JP6131921B2 - Heat pump hot water supply - Google Patents

Description

  The present invention relates to a heat pump hot water supply.

  In general boiling operation of a hot water storage type heat pump water heater, the water supplied from the lower part of the hot water storage tank and the refrigerant compressed by the compressor are heat-exchanged by a heat exchanger (gas cooler), and hot water is supplied. Boil up and return to the top of the hot water storage tank to store hot water. Therefore, within a predetermined period from the start of boiling, a low temperature water layer is formed on the lower side of the hot water storage tank, and a high temperature hot water layer is formed on the upper side. As boiling operation proceeds and hot water begins to accumulate to the bottom of the hot water storage tank, the temperature of the water supplied to the heat exchanger also begins to rise suddenly. Along with this, the temperature of the refrigerant outlet temperature of the heat exchanger also starts to rise suddenly. Generally, when the refrigerant outlet temperature of the heat exchanger rises, the amount of heat exchange in the heat exchanger decreases, and the boiling capacity of the compressor with respect to the power consumption decreases. Therefore, when the boiling has progressed to some extent, the boiling ability suddenly decreases, and it takes time to boil.

  The technology for adjusting the hot water heating capacity is to detect the hot water heating capacity during operation based on the difference between the temperature of the low-temperature water before heating and the temperature of the high-temperature water after heating, and adjust the operating frequency of the compressor. Therefore, there is known a heat pump type water heater that brings hot water heating capacity close to necessary hot water heating capacity (Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-116891

  However, when adjusting the hot water heating capacity based on the difference between the feed water temperature and the tapping temperature as in the technique described in Patent Document 1, the boiling operation has progressed, and high temperature hot water has begun to accumulate to the bottom of the hot water storage tank. The hot water heating capacity cannot be increased immediately from that point. That is, when the temperature of the water supply to the heat exchanger rises, the temperature of the hot water from the heat exchanger rises accordingly, so that hot water has begun to accumulate to the bottom of the hot water storage tank, that is, the boiling capacity has begun to decline. This is unlikely to appear in the difference between the feed water temperature and the tapping temperature. Therefore, it has not been possible to solve the problem that it takes time to boil up as the hot water heating capacity decreases.

  The present invention has been made to solve the above-described problems, and it is intended to provide a heat pump water heater that can boil in a short time without lowering the boiling capacity even when the boiling proceeds to some extent. Objective.

  The heat pump water heater according to the present invention has a refrigerant circuit in which a compressor, a refrigerant water heat exchanger, an expansion valve, and an air refrigerant heat exchanger are connected in an annular shape, and heats water by the refrigerant water heat exchanger. A heat pump for generating hot water, a hot water storage tank for storing hot water heated by the heat pump, a water supply pump for circulating hot water between the hot water storage tank and the refrigerant water heat exchanger, and the refrigerant water heat exchanger. An inlet temperature detection unit that detects an inlet temperature that is the temperature of the inflowing water, and a difference between a current value of the inlet temperature and an average value of the inlet temperature in a preset period is equal to or greater than a preset temperature difference threshold value The degree of opening of the expansion valve is smaller than the degree of opening of the expansion valve when the difference between the current value of the inlet temperature and the average value of the inlet temperature is less than the temperature difference threshold. Strange Characterized in that it comprises a means.

  According to the heat pump water heater of the present invention, it is possible to boil in a short time without lowering the boiling capacity even when the boiling proceeds to some extent.

It is a block diagram of the heat pump water heater in Embodiment 1 of this invention. It is a time chart which shows the change of the feed water temperature at the time of the boiling operation of the heat pump water heater of FIG. It is a flowchart which shows the opening degree control of the expansion valve 3 at the time of the boiling operation of the heat pump water heater of FIG.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a heat pump water heater 100 according to Embodiment 1 of the present invention. The heat pump water heater 100 expands the compressor 1 that compresses the refrigerant, the refrigerant water heat exchanger 2 that exchanges heat between the refrigerant compressed by the compressor 1 and water, and the refrigerant that dissipates heat in the refrigerant water heat exchanger 2. An expansion valve 3 and an air refrigerant heat exchanger 4 that exchanges heat between the refrigerant expanded by the expansion valve 3 and the outside air are provided. The compressor 1, the refrigerant water heat exchanger 2, the expansion valve 3, and the air refrigerant heat exchanger 4 are annularly connected by a refrigerant pipe to form heat pump circuits 1 to 4. In addition, a blower fan 5 is provided as means for blowing outside air to the air refrigerant heat exchanger 4.

