JP4691138B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump water heater that transfers heat of outdoor air to water using a pressure difference of a refrigerant.

  A conventional heat pump water heater is a water circulation circuit that circulates hot water from the bottom to the top of the hot water tank so that the hot water at the top of the hot water tank does not reversely circulate and dissipate heat in the water heat exchanger when the heat pump operation stops. In addition, a water heat exchanger that exchanges heat with the condenser of the refrigerant circulation circuit is connected, and an on-off valve that closes when the heat pump operation is stopped is provided on the downstream side of the water heat exchanger of the water circulation circuit (for example, (See Patent Document 1).

JP 2004-144475 A

  However, in the heat pump water heater described in Patent Document 1, when the heat pump operation is stopped, the refrigerant flowing from the compressor to the expansion valve via the water heat exchanger during the operation of the compressor flows in the reverse direction. The cold refrigerant flows into the water heat exchanger and the heat absorbed by the evaporator (outdoor heat exchanger) cannot be recovered in the hot water storage tank via the water heat exchanger, causing heat loss. there were.

  Further, the liquid refrigerant accumulated in the evaporator when the compressor is stopped flows into the compressor when the compressor is restarted (so-called liquid back), and the compressor may be damaged.

  Furthermore, the design pressure of the evaporator is set based on the refrigerant pressure when the compressor is stopped, and when a supercritical refrigerant such as carbon dioxide is used as the refrigerant, the refrigerant pressure when the compressor is stopped is high. It was necessary to increase the thickness of the evaporator piping, which caused an increase in cost.

  The present invention has been made in view of such problems of the prior art, and can effectively recover the heat in the evaporator to the hot water storage tank when the compressor operation is stopped, and at the same time the liquid to the compressor. It is an object of the present invention to provide a heat pump water heater that can prevent back-up and ensure the starting stability of the compressor and can reduce the pipe wall thickness of the evaporator.

In order to achieve the above object, a heat pump water heater according to the present invention includes a refrigerant circulation circuit in which a compressor, a refrigerant-water heat exchanger, a decompressor, and an evaporator are sequentially connected , a hot water tank, and the refrigerant-water heat exchange. And a hot water circulation circuit having a circulation pump, and a controller that controls the operation of the compressor, the pressure reducer, and the circulation pump, and the refrigerant flowing through the refrigerant circulation circuit in the refrigerant-water heat exchanger. And the water flowing through the hot water circulation circuit, and when the controller receives the operation stop signal of the compressor, before stopping the operation of the compressor, the controller The compressor is operated to operate the compressor for a first predetermined time , the refrigerant of the evaporator is transported to the refrigerant-water heat exchanger, and the circulation pump is operated for a second predetermined time longer than the first predetermined time. is operated, the refrigerant - water heat exchanger Of hot water, characterized in that to transport the hot water storage tank.

  With the above configuration, the heat in the evaporator can be effectively recovered in the hot water storage tank when the compressor is stopped, and at the same time, the liquid back to the compressor can be prevented to ensure the starting stability of the compressor. . Moreover, the pipe | tube thickness of an evaporator can be made thin by collect | recovering the refrigerant | coolants in an evaporator.

The first invention includes a refrigerant circulation circuit in which a compressor, a refrigerant-water heat exchanger, a decompressor, and an evaporator are sequentially connected , a hot water tank, the refrigerant-water heat exchanger, a hot water circulation circuit having a circulation pump , A controller for controlling the operation of the compressor, the pressure reducer, and the circulation pump, and heats the refrigerant flowing through the refrigerant circulation circuit and the water flowing through the hot water circulation circuit in the refrigerant-water heat exchanger. with exchanges, the controller, the receives the operation stop signal of the compressor, before stopping the operation of the compressor, predetermined the compressor first is operated in the closing direction the pressure reducer Operating for a period of time , transporting the refrigerant of the evaporator to the refrigerant-water heat exchanger, operating the circulation pump for a second predetermined time longer than the first predetermined time , It controls to convey the hot water in the hot water storage tank Was Unishi.

  With this configuration, when the operation of the compressor is stopped, the heat in the evaporator can be effectively recovered in the hot water storage tank, and at the same time, the liquid back to the compressor can be prevented to ensure the starting stability of the compressor. At the same time, the pipe thickness of the evaporator can be reduced.

  According to a second aspect of the present invention, there is provided a check valve between the evaporator and the compressor, the check valve for allowing the refrigerant flowing from the evaporator to the compressor and blocking the refrigerant flowing from the compressor to the evaporator. It is possible to prevent the refrigerant collected on the condenser side when the operation is stopped from returning to the evaporator via the compressor.

