JP4698697B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump water heater.

  A conventional heat pump water heater includes a refrigeration cycle including a compressor, a water refrigerant heat exchanger, an expansion valve, and an evaporator, and a hot water supply circuit including a tank, a pump, and a water refrigerant heat exchanger (for example, , See Patent Document 1). In the heat pump operation of this heat pump water heater, the refrigerant compressed to high temperature and high pressure by the compressor flows into the water refrigerant heat exchanger, and is transferred to the water flow path in the water refrigerant heat exchanger from the bottom of the tank by the pump. The water is cooled by exchanging heat with water, depressurized by an expansion valve, absorbs atmospheric heat by an evaporator, and returns to the compressor. Water heated by the refrigerant in the water-refrigerant heat exchanger flows into the tank from the upper part of the tank and is stored in hot water.

  This type of heat pump water heater has the following problems. Water such as tap water and groundwater usually contains hardness components such as calcium and magnesium, and some regions contain many hardness components. When water containing a large amount of this hardness component is heated by the water refrigerant heat exchanger of the heat pump water heater, scale (for example, calcium carbonate) is deposited near the outlet of the water flow path of the water refrigerant heat exchanger that becomes high temperature, and water refrigerant heat exchange is performed. Deposits on the inner surface of the water pipe of the vessel. In this case, heat transfer is hindered and the performance of the water-refrigerant heat exchanger decreases. Moreover, since the flow path is blocked, the pressure loss is increased, and the pump input is increased. Further, when the scale adheres, the water flow path is blocked and the operation by the heat pump water heater becomes impossible.

  In order to eliminate such inconvenience, conventionally, the following heat pump water heater has been proposed. For example, a heat pump hot water supply provided with a core tube serving as a water passage spirally formed so as to have an oval shape on the same plane, and a winding tube serving as a refrigerant passage spirally wound around the outer periphery of the core tube In some machines, there is a core pipe in which the winding pitch of the winding pipe of the portion (the water inlet side of the core pipe) that is higher than the temperature at which the scale component precipitates is increased (for example, see Patent Document 2). By adopting this structure, it was possible to reduce the amount of heat transferred from the wound tube to the core tube, to reduce the tube wall temperature of the core tube, and to suppress the precipitation of scale components. In addition, the connecting pipe connected to the water outlet side of the water refrigerant heat exchanger has a larger inner diameter than the water pipe of the water refrigerant heat exchanger and expands in accordance with the water flow direction, thereby extending the blockage life due to the scale. (For example, refer to Patent Document 3).

JP-A-60-221661 (2nd page, Fig. 2) Japanese Patent No. 3649181 (pages 6-8, FIGS. 1 and 4) Japanese Patent No. 3966260 (page 4-5, FIG. 1)

  By the way, during operation of the heat pump water heater, since water is flowing through the water refrigerant heat exchanger, even if scale is deposited in the vicinity of the water outlet of the water refrigerant heat exchanger, it accumulates in the water refrigerant heat exchanger. The amount is not large. Instead, when water stops after the heat pump is stopped, the deposited scale tends to adhere to the inner surface of the connection pipe, and the deposition is promoted. Therefore, although it is necessary to consider prevention of scale accumulation after the heat pump is stopped, there is no technology in consideration of this point in the conventional heat pump water heater.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a heat pump water heater capable of suppressing scale accumulation when the heat pump operation is stopped.