  The heat pump water heater 100 also includes a hot water storage tank 6 that stores water supplied to the refrigerant water heat exchanger 2 that performs heat exchange between the refrigerant and water and water that has been boiled, and water stored in the hot water storage tank 6. 6 is supplied to the refrigerant water heat exchanger 2 and returned to the hot water storage tank 6 from the refrigerant water heat exchanger 2, that is, hot water is supplied between the hot water storage tank 6 and the refrigerant water heat exchanger 2. A water pump 7 for circulation; The hot water storage tank 6, the water pump 7, and the refrigerant water heat exchanger 2 are connected in a ring shape by a circulation pipe 13. The water supply pipe 15 is connected to the lower part of the hot water storage tank 6 and supplies water to the hot water storage tank 6. The water supply pipe 15 is branched on the upstream side of the hot water storage tank 6 and is connected to the hot water supply pipe 16 via the three-way valve 14. The hot water supply pipe 16 is connected to the upper part of the hot water storage tank 6 and is used to supply hot water stored in the hot water storage tank 6 to, for example, a bathtub (not shown) in the house.

  The control device 8 controls the compressor 1, the expansion valve 3, and the blower fan 5. The control device 8 includes opening degree changing means for changing the opening degree of the expansion valve 3. The discharge temperature thermistor 9 detects the temperature of the refrigerant discharged from the compressor 1, that is, the discharge temperature of the compressor 1. The incoming water temperature thermistor 10 detects the temperature of water supplied from the hot water storage tank 6 to the refrigerant water heat exchanger 2, that is, the inlet temperature of the refrigerant water heat exchanger 2. The hot water temperature thermistor 11 detects the temperature of hot water boiled by the refrigerant water heat exchanger 2, that is, the outlet temperature of the refrigerant water heat exchanger 2. The outside air temperature thermistor 12 detects the outside air temperature.

  During the boiling operation, water is supplied from the hot water storage tank 6 to the refrigerant water heat exchanger 2 by the water supply pump 7. In the refrigerant water heat exchanger 2, the water is heat-exchanged with the high-temperature and high-pressure refrigerant discharged from the compressor 1 to become high-temperature hot water. Hot water is sent to the hot water storage tank 6 and stored from the upper part of the hot water storage tank 6. The refrigerant that exchanges heat with water in the refrigerant water heat exchanger 2 is expanded by the expansion valve 3, exchanges heat with the outside air in the air refrigerant heat exchanger 4, and is sucked into the compressor 1.

  Hereinafter, the operation of the heat pump water heater 100 during the boiling operation will be described. During the boiling operation, the control device 8 has a difference between the current value of the inlet temperature detected by the incoming water temperature thermistor 10 and the average value of the inlet temperatures within a preset period (hereinafter referred to as inlet temperature difference) in advance. The opening degree of the expansion valve 3 when it is equal to or larger than the set temperature difference threshold value is made smaller than the opening degree of the expansion valve 3 when the inlet temperature difference is less than the temperature difference threshold value. The period can be, for example, the past 10 minutes from the present time. Hereinafter, among the boiling operations, an operation when the inlet temperature difference is less than the temperature difference threshold is referred to as a normal boiling operation, and an operation when the inlet temperature difference is equal to or greater than the temperature difference threshold is referred to as a strong boiling operation.

  In addition, the control device 8 determines that the state where the inlet temperature difference is equal to or greater than the temperature difference threshold value and the change amount of the inlet temperature within a certain period is equal to or greater than a preset change amount threshold value continues for a preset period or more. The opening degree of the expansion valve 3 can be reduced. For example, the control device 8 can reduce the opening of the expansion valve 3 when the state in which the amount of increase in the inlet temperature in one minute is 0.5 ° C. continues for 5 minutes or more.

