressor unit) Compressor unit A includes a compressor A1, a heat exchanger A2 (an example of a heat recovery unit), an oil cooler A3, a motor AM, and an inverter AP.

[0029] Compressor A1 is, for example, a screw-type compressor, and operates by the rotation of motor AM. Motor AM is controlled by inverter AP.

[0030] Compressor A1, upon operation, draws in and compresses gases such as air and refrigerant, and discharges the compressed gas (hereinafter referred to as "compressed gas"). In this embodiment, it is an oil-free compressor and is composed of a two-stage compressor including a low-pressure stage compressor A11 and a high-pressure stage compressor A12. Note that compressor A1 is not limited to a two-stage type, but may be a one-stage type or a compressor with three or more stages.

[0031] Heat exchanger A2 consists of an inter-heat exchanger A21 and an after-heat exchanger A22. Heat exchanger A2 exchanges heat between the compressed gas discharged from compressor A1 and the water circulating in heat recovery unit B. This cools the compressed gas and heats the water. Note that the water may be a heat transfer medium (liquid or gas) other than pure water, such as saltwater containing salt.

[0032] Oil cooler A3 exchanges heat between the oil used for cooling and lubricating compressor A1 and the water circulating in heat recovery unit B. This cools the oil and heats the water.

[0033] (Heat recovery unit) The heat recovery unit B provides hot water to the customer using heat recovered from the compressor unit A. The heat recovery unit B includes a first water circulation section 1 (an example of a second suction-side water circulation section), a second water circulation section 2 (an example of a first suction-side water circulation section), a third water circulation section 3 (an example of a first discharge-side water circulation section), and a fourth water circulation section 4 (an example of a second discharge-side water circulation section) that circulate water. In the following, the upstream direction of water flow in each of the first water circulation section 1, the second water circulation section 2, the third water circulation section 3, and the fourth water circulation section 4 will be simply referred to as "upstream," and the downstream direction of water flow will be simply referred to as "downstream."

[0034] (tank) Furthermore, the heat recovery unit B further comprises a first tank R1 and a second tank R2.

[0035] The first tank R1 is connected to the first water circulation section 1 and the second water circulation section 2, and stores the water flowing through the first water circulation section 1 and the second water circulation section 2. The second tank R2 is connected to the third water circulation section 3 and the fourth water circulation section 4, and stores the water flowing through the third water circulation section 3 and the fourth water circulation section 4.

[0036] The water stored in the first tank R1 exchanges heat with the refrigerant drawn into the refrigerant compressor 52 of the refrigerant circulation unit 5, which will be described later. On the other hand, the water stored in the second tank R2 exchanges heat with the refrigerant discharged from the refrigerant compressor 52. For this reason, in the following, the water stored in the first tank R1 will be referred to as "suction water," and the water stored in the second tank R2 will be referred to as "discharge water." Furthermore, the first tank R1 will be referred to as the "suction tank," and the second tank R2 will be referred to as the "discharge tank."

[0037] (1st water circulation section) The first water circulation unit 1 includes a first water line 11 (an example of a second suction side water line) and a first pump 12.

[0038] The first water line 11 is composed of piping or the like through which water (suction water) can flow. The first water line 11 has a first upstream end 11a and a first downstream end 11b, both of which are connected to the suction tank R1, and together with the suction tank R1, it forms a first circulation line L1 (circuit) through which suction hot water can circulate. The first upstream end 11a of the first water line 11 is an inlet through which suction water flows from the suction tank R1 to the first water line 11, and the first downstream end 11b is an outlet through which suction water flows from the first water line 11 to the suction tank R1.

[0039] The first pump 12 is positioned in the first water line 11 (specifically, the section through which suction water flows from the suction tank R1 to the compressor unit A) and pumps the suction water flowing through the first water line 11. This causes the suction water to circulate in the first circulation line L1. The temperature of the suction water circulating in the first circulation line L1 is, for example, 30°C to 35°C. More specifically, the temperature of the suction water flowing from the suction tank R1 into the first water line 11 is 30°C (approximately 30°C), and the temperature of the suction water flowing from the first water line 11 back into the suction tank R1 is 35°C (approximately 35°C).

[0040] (2nd water circulation section) The second water circulation unit 2 includes a second water line 21 (an example of the first suction-side water line), a second pump 22, a suction-side bypass line 23, a suction-side three-way valve 24 (an example of a suction-side three-way solenoid valve), and a suction-side on-off valve 25 (an example of a suction-side solenoid valve). The suction-side three-way valve 24 is also an example of a suction-side flow adjustment unit that adjusts the flow direction of the suction-side water. In this embodiment, the suction-side three-way valve 24 and the suction-side on-off valve 25 are solenoid valves operated by electromagnets, but they may also be motor-driven electric valves.

[0041] The second water line 21 is composed of piping or the like through which water (suction water) can flow. The second water line 21 has a second upstream end 21a and a second downstream end 21b, both of which are connected to the suction tank R1, forming a second circulation line L2 (circuit) with the suction tank R1 through which the suction water can circulate. In other words, the second water line 21 is in communication with the first water line 11 via the suction tank R1. The second upstream end 21a of the second water line 21 is the inlet through which suction water flows from the suction tank R1 to the second water line 21, and the second downstream end 21b is the outlet through which suction water flows from the second water line 21 to the suction tank R1.

[0042] An evaporator 57, through which the suction water described later flows in and out, is located in the middle of the second water line 21. Hereinafter, the part of the second water line 21 through which the suction water flows from the suction tank R1 to the evaporator 57 will be referred to as the "upstream suction section 21u," and the part through which the suction water flows from the evaporator 57 to the suction tank R1 will be referred to as the "downstream suction section 21d."