A heat pump water heater according to the present invention includes a refrigeration cycle having a compressor, a water refrigerant heat exchanger for exchanging heat between refrigerant flowing through the refrigeration cycle and water flowing inside, and low-temperature water by a pump from a water intake at the bottom of the tank. Is a circuit that pumps low-temperature water back to the hot water outlet at the top of the tank by heat exchange by the water-refrigerant heat exchanger and flows out from the water outlet of the water-refrigerant heat exchanger. A flow path after the water outlet of the water-refrigerant heat exchanger, further comprising a bypass pipe for bypassing the water to the inlet side of the pump and a flow path switching valve capable of switching the flow path to the tank side or the bypass pipe side, A hot water supply circuit that can be switched from the tank side to the bypass piping side, and a pump provided in the compressor and hot water supply circuit of the refrigeration cycle are operated, and water from the tank is sent to the water refrigerant heat exchanger by the pump. Refrigerant A heating operation and returns to the tank boiling by heat exchange with the refrigerant in the exchanger, when the operation stop boiling, the channel switching valve with switching from the tank side to the bypass pipe side, the compressor is stopped, then a certain time A control means for performing a scale generation preventing operation for continuing the operation of the pump until a lapse of time and stopping the operation of the pump after a lapse of a certain time, and according to the target hot water temperature of the water refrigerant heat exchanger during the boiling operation The fixed time is variable, and the fixed time is lengthened as the target hot water temperature of the water-refrigerant heat exchanger during the boiling operation increases .

  According to the heat pump water heater of the present invention, the outlet temperature of the water-refrigerant heat exchanger can be reduced to the same as the inlet temperature by continuing the pump operation even after the compressor is stopped. Therefore, it is possible to reduce the solubility difference between the water sent to the water refrigerant heat exchanger and the calcium carbonate at the outlet of the water refrigerant heat exchanger, and it is possible to prevent scale accumulation when the heat pump is stopped.

Embodiment 1 FIG.
A first embodiment of the present invention is shown in FIG. FIG. 1 is a schematic diagram showing an overall configuration of a heat pump water heater according to Embodiment 1 of the present invention.
The heat pump water heater includes a heat pump unit 1 and a tank unit 2. In the heat pump unit 1, a compressor 3, a water / refrigerant heat exchanger 4, an expansion valve 5, and an evaporator 6 are sequentially connected in an annular manner, and a refrigeration cycle 100 in which refrigerant circulates and a fan that blows outside air to the evaporator 6. 7 is installed. On the other hand, in the tank unit 2, a pump 8 that supplies water, which is a load-side medium, to the water-refrigerant heat exchanger 4, and a tank that stores water that is supplied by the pump 8 and heated by the water-refrigerant heat exchanger 4. 9 is installed. And the hot-water supply water circuit 200 is comprised by connecting the water-refrigerant heat exchanger 4, the tank 9, and the pump 8 by connection piping 10a-10f. The pump 8 is not necessarily installed in the tank unit 2 and may be mounted on the heat pump unit 1 side.

  In the schematic diagram of the heat pump water heater shown in FIG. 1, a hot water supply device that supplies hot water having a constant temperature stored in the tank 9 of the hot water supply circuit 200 to, for example, a bath is omitted. A circuit for supplying water from the hot water supply circuit 200 is also omitted. In addition, the compressor drive device (not shown) uses an inverter-controlled DC brushless motor so that the rotation speed is variable so that the pressure and temperature of the refrigerant discharged from the compressor 3 can be changed. A plurality of compressors 3 may be combined, and this combination may be switched to make the overall capacity variable. 1 is provided with a container such as a suction muffler for reducing refrigerant noise on the suction side of the compressor 3, and a device for collecting the lubricating oil flowing out on the discharge side of the compressor 3. It is permissible to add this structure. That is, FIG. 1 illustrates only the basic circuit. As a refrigerant of this heat pump water heater, a refrigerant capable of producing high temperature hot water, for example, a refrigerant such as carbon dioxide, R410A, propane or propylene is suitable, but is not particularly limited thereto.

  In the heat pump unit 1, in the hot water supply circuit 200, the incoming water temperature sensor 11a is provided on the water inlet side of the water refrigerant heat exchanger 4, and the outgoing hot water temperature sensor 11b is provided on the water outlet side of the water refrigerant heat exchanger 4. Measure the water temperature at each installation location. In addition, an outside air temperature sensor 11 c provided at or near the heat pump unit 1 measures the outside air temperature around the heat pump unit 1. In the refrigeration cycle 100, the discharge temperature sensor 11d is provided at the outlet side of the compressor 3, the suction temperature sensor 11e is provided at the inlet side of the compressor 3, and the evaporation temperature sensor 11f is provided at the intermediate portion from the inlet of the evaporator 6, and the refrigerant temperature at the arrangement location is provided. Measure.