  According to a third aspect of the present invention, a two-way valve is provided between the pressure reducer and the evaporator, and the two-way valve is closed after the pressure reducer operates in the valve closing direction. It is possible to prevent the recovered refrigerant from returning to the evaporator via the decompressor.

  In the fourth invention, the first two-way valve is provided between the evaporator and the compressor, and the second two-way valve is provided between the pressure reducer and the evaporator so that the pressure reducer operates in the valve closing direction. By closing the first two-way valve and the second two-way valve later, the refrigerant recovered on the condenser side when the compressor is stopped is prevented from returning to the evaporator via the compressor and the decompressor. can do.

  In the fifth aspect of the present invention, when the controller receives the compressor stop signal, the heat remaining in the evaporator can be efficiently recovered by reducing the capacity of the compressor and operating for a predetermined time. .

  According to a sixth aspect of the present invention, when the controller receives a compressor shutdown signal, the capacity of the circulating pump is reduced and operated for a predetermined time, so that the heat absorbed by the water heat exchanger is efficiently stored in the hot water storage tank. It can be recovered.

  According to a seventh aspect of the present invention, when the controller receives the compressor stop signal, the capacity of the compressor is reduced and the compressor is operated for a first predetermined time, and the capacity of the circulation pump is reduced by a second predetermined time. Since control is performed so as to operate for a long time, the heat remaining in the evaporator can be efficiently recovered, and the heat absorbed by the water heat exchanger can be efficiently recovered in the hot water storage tank. Further, since the second predetermined time is set longer than the first predetermined time, the heat absorbed by the refrigerant from the outdoor air can be recovered to the maximum extent in the water.

  In the eighth invention, after the controller receives the compressor stop signal, the compressor temperature is stopped when the pipe temperature sensor that detects the refrigerant temperature of the evaporator detects a predetermined temperature. The pressure on the low pressure side of the compressor does not become negative, and the reliability of the compressor can be ensured.

  In the ninth aspect, after the controller receives the compressor operation stop signal, one operating time is selected from a plurality of operating times stored in the controller based on the outside air temperature detected by the outside air temperature sensor. Since the operation of the compressor is stopped after the selected operation time has elapsed, the refrigerant can be efficiently recovered by appropriately operating the compressor according to the outside air temperature.

  A tenth invention is provided with an inlet water temperature sensor for detecting the temperature of water flowing into the refrigerant-water heat exchanger, and an outlet water temperature sensor for detecting the temperature of water flowing out of the refrigerant-water heat exchanger. After receiving the compressor shutdown signal, the circulating pump is stopped when the difference between the water temperature detected by the inlet water temperature sensor and the water temperature detected by the outlet water temperature sensor is equal to or lower than a predetermined temperature. Therefore, the heat absorbed by the water heat exchanger can be efficiently recovered in the hot water storage tank.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a heat pump unit according to the present invention, in particular, a heat pump water heater provided with a hot water tank.

  As shown in FIG. 1, the heat pump water heater according to the present invention is formed by sequentially connecting a variable capacity compressor 2, a condenser 4, a decompressor 6, and an evaporator (outdoor heat exchanger) 8. A refrigerant circulation circuit, a hot water tank 10, a capacity variable circulation pump 12, and a water heat exchanger 14 are sequentially connected to form a hot water circulation circuit. Further, the condenser 4 and the water heat exchanger 14 constitute a refrigerant-water heat exchanger that performs heat exchange between the refrigerant and water.

  A water supply valve 16 is provided in the water supply pipe of the hot water storage tank 10, and the compressor 2, the decompressor 6, the circulation pump 12, and the water supply valve 16 are electrically connected to the controller 18 and controlled by the controller 18. The

  In the heat pump water heater having the above configuration, the high-temperature and high-pressure refrigerant gas discharged from the compressor 2 flows into the condenser 4 and exchanges heat with the water supplied from the circulation pump 12 and flowing into the water heat exchanger 14. The water is heated. The refrigerant that exchanges heat with water in the condenser 4 is decompressed by the decompressor 6, further flows into the evaporator 8, absorbs heat from the outdoor air, becomes a gas refrigerant, and returns to the compressor 2.

  On the other hand, the water flowing out from the lower part of the hot water tank 10 is supplied to the hydrothermal exchanger 14 by the circulation pump 12, heated by the condensation heat of the refrigerant, and stored in the upper part of the hot water tank 10. By repeating this operation, hot water (heated water) is gradually laminated from the upper part to the lower part in the hot water storage tank 10 having a predetermined capacity (for example, 370 liters).