[0043] The second pump 22 is located in the second water line 21 (specifically, the upstream section 21u on the suction side) and pumps the suction water flowing through the second water line 21. This causes the suction water to circulate in the second circulation line L2. The temperature of the suction water circulating in the second circulation line L2 is, for example, 25°C to 30°C. More specifically, the temperature of the suction water flowing from the suction tank R1 into the second water line 21 is 30°C (approximately 30°C), and the temperature of the suction water flowing from the second water line 21 back into the suction tank R1 is 25°C (approximately 25°C).

[0044] The suction-side bypass line 23 is provided to shorten the flow path (route) of the suction-side water flowing through the second water circulation section 2. Specifically, the suction-side bypass line 23 branches off from the second water line 21 and merges with the second water line 21 to short-circuit it. More precisely, the suction-side bypass line 23 branches off from the downstream suction-side portion 21d of the second water line 21 and merges with the upstream suction-side portion 21u of the second water line 21. In other words, in this embodiment, the suction-side bypass line 23 is a detour route that allows the suction-side water to bypass the suction-side tank R1.

[0045] Hereinafter, the point where the suction bypass line 23 branches off from the second water line 21 will be referred to as the "suction branch point P11," and the point where it merges with the second water line 21 will be referred to as the "suction confluence point P12."

[0046] The suction-side three-way valve 24 is located at the suction-side branching point P11. The suction-side three-way valve 24 controls the flow direction of the suction-side water by changing its orientation. Specifically, the suction-side three-way valve 24 switches the flow path (route) of the suction-side water between a route that goes towards the suction-side tank R1 and a route that bypasses the suction-side tank R1 and flows through the suction-side bypass line 23. In the following, the route through which the suction-side water goes towards the suction-side tank R1 will be referred to as the "normal suction-side route," and the route through which the suction-side water flows through the suction-side bypass line 23 will be referred to as the "suction-side bypass route."

[0047] In other words, the suction-side three-way valve 24 is positioned such that, in the normal suction route, the suction-side water flows towards the suction-side tank R1, and in the suction-side bypass route, the direction of flow of the suction-side water becomes the suction-side bypass line 23.

[0048] The suction-side shut-off valve 25 is located upstream of the suction-side confluence point P12 (towards the suction-side tank R1) in the upstream section 21u of the suction side. The suction-side shut-off valve 25 controls the flow of suction-side water by opening and closing. Specifically, the suction-side shut-off valve 25 prevents or allows the inflow of suction-side water from the suction-side tank R1 into the second water line 21. In this embodiment, the suction-side shut-off valve 25 is open (allows) in the normal suction-side route and closed (blocks) in the suction-side bypass route.

[0049] With the above configuration, the second water circulation unit 2 can change the route of the suction-side water between the suction-side normal route and the suction-side bypass route.

[0050] (3rd water circulation section) The third water circulation unit 3 includes a third water line 31 (an example of a first discharge-side water line), a third pump 32, a discharge-side bypass line 33, a discharge-side three-way valve 34 (an example of a discharge-side three-way solenoid valve), and a discharge-side on-off valve 35 (an example of a discharge-side solenoid valve). The discharge-side three-way valve 34 is also an example of a discharge-side flow adjustment unit that adjusts the flow direction of the discharge-side water. In this embodiment, the discharge-side three-way valve 34 and the discharge-side on-off valve 35 are solenoid valves operated by electromagnets, but they may also be motor-driven electric valves.

[0051] The third water line 31 is composed of piping, etc., through which water (discharge water) can flow. The third water line 31 has a third upstream end 31a and a third downstream end 31b, both of which are connected to the discharge tank R2, forming a third circulation line L3 (circuit) together with the discharge tank R2 through which the discharge water can circulate. The third upstream end 31a of the third water line 31 is an inlet through which discharge water flows from the discharge tank R2 to the third water line 31, and the third downstream end 31b is an outlet through which discharge water flows from the third water line 31 to the discharge tank R2.

[0052] A condenser 55, through which discharge water (described later) flows in and out, is located in the middle of the third water line 31. Hereinafter, the portion of the third water line 31 through which discharge water flows from the discharge tank R2 to the condenser 55 will be referred to as the "upstream discharge section 31u," and the portion through which discharge water flows from the condenser 55 to the discharge tank R2 will be referred to as the "downstream discharge section 31d."

[0053] The third pump 32 is located in the third water line 31 (specifically, the upstream discharge section 31u) and pumps the discharge water flowing through the third water line 31. This causes the discharge water to circulate in the third circulation line L3. The temperature of the discharge water circulating in the third water circulation section 3 is, for example, 80°C to 85°C. More specifically, the temperature of the discharge water flowing from the discharge tank R2 into the third water line 31 is 80°C (approximately 80°C), and the temperature of the discharge water flowing from the third water line 31 into the discharge tank R2 is 85°C (approximately 85°C). During normal operation of the heat recovery unit B, the temperature of the suction water is lower than the temperature of the discharge water. For this reason, the suction water may be referred to as "low-temperature water" and the discharge water as "high-temperature water" below. However, "low-temperature water" and "high-temperature water" are relative expressions of the water temperature in the heat recovery unit B and do not limit the definition of low-temperature water and high-temperature water to specific temperatures.

[0054] The discharge-side bypass line 33 is provided to shorten the flow path (route) of the discharge-side water flowing through the third water circulation section 3. Specifically, the discharge-side bypass line 33 branches off from the third water line 31 and merges with the third water line 31 to short-circuit it. More precisely, the discharge-side bypass line 33 branches off from the downstream discharge side 31d of the third water line 31 and merges with the upstream discharge side 31u of the third water line 31. In other words, in this embodiment, the discharge-side bypass line 33 is a detour that allows the discharge-side water to bypass the discharge-side tank R2.

[0055] Hereinafter, the point where the discharge bypass line 33 branches off from the third water line 31 will be referred to as the "discharge branch point P21," and the point where it merges with the second water line 21 will be referred to as the "discharge confluence point P22."

