JP7243300B2 - heat pump system - Google Patents

Description

The present invention relates to heat pump systems. More specifically, the refrigerant is circulated in a refrigerant circulation line in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring, and heat is passed through the condenser while pumping heat from the heat source fluid that passes through the evaporator. The present invention relates to a heat pump system that heats a fluid to be heated.

Conventionally, a water supply heating system using a heat pump is known.
For example, in Patent Document 1, a heat pump of such a water supply heating system is provided with a supercooler that exchanges heat between the liquid refrigerant and the water supply, and further, the liquid refrigerant flowing from the condenser toward the supercooler and the evaporation A configuration is shown in which a liquid-gas heat exchanger is provided to exchange heat with gas refrigerant flowing from the compressor toward the compressor.

JP 2016-48126 A

In the heat pump as shown in Patent Document 1, even if the temperature of the heat source fluid is low, the gas refrigerant heated by the evaporator is further heated by the liquid-gas heat exchanger, so that the gas refrigerant that can be compressed by the compressor is heated. Mass flow rate can be increased. Therefore, a large amount of heat can be exchanged between the condenser and the supercooler, and a large amount of hot water can be obtained.
However, in such a heat pump, the liquid refrigerant flowing into the expansion valve may be excessively cooled by passing through the liquid-gas heat exchanger and the supercooler. If the degree of supercooling of the liquid refrigerant is extremely large and the supercooled liquid is supplied to the evaporator, wet steam will be sent to the compressor while vaporization in the evaporator is insufficient. When the wet steam is sucked into the compressor, the compressor may be damaged by a liquid hammer or the like due to liquid compression.

The present invention has been made in view of the above problems, and its object is to provide a heat pump system that can prevent damage to the compressor in a configuration in which a liquid-gas heat exchanger is provided in the heat pump circuit. be.

In one aspect of the present invention, a refrigerant is circulated in a refrigerant circulation line in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring, and heat is drawn from the heat source fluid passing through the evaporator while the condenser is A heat pump system for heating a fluid to be heated passing through the condenser, wherein heat is exchanged between liquid refrigerant flowing from the condenser toward the expansion valve and gas refrigerant flowing from the evaporator toward the compressor. a gas heat exchanger; a refrigerant bypass line branching from an inlet channel of the liquid-gas heat exchanger and joining an outlet channel in the refrigerant circulation line on the liquid refrigerant side of the liquid-gas heat exchanger ; a bypass flow rate adjusting unit that adjusts a flow rate ratio between a flow rate of the liquid refrigerant distributed to the liquid-gas heat exchanger and a flow rate of the liquid refrigerant distributed to the refrigerant bypass line without reducing the pressure of the liquid refrigerant; A temperature sensor that measures temperature information of the liquid refrigerant flowing into the expansion valve, and a control unit that controls the bypass flow rate adjustment unit , wherein the confluence point of the bypass line is located at the inlet flow path of the expansion valve. The temperature sensor is arranged downstream of the confluence point of the bypass line, and the controller determines the degree of subcooling of the liquid refrigerant flowing into the expansion valve based on temperature information from the temperature sensor. to a constant value or within a constant range .

In one aspect of the present invention, a refrigerant is circulated in a refrigerant circulation line in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring, and heat is drawn from the heat source fluid passing through the evaporator while the condenser is A heat pump system for heating a fluid to be heated passing through the
a liquid-gas heat exchanger that exchanges heat between liquid refrigerant flowing from the condenser toward the expansion valve and gas refrigerant flowing from the evaporator toward the compressor;
a refrigerant bypass line that branches from an inlet channel of the liquid-gas heat exchanger and merges with an outlet channel in the refrigerant circulation line on the gas refrigerant side of the liquid-gas heat exchanger;
a bypass flow rate adjustment unit that adjusts the flow rate ratio between the flow rate of the gas refrigerant distributed to the liquid-gas heat exchanger and the flow rate of the gas refrigerant distributed to the refrigerant bypass line;
a temperature sensor for measuring temperature information of the liquid refrigerant flowing into the expansion valve;
a control unit that controls the bypass flow rate adjustment unit,
The control unit controls the bypass flow rate adjustment unit based on the temperature information from the temperature sensor so as to keep the degree of subcooling of the liquid refrigerant flowing into the expansion valve at a constant value or within a certain range. .

Moreover, it is preferable that the control unit controls the bypass flow rate adjustment unit so that the temperature of the liquid refrigerant flowing into the expansion valve becomes a target temperature.

Moreover, it is preferable that the target temperature is set based on the pressure of the liquid refrigerant flowing into the expansion valve .

The liquid-gas heat exchanger further comprises a supercooler for exchanging heat between the fluid to be heated upstream of the condenser and the liquid refrigerant flowing from the condenser toward the expansion valve, wherein the liquid-gas heat exchanger Heat exchange is preferably performed between the liquid refrigerant flowing from the subcooler toward the expansion valve and the gas refrigerant flowing from the evaporator toward the compressor.

The liquid-gas heat exchanger further comprises a supercooler for exchanging heat between the fluid to be heated upstream of the condenser and the liquid refrigerant flowing from the condenser toward the expansion valve, wherein the liquid-gas heat exchanger Heat exchange is preferably performed between the liquid refrigerant flowing from the condenser toward the supercooler and the gas refrigerant flowing from the evaporator toward the compressor.