  The heat pump water heater according to the present invention basically stores hot water at a predetermined temperature (for example, 75 ° C. to 85 ° C.) in the hot water storage tank 10 using nighttime electric power that is cheaper than daytime, and uses hot water for one day. The heating operation is performed by calculating the amount of heat necessary for boiling the entire amount in the hot water storage tank 10 at a predetermined time (for example, 7:00 am) according to the amount and the feed water temperature.

  The hot water storage tank 10 is provided with a plurality of (for example, five) temperature sensors (not shown) for detecting the temperature of hot water at a plurality of water levels, one of which (for example, the amount of remaining hot water). When the temperature sensor located at a water level of 200 liters detects a predetermined temperature (for example, 45 ° C.) or higher, it is determined that there is remaining hot water, and when it is determined that there is no remaining hot water, the controller 18 and the compressor 2 and The operation signal can be sent to the circulation pump 12 and the opening signal can be sent to the water supply valve 16.

  The present invention is characterized in refrigerant recovery when the heat pump water heater configured as described above is stopped. This characteristic will be described below with reference to FIG.

  FIG. 2 shows a timing chart when the operation of the heat pump water heater according to the present invention is stopped. As shown in FIG. 2, when a stop signal is input from the controller 18 to the compressor 2 at time t1, The compressor 2 decreases the frequency without stopping immediately and is operated for a predetermined time T1 (for example, 5 minutes), and then stops at time t2. When the frequency during the steady operation of the compressor 2 is 60 to 80 Hz, the operation for the predetermined time T1 is performed at, for example, 30 to 40 Hz.

  The pressure reducer 6 is controlled to close at time t1, gradually operates in the valve closing direction, and closes with a slight delay from the compressor stop signal input at time t1.

  The compressor 2 stopped at time t2 continues to be stopped until time t3 when the next operation signal is input, and the decompressor 6 is in a closed state until time t3. At time t3, the compressor 2 Is restarted, and the pressure reducer 6 operates in the valve opening direction.

  On the other hand, in the hot water circulation circuit, at time t1, the circulation pump 12 is operated at a reduced speed without stopping immediately (for example, about 1/3 of the speed during steady operation), and the predetermined time T2 ( For example, stop after one minute).

  The stopped state of the circulation pump 12 continues until time t3 and restarts at time t3.

  By controlling in this way, after the stop signal of the compressor 2 is input, the refrigerant present on the refrigerant outlet side of the decompressor 6 on the suction side of the compressor 2 can be recovered on the condenser 4 side, and the evaporator 8 Then, the heat recovered by the refrigerant from the outdoor air is sent to the condenser 4 and the water flowing through the water heat exchanger 14 absorbs heat, so that the heat can be recovered in the hot water storage tank 10 via the water heat exchanger.

  Note that the operation of the circulation pump 12 is continued for a predetermined time T2 after the compressor 2 is stopped because the heat that can be recovered remains in the condenser 4 immediately after the compressor 2 is stopped, and the refrigerant flows from the outdoor air. This is to recover the absorbed heat to the maximum extent in the water.

  Referring further to FIG. 2, the temperature of the evaporator 8 at the time of refrigerant recovery is low during the operation of the compressor 2 and increases somewhat when the frequency of the compressor 2 decreases at time t1, and then with refrigerant recovery. Although the temperature gradually decreases, the refrigerant on the condenser 4 side leaks to the evaporator 8 side through the compressor 2 or the decompressor 6, so that the temperature of the evaporator 8 gradually increases.

  Further, the temperature of the refrigerant-water heat exchanger is high during the operation of the compressor 2, gradually decreases at time t1, further decreases at time t2, and further decreases with the stop of operation of the circulation pump 12, and at time t3. Rise gradually.

  As described above, when the refrigerant existing on the suction side of the compressor 2 is recovered to the condenser 4 side when the compressor 2 is stopped, the heat loss can be reduced as much as possible and recovered in the hot water tank 10. The liquid back | bag at the time of restart of 2 can be avoided, and the reliability of the compressor 2 improves. Moreover, since the refrigerant | coolant pressure in the evaporator 8 at the time of the stop of the compressor 2 falls, the thickness of refrigerant | coolant piping can be reduced and piping material can be reduced.

  The heat pump water heater according to the present invention can use various refrigerants such as HFC refrigerants, natural refrigerants such as hydrocarbons and carbon dioxide, but the high pressure of supercritical refrigerants such as carbon dioxide is different from that of other refrigerants. Since it is higher than the high pressure, the effect of reducing the thickness of the refrigerant pipe is particularly effective when a supercritical refrigerant such as carbon dioxide is used.