[0056] The discharge-side three-way valve 34 is located at the discharge-side branching point P21. The discharge-side three-way valve 34 controls the flow direction of the discharge-side water by changing its orientation. Specifically, the discharge-side three-way valve 34 switches the flow path (route) of the discharge-side water between a route toward the discharge-side tank R2 and a route through the discharge-side bypass line 33. In the following, the route through which the discharge-side water flows toward the discharge-side tank R2 will be referred to as the "discharge-side normal route," and the route through which the discharge-side water flows through the discharge-side bypass line 33 will be referred to as the "discharge-side bypass route."

[0057] In other words, the discharge-side three-way valve 34 is positioned such that, in the normal discharge-side route, the direction of water flow on the discharge-side is toward the discharge-side tank R2, and in the discharge-side bypass route, the direction of water flow on the discharge-side is toward the discharge-side bypass line 33.

[0058] The discharge-side shut-off valve 35 is located upstream of the discharge-side confluence point P22 (towards the discharge-side tank R2) in the discharge-side upstream section 31u. The discharge-side shut-off valve 35 controls the flow of discharge-side water by opening and closing. Specifically, the discharge-side shut-off valve 35 blocks or allows the inflow of discharge-side water from the discharge-side tank R2 to the discharge-side bypass line 33. In this embodiment, the discharge-side shut-off valve 35 is open (allows) in the discharge-side normal route and closed (blocks) in the discharge-side bypass route.

[0059] With the above configuration, the third water circulation unit 3 can change the route of the discharged water between the discharged normal route and the discharged bypass route.

[0060] (4th water circulation section) The fourth water circulation unit 4 includes a fourth water line 41 (an example of a second discharge water line), a fourth pump 42, and a heat exchanger 43.

[0061] The fourth water line 41 is composed of piping, etc., through which water (discharge water) can flow. The fourth water line 41 has a fourth upstream end 41a and a fourth downstream end 41b, both of which are connected to the discharge tank R2, forming a fourth circulation line L4 (circuit) with the discharge tank R2 through which the discharge water can circulate. In other words, the fourth water line 41 is in communication with the third water line 31 via the discharge tank R2. The fourth upstream end 41a of the fourth water line 41 is the inlet through which discharge water flows from the discharge tank R2 to the fourth water line 41, and the fourth downstream end 41b is the outlet through which discharge water flows from the fourth water line 41 to the discharge tank R2.

[0062] The fourth pump 42 is located in the fourth water line 41 (specifically, the section from the discharge tank R2 to the heat exchanger 43) and pumps the discharge water flowing through the fourth water line 41. This causes the discharge water to circulate in the fourth circulation line L4. The temperature of the discharge water circulating in the fourth water circulation section 4 is, for example, 75°C to 80°C. More specifically, the temperature of the discharge water flowing from the discharge tank R2 into the fourth water line 41 is 80°C (approximately 80°C), and the temperature of the discharge water flowing from the fourth water line 41 to the discharge tank R2 is 75°C (approximately 75°C). The discharge water flowing through the fourth water line 41 exchanges heat with the water flowing through the supply water circulation section D (water supplied to the customer) in the heat exchanger 43. This allows, for example, water at a temperature of 80°C (hot water) to be supplied to the customer.

[0063] The heat recovery unit B further includes a refrigerant circulation unit 5 for circulating a refrigerant. In this embodiment, the refrigerant circulation unit 5, together with the second water circulation unit 2 and the third water circulation unit 3 described above, constitutes a heat pump.

[0064] (refrigerant circulation section) The refrigerant circulation unit 5 comprises a refrigerant compressor 52, a refrigerant line 51, an oil separation unit 53, a discharge-side pressure sensor 54, a condenser 55, an expansion valve 56, an evaporator 57, and an intake-side pressure sensor 58, constituting the refrigeration cycle L5. The refrigerant circulation unit 5 further includes a motor 5M that operates the refrigerant compressor 52 and an inverter 5P that controls the operation of the motor.

[0065] The refrigerant line 51 consists of piping through which the refrigerant can flow. The refrigerant compressor 52, oil separator 53, discharge-side pressure sensor 54, condenser 55, expansion valve 56, evaporator 57, and suction-side pressure sensor 58 are connected in this order via the refrigerant line 51. The refrigerant discharged from the refrigerant compressor 52 flows through the oil separator 53, condenser 55, expansion valve 56, and evaporator 57 in this order before flowing back into the refrigerant compressor 52.

[0066] The refrigerant compressor 52 is a screw-type compressor that draws in refrigerant, compresses it, and discharges the refrigerant. The refrigerant compressor 52 has a screw 521, a bearing 522 that rotatably supports the screw 521, and a casing 523 that houses the screw 521 and the bearing 522. In this embodiment, the bearing 522 is a rolling bearing.

[0067] The screw 521 rotates as the motor 5M rotates. The motor 5M is controlled by the inverter 5P. As the screw 521 rotates, the refrigerant compressor 52 draws the refrigerant flowing through the refrigerant line 51 into the casing 523, compresses it, and discharges the compressed refrigerant to the outside of the casing 523.

[0068] Hereinafter, the pressure on the intake side of the refrigerant flowing through the refrigerant circulation unit 5 will be called the "suction side pressure Ps," and the pressure on the discharge side will be called the "discharge side pressure Pd." The difference between the discharge side pressure Pd and the suction side pressure Ps (discharge side pressure Pd - suction side pressure Ps) will be called the "pressure difference ΔP." The refrigerant compressor 52 is a self-lubricating compressor, and oil is supplied from the oil separation unit 53 by utilizing the pressure difference ΔP.

[0069] The oil separation unit 53 includes an oil separator 531 and an oil supply line 532. The oil separator 531 separates oil from the refrigerant discharged from the refrigerant compressor 52.