ADVANTAGE OF THE INVENTION According to this invention, the heat pump system which can prevent damage to a compressor in the structure which provided the liquid gas heat exchanger in the heat pump circuit can be provided.

1 is a schematic diagram showing a heat pump system according to a first embodiment of the invention; FIG. It is a Mollier diagram for explaining the heat pump cycle of the heat pump system according to the embodiment. It is a Mollier diagram for explaining the heat pump cycle of the heat pump system according to the embodiment. It is a schematic diagram showing a heat pump system according to a second embodiment of the present invention. It is a Mollier diagram for explaining the heat pump cycle of the heat pump system according to the embodiment. It is a schematic diagram showing a heat pump system according to a third embodiment of the present invention. It is a schematic diagram showing a heat pump system according to a fourth embodiment of the present invention.

<First embodiment>
A heat pump system 1 according to a first embodiment of the present invention will be described below with reference to the drawings. In this specification, "line" is a general term for lines through which fluid can flow, such as channels, routes, and pipelines.

FIG. 1 is a schematic diagram showing a heat pump circuit of a heat pump system 1 of this embodiment.
The heat pump system 1 of the present embodiment is a heat pump system that functions as a hot water production system that heats service water W1 (tap water, industrial water, etc.) as a fluid to be heated, and includes a vapor compression heat pump 10.

As shown in FIG. 1 , heat pump 10 includes compressor 11 , condenser 12 , expansion valve 14 , and evaporator 15 . The compressor 11, the condenser 12, the expansion valve 14 and the evaporator 15 are sequentially connected in a loop by a refrigerant circulation line L10 through which the refrigerant R flows, thereby forming a heat pump circuit. A supercooler 13 and a liquid-gas heat exchanger 16, which will be described later, are further provided in the refrigerant circulation line L10 of the heat pump 10 of the present embodiment.
Refrigerant R circulating in refrigerant circulation line L10 undergoes a phase change among gas refrigerant _RG , liquid refrigerant _RL , and wet steam state refrigerant _RW during its circulation process.

The compressor 11 is an electrically driven refrigerant compressor. The compressor 11 has a motor 17 as a drive source, and adiabatically compresses the gas refrigerant _RG into a high-temperature and high-pressure gas refrigerant _RG . The condenser 12 condenses and liquefies the gas refrigerant _RG from the compressor 11 by releasing heat to the service water W1 (fluid to be heated) sent through the service water line L1. As a result, the refrigerant R becomes liquid refrigerant _RL . The expansion valve 14 adiabatically expands the liquid refrigerant _RL sent from the condenser 12, thereby lowering the pressure and temperature of the liquid refrigerant _RL . As a result, the liquid refrigerant _RL undergoes a phase change to wet vapor, and becomes refrigerant _RW in a wet vapor state. The evaporator 15 absorbs heat from the heat source water W2 (heat source fluid) sent through the heat source water line L2 to evaporate the wet steam refrigerant _RW sent from the expansion valve 14 . As a result, the refrigerant R becomes a gas refrigerant _RG .

The heat source of the heat pump circuit is not limited to heat source water such as waste hot water, but various types of exhaust gas (combustion gas, exhaust steam, etc.) from factory equipment, cooling air containing waste heat, outside air not containing waste heat, etc. A heat source gas can be used.
In the structure of the evaporator 15, when the heat transfer surface is exposed to the outside, the heat source gas is supplied to the heat transfer surface by a fan (for example, ventilation of the atmosphere). Further, in the structure of the evaporator 15, when the heat transfer surface exists in a closed space (for example, a shell), the heat source gas is supplied to the heat transfer surface by a blower.

In this manner, in the evaporator 15, the refrigerant _RW in the state of wet steam absorbs heat from the outside and vaporizes to become the gas refrigerant _RG , while in the condenser 12, the high-temperature and high-pressure gas refrigerant _RG releases heat to the outside. and condensed to become liquid refrigerant _RL . Using this principle, the heat pump 10 draws heat from the heat source water W2 in the evaporator 15, and heats the water W1 flowing from the primary side of the water line L1 in the condenser 12.
The utility water W1 that has been heated and turned into hot water by passing through the condenser 12 is supplied through the secondary side of the utility water line L1 to a hot water demand point (not shown).

The heat pump 10 of this embodiment further includes a supercooler 13 downstream of the condenser 12 in the refrigerant circulation line L10. The supercooler 13 exchanges heat between the service water W1 on the upstream side of the condenser 12 and the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve 14 . With this supercooler 13, the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve 14 can be supercooled using the service water W1 on the upstream side of the condenser 12. The liquid refrigerant _RL flowing toward 14 can be used to heat the service water W1 on the upstream side of the condenser 12 .

Thus, the condenser 12 releases the latent and sensible heat of the gas refrigerant _RG to change the gas refrigerant _RG to the liquid refrigerant _RL , and the supercooler 13 releases the sensible heat of the liquid refrigerant _RL . is released to supercool the liquid refrigerant _RL . Separating the heat exchanger for condensation and the heat exchanger for supercooling in this way facilitates the design of the heat exchangers and reduces the cost.