  In addition, in the heat pump unit 1, a measurement control device 12 as a control means is provided. The measurement control device 12 is based on the measurement information from the temperature sensors 11a to 11f and the content of the operation command information instructed by the heat pump water heater user from the remote control device or the like. And the operation method of the pump 8, a boiling operation and a scale generation preventing operation, which will be described later, and the like.

  Next, the operation of the heat pump water heater will be described. Here, the boiling operation will be described. In the boiling operation, the refrigeration cycle 100 and the hot water supply circuit 200 are operated, low temperature water is discharged from the water intake 9b at the bottom of the tank 9 by the pump 8, and is sent to the water refrigerant heat exchanger 4 to perform water refrigerant heat exchange. This is an operation in which the heat is exchanged with the refrigerant in the vessel 4 and boiled up and returned from the hot water storage port 9 a at the top of the tank 9 into the tank 9.

  In the refrigeration cycle 100 of the heat pump unit 1, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 decreases in temperature while radiating heat (heats water) to the hot water supply circuit 200 side by the water refrigerant heat exchanger 4. At this time, if the high-pressure side refrigerant pressure is equal to or higher than the critical pressure, the refrigerant radiates heat at a reduced temperature without undergoing a gas-liquid phase transition in a supercritical state. If the high-pressure side refrigerant pressure is equal to or lower than the critical pressure, the refrigerant radiates heat while liquefying. That is, hot water supply heating (boiling) is performed by applying heat radiated from the refrigerant to the load-side medium (here, water flowing through the hot water supply water circuit 200). The high-pressure and low-temperature refrigerant flowing out of the water-refrigerant heat exchanger 4 through hot water heating passes through the expansion valve 5.

  The refrigerant that has passed through the expansion valve 5 is decompressed to a low-pressure gas-liquid two-phase state. The refrigerant that has passed through the expansion valve 5 flows into the evaporator 6, where it absorbs heat from the outside air and is vaporized into gas. The low-pressure refrigerant exiting the evaporator 6 is sucked into the compressor 3 and circulated to form a refrigeration cycle 100.

  On the hot water supply circuit 200 side, the water in the tank 9 is guided by the pump 8 from the water intake 9b at the bottom of the tank 9, passes through the connecting pipes 10d to 10f, and is conveyed into the water / refrigerant heat exchanger 4. The Then, it is heated (boiling) by exchanging heat with the refrigerant, passes through the connecting pipes 10 a to 10 c, and flows into the tank 9 from the hot water storage port 9 a at the upper part of the tank 9. As a result, the upper portion of the tank 9 is hot water and the lower portion is cold water.

Next, the operation control operation in this heat pump water heater will be described.
First, the operating capacity of the compressor 3 controlled by the number of revolutions and the like and the number of revolutions of the pump 8 are information on the ambient outside temperature measured and detected by the outside temperature sensor 11c and the feed water temperature measured and detected by the incoming water temperature sensor 11a. It is adjusted based on etc. That is, based on the information, the temperature of the water at the water outlet of the water-refrigerant heat exchanger 4 (measured by the hot water temperature and the hot water temperature sensor 11b) is determined to be a predetermined target value. The adjustment is controlled. The target hot water temperature is set from the operation command information instructed by the remote controller from the user, or the heat storage energy calculated from the past hot water use amount by the microcomputer provided in the remote controller or the measurement control device 12 It is set so that it can be secured. Further, the target hot water temperature has a predetermined range, for example, a range of 65 ° C. to 90 ° C.