[0070] The refrigeration line 532 is connected to the oil separator 531 and the refrigerant compressor 52, and the oil separated by the oil separator 531 is supplied to the refrigerant compressor 52 via the refrigeration line 532.

[0071] In this embodiment, oil is supplied to the refrigerant compressor 52 via the oil supply line 532 when the pressure difference ΔP exceeds a predetermined value (hereinafter referred to as predetermined pressure Pt). The predetermined pressure Pt (see Figure 5) is a pressure (value) based on the specifications of the refrigerant compressor 52, and is, for example, 0.3 MPa.

[0072] The discharge-side pressure sensor 54 is positioned between the oil separator 531 and the condenser 55. The discharge-side pressure sensor 54 measures the pressure of the refrigerant discharged from the refrigerant compressor 52. For example, the discharge-side pressure sensor 54 measures the internal pressure of the refrigerant line 51 between the oil separator 531 and the condenser 55 and obtains it as the discharge-side pressure Pd. Information indicating the obtained discharge-side pressure Pd is transmitted to the controller C.

[0073] The condenser 55 exchanges heat between the refrigerant from which oil has been separated by the oil separator 531 (the refrigerant after it has been compressed by the refrigerant compressor 52) and the discharge water circulating in the third water circulation section 3. As a result, the refrigerant is condensed and liquefied, and the discharge water circulating in the third water circulation section 3 is heated.

[0074] The expansion valve 56 expands and cools the refrigerant liquefied in the condenser 55, thereby reducing the pressure of the refrigerant.

[0075] The evaporator 57 exchanges heat between the refrigerant expanded by the expansion valve 56 and the suction water circulating in the second water circulation section 2. As a result, the refrigerant evaporates, and the suction water circulating in the second water circulation section 2 is cooled. The refrigerant evaporated in the evaporator 57 is drawn into the refrigerant compressor 52 and compressed by the refrigerant compressor 52. In this way, the refrigerant circulates in the refrigerant circulation section 5, repeatedly undergoing compression, expansion, and compression.

[0076] The suction-side pressure sensor 58 is positioned between the evaporator 57 and the refrigerant compressor 52. The suction-side pressure sensor 58 measures the pressure of the refrigerant being drawn into the refrigerant compressor 52. For example, the suction-side pressure sensor 58 measures the internal pressure of the refrigerant line 51 between the evaporator 57 and the refrigerant compressor 52 and obtains it as the suction-side pressure Ps. Information indicating the obtained suction-side pressure Ps is transmitted to the controller C.

[0077] (Control Unit) Controller C controls the operation of each part of the hot water generation system S (compressor unit A and heat recovery unit B). Controller C consists of hardware such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory), and software implemented on them.

[0078] In the hot water generation system S configured as described above, if the refrigerant compressor 52 remains stopped for a predetermined period (for example, 24 hours) or longer, the temperature of the discharge water (high-temperature water) decreases, and the temperature difference between it and the suction water (low-temperature water) decreases. The discharge pressure Pd depends on the temperature of the discharge water circulating in the third water circulation section 3 (it is proportional to the temperature), and the suction pressure Ps depends on the temperature of the suction water circulating in the second water circulation section 2 (it is proportional to the temperature). Therefore, as the temperature difference between the discharge water and the suction water decreases, the pressure difference ΔP also decreases.

[0079] When the pressure difference ΔP decreases and falls below a predetermined pressure Pt, oil will not be supplied from the oil separator 531 to the refrigerant compressor 52 even if the refrigerant compressor 52 is started. In this state, if the refrigerant compressor 52 continues to operate for a predetermined time (for example, 10 seconds) or longer, the bearing 522 of the refrigerant compressor 52 may be damaged. In other words, if the pressure difference ΔP is raised to a predetermined pressure Pt or higher within a predetermined time and oil supply is started, damage to the bearing 522 of the refrigerant compressor 52 can be suppressed. The predetermined time is the amount of time during which the refrigerant compressor 52 can operate without damaging the bearing 522 in the state where oil is not supplied.

[0080] Controller C performs startup operation control to make the pressure difference ΔP equal to or greater than a predetermined pressure Pt within a predetermined time. The termination of the startup operation control is determined based on whether the pressure difference ΔP is equal to or greater than the predetermined pressure Pt.

[0081] In this embodiment, the startup operation control is initiated immediately after the refrigerant compressor 52 of the refrigerant circulation unit 5 starts up, provided that the preset execution conditions are met. The execution conditions are preset by the designer of the hot water generation system S based on conditions such as room temperature and atmospheric pressure. For example, one of the execution conditions is that 24 hours or more have elapsed since the refrigerant compressor 52 stopped (the period during which it has been continuously stopped). The startup operation control may also be initiated immediately before or at the same time as the refrigerant compressor 52 of the refrigerant circulation unit 5 starts up.

[0082] If the above execution conditions are not met and startup operation control is not performed, or if the pressure difference ΔP becomes equal to or greater than a predetermined pressure Pt and startup operation control is terminated, the controller C performs normal operation control as the operation control of the hot water generation system S.

[0083] The following describes the operation process performed by controller C (an example of how to operate the heat pump) with reference to Figure 2. Figure 2 is a flowchart showing the operation process performed by controller C. The operation process starts, for example, when a signal indicating the start of the hot water generation system S (an instruction from an operator, etc.) is input to controller C.

[0084] As shown in Figure 2, controller C determines whether the execution conditions for startup operation control are met (step S1), and if it determines that the execution conditions are met (step S1; YES), it starts startup operation control (step S2). During startup operation control, controller C controls the operation of the discharge-side three-way valve 34 and the discharge-side on-off valve 35 so that the route of the discharge-side water flowing through the third water circulation section 3 becomes the discharge-side bypass route. At the same time, controller C controls the operation of the suction-side three-way valve 24 and the suction-side on-off valve 25 so that the route of the suction-side water flowing through the second water circulation section 2 becomes the suction-side bypass route. Hereinafter, the discharge-side bypass route and the suction-side bypass route will be collectively referred to as the "bypass route".