The heat pump 10 of the present embodiment further performs liquid-gas heat exchange for exchanging heat between the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve 14 and the gas refrigerant _RG flowing from the evaporator 15 toward the compressor 11. A vessel 16 is provided. More specifically, the liquid-gas heat exchanger 16 in this embodiment includes liquid refrigerant _RL flowing from the supercooler 13 toward the expansion valve 14 and gas refrigerant R flowing from the evaporator 15 toward the compressor 11. heat exchange with _G.
By providing such a liquid-gas heat exchanger 16, even when the temperature of the heat source water W2 supplied to the evaporator 15 is low, the wet steam state refrigerant _RW after passing through the expansion valve 14 is , the evaporator 15 and the liquid-gas heat exchanger 16, the temperature and pressure of the gas refrigerant _RG sucked into the compressor 11 can be increased. As a result, the amount of heat generated by the condenser 12 (the amount of heat released by the refrigerant _R in the condenser 12) increases, and the COP (energy consumption efficiency) increases.

Here, an example of how the temperature of the refrigerant R changes due to the heat pump cycle of the heat pump 10 will be described. Here, fluorocarbon gas is used as the refrigerant R, the temperature of the service water W1 flowing into the supercooler 13 is 20°C, the temperature of the service water W1 discharged from the condenser 12 is 70°C, and the temperature of the heat source water W2 is 10°C. Here is an example.
The refrigerant R compressed by the compressor 11 becomes a high-temperature and high-pressure gas refrigerant _RG with a gauge pressure of 2.0 MPaG and a temperature of 86° C. (the degree of superheat is 16° C. relative to the saturation temperature of 70° C.). After that, the refrigerant R that has passed through the condenser 12 and the supercooler 13 becomes the liquid refrigerant _RL at 23°C, and the refrigerant R that has further passed through the liquid-gas heat exchanger 16 becomes the liquid refrigerant _RL at 13°C. . After that, the refrigerant R that has passed through the expansion valve 14 becomes refrigerant _RW in a wet vapor state at 7°C. Refrigerant _RW in a wet vapor state passes through evaporator 15 and liquid-gas heat exchanger 16 to become gaseous refrigerant RG with gauge pressure of 0.27 MPaG and 17°C (degree of superheat is 10°C with respect to saturation temperature of 7°C) _. becomes. This gas refrigerant _RG is compressed again by the compressor 11 to become a high-temperature and high-pressure gas refrigerant _RG . Such a cycle is repeated, and the coolant R circulates.

Next, the heat pump cycle of this embodiment will be described using the Mollier diagram (ph diagram) shown in FIG.
The vertical axis of this Mollier diagram is the pressure (p) of the refrigerant, and the horizontal axis is the specific enthalpy (h) of the refrigerant. The Mollier diagram shows a saturated liquid line Y1 and a saturated vapor line Y2. Such a Mollier diagram can represent the state change of the refrigerant R during the heat pump cycle. Refrigerant R is in a supercooled liquid state (liquid refrigerant _RL state) on the left side of the saturated liquid line Y1, and in a wet vapor state (refrigerant R _W state), and on the right side of the saturated vapor line Y2, it becomes a superheated vapor state (state of gas refrigerant _RG ).

The solid line indicated by R in FIG. 2 shows the transition of the state of the refrigerant R in the proper heat pump cycle.
The superheated vapor state gas refrigerant _RG sucked into the compressor 11 is adiabatically compressed in the compressor 11 to become a high temperature and high pressure superheated vapor state gas refrigerant _RG (a→b), and then condensed in the condenser 12. is further supercooled by the supercooler 13 and the liquid-gas heat exchanger 16 to become a liquid refrigerant _RL in a supercooled liquid state (b→c), and then adiabatically expanded by the expansion valve 14. becomes a refrigerant _RW in a wet vapor state (c→d). Then, the refrigerant _RW in the wet vapor state is evaporated in the evaporator 15 and further heated in the liquid-gas heat exchanger 16 to become the gas refrigerant _RG in the superheated vapor state (d→a). The refrigerant R circulates in such a cycle.

Here, _the process of (b→c) in FIG _. 2 will be described _in detail. The supercooler 13 and the liquid-gas heat exchanger 16 release the sensible heat of the liquid refrigerant _RL to supercool the liquid refrigerant _RL .

In this embodiment, since the liquid-gas heat exchanger 16 is provided in addition to the evaporator 15, even when the temperature of the heat source water W2 supplied to the evaporator 15 is low, the expansion valve 14 is It is possible to more stably change the refrigerant _RW in the wet vapor state after passing through to the gas refrigerant _RG in the superheated vapor state (d→a). That is, the refrigerant _RW can be changed to the state of the region on the right side of the saturated vapor line Y2 in the Mollier diagram.
In addition, since the temperature (degree of superheat) of the gas refrigerant _RG can be increased by the liquid-gas heat exchanger 16, the amount of heat generated in the condenser 12 (the amount of heat released by the refrigerant R in the condenser 12) is increased, The COP of heat pump 10 can be increased.

Here, the temperature of the service water W1 supplied from the service water line L1 is low (for example, the use of low temperature water of 15 ° C. or less in winter). Consider a case where the liquid refrigerant _RL after passing through is extremely cooled.
In this case, as indicated by the dashed line _R2 in the Mollier diagram of FIG. It shifts to the left compared to the normal case. In this case, the liquid refrigerant _RL in the state of “c2” may not change its phase state even after passing through the expansion valve 14 and may maintain the state of the liquid refrigerant _RL (c2→d2 ). That is, as indicated by the dashed line R2, the position of "d2" indicating the state of the refrigerant R after passing through the expansion valve 14 may remain in the area on the left side of the saturated liquid line Y1.