  If the predetermined heating capacity can be ensured with the maximum value in the target hot water temperature range, the predetermined heating capacity can be secured within the target hot water temperature range. Therefore, the rotation speed of the compressor 3 which is the heating capacity of the water refrigerant heat exchanger 4 is adjusted based on, for example, the outside air temperature and the feed water temperature as described above, so that a predetermined heating is possible at any target hot water temperature. Capability can be secured. In other words, the output of the compressor 3 is prepared with a heating capacity that can ensure the temperature of hot water required as a water heater for any external conditions at any time. Can be obtained as a water heater. Moreover, the rotation speed of the compressor 3 is provided with an upper limit rotation speed and a lower limit rotation speed from the viewpoint of compressor durability.

  The opening degree of the expansion valve 5 is controlled so that the discharge temperature becomes a predetermined value (target discharge temperature). The target discharge temperature is set to a temperature higher than the target hot water temperature, that is, the target hot water temperature + α [° C.] in order to make the target hot water temperature secureable. The value α is, for example, a function of the outside air temperature or the target hot water temperature. Thus, the required hot water temperature can be ensured by setting it as the target discharge temperature according to the target hot water temperature. Also, from the viewpoint of compressor durability and refrigeration machine oil degradation, an upper limit temperature is usually provided for the discharge temperature.

  The rotation speed of the pump 8 is controlled so that the tapping temperature becomes the target tapping temperature. Since the discharge temperature is controlled to the target hot water temperature + α [° C.] by the expansion valve 5, that is, the heating capacity on the refrigeration cycle 100 side is kept constant, the hot water temperature can be reliably ensured.

  Next, the scale generation preventing operation that is a characteristic part of the heat pump water heater of the first embodiment will be described. Here, prior to detailed description of the scale generation prevention operation, scale generation will be described.

FIG. 2 is a graph showing the relationship between temperature and solubility of calcium carbonate (the main component of scale) in water.
As shown in FIG. 2, the solubility of calcium carbonate in water has the property of decreasing as the water temperature increases. For this reason, for example, when the water temperature rises from the temperature T1 to the temperature T2 and the saturation solubility is lowered, calcium carbonate corresponding to the difference in solubility is deposited. Therefore, it increases when the temperature difference between the water inlet temperature and the water outlet temperature of the water refrigerant heat exchanger 4 is large during the boiling operation. However, during the operation of the heat pump water heater, as described in the above prior art, since water flows through the water-refrigerant heat exchanger 4, even if the scale deposits due to the difference in solubility, most of the water-refrigerant heat exchanger The amount discharged from 4 and deposited on the water-refrigerant heat exchanger 4 is not large. However, when the circulation of water is stopped after the operation of the heat pump water heater, the deposited scale tends to adhere to the inner surface of the connection pipe, and the deposition is promoted.

  Therefore, in the scale generation prevention operation of this example, the pump 8 is continuously driven even after the boiling operation is stopped, and the temperature difference between the water inlet temperature and the water outlet temperature of the water refrigerant heat exchanger 4 is reduced. Thus, the generation of scale is prevented, and the flow of water is continued to prevent accumulation on the inner surface of the connecting pipe of the scale. This scale generation prevention operation is an operation performed after the necessary heat storage amount is secured by the above-described boiling operation, and is a post-processing operation performed when the boiling operation is stopped.

FIG. 3 is a flowchart showing the scale generation preventing operation of the first embodiment.
When the measurement control device 12 determines that the boiling is stopped, the measurement control device 12 first stops the operation of the compressor 3. First, the pump is operated at a rotational speed β (greater than the rotational speed during the boiling operation) [rpm] (ST1). Here, since the operation of the compressor 3 is stopped in this scale generation prevention operation, the high-temperature water in the connection pipes 10a to 10c on the water outlet side of the water-refrigerant heat exchanger 4 is taken into the intake port at the bottom of the tank 9 The temperature is lowered by mixing with low-temperature water that has been conveyed by the pump 8. That is, by continuing the pump operation and circulating water in the hot water supply circuit 200, the temperature of the water outlet of the water refrigerant heat exchanger 4 can be gradually lowered. Thus, there exists an effect which suppresses generation | occurrence | production of a scale by eliminating the high temperature water which exists in the connection piping 10a-10c.