  Also, as shown in FIG. 3, a check valve that allows refrigerant to flow from the former to the latter between the evaporator 8 and the compressor 2 in the refrigerant circulation circuit and blocks the flow of refrigerant from the latter to the former. It is preferable to provide the refrigerant 22 because the refrigerant collected on the condenser 4 side when the operation of the compressor 2 is stopped does not return to the evaporator 8 via the compressor 2.

  Furthermore, as shown in FIG. 4, a two-way electromagnetic valve 22 controlled by the controller 18 is provided between the decompressor 6 and the evaporator 8, and when a stop signal for the compressor 2 is input, When the operation signal of the compressor 2 is input while the two-way electromagnetic valve 22 is closed, when the two-way electromagnetic valve 22 is controlled to open (see FIG. 2), it is recovered to the condenser 4 side when the compressor 2 is stopped. The recovered refrigerant does not return to the evaporator 8 via the decompressor 6, and the refrigerant can be recovered more reliably.

  In addition, as shown in FIG. 5, a two-way electromagnetic valve 24 controlled by the controller 18 is provided between the evaporator 8 and the compressor 2, and after the refrigerant recovery is finished (after the compressor 2 is stopped). On the other hand, when the two-way solenoid valve 24 is controlled to be closed and the operation signal of the compressor 2 is input, the two-way solenoid valve 24 is controlled to be opened, so that the refrigerant can be recovered more reliably.

  In the above-described embodiment, the compressor 2 and the circulation pump 12 are used with variable capacity. However, it is not always necessary to change the capacity. After the signal is input, the compressor 2 may be stopped in a time shorter than the time T1, and the circulation pump 12 may be stopped in a time shorter than the time T1 + T2.

  In the above embodiment, the compressor 2 receives the stop signal and stops the operation after a predetermined time has elapsed. As shown in FIG. 1, the compressor 2 controls the temperature of the refrigerant flowing through the evaporator 8. An evaporator pipe temperature sensor 26 to be detected is provided. When a predetermined temperature is detected by the evaporator pipe temperature sensor 26 so that the pressure on the low pressure side of the compressor 2 does not become negative, the operation of the compressor 2 is stopped. It may be.

  This configuration is particularly effective when a scroll compressor having a fixed scroll and an orbiting scroll is used as the compressor 2. In the case of a scroll compressor, if the suction side becomes negative pressure, the circulation of lubricating oil becomes insufficient and the sliding This is because the moving part may be worn.

  In addition, an outside air temperature sensor (not shown) for detecting the temperature of the outdoor air is provided, and a plurality of operation times of the compressor 2 set in advance according to the outside air temperature are stored in the storage unit of the controller 18. One of the operation times is selected based on the temperature detected by the outside air temperature sensor, and after the stop signal of the compressor 2 is received, the operation of the compressor 2 can be stopped after the selected operation time has elapsed.

  Alternatively, the operation time is set to be constant, and a plurality of operation frequencies of the compressor 2 set in advance according to the outside air temperature and the time interval from the operation stop to the operation start are stored in the storage unit of the controller 18. One of a plurality of operating frequencies is selected based on the temperature detected by the outside air temperature sensor, and after receiving a stop signal for the compressor 2, the compressor 2 may be controlled based on the selected operating frequency. Good.

  In the above embodiment, the operation of the circulation pump 12 is stopped after a predetermined time T2 has elapsed after the operation of the compressor 2 is stopped. However, as shown in FIG. An inlet water temperature sensor 28 for detecting the temperature of the water flowing into the water heat exchanger 14 and the temperature of the water flowing out of the water heat exchanger 14 are detected in the incoming and outgoing piping of the water heat exchanger 14 in the circuit. Each of the outlet water temperature sensors 30 is provided, and after receiving a stop signal of the compressor 2, the controller 18 calculates a temperature difference between the water temperature detected by the inlet water temperature sensor 28 and the water temperature detected by the outlet water temperature sensor 30 in the controller 18. When the temperature difference is equal to or lower than a predetermined temperature (for example, 2 ° C.), the circulation pump 12 may be stopped by determining that the heat recovery from the refrigerant to the water has been substantially completed.

  Alternatively, only the outlet water temperature sensor 30 may be provided, and the circulation pump 12 may be stopped when the water temperature detected by the outlet water temperature sensor 30 falls below a predetermined temperature.

  The heat pump unit according to the present invention can effectively recover the heat of outdoor air in a hot water storage tank, and at the same time, can prevent liquid back to the compressor and reduce the pipe wall thickness of the evaporator. Therefore, it is useful as various water heaters including general household water heaters, heating devices using hot water, floor heating devices, and the like.