When the refrigerant R after passing through the expansion valve 14 is in a supercooled liquid state, the vaporization of the refrigerant R becomes insufficient in the evaporator 15 and the liquid-gas heat exchanger 16 (d2→a2), and the compressor 11 produces wet steam. Refrigerant _RW in the state is sent. When the compressor 11 sucks the refrigerant _RW in a wet vapor state, the compressor 11 may be damaged by a liquid hammer or the like due to liquid compression.
Luckily, even under conditions where liquid hammer does not occur, the liquid portion of the wet vapor is incompressible, so the refrigerant _RW that has undergone adiabatic compression remains in a wet vapor state. As a result, the temperature and pressure of _the refrigerant _RW discharged from the compressor 11 decrease (a2→b2). Supercooling also progresses easily. As a result, the initially planned refrigeration cycle cannot be realized.

Therefore, in order to prevent such a situation, the heat pump circuit of this embodiment includes a liquid refrigerant bypass means 20 for bypassing the liquid refrigerant _RL from passing through the liquid-gas heat exchanger 16, as shown in FIG. It has The liquid refrigerant bypass means 20 includes a refrigerant bypass line L20 and a bypass flow rate adjusting section that adjusts the flow rate of the liquid refrigerant _RL flowing through the refrigerant bypass line L20. The refrigerant bypass line L20 branches from the refrigerant circulation line L10 at a branching portion A, and joins the refrigerant circulation line L10 at a junction portion B. As shown in FIG.
The bypass flow rate adjusting unit may distribute the flow rate of the liquid refrigerant _RL toward the liquid-gas heat exchanger 16 and the flow rate of the liquid refrigerant _RL flowing into the refrigerant bypass line L20. It may be provided, or may be provided in the refrigerant circulation line L10. Alternatively, it may be provided in both of them or in the branch. In this embodiment, the branch portion A is provided with a three-way valve 21 .

The three-way valve 21 is a valve mechanism (three-way proportional control valve) that is operated at an opening degree corresponding to an opening designation signal input from the control unit 100, which will be described later. The three-way valve 21 controls the flow rate of the liquid refrigerant _RL flowing toward the first outlet port side toward the liquid-gas heat exchanger 16 and the flow rate of the liquid refrigerant _RL flowing toward the second outlet port side toward the refrigerant bypass line L20. Adjustable flow rate. That is, the three-way valve 21 is provided with an actuator circuit (not shown) that adjusts the degree of opening, and by inputting an opening designation signal of 0 to 100% to this actuator circuit, the degree of opening of the first outlet port side is adjusted. and the degree of opening on the side of the second outlet port are adjusted. However, the sum of the flow rate ratios on the first outlet port side and the second outlet port side is always 100%. The degree of opening of the three-way valve 21 is based on the degree of opening on the side of the first outlet port, and the degree of opening on the side of the first outlet port is 0%→25%→50%→75%→100%. In this case, the degree of opening on the side of the second outlet port is 100%→75%→50%→25%→0%.

A temperature sensor 22 for measuring temperature information of the liquid refrigerant _RL flowing into the expansion valve 14 is provided in the refrigerant circulation line L10. The temperature sensor 22 is arranged downstream of the confluence B of the refrigerant circulation line L10 and the refrigerant bypass line L20 extending from the liquid-gas heat exchanger 16 to the expansion valve 14 . Thereby, the temperature of the liquid refrigerant _RL flowing into the expansion valve can be measured. More preferably, the temperature sensor 22 is arranged upstream of the expansion valve 14 and in the vicinity of the expansion valve 14 in order to measure the temperature of the liquid refrigerant _RL just before it flows into the expansion valve 14 .

Here, the heat pump system 1 of this embodiment includes a controller 100 . This control unit 100 controls the three-way valve 21 as a bypass flow control unit based on the temperature information measured by the temperature sensor 22 and the target temperature. The control unit 100 controls the degree of supercooling of the liquid refrigerant _RL flowing into the expansion valve 14 to be maintained at a constant value or within a certain range by adjusting the bypass flow rate (fixed degree of supercooling control).

Specifically, the control unit 100 controls the three-way valve 21 based on the temperature information measured by the temperature sensor 22 so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 reaches a target temperature. As a result, the flow rate ratio between the flow rate of the liquid refrigerant _RL flowing toward the first outlet port side toward the liquid-gas heat exchanger 16 and the flow rate of the liquid refrigerant _RL flowing toward the second outlet port side toward the refrigerant bypass line L20 is adjust.
For example, the control unit 100 compares the temperature information measured by the temperature sensor 22 with the target temperature, and when the temperature of the liquid refrigerant _RL is lower than the target temperature, the opening degree increases the bypass flow rate. A designated signal is generated and supplied to the three-way valve 21 . On the other hand, when the temperature of the liquid refrigerant _RL is higher than the target temperature, an opening designation signal is generated to decrease the bypass flow rate, and the signal is supplied to the three-way valve 21 . Feedback control by a PID algorithm is preferably used for adjusting the flow rate.