  And the measurement control apparatus 12 detects each temperature of the tapping temperature sensor 11b and the incoming water temperature sensor 11a, and determines the temperature difference between the outgoing hot water temperature and the incoming water temperature (ST2). When it is determined in this temperature difference determination step ST2 that the temperature difference exceeds a predetermined value γ [° C.], that is, when the temperature of the hot water on the water outlet side of the water refrigerant heat exchanger 4 is not sufficiently lowered. The operation of the pump 8 is continued.

  When it is determined that the temperature difference has decreased to a predetermined value γ or less, a timer operation is started (ST3). When a predetermined time has elapsed from the start of the timer operation (ST4), the pump 8 is stopped (ST5), and the scale generation preventing operation is ended.

  This timer operation takes into consideration the influence of variations in the measured values of the temperature sensors (the hot water temperature sensor 11b and the incoming water temperature sensor 11a) for each heat pump water heater. That is, even when it is determined that the temperature difference is equal to or less than the predetermined value γ, due to the variation in the measurement value of the temperature sensor, in consideration of the case where a sufficient temperature difference reduction is not actually obtained, the predetermined time, Furthermore, the pump operation is continued to ensure the reliability.

  The temperature difference determination step ST2 has an effect that the generation of scale can be surely suppressed by firmly managing the temperature drop on the water outlet side of the water-refrigerant heat exchanger 4. Further, ST3 and ST4 have an effect of reliably cooling the water refrigerant heat exchanger 4 in consideration of a temperature increase after the pump is stopped due to the heat capacity of the water refrigerant heat exchanger 4.

  Note that the predetermined value of the temperature difference determination in step ST2 is variable according to the target hot water temperature of the water-refrigerant heat exchanger 4 during the boiling operation, and the predetermined value is decreased as the target hot water temperature increases. Good. In this case, there is an effect that the water refrigerant heat exchanger 4 is reliably cooled in consideration of the heat capacity of the water refrigerant heat exchanger 4. Similarly, the predetermined time in step ST4 may be made variable and become longer as the target hot water temperature becomes higher. In this case, the water-refrigerant heat exchanger 4 can be reliably cooled, and high temperature water present in the connection pipes 10a to 10c can be eliminated.

  Also, depending on the installation location of the heat pump unit 1 and the tank unit 2, the pipe lengths of the connecting pipes 10b and 10e that connect the two vary, but when the pipe length is long, the high-temperature load side that exists in the pipe The amount of media also increases. Therefore, the time required to eliminate the temperature difference between the water inlet and the water outlet of the water refrigerant heat exchanger 4 becomes longer. Therefore, the predetermined time of the timer in step ST4 is set longer as the pipe length becomes longer. Thereby, the high temperature water which exists in connection piping reliably can be eliminated, and scale generation | occurrence | production prevention can be aimed at.

  As described above, according to the first embodiment, the outlet temperature of the water-refrigerant heat exchanger 4 can be reduced to be equal to the inlet temperature by continuing the pump operation even after the compressor is stopped. Therefore, it is possible to reduce the solubility difference of calcium carbonate, and to prevent scale deposition when the heat pump is stopped. Moreover, the outlet temperature of the water-refrigerant heat exchanger 4 can be reduced in a short time by raising the rotation speed of the pump 8 as compared with the boiling operation.

  In the first embodiment, the pump operation is continued for a predetermined time in steps ST3 and ST4 even after it is determined in step ST2 that the temperature difference has become small. It can be omitted.

  In the first embodiment, the timing for stopping the pump operation is determined according to the result of the temperature difference determination. However, the temperature difference determination is not performed, and the pump is simply stopped after a certain time has elapsed after the compressor is stopped. The operation may be stopped. In addition, as with the predetermined time, it is preferable that the predetermined time is longer as the target hot water temperature is higher, and is longer as the pipe length is longer.