Refrigeration cycle configuration diagram of a heat pump water heater according to the present invention Timing chart when operation of the heat pump water heater of FIG. 2 is stopped Refrigeration cycle configuration diagram of a modification of the heat pump water heater of FIG. Refrigeration cycle configuration diagram of another modification of the heat pump water heater of FIG. Refrigeration cycle configuration diagram of still another modification of the heat pump water heater of FIG.

DESCRIPTION OF SYMBOLS 2 Compressor 4 Condenser 6 Decompressor 8 Evaporator 10 Hot water storage tank 12 Circulation pump 14 Water heat exchanger 16 Water supply valve 18 Controller 20 Check valve 22 Two-way solenoid valve 24 Two-way solenoid valve 26 Evaporator piping temperature sensor 28 Inlet water temperature sensor 30 Outlet water temperature sensor

Claims (10)

A refrigerant circulation circuit in which a compressor, a refrigerant-water heat exchanger, a decompressor, and an evaporator are sequentially connected , a hot water tank, the refrigerant-water heat exchanger, a hot water circulation circuit having a circulation pump , the compressor, and the decompression And a controller for controlling the operation of the circulation pump ,
In the refrigerant-water heat exchanger, heat exchange is performed between the refrigerant flowing through the refrigerant circulation circuit and the water flowing through the hot water circulation circuit,
When the controller receives an operation stop signal of the compressor, before stopping the operation of the compressor, the controller operates the decompressor in a valve closing direction to operate the compressor for a first predetermined time , The refrigerant of the evaporator is conveyed to the refrigerant-water heat exchanger, and the circulation pump is operated for a second predetermined time longer than the first predetermined time, so that the hot water of the refrigerant-water heat exchanger is stored in the hot water storage. A heat pump water heater characterized by being conveyed to a tank . A check valve is provided between the evaporator and the compressor to allow a refrigerant to flow from the evaporator to the compressor and to block a refrigerant flow from the compressor to the evaporator. The heat pump water heater according to claim 1. The heat pump water heater according to claim 1, wherein a two-way valve is provided between the pressure reducer and the evaporator, and the two-way valve is closed after the pressure reducer operates in a valve closing direction. A first two-way valve is provided between the evaporator and the compressor, and a second two-way valve is provided between the pressure reducer and the evaporator, and the pressure reducer operates in the valve closing direction. The heat pump water heater according to claim 1, wherein the first two-way valve and the second two-way valve are closed. The compressor is composed of a variable capacity compressor, and when the controller receives an operation stop signal of the compressor, the compressor is controlled to reduce its capacity and operate for a predetermined time. The heat pump water heater according to any one of claims 1 to 4. The circulation pump is constituted by a variable capacity circulation pump, and when the controller receives an operation stop signal of the compressor, the circulation pump is controlled to reduce its capacity and operate for a predetermined time. The heat pump water heater according to any one of claims 1 to 4. The compressor is configured with a variable capacity compressor, and the circulation pump is configured with a variable capacity circulation pump. When the controller receives the compressor shutdown signal, the capacity of the compressor is reduced. Then, while operating for the first predetermined time, the circulating pump is controlled to operate for the second predetermined time by reducing its capacity, and the second predetermined time is set longer than the first predetermined time. The heat pump water heater according to any one of claims 1 to 4, wherein the heat pump water heater is provided. A pipe temperature sensor for detecting the refrigerant temperature of the evaporator is provided, and after the controller receives a compressor operation stop signal, the compressor operation is stopped when the pipe temperature sensor detects a predetermined temperature. The heat pump water heater according to any one of claims 1 to 4, wherein: After providing an outside air temperature sensor for detecting the outside air temperature, storing a plurality of operation times of the compressor set according to the outside air temperature in the controller, and the controller receiving an operation stop signal of the compressor The operation time is selected from a plurality of operation times stored in the controller based on the outside air temperature detected by the outside air temperature sensor, and the operation of the compressor is stopped after the selected operation time elapses. The heat pump water heater according to any one of claims 1 to 4, wherein the heat pump water heater is provided. In the hot water circulation circuit, an inlet water temperature sensor for detecting the temperature of water flowing into the refrigerant-water heat exchanger and an outlet water temperature sensor for detecting the temperature of water flowing out of the refrigerant-water heat exchanger are provided, After the controller receives an operation stop signal of the compressor, when the temperature difference between the water temperature detected by the inlet water temperature sensor and the water temperature detected by the outlet water temperature sensor is equal to or lower than a predetermined temperature, The heat pump water heater according to any one of claims 1 to 4, wherein the circulation pump is stopped.

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