[0085] In other words, as shown in Figure 3A, controller C controls the position of the discharge-side three-way valve 34 to allow the flow of discharge-side water to the discharge-side bypass line 33 and to prevent the outflow of discharge-side water from the third water line 31 to the discharge-side tank R2. At the same time, controller C controls (closes) the discharge-side on-off valve 35 to prevent the inflow of discharge-side water from the discharge-side tank R2 to the third water line 31.

[0086] Furthermore, as shown in Figure 3B, controller C controls the position of the suction-side three-way valve 24 to allow the flow of suction-side water to the suction-side bypass line 23 and to prevent the outflow of suction-side water from the second water line 21 to the suction-side tank R1. In addition, controller C controls (closes) the suction-side on-off valve 25 to prevent the inflow of suction-side water from the suction-side tank R1 to the second water line 21.

[0087] As described above, controller C controls the flow so that the discharge water bypasses the discharge tank R2 through the discharge bypass line 33, and the suction water bypasses the suction tank R1 through the suction bypass line 23. As a result, immediately after the refrigerant compressor 52 is started, discharge water flows through the discharge bypass line 33 and suction water flows through the suction bypass line 23.

[0088] Controller C performs startup operation control until the pressure difference ΔP, which is the difference between the discharge pressure Pd obtained from the discharge pressure sensor 54 and the suction pressure Ps obtained from the suction pressure sensor 58, becomes equal to or greater than a predetermined pressure Pt (Step S3; NO).

[0089] If controller C determines that the execution conditions are not met (step S1; NO), or if the pressure difference ΔP becomes equal to or greater than the predetermined pressure Pt and the startup operation control ends (step S3; YES), it starts normal operation control (step S4).

[0090] In normal operation control, controller C controls the operation of the discharge-side three-way valve 34 and the discharge-side on-off valve 35 to set the route of discharge-side water flowing through the third water circulation section 3 as the normal discharge route, and reduces the amount of discharge-side water flowing through the discharge-side bypass line 33 compared to the time of startup operation control. In addition, in this embodiment, controller C also controls the operation of the suction-side three-way valve 24 and the suction-side on-off valve 25 to set the route of suction-side water flowing through the second water circulation section 2 as the normal suction route, and reduces the amount of suction-side water flowing through the suction-side bypass line 23 compared to the time of startup operation control. Hereinafter, the normal discharge route and the normal suction route will be collectively referred to as the "normal route".

[0091] In other words, as shown in Figure 4A, controller C controls the position of the discharge-side three-way valve 34 to block the flow of discharge-side water to the discharge-side bypass line 33 and to allow the outflow of discharge-side water from the third water line 31 to the discharge-side tank R2. At the same time, controller C controls (opens) the discharge-side on-off valve 35 to allow the inflow of discharge-side water from the discharge-side tank R2 to the third water line 31.

[0092] Furthermore, as shown in Figure 4B, controller C controls the position of the suction-side three-way valve 24 to block the flow of suction-side water to the suction-side bypass line 23, while allowing the outflow of suction-side water from the second water line 21 to the suction-side tank R1. In addition, controller C controls (opens) the suction-side on-off valve 25 to allow the inflow of suction-side water from the suction-side tank R1 to the second water line 21.

[0093] As described above, controller C controls the system so that the discharge water circulates through the third water circulation section 3 via the discharge tank R2 (without detouring). Simultaneously, the suction water circulates through the second water circulation section 2 via the suction tank R1 (without detouring).

[0094] The operation process ends when, for example, a signal indicating the stop of the hot water generation system S (an instruction from an operator) is input to the controller C by an operator or other person.

[0095] The effects of implementing the startup operation control according to this embodiment will be explained below with reference to Figure 5. Figure 5 is an example of a graph showing the relationship between discharge pressure Pd and suction pressure Ps and time for startup operation control (control using the bypass route) and normal operation control (control using the normal route), respectively. In Figure 5, the horizontal axis represents time t, and the vertical axis represents pressure P.

[0096] The solid lines in Figure 5 show the time variation of the discharge pressure Pd and suction pressure Ps when startup operation control is performed, and the dashed lines in Figure 5 show the time variation of the discharge pressure Pd and suction pressure Ps when startup operation control is not performed in this embodiment, i.e., when normal operation control is performed. Figure 5 shows the time variation of the discharge pressure Pd and suction pressure Ps when the discharge water temperature is at a certain temperature (for example, 80°C).

[0097] As shown in Figure 5, during the period when the refrigerant compressor 52 is stopped, after a predetermined time has elapsed since the compressor stopped, the discharge pressure Pd and the suction pressure Ps become equal.

[0098] When normal operation control is performed at time t0, and the refrigerant compressor 52 starts operating, the discharge pressure Pd increases and the suction pressure Ps decreases, as shown by the dashed line in Figure 5, and the pressure difference ΔP becomes greater than or equal to a predetermined pressure Pt after time t2 has elapsed from the start of operation of the refrigerant compressor 52.

[0099] On the other hand, if startup operation control is performed at time t0, as explained with reference to Figure 3A, the route of discharge water flowing through the third water circulation unit 3 becomes a bypass route (discharge-side bypass route), and the discharge water flows through the discharge-side bypass line 33 so as to short-circuit the third water line 31. This reduces the amount of discharge water that undergoes heat exchange in the condenser 55. Similarly, as explained with reference to Figure 3B, the route of discharge water flowing through the second water circulation unit 2 becomes a bypass route (suction-side bypass route), and the suction water flows through the suction-side bypass line 23 so as to short-circuit the second water line 21. This reduces the amount of suction water that undergoes heat exchange in the evaporator 57. As a result, as shown by the solid line in Figure 5, the pressure difference ΔP can be set to a predetermined pressure Pt or higher after an earlier time t1 (< time t2) than in normal operation control, from the start of operation of the refrigerant compressor 52.