Embodiment 2. FIG.
In the first embodiment, the low-temperature water stored on the lower side of the tank 9 is guided to the water / refrigerant heat exchanger 4 by the pump 8, and the water in the connection pipes 10 a to 10 c on the water outlet side of the water / refrigerant heat exchanger 4. The temperature is lowered and flows into the upper side of the tank 9. For this reason, the temperature of the high temperature water stored on the upper side of the tank 9 is lowered by the water flowing from the upper part of the tank 9. Therefore, in the second embodiment, the temperature of the high temperature water in the upper part of the tank 9 is prevented from lowering.

FIG. 4 is a schematic diagram showing an overall configuration of a heat pump water heater according to Embodiment 2 of the present invention. In FIG. 4, the same parts as those in FIG.
In the second embodiment, a bypass pipe 20 for bypassing water flowing out from the water outlet of the water-refrigerant heat exchanger 4 to the inlet side of the pump 8 without passing through the tank 9 is provided, and the flow path switching valve 21 is provided at the branch portion. Is arranged. In addition, let the connection piping between the connection piping 10b and the flow-path switching valve 21 be 10ca among the connection piping 10c. The flow path switching valve 21 is provided on the inlet side of the bypass pipe 20, and the water flow in the hot water supply circuit 200 is transferred to the tank 9 side (A side in FIG. 4) and the bypass pipe side (B side in FIG. 4). It is to switch. In the second embodiment, the other configuration is the same as that of the first embodiment shown in FIG. Further, since the operation and operation control operation of the heat pump water heater are the same as those in the first embodiment, the description thereof is omitted.

FIG. 5 is a flowchart showing the scale generation preventing operation of the second embodiment. In FIG. 5, the same step numbers are assigned to the same processing parts as the scale generation preventing operation of the first embodiment shown in FIG. 3.
When the measurement control device 12 determines that the boiling is stopped, the measurement control device 12 first stops the operation of the compressor 3. In the scale generation preventing operation of the second embodiment, first, the flow path switching valve 21 is switched to the B side, that is, the bypass pipe 20 side (ST1a). Then, the pump 8 is operated at a rotational speed of β [rpm] as in the first embodiment (ST1). Thereby, the temperature of the high-temperature water on the water outlet side of the water-refrigerant heat exchanger 4 is lowered by mixing with the low-temperature water conveyed by the pump 8 from the water intake port 9b at the bottom of the tank 9. And it flows into the bypass piping 20 side via the flow path switching valve 21 . In this way, the water on the water outlet side of the water-refrigerant heat exchanger 4 does not flow into the tank 9 but flows into the bypass pipe 20 via the flow path switching valve 21 , so that the high temperature of the upper portion of the tank 9 is increased. The temperature drop of water can be prevented. Further, the water flowing into the bypass pipe 20 flows into the water refrigerant heat exchanger 4 as in the first embodiment, and circulates through the water refrigerant heat exchanger 4, the flow path switching valve 21 and the pump 8. Gradually decreases. The subsequent operation is the same as that of the first embodiment shown in FIG.

  As described above, the second embodiment provides the same operational effects as those of the first embodiment, and the bypass pipe 20 is provided, and the water in the connection pipes 10a, 10b, and 10ca after the compressor is stopped is stored in the hot water in the tank 9. Since it was made not to flow in from the opening | mouth 9a, the temperature fall in the tank 9 can be prevented and the temperature in the tank 9 can be maintained.

Embodiment 3 FIG.
In the second embodiment, in the scale generation prevention operation, water is prevented from flowing into the tank 9, thereby preventing a temperature drop in the tank 9 and maintaining the temperature in the tank 9. In the third embodiment, in addition to maintaining the temperature in the tank 9 as in the second embodiment, the temperature of the water in the hot water supply circuit 200 during the scale generation prevention operation is lower than that in the second embodiment. It is intended to improve efficiency.

