JP3856025B2 - Heat pump water heater - Google Patents

Description

    The present invention relates to a hot water storage type heat pump water heater.

A conventional heat pump water heater of this type is shown in Patent Document 1. FIG. 16 is a configuration diagram of a conventional heat pump water heater. In FIG. 16, a refrigerant circulation circuit including a compressor 1, a refrigerant-to-water heat exchanger 2, a decompression device 3, and an evaporator 4, a hot water tank 5, a circulation pump 6, a refrigerant-to-water heat exchanger 2, and an auxiliary heater 7. The high-temperature and high-pressure superheated gas refrigerant discharged from the compressor 1 flows into the refrigerant-to-water heat exchanger 2 where the water sent from the circulation pump 6 is heated. Then, the refrigerant radiated by the refrigerant