  The controller 8 controls the opening and closing of the expansion valve 3 so that the discharge temperature detected by the discharge thermistor 9 becomes the expansion valve control target temperature during the boiling operation. The initial value of the expansion valve control target temperature can be set based on the outside air temperature obtained by the outside air temperature thermistor 12 at the start of the boiling operation and the target value of the boiling temperature. Further, the initial value of the expansion valve control target temperature can be set based on the outside air temperature detected by the outside air temperature thermistor 12 and the required boiling capacity. The control device 8 updates the expansion valve control target temperature by adding the correction temperature to the expansion valve control target temperature during the strong boiling operation. The control device 8 changes the opening degree of the expansion valve 3 so that the discharge temperature approaches the expansion valve control target temperature. By such an operation, the discharge temperature of the compressor 1 rises, and it is possible to prevent the boiling capacity from being lowered as compared with the normal boiling operation. Details of setting the expansion valve control target temperature will be described later (FIG. 3).

  In the heat pump water heater 100 during the boiling operation, the water supplied from the lower part of the hot water storage tank 6 is heat-exchanged with the refrigerant compressed to high temperature and high pressure by the compressor 1 in the refrigerant water heat exchanger 2, The water is boiled in hot water (for example, 65 ° C. to 90 ° C.) and returned to the upper part of the hot water storage tank 6 to store the hot water. When the boiling operation proceeds, hot water is stored in the hot water storage tank 6 and hot water starts to be stored up to the lower part of the hot water storage tank 6, the temperature of the water supplied to the refrigerant water heat exchanger 2 also increases.

  In normal boiling operation, the water layer in the hot water storage tank 6 is composed of a low temperature water layer and a high temperature hot water layer, and when the supply to the refrigerant water heat exchanger 2 changes from low temperature water to high temperature hot water, The feed water temperature to the refrigerant water heat exchanger 2 starts to rise suddenly. For example, as shown in FIG. 2, assuming that the total amount of water in the hot water storage tank is boiled from about 10 ° C. to about 60 ° C., refrigerant water heat exchange is performed for about 3.3 hours from the start of the boiling operation for about 5 hours. The feed water temperature to the vessel 2 is almost constant, but rises by about 50 ° C. in about 1.7 hours thereafter.

  As the temperature of the supplied water rises, the refrigerant outlet temperature of the refrigerant water heat exchanger 2 also rises. When the normal boiling operation is continued even after the refrigerant outlet temperature of the refrigerant water heat exchanger 2 starts to rise, the amount of heat exchange in the refrigerant water heat exchanger 2 decreases, and the boiler 1 heats up with respect to the power consumption of the compressor 1. Since the capacity is reduced, the efficiency of the boiling operation is lowered. Therefore, in the heat pump water heater 100, a strong boiling operation is performed, and the opening temperature of the expansion valve 3 is controlled to increase the discharge temperature of the compressor 1, thereby reducing the heat exchange amount in the refrigerant water heat exchanger 2. Suppress. Thereby, it is possible to prevent a decrease in efficiency of the boiling operation.

  Hereinafter, the opening degree control of the expansion valve 3 during the boiling operation by the control device 8 of the heat pump water heater 100 will be described with reference to FIG. 3.

  First, the control device 8 acquires the current outside air temperature Ta detected by the outside air temperature thermistor 12 (step S1).

  Next, the control apparatus 8 acquires the setting boiling temperature TP set by the user (step S2). Note that the user can set the set boiling temperature TP using a setting panel provided on the surface of the heat pump water heater 100 or a remote controller (not shown).

  Next, the control device 8 determines the expansion valve control target temperature Tdt based on the outside air temperature Ta and the set boiling temperature TP acquired in Steps S1 and S2 (Step S3). For example, Tdt = TP + (20−Ta). The control device 8 adjusts the opening degree of the expansion valve 3 so that the discharge temperature of the compressor 1 becomes the expansion valve control target temperature Tdt, and starts the boiling operation.