FIG. 6 is a schematic diagram showing an overall configuration of a heat pump water heater according to Embodiment 3 of the present invention. In FIG. 6, the same parts as those in FIG.
The third embodiment is provided with a bypass pipe 30 for returning the water flowing out from the water outlet of the water-refrigerant heat exchanger 4 into the tank 9 from a bypass return port 9c provided below the center of the tank 9, The flow path switching valve 31 is arranged at the branching portion. The flow path switching valve 31 is provided on the inlet side of the bypass pipe 30 and switches the flow of water in the hot water supply circuit 200 between the tank side (A side in FIG. 6) and the bypass pipe side (B side in FIG. 6). Is. In the third embodiment, other configurations are the same as those in FIG. Further, since the operation and operation control operation of the heat pump water heater are the same as those in the first embodiment, the description thereof is omitted.

The flowchart of the scale generation prevention operation of the third embodiment is the same as the scale generation prevention operation of the second embodiment shown in FIG.
In the scale generation preventing operation of the third embodiment, as in the second embodiment, after the operation of the compressor 3 is stopped, the flow path switching valve 31 is switched to the B side, that is, the bypass pipe 30 side (ST1a). Then, the pump 8 is operated at a rotational speed of β [rpm] as in the first embodiment (ST2). Thereby, the temperature of the high-temperature water on the water outlet side of the water-refrigerant heat exchanger 4 is lowered by mixing with the low-temperature water conveyed by the pump 8 from the water intake port 9b at the bottom of the tank 9. Then, it flows into the tank 9 from the bypass return port 9 c of the tank 9 via the flow path switching valve 31 and the bypass pipe 30. Here, since the temperature on the lower side of the tank 9 is originally lower than that on the upper side, the temperature in the tank 9 is prevented from lowering as compared with the case of flowing into the upper part of the tank 9 as in the first embodiment. can do. And the low temperature water of the tank 9 lower part is conveyed by the pump 8 to the water refrigerant | coolant heat exchanger 4, and the low temperature water is the connection piping 10a, 10b between the exit of the water refrigerant heat exchanger 4, and the flow-path switching valve 31. 10ca, and the temperature of the high-temperature water in the connection pipes 10a, 10b, and 10ca is lowered. Then, the water whose temperature has decreased is returned into the tank 9 from the bypass return port 9c at the bottom of the tank.

  As described above, the third embodiment provides the same effect as that of the first embodiment, and replaces the water on the outlet side of the water-refrigerant heat exchanger 4 with the hot water storage port 9a at the upper part of the tank 9 and the lower part of the tank. Since this is returned to the bypass return port 9c, a temperature drop in the tank 9 can be prevented as in the second embodiment. In the second embodiment, the high-temperature water between the water-refrigerant heat exchanger 4 and the flow path switching valve 21 is passed through the circulation circuit that passes through the water-refrigerant heat exchanger 4, the flow path switching valve 21, and the pump 8. In contrast to the case where the temperature is lowered by circulation, in the third embodiment, the low temperature water stored in the lower part of the tank 9 is taken into the circulation circuit to lower the temperature. Compared with 2, it is possible to realize a temperature drop more efficiently. Therefore, a higher scale generation prevention effect can be obtained.