[0100] In other words, by performing startup control, the time required for the pressure difference ΔP to reach a predetermined pressure Pt or higher can be shortened.

[0101] (Effects of the first embodiment) As explained above, by performing startup control (bypassing the water routes through the second water circulation section 2 and the third water circulation section 3), the pressure difference ΔP can be raised to a predetermined pressure or higher in a shorter time compared to when startup control is not performed. This allows the supply of oil to the refrigerant compressor 52 to start earlier, thereby suppressing damage to the bearing 522. As a result, the refrigerant compressor 52 can be started stably.

[0102] Furthermore, the configuration can be simplified compared to a configuration in which the cooling unit 99 is operated before the refrigerant compressor 92 is started, as shown in the comparative example 9 in Figure 6. Figure 6 is a diagram showing the configuration of the refrigerant circulation unit 9 in the comparative example. The refrigerant circulation unit 9 in the comparative example includes a refrigerant line 91, a refrigerant compressor 92, an oil separation unit 93, a discharge-side pressure sensor 94, a condenser 95, an expansion valve 96, an evaporator 97, and an intake-side pressure sensor 98, as well as a cooling unit 99 through which water is circulated. In the refrigerant circulation unit 9 in the comparative example, it is necessary to operate the pump 991 of the cooling unit 99 to circulate water via the cooling tower 992 before the refrigerant compressor 92 is started.

[0103] (Modification of the first embodiment) Furthermore, as shown in Figure 1, the refrigerant circulation unit 5 may also include a pressure-holding valve 59 between the discharge-side pressure sensor 54 and the condenser 55. This allows the discharge-side pressure Pd to be increased.

[0104] Furthermore, the execution conditions for startup operation control are not limited to a 24-hour shutdown period, but can be changed as appropriate to a 36-hour shutdown period, a 12-hour shutdown period, etc. In addition, the execution conditions for startup operation control may be based on conditions other than the shutdown period, such as the pressure difference ΔP, the temperature of the discharge water, the temperature of the suction water, etc.

[0105] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 7 and 8. The second embodiment differs from the first embodiment in that the termination of the startup operation control is determined not based on a pressure difference ΔP (whether the pressure difference ΔP is equal to or greater than a predetermined pressure Pt), but on the temperature of the discharge water and the temperature of the suction water. Since the other configurations are the same as in the first embodiment, the same reference numerals are used for the same or similar configurations as in the first embodiment, and detailed descriptions are omitted.

[0106] The second water circulation unit 2 further includes a suction-side temperature sensor 26 that measures the temperature of the suction-side water flowing into the evaporator 57 (an example of the suction-side temperature). The suction-side temperature sensor 26 is located downstream of the suction-side confluence point P12 (upstream of the second pump 22) in the upstream suction-side section 21u and acquires information indicating the temperature of the suction-side water flowing into the evaporator 57. The acquired temperature information is transmitted to the controller C.

[0107] The third water circulation unit 3 further includes a discharge-side temperature sensor 36 that measures the temperature of the discharge-side water flowing into the condenser 55 (an example of the discharge-side temperature). The discharge-side temperature sensor 36 is located downstream of the discharge-side confluence point P22 (upstream of the third pump 32) in the discharge-side upstream section 31u and acquires information indicating the temperature of the discharge-side water flowing into the condenser 55. The acquired temperature information is transmitted to the controller C.

[0108] In the second embodiment, the refrigerant circulation unit 5 omits the discharge-side pressure sensor 54 and the suction-side pressure sensor 58, and the controller C determines whether or not to terminate the startup operation control based on the water temperature (temperature difference) obtained from the discharge-side temperature sensor 36 and the suction-side temperature sensor 26, instead of the pressure information obtained from the discharge-side pressure sensor 54 and the suction-side pressure sensor 58.

[0109] The following describes the operation process (an example of a heat pump operation method) performed by the controller C according to the second embodiment, with reference to Figure 8.

[0110] As shown in Figure 8, controller C performs startup operation control until the water temperatures obtained from the discharge-side temperature sensor 36 and the suction-side temperature sensor 26 meet the preset temperature conditions (discharge-side water temperature is above the first threshold temperature, and suction-side water temperature is below the second threshold temperature) (step S13; NO in Figure 8). Specifically, controller C performs startup operation control until the discharge-side water temperature obtained from the discharge-side temperature sensor 36 is above the first threshold temperature (e.g., 45°C) and the suction-side water temperature obtained from the suction-side temperature sensor 26 is below the second threshold temperature (e.g., 25°C).

[0111] On the other hand, if controller C determines that the temperature conditions are met (step S13; YES), it terminates the startup operation control and thereafter starts normal operation control in the same manner as in the first embodiment (step S4).

[0112] As described above, according to this embodiment, it is possible to determine whether or not to terminate the startup operation control based on the information obtained from the discharge-side temperature sensor 36 and the suction-side temperature sensor 26, and to start the execution of normal operation control.

[0113] As shown in Figure 9, the temperature difference between the suction water temperature and the discharge water temperature is correlated (proportional) with the pressure difference ΔP. When the temperature difference increases, the pressure difference ΔP also increases, and when the temperature difference decreases, the pressure difference ΔP also decreases. Figure 9 is an example of a graph showing the relationship between the discharge pressure Pd (discharge water temperature) and suction pressure Ps (suction water temperature) and time when startup operation control is performed. In Figure 9, the horizontal axis represents time t, and the vertical axis represents the pressure P and the water temperature T correlated with the pressure P (below 30°C: suction water temperature, 30°C or more: discharge water temperature).

[0114] As described above, in this embodiment as well, sufficient oil is supplied to the refrigerant compressor 52, allowing the refrigerant compressor to operate stably.