  Next, the control device 8 calculates the average value Twi0 of the inlet temperature detected by the incoming water temperature thermistor 10, calculates the inlet temperature difference Tdi that is the difference between the average value Twi0 and the current value Twi1, and calculates the inlet temperature. It is determined whether or not the difference Tdi is greater than or equal to the temperature difference threshold value Tha (step S4). The determination is started after elapse of a preset time such as 10 minutes after starting the boiling operation. The average value Twi0 is an average value within a preset fixed period such as 10 minutes, and is calculated at a preset interval such as 1 minute. In this case, the control device 8 performs the determination at an interval of 1 minute.

  The control device 8 calculates the correction temperature Tdh when the inlet temperature difference Tdi is equal to or greater than the threshold value Tha. The correction temperature Tdh can be calculated by, for example, the equation Tdh = (Twi1−Twi0) × α. The calculated correction temperature Tdh is added to the expansion valve control target temperature Tdt to update the expansion valve control target temperature Tdt (step S5).

  In addition, the controller 8 has the state where the inlet temperature difference Tdi is equal to or greater than the temperature difference threshold value Tha and the change amount of the inlet temperature within a certain period is equal to or greater than the preset change amount threshold value for a preset period or more. In this case, the expansion valve control target temperature Tdt can be updated. For example, the expansion valve control target temperature Tdt may be updated when a state where the amount of increase in the inlet temperature in one minute is 0.5 ° C. continues for 5 minutes or more. According to such a configuration, it is possible to prevent the inlet temperature from temporarily rising due to erroneous detection of the inlet temperature by the incoming water temperature thermistor 10 and shifting to the strong boiling operation.

  In order to prevent an excessive increase in the refrigerant pressure, an upper limit value Tm of the expansion valve control target temperature Tdt can also be provided. The upper limit value Tm is, for example, 20 ° C. When the calculated value of the expansion valve control target temperature Tdt exceeds the upper limit value Tm, the control device 8 sets the expansion valve control target temperature Tdt to the upper limit value Tm.

  The control device 8 changes the opening degree of the expansion valve 3 based on the expansion valve control target temperature Tdt. For example, the control device 8 can change the opening degree of the expansion valve 3 so as to be inversely proportional to the expansion valve control target temperature Tdt. Further, the control device 8 includes a table in which the correspondence between the expansion valve control target temperature Tdt and the opening degree of the expansion valve 3 is set in advance, and the opening degree of the expansion valve 3 is opened corresponding to the current expansion valve control target temperature Tdt. It can be changed at any time.

  Next, the control device 8 ends the boiling operation when the feed water temperature reaches the set boiling temperature TP or when there is a boiling end instruction from the user. Until then, the control of steps S4 and S5 is performed. (Step S6).

  As described above, in the heat pump water heater 100 of the present embodiment, the inlet temperature difference Tdi, which is the difference between the average value Twi0 of the refrigerant water heat exchanger 2 within a certain period and the current value Twi1, is a temperature difference. The opening degree of the expansion valve 3 is reduced when it is equal to or greater than the threshold Tha. Since hot water is gradually stored from the upper layer toward the lower layer of the hot water storage tank 6 and is supplied to the refrigerant water heat exchanger 2 from the lower layer, the refrigerant water is used until a predetermined period elapses from the start of the boiling operation. The inlet temperature of the heat exchanger 2 hardly changes. Since there is almost no change in the average value of the inlet temperature during this period, the control device 8 performs the normal boiling operation, does not calculate the correction value Tdh, and does not update the expansion valve control target temperature Tdt. The inlet temperature of the refrigerant water heat exchanger 2 also rises from the time when the hot water is stored in the lower layer of the hot water storage tank 6, that is, from the time when the amount of heat exchange in the refrigerant water heat exchanger 2 decreases and the boiling capacity starts to decrease. . As the inlet temperature rises, the current value Twi1 of the inlet temperature starts to deviate from the average value Twi0 for a predetermined period. In the heat pump water heater 100, the correction temperature Tdh is calculated when the inlet temperature difference Tdi becomes equal to or higher than the temperature difference threshold value Tha, and this is added to the expansion valve control constant temperature Tdt to update the expansion valve control target temperature Tdt. . By reducing the opening of the expansion valve 3 so that the discharge temperature of the compressor 1 approaches the expansion valve control target temperature Tdt, the temperature of the refrigerant supplied to the refrigerant water heat exchanger 2 is increased, and the boiling point is increased. Operate and prevent the heat exchange rate from decreasing.