Also, a configuration may be adopted in which switching control of the bypass flow rate adjusting section is performed based on the temperature threshold. For example, when the measured temperature information falls below the first temperature threshold value, the bypass flow control unit is controlled so that 100% of the flow is directed to the refrigerant bypass line L20. On the other hand, when the measured temperature information exceeds the second temperature threshold, the bypass flow rate adjusting section is controlled so that 100% of the flow rate goes to the liquid-gas heat exchanger 16 . This control is performed, for example, by opening/closing control of a valve that constitutes the bypass flow rate adjusting section. The first temperature threshold and the second temperature threshold may be the same temperature, or the second temperature threshold may be higher than the first temperature threshold.

Thus, by adjusting the flow rate of the liquid refrigerant RL passing through the liquid-gas heat exchanger 16 based on the temperature information of the liquid refrigerant _RL before it flows into the expansion valve 14, the liquid refrigerant _RL flows into the expansion valve 14. The preceding liquid refrigerant _RL is no longer excessively cooled. Therefore, the phase of the refrigerant R after passing through the expansion valve 14 is reliably changed to a wet vapor state.
That is, by adjusting the flow rate of the liquid refrigerant _RL passing through the liquid-gas heat exchanger 16, the liquid after passing through the liquid-gas heat exchanger 16 can be changed as indicated by the solid line R3 in the Mollier diagram of FIG. The position indicating the state of the refrigerant _RL is "c3", which is an appropriate position. In this case, after passing through the expansion valve 14, the liquid refrigerant _RL in the state of "c3" becomes the refrigerant _RW in the proper wet vapor state (c3→d3). That is, as indicated by the solid line R3, the position of "d3", which indicates the state of the refrigerant R after passing through the expansion valve 14, falls within the area on the right side of the saturated liquid line Y1.
In this way, by adjusting the flow rate of the liquid refrigerant RL passing through the liquid-gas heat exchanger 16 so that the refrigerant _{R after passing through the expansion valve 14 becomes the refrigerant RW in} a wet vapor state, Vaporization of the refrigerant R proceeds efficiently in the evaporator 15 and the liquid-gas heat exchanger 16 . As a result, the degree of superheat of the discharged gas refrigerant _RG can be increased while preventing liquid compression in the compressor 11 .

As shown in FIG. 1, the heat pump system 1 may include a hot water supply temperature sensor 42 that detects the temperature of the service water W1 heated by the heat pump 10 and turned into hot water.
Further, the compressor 11 of the heat pump 10 may be configured such that its output can be changed. For example, it may be configured such that the rotation speed of the motor 17 of the compressor 11 can be changed by inverter control. In this case, it is possible to employ a configuration that controls the rotational speed of the compressor 11 so that the temperature detected by the hot water supply temperature sensor 42 becomes the target temperature. Feedback control based on a PID algorithm is preferably used for adjusting the rotational speed of the compressor 11 .

Further, a configuration may be adopted in which the degree of opening of a flow control valve (not shown) provided in the water line L1 or the rotation speed of a water supply pump (not shown) is controlled based on the detected temperature detected by the hot water supply temperature sensor 42. In this case, the supply flow rate of water W1 to heat pump 10 can be adjusted so that the detected temperature detected by hot water supply temperature sensor 42 becomes the target temperature. Feedback control by a PID algorithm is preferably used for adjusting the supply flow rate.

According to the heat pump system 1 of this embodiment described above, the following effects are obtained.

(1) In the heat pump system 1 of the present embodiment, the compressor 11, the condenser 12, the expansion valve 14, and the evaporator 15 are sequentially connected in a ring to circulate the refrigerant R. is a heat pump system 1 that draws heat from the heat source water W2 and heats service water W1 as a fluid to be heated that is passed through a condenser 12, and the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve 14 and a liquid-gas heat exchanger 16 that exchanges heat with the gas refrigerant _RG flowing from the _evaporator 15 toward the compressor 11, and a refrigerant for bypassing the liquid-gas heat exchanger 16 A bypass line L20, a three-way valve 21 as a bypass flow rate adjusting unit that adjusts the flow rate of the liquid refrigerant _RL flowing through the refrigerant bypass line L20, and a temperature sensor 22 that measures temperature information of the liquid refrigerant _RL flowing into the expansion valve 14. and a control unit 100 that controls the three-way valve 21 as a bypass flow control unit based on the measured temperature information.
As a result, even when the temperature of the heat source water W2 passing through the evaporator 15 is low, the refrigerant _RW after passing through the expansion valve 14 passes through the liquid-gas heat exchanger 16 in addition to the evaporator 15. Therefore, the temperature of the gas refrigerant _RG sucked into the compressor 11 can be raised. Therefore, the temperature of the gas refrigerant _RG discharged from the compressor 11 rises (that is, the degree of superheat rises), so the amount of heat generated in the condenser 12 increases and the COP of the heat pump 10 increases.
Furthermore, based on the temperature information of the liquid refrigerant _RL before flowing into the expansion valve 14 _, the flow rate of the liquid refrigerant _RL passing through the liquid-gas heat exchanger 16 can be adjusted. is no longer cooled down. Therefore, since the refrigerant R after passing through the expansion valve 14 undergoes a phase change to wet vapor, the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16. Damage to the compressor 11 can be prevented.