[0115] (Another embodiment) In the startup operation control of the above embodiment, controller C controlled both the second water circulation unit 2 and the third water circulation unit 3 to become bypass routes (suction-side bypass route and discharge-side bypass route). However, controller C may also control the system so that at least one of the second water circulation unit 2 and the third water circulation unit 3 becomes a bypass route during startup operation control. More specifically, controller C may control the system so that only the second water circulation unit 2 or only the third water circulation unit 3 becomes a bypass route.

[0116] Furthermore, in the above embodiment, a suction-side three-way valve 24 was used in the second water circulation unit 2 to switch between the suction-side bypass route and the suction-side normal route. However, the second water circulation unit 2 may have a suction-side on-off valve downstream of the suction-side three-way valve 24 (suction-side branching point P11) instead of the suction-side three-way valve 24, and the controller C may switch between the suction-side bypass route and the suction-side normal route by opening and closing the suction-side on-off valve. Similarly, the third water circulation unit 3 may have a discharge-side on-off valve downstream of the discharge-side three-way valve 34 (discharge-side branching point P21) instead of the discharge-side three-way valve 34, and the controller C may switch between the discharge-side bypass route and the discharge-side normal route by opening and closing the discharge-side on-off valve.

[0117] In the suction-side normal route (normal operation control) described in the above embodiment, the amount of suction-side water flowing through the suction-side bypass line 23 should be reduced compared to the suction-side bypass route (during startup operation control). The flow through the suction-side bypass line 23 may be blocked (completely stopped) or it may flow (a small amount flows) without being blocked (completely stopped). The same applies to the discharge-side water. [Explanation of Symbols]

[0118] 1. First water circulation section (an example of the second suction side water circulation section) 2. Second water circulation section (an example of the first suction side water circulation section) 3. Third water circulation section (an example of the first discharge side water circulation section) 4. Fourth water circulation section (an example of the second discharge side water circulation section) 5 Refrigerant circulation section 5M Motor 5P Inverter 9 Refrigerant circulation section 11. First water line (an example of a second suction side water line) 11a 1st upstream end 11b 1st downstream end 12. Pump No. 1 21. Second water line (an example of the first suction side water line) 21a 2nd upstream end 21b 2nd downstream end 21d Downstream section of the suction side 21u Upstream section of the suction side 22 Pump No. 2 23 Intake bypass line 24. Suction-side three-way valve (an example of a suction-side three-way solenoid valve) 25. Suction-side on / off valve (an example of a suction-side solenoid valve) 26. Inlet temperature sensor 31. Third water line (an example of the first discharge side water line) 31a 3rd upstream end 31b 3rd downstream end 31d Discharge side downstream part 31u Discharge side upstream part 32 Third pump 33 Discharge side bypass line 34. Discharge-side three-way valve (an example of a discharge-side three-way solenoid valve) 35. Discharge-side on / off valve (an example of a discharge-side solenoid valve) 36 Discharge side temperature sensor 41. Fourth water line (an example of a second discharge side water line) 41a 4th upstream end 41b 4th downstream end 42. Pump No. 4 43 Heat exchanger 51 Refrigerant line 52 Refrigerant compressor 53 Oil separation section 54 Discharge-side pressure sensor 55 Condenser 56 Expansion valve 57 Evaporator 58 Suction side pressure sensor 59 Pressure-holding valve 521 Screw 522 Bearing 523 Casing 531 Oil separator 532 Fueling line 91 Refrigerant line 991 pump A Compressor Unit A1 Compressor A2 Heat exchanger (an example of a heat recovery unit) A3 Oil Cooler A11 Low-Pressure Stage Compressor A12 High-pressure stage compressor A21 Interheat Exchanger A22 Afterheat Exchanger AM Motor AP Inverter B Heat Recovery Unit C Controller (an example of a control unit) D Supply water circulation section L1 First Circulation Line L2 Second Circulation Line L3 Third Circulation Line L4 4th circulation line M1 Startup Operation Control M2 Normal Operation Control P11 Intake side branch point P12 Suction side confluence point P21 Discharge side branch point P22 Discharge side confluence point Pd discharge pressure Ps Suction pressure Pt specified pressure R1 Intake Tank R2 Discharge side tank ΔP pressure difference S Hot water generation system (an example of a hot water generation device)

Claims

1. It has a refrigerant compressor that sucks in refrigerant, compresses it, and discharges the refrigerant, and a refrigerant circulation unit that circulates the refrigerant, A first discharge-side water circulation unit circulates discharge-side water that exchanges heat with the refrigerant discharged from the refrigerant compressor, It comprises a control unit and, The refrigerant circulation unit is, A refrigerant line through which the aforementioned refrigerant can flow, An oil separator for separating oil from the refrigerant discharged from the refrigerant compressor, A supply line for supplying the oil separated by the oil separator to the refrigerant compressor, A condenser that heats the discharge water by exchanging heat between the refrigerant, which has been compressed by the refrigerant compressor, and the discharge water, The condenser further includes an expansion valve for expanding and cooling the refrigerant after heat exchange, The first discharge-side water circulation section is, A first discharge water line through which the discharge water can flow, A discharge bypass line is provided, which branches off from the first discharge water line and merges with the first discharge water line, such that the discharge water flowing into and out of the condenser short-circuits the first discharge water line. It has a discharge-side flow adjustment unit that adjusts the flow direction of the discharge-side water, The control unit performs startup operation control, The control unit controls the operation of the discharge-side flow adjustment unit in the startup operation control, thereby ensuring that the discharge-side water flows through the discharge-side bypass line immediately after the refrigerant compressor is started up, in this heat pump.