  As described above, in the heat pump water heater 100, the refrigerant water heat exchanger 2 has an inlet that the heat exchange efficiency in the refrigerant water heat exchanger 2 has started to decrease after a certain amount of time has elapsed since the start of the boiling operation. This is detected when the current temperature value Twi1 is more than the temperature difference threshold value Tha from the average value Twi0. Therefore, the discharge temperature of the compressor 1 can be increased immediately from the time when the heat exchange efficiency starts to decrease, and the heat exchange amount can be prevented from decreasing.

  Further, the control device 8 reduces the opening degree of the expansion valve 3 when a state in which the amount of change in the inlet temperature within a certain period is equal to or greater than a preset change amount threshold value continues for a preset period. You can also. According to such a configuration, even when the inlet temperature temporarily rises due to erroneous detection of the inlet temperature by the incoming water temperature thermistor 10, it is possible to prevent a malfunction in the transition from the normal boiling operation to the strong boiling operation. it can.

  In addition, an upper limit value can be set for the correction temperature Tdt. According to such a configuration, it is possible to prevent the compressor 1 from malfunctioning by preventing an excessive increase in the refrigerant pressure.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Heat exchanger 3 Expansion valve 4 Evaporator 5 Blower fan 6 Hot water storage tank 7 Water supply pump 8 Control means 9 Discharge temperature thermistor 10 Incoming temperature thermistor 11 Outlet temperature thermistor 12 Outside temperature thermistor 13 Circulation piping 14 Three-way valve 15 Supply piping 16 Hot water supply piping

Claims (4)

A heat pump that has a refrigerant circuit in which a compressor, a refrigerant water heat exchanger, an expansion valve, and an air refrigerant heat exchanger are annularly connected, and generates water by heating water by the refrigerant water heat exchanger;
A hot water storage tank for storing hot water heated by the heat pump;
A water supply pump for circulating hot water between the hot water storage tank and the refrigerant water heat exchanger;
An inlet temperature detection unit that detects an inlet temperature that is a temperature of water flowing into the refrigerant water heat exchanger,
The degree of opening of the expansion valve when the difference between the current value of the inlet temperature and the average value of the inlet temperature in a preset period is equal to or greater than a preset temperature difference threshold, the current value of the inlet temperature and the inlet A heat pump water heater, comprising: an opening changing means for making the difference between the average value of the temperatures smaller than the opening of the expansion valve when the difference is less than the temperature difference threshold.   The opening degree changing means reduces the opening degree of the expansion valve when a state in which the change amount of the inlet temperature within a certain period is equal to or greater than a preset change amount threshold value continues for a preset period or longer. The heat pump water heater according to claim 1. Including a discharge temperature thermistor for detecting the discharge temperature of the compressor;
The opening changing means calculates a correction value when the difference between the current value of the inlet temperature and the average value of the inlet temperature is equal to or greater than the temperature difference threshold value, and the correction value is set in advance by the expansion valve control. 2. The expansion valve control target temperature is updated by adding to a target temperature, and the opening degree of the expansion valve is decreased so that the discharge temperature becomes the updated expansion valve control target temperature. Or the heat pump hot-water supply apparatus of 2. An upper limit value is set in advance for the expansion valve control target temperature,
The opening degree changing means sets the upper limit value as the expansion valve control target temperature when a value obtained by adding the correction value to the expansion valve control target temperature exceeds the upper limit value. The heat pump water heater according to claim 3.

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