(2) The heat pump system 1 of the present embodiment performs heat exchange between the service water W1 as the fluid to be heated on the upstream side of the condenser 12 and the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve . The liquid-gas heat exchanger 16 further includes a cooler 13, and the liquid-gas heat exchanger 16 separates the liquid refrigerant _RL flowing from the subcooler 13 toward the expansion valve 14 and the gas refrigerant _RG flowing from the evaporator 15 toward the compressor 11. exchange heat.
As a result, the water W1 passes through the supercooler 13 and the condenser 12, so that the supercooler 13 utilizes the sensible heat of the liquid refrigerant _RL , and the condenser 12 utilizes the sensible heat and latent heat of the gas refrigerant _RG . can be used to efficiently heat the water W1.

(3) The refrigerant bypass line L20 of the present embodiment is a line through which the liquid refrigerant _RL flows from the condenser 12 toward the expansion valve 14 without passing through the liquid-gas heat exchanger 16, and the temperature sensor 22 is , is disposed downstream of the confluence B between the line through which the liquid refrigerant _RL flows from the liquid-gas heat exchanger 16 toward the expansion valve 14 and the refrigerant bypass line L20.
As a result, the control of the three-way valve 21 as the bypass flow rate adjusting section can be appropriately executed based on the temperature information of the liquid refrigerant _RL flowing into the expansion valve 14, that is, the degree of supercooling.

(4) The control unit 100 of the present embodiment controls the three-way valve 21 as a bypass flow rate adjustment unit so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 becomes the target temperature.
As a result, since the bypass flow rate is controlled so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 reaches the target temperature, the phase of the refrigerant after passing through the expansion valve 14 can be reliably changed to wet vapor. . Therefore, since the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16, damage to the compressor 11 due to liquid compression can be prevented.

<Second embodiment>
Next, a second embodiment will be described with reference to FIGS. 4 and 5. FIG. In addition, the description is abbreviate|omitted about the structure similar to 1st Embodiment.

The heat pump system 1 of the second embodiment includes a pressure sensor 23 for measuring the pressure of the liquid refrigerant _RL flowing into the expansion valve 14 in the refrigerant circulation line L10, as shown in FIG.
Then, the control unit 100 sets the above-described target temperature based on the pressure measured by the pressure sensor 23, and based on this target temperature and the temperature information measured by the temperature sensor 22, the three-way valve 21 as a bypass flow rate adjusting unit. to control.

Here, the reason why such control is performed will be described with reference to the Mollier diagram of FIG.
As indicated by the dashed line R4 in FIG. 5, when the pressure of the liquid refrigerant _RL in the supercooled liquid state flowing into the expansion valve 14 is high, if the amount of pressure reduction in the expansion valve 14 is insufficient, the refrigerant R becomes a wet vapor. (c4→d4). That is, in order to bring the refrigerant R into a state of wet steam, the amount of pressure reduction in the expansion valve 14 must be increased (c4→d5), as indicated by the dashed line R5.

In such a situation, by setting the target temperature of the liquid refrigerant _RL in the supercooled liquid state flowing into the expansion valve 14 to a higher temperature (that is, by setting the degree of supercooling of the refrigerant R to a lower value), As indicated by the solid line R6 in the Mollier diagram of FIG. 5, even with a small amount of pressure reduction, the refrigerant R after passing through the expansion valve can be turned into the refrigerant _RW in the wet vapor state (c6→d6). .

In this way, by adopting a configuration in which the target temperature is set based on the pressure of the liquid refrigerant _RL flowing into the expansion valve 14, the refrigerant R after passing through the expansion valve 14 is appropriately converted into a wet vapor state. It can be phase-changed to _RW . Therefore, since the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16, damage to the compressor 11 due to liquid compression can be prevented.

According to the heat pump system 1 of the present embodiment described above, in addition to (1) to (4), the following effects are achieved.

(5) The target temperature in the heat pump system 1 of this embodiment is set based on the pressure of the liquid refrigerant _RL flowing into the expansion valve 14 .
The higher the pressure of the liquid refrigerant _RL as the supercooled liquid flowing into the expansion valve 14, the larger the decompression amount in the expansion valve 14 is required to generate wet steam. In this case, by causing the supercooled liquid to flow into the expansion valve 14 at a higher target temperature, it is possible to generate wet steam with a small amount of pressure reduction. As a result, the phase of the refrigerant R after passing through the expansion valve 14 can be reliably changed into wet steam. Therefore, since the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16, damage to the compressor 11 due to liquid compression can be prevented.

<Third Embodiment>
Next, a third embodiment will be described with reference to FIG. In addition, the description is abbreviate|omitted about the structure similar to 1st Embodiment.

In the heat pump system 1 of the third embodiment, as shown in FIG. 6, the liquid refrigerant R _L flowing out from the condenser 12 flows into the liquid-gas heat exchanger 16, and _L flows into the subcooler 13 . That is, the liquid-gas heat exchanger 16 of the present embodiment heats the liquid refrigerant _RL flowing from the condenser 12 toward the subcooler 13 and the gas refrigerant _RG flowing from the evaporator 15 toward the compressor 11. Exchange.

Even with such a configuration, since the water W1 passes through the supercooler 13 and the condenser 12, the sensible heat and latent heat of the gas refrigerant _RG are used in the condenser 12, and the liquid refrigerant is used in the supercooler 13. The sensible heat of _RL can be used to efficiently heat the water W1.