1 is a system circuit diagram of a heat pump water heater according to Embodiment 1 of the present invention. It is a figure which shows the relationship between temperature and the solubility to the water of calcium carbonate (the main component of a scale). It is a flowchart of the scale production | generation prevention operation | movement which concerns on Embodiment 1 of this invention. It is a system circuit diagram of the heat pump water heater which concerns on Embodiment 2 of this invention. It is a flowchart of the scale production | generation prevention operation which concerns on Embodiment 2 of this invention. It is a system circuit diagram of the heat pump water heater which concerns on Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Heat pump unit, 2 Tank unit, 3 Compressor, 4 Water refrigerant heat exchanger, 5 Expansion valve, 6 Evaporator, 7 Fan, 8 Pump, 9 Tank, 9a Hot water inlet, 9b Water intake, 9c Bypass return port, 10a -10f connection piping, 10ca connection piping, 11a incoming water temperature sensor, 11b hot water temperature sensor, 11c outside air temperature sensor, 11d discharge temperature sensor, 11e suction temperature sensor, 11f evaporating temperature sensor, 12 measurement control device, 20 bypass piping, 21 flow Path switching valve, 30 bypass piping (second bypass piping), 31 channel switching valve, 100 refrigeration cycle, 200 hot water supply circuit.

Claims (3)

A refrigeration cycle having a compressor;
A water refrigerant heat exchanger for exchanging heat between the refrigerant flowing through the refrigeration cycle and the water flowing through the interior;
A circuit that causes low-temperature water to flow out from the water intake at the bottom of the tank with a pump, feeds the water to the water-refrigerant heat exchanger, and heats the water-refrigerant heat exchanger to boil up the low-temperature water and return it to the hot water storage at the top of the tank A bypass pipe for bypassing water flowing out from the water outlet of the water refrigerant heat exchanger to the inlet side of the pump, and a flow path switching valve capable of switching the flow path to the tank side or the bypass pipe side. A hot water supply circuit that can further switch the flow path after the water outlet of the water refrigerant heat exchanger from the tank side to the bypass pipe side ,
The compressor provided in the refrigeration cycle and the pump provided in the hot water supply circuit are operated, the water of the tank is sent to the water refrigerant heat exchanger by the pump, and the refrigerant in the water refrigerant heat exchanger is At the time of boiling operation to boil up by heat exchange and return to the tank, and when the boiling operation is stopped, the flow path switching valve is switched from the tank side to the bypass piping side, the compressor is stopped, and then for a certain time Control means for continuing the operation of the pump until it elapses, and performing a scale generation preventing operation for stopping the operation of the pump after elapse of the predetermined time ,
The predetermined time is made variable according to the target hot water temperature of the water refrigerant heat exchanger during the boiling operation, and the target hot water temperature of the water refrigerant heat exchanger during the boiling operation becomes higher during the predetermined time. A heat pump water heater characterized by lengthening as A refrigeration cycle having a compressor;
A water refrigerant heat exchanger for exchanging heat between the refrigerant flowing through the refrigeration cycle and the water flowing through the interior;
A circuit that causes low-temperature water to flow out from the water intake at the bottom of the tank with a pump, feeds the water to the water-refrigerant heat exchanger, and heats the water-refrigerant heat exchanger to boil off the low-temperature water and return it to the hot water storage port at the top of the tank A bypass pipe for bypassing water flowing out from the water outlet of the water refrigerant heat exchanger to the inlet side of the pump, and a flow path switching valve capable of switching the flow path to the tank side or the bypass pipe side. A hot water supply circuit that can further switch the flow path after the water outlet of the water refrigerant heat exchanger from the tank side to the bypass pipe side,
The compressor provided in the refrigeration cycle and the pump provided in the hot water supply circuit are operated, the water of the tank is sent to the water refrigerant heat exchanger by the pump, and the refrigerant in the water refrigerant heat exchanger is At the time of boiling operation to boil up by heat exchange and return to the tank, and when the boiling operation is stopped, the flow path switching valve is switched from the tank side to the bypass piping side, the compressor is stopped, and then for a certain time Control means for continuing the operation of the pump until it elapses, and performing a scale generation preventing operation for stopping the operation of the pump after elapse of the predetermined time,
The heat pump water heater according to claim 1 , wherein the predetermined time is increased as a length of a pipe connecting the refrigeration cycle and the hot water supply circuit increases . The heat pump water heater according to claim 1 or 2, wherein the number of rotations of the pump in the scale generation prevention operation is higher than that in the boiling operation .

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