2. The refrigerant compressor further comprises a first suction-side water circulation unit that circulates suction-side water that exchanges heat with the refrigerant drawn in by the refrigerant compressor, The refrigerant circulation unit further includes an evaporator that cools the suction water by evaporating the refrigerant through heat exchange between the refrigerant and the suction water. The first suction-side water circulation section is, A first suction water line through which the suction water can flow, A suction bypass line is provided, which branches off from the first suction water line and merges with the first suction water line, such that the suction water flowing into and out of the evaporator short-circuits the first suction water line. It has a suction-side flow adjustment unit that adjusts the flow direction of the suction-side water, The heat pump according to claim 1, wherein the control unit further controls the operation of the suction side flow adjustment unit in the startup operation control, thereby ensuring that the suction side water flows through the suction side bypass line.

3. The refrigerant circulation unit is, A suction-side pressure sensor for measuring the pressure of the refrigerant being drawn into the refrigerant compressor, The system further includes a discharge-side pressure sensor for measuring the pressure of the refrigerant discharged from the refrigerant compressor, The control unit, When the pressure difference between the discharge pressure measured by the discharge pressure sensor and the suction pressure measured by the suction pressure sensor exceeds a predetermined value, the startup operation control is stopped and the normal operation control is started. The heat pump according to claim 2, wherein in the normal operation control, the operation of the discharge-side flow adjustment unit is controlled to reduce the amount of discharge-side water flowing through the discharge-side bypass line compared to that during the startup operation control.

4. The first discharge-side water circulation unit further includes a discharge-side temperature sensor for measuring the temperature of the discharge-side water flowing into the condenser. The first suction-side water circulation unit further includes a suction-side temperature sensor for measuring the temperature of the suction-side water flowing into the evaporator. The control unit, When the discharge side temperature measured by the discharge side temperature sensor becomes equal to or above a predetermined first threshold temperature, and the suction side temperature measured by the suction side temperature sensor becomes equal to or below a predetermined second threshold temperature, the startup operation control is stopped and the normal operation control is started. The heat pump according to claim 2, wherein in the normal operation control, the operation of the discharge-side flow adjustment unit is controlled to reduce the discharge-side water flowing through the discharge-side bypass line compared to the time of the startup operation control, and the operation of the suction-side flow adjustment unit is controlled to reduce the suction-side water flowing through the suction-side bypass line compared to the time of the startup operation control.

5. The heat pump described in claim 3, A suction side tank for storing the suction side water, A heat recovery unit that recovers heat using the aforementioned suction side water, A second suction water circulation unit has a second suction water line through which the suction water flows, and which is connected to the first suction water line via the suction tank. A discharge tank for storing the discharge water, A hot water generating device comprising: a second discharge water circulation unit having a second discharge water line through which the discharge water flows, and which communicates with the first discharge water line via the discharge tank.

6. The control unit, In the above-mentioned normal operation control, The hot water generating apparatus according to claim 5, which allows the outflow of suction water into the suction tank and the inflow of suction water from the suction tank in the first suction water line, and also allows the inflow of discharge water into the discharge tank and the outflow of discharge water from the discharge tank in the first discharge water line.

7. The discharge-side bypass line branches off from the downstream discharge-side section of the first discharge-side water line through which the discharge-side water flows from the condenser to the discharge-side tank, and merges with the upstream discharge-side section of the first discharge-side water line through which the discharge-side water flows from the discharge-side tank to the condenser. The discharge-side flow adjustment unit is, The discharge-side three-way solenoid valve is located at the branching point from the downstream discharge side, and the discharge-side solenoid valve is located upstream of the discharge-side bypass line's confluence point in the upstream discharge side. The control unit, In the startup operation control described above, the discharge-side three-way solenoid valve is controlled to allow flow to the discharge-side bypass line and to prevent the discharge-side water from flowing into the discharge-side tank. The hot water generating apparatus according to claim 5, wherein the discharge-side solenoid valve is controlled to prevent the outflow of the discharge-side water from the discharge-side tank.

8. The suction bypass line branches off from the downstream suction section of the first suction water line through which the suction water flows from the evaporator to the suction tank, and merges with the upstream suction section of the first suction water line through which the suction water flows from the suction tank to the evaporator. The aforementioned suction-side flow adjustment unit is The suction side includes a three-way solenoid valve positioned at the branching point from the downstream section of the suction side, and a suction side solenoid valve positioned upstream of the suction side bypass line's merging point in the upstream section of the suction side. The control unit, In the startup operation control described above, the suction-side three-way solenoid valve is controlled to allow flow to the suction-side bypass line and to prevent flow to the suction-side tank. The hot water generating apparatus according to claim 5, wherein the suction-side solenoid valve is controlled to prevent the outflow of the suction-side water from the suction-side tank.

9. It has a refrigerant compressor that sucks in refrigerant, compresses it, and discharges the refrigerant, and a refrigerant circulation unit that circulates the refrigerant, A first discharge-side water circulation unit circulates discharge-side water that exchanges heat with the refrigerant discharged from the refrigerant compressor, A method for operating a heat pump comprising a control unit, The refrigerant circulation unit is, A refrigerant line through which the aforementioned refrigerant can flow, An oil separator for separating oil from the refrigerant discharged from the refrigerant compressor, A supply line for supplying the oil separated by the oil separator to the refrigerant compressor, A condenser that heats the discharge water by exchanging heat between the refrigerant, which has been compressed by the refrigerant compressor, and the discharge water, The condenser further comprises an expansion valve for expanding and cooling the refrigerant after heat exchange, The first discharge-side water circulation section is, A first discharge water line through which the discharge water can flow, A discharge bypass line is provided, which branches off from the first discharge water line and merges with the first discharge water line, such that the discharge water flowing into and out of the condenser short-circuits the first discharge water line. It has a discharge-side flow adjustment unit that adjusts the flow direction of the discharge-side water, A method for operating a heat pump, wherein the control unit controls the operation of the discharge-side flow adjustment unit so that, immediately after starting the refrigerant compressor, the discharge-side water is flowing through the discharge-side bypass line.

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