Also in the third embodiment, similarly to the second embodiment, a pressure sensor 23 is provided to measure the pressure of the liquid refrigerant _RL flowing into the expansion valve 14, and the target temperature is set based on the detection result. You may

According to the heat pump system 1 of the present embodiment described above, in addition to (1) and (3) to (5), the following effects are achieved.

(6) The heat pump system 1 of the present embodiment performs heat exchange between the service water W1 as the fluid to be heated on the upstream side of the condenser 12 and the liquid refrigerant _RL flowing from the condenser 12 toward the expansion valve . The liquid-gas heat exchanger 16 further comprises a cooler 13, and the liquid-gas heat exchanger 16 separates the liquid refrigerant _RL flowing from the condenser 12 toward the supercooler 13 and the gas refrigerant _RG flowing from the evaporator 15 toward the compressor 11. exchange heat.
As a result, the water W1 passes through the supercooler 13 and the condenser 12, so that the supercooler 13 utilizes the sensible heat of the liquid refrigerant _RL , and the condenser 12 utilizes the sensible heat and latent heat of the gas refrigerant _RG . can be used to efficiently heat the fluid to be heated.

<Fourth Embodiment>
Next, a fourth embodiment will be described with reference to FIG. In addition, the description is abbreviate|omitted about the structure similar to 1st Embodiment.

In the heat pump system 1 of the fourth embodiment, as shown in FIG. 7, instead of the liquid refrigerant bypass means 20 for bypassing the passage of the liquid refrigerant _RL through the liquid-gas heat exchanger 16, the gas refrigerant _RG gas refrigerant bypass means 30 for bypassing the liquid-gas heat exchanger 16. The gas refrigerant bypass means 30 includes a refrigerant bypass line L30 and a bypass flow rate adjusting section that adjusts the flow rate of the gas refrigerant _RG flowing through the refrigerant bypass line L30. The refrigerant bypass line L30 branches from the refrigerant circulation line L10 at a branching portion C, and joins the refrigerant circulation line L10 at a junction portion D. As shown in FIG.
The refrigerant bypass flow rate adjusting unit appropriately distributes the flow rate of the gas refrigerant _RG flowing through the refrigerant circulation line L10 toward the liquid-gas heat exchanger 16 and the flow rate of the gas refrigerant _RG flowing into the refrigerant bypass line L30. It may be provided in the refrigerant bypass line L30, or may be provided in the refrigerant circulation line L10. Alternatively, it may be provided in both of them or in the branch. In this embodiment, the branch portion C is provided with a three-way valve 31 .

Based on the temperature information measured by the temperature sensor 22 and the target temperature, the control unit 100 controls the three-way valve 31 as a bypass flow rate adjusting unit.

Specifically, based on the temperature information measured by the temperature sensor 22, the control unit 100 controls the three-way valve 31 so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 reaches a target temperature. For example, the control unit 100 compares the temperature information measured by the temperature sensor 22 with the target temperature, and when the temperature of the liquid refrigerant _RL is lower than the target temperature, the opening degree increases the bypass flow rate. A designated signal is generated and supplied to the three-way valve 31 . On the other hand, when the temperature of the liquid refrigerant _RL is higher than the target temperature, an opening designation signal is generated to reduce the bypass flow rate and is supplied to the three-way valve 31 . The control unit 100 performs such control using various control methods such as PID control.

Also, a configuration may be adopted in which switching control of the bypass flow rate adjusting section is performed based on the temperature threshold. For example, when the measured temperature information falls below the first temperature threshold value, the bypass flow control unit is controlled so that 100% of the flow is directed to the refrigerant bypass line L30. On the other hand, when the measured temperature information exceeds the second temperature threshold, which is higher than the first temperature threshold, the refrigerant bypass flow rate adjuster is controlled so that 100% of the flow goes to the liquid-gas heat exchanger 16 . This control is performed, for example, by opening/closing control of a valve that constitutes the bypass flow rate adjusting section. The first temperature threshold and the second temperature threshold may be the same temperature, or the second temperature threshold may be higher than the first temperature threshold.

Even with such a configuration, the flow rate of the gas refrigerant _RG passing through the liquid-gas heat exchanger 16 can be adjusted based on the temperature information of the liquid refrigerant _RL before flowing into the expansion valve. The liquid refrigerant _RL is not excessively cooled. Therefore, the phase of the refrigerant R after passing through the expansion valve 14 is reliably changed to a wet vapor state, and the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16. Damage to the machine 11 can be prevented.

Also in the fourth embodiment, similarly to the second embodiment, a pressure sensor 23 is provided to measure the pressure of the liquid refrigerant _RL flowing into the expansion valve 14, and the target temperature is set based on the detection result. You may

According to the heat pump system 1 of the present embodiment described above, in addition to (1) to (2) and (4) to (6), the following effects are achieved.

(7) The refrigerant bypass line L30 of the present embodiment is a line through which the gas refrigerant _RG flows from the evaporator 15 toward the compressor 11 without passing through the liquid-gas heat exchanger 16. , the three-way valve 31 as a bypass flow rate adjusting unit is controlled so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 becomes a target temperature.
As a result, since the bypass flow rate is controlled so that the temperature of the liquid refrigerant _RL flowing into the expansion valve 14 reaches the target temperature, the phase of the refrigerant after passing through the expansion valve 14 can be reliably changed to wet vapor. . Therefore, since the refrigerant R is reliably vaporized in the evaporator 15 and the liquid-gas heat exchanger 16, damage to the compressor 11 due to liquid compression can be prevented.

As shown in each embodiment and the like, the heat pump system 1 preferably includes a supercooler 13 in addition to the condenser 12. It is good also as a structure which performs supercooling.

Note that the fluid to be heated by the heat pump system 1 is not limited to the service water W1, and may be other liquids or gases. That is, it can be applied not only to a hot water production system but also to a system for heating various fluids to be heated.

Although preferred embodiments of the heat pump system of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate. It is also possible to combine multiple embodiments.

REFERENCE SIGNS LIST 1 heat pump system 10 heat pump 11 compressor 12 condenser 13 supercooler 14 expansion valve 15 evaporator 16 liquid-gas heat exchanger 20 liquid refrigerant bypass means 21 three-way valve (bypass flow rate adjusting unit )
22... Temperature sensor 23... Pressure sensor 30... Gas refrigerant bypass means 31... Three-way valve (bypass flow rate adjusting unit)
DESCRIPTION OF SYMBOLS 100... Control part L1... Service water line L2... Heat source water line L10... Refrigerant circulation line L20... Refrigerant bypass line L30... Refrigerant bypass line R... Refrigerant _RG ... Gas refrigerant _RL ... Liquid refrigerant _RW ... Refrigerant in a wet vapor state W1 …Water (fluid to be heated)
W2 ... heat source water (heat source fluid)
B... confluence

Claims (6)

Refrigerant is circulated in a refrigerant circulation line in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring, and the fluid to be heated passes through the condenser while drawing heat from the heat source fluid that passes through the evaporator. A heat pump system for heating the
a liquid-gas heat exchanger that exchanges heat between liquid refrigerant flowing from the condenser toward the expansion valve and gas refrigerant flowing from the evaporator toward the compressor;
a refrigerant bypass line that branches from an inlet channel of the liquid-gas heat exchanger and merges with an outlet channel in the refrigerant circulation line on the liquid refrigerant side of the liquid-gas heat exchanger;
a bypass flow rate adjusting unit that adjusts the flow rate ratio between the flow rate of the liquid refrigerant distributed to the liquid-gas heat exchanger and the flow rate of the liquid refrigerant distributed to the refrigerant bypass line without reducing the pressure of the liquid refrigerant;
a temperature sensor for measuring temperature information of the liquid refrigerant flowing into the expansion valve;
a control unit that controls the bypass flow rate adjustment unit ,
a confluence point of the refrigerant bypass line is located at an inlet channel of the expansion valve;
The temperature sensor is arranged downstream of a junction of the refrigerant bypass lines,
The control unit controls the bypass flow rate adjustment unit based on temperature information from the temperature sensor so as to keep the degree of subcooling of the liquid refrigerant flowing into the expansion valve at a constant value or within a certain range. Refrigerant is circulated in a refrigerant circulation line in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring, and the fluid to be heated passes through the condenser while drawing heat from the heat source fluid that passes through the evaporator. A heat pump system for heating the
a liquid-gas heat exchanger that exchanges heat between liquid refrigerant flowing from the condenser toward the expansion valve and gas refrigerant flowing from the evaporator toward the compressor;
a refrigerant bypass line that branches from an inlet channel of the liquid-gas heat exchanger and merges with an outlet channel in the refrigerant circulation line on the gas refrigerant side of the liquid-gas heat exchanger;
a bypass flow rate adjustment unit that adjusts the flow rate ratio between the flow rate of the gas refrigerant distributed to the liquid-gas heat exchanger and the flow rate of the gas refrigerant distributed to the refrigerant bypass line;
a temperature sensor for measuring temperature information of the liquid refrigerant flowing into the expansion valve;
a control unit that controls the bypass flow rate adjustment unit,
The control unit controls the bypass flow rate adjustment unit based on temperature information from the temperature sensor so as to keep the degree of subcooling of the liquid refrigerant flowing into the expansion valve at a constant value or within a certain range. 3. The heat pump system according to claim 1, wherein said control section controls said bypass flow rate adjusting section such that the temperature of said liquid refrigerant flowing into said expansion valve reaches a target temperature. 4. The heat pump system according to claim 3 , wherein said target temperature is set based on the pressure of liquid refrigerant flowing into said expansion valve. further comprising a supercooler that exchanges heat between the fluid to be heated upstream of the condenser and the liquid refrigerant flowing from the condenser toward the expansion valve;
The liquid-gas heat exchanger heat-exchanges the liquid refrigerant flowing from the supercooler toward the expansion valve and the gas refrigerant flowing from the evaporator toward the compressor . The heat pump system according to any one of claims 1 to 3 . further comprising a supercooler that exchanges heat between the fluid to be heated upstream of the condenser and the liquid refrigerant flowing from the condenser toward the expansion valve;
The liquid-gas heat exchanger heat-exchanges the liquid refrigerant flowing from the condenser toward the supercooler and the gas refrigerant flowing from the evaporator toward the compressor . The heat pump system according to any one of claims 1 to 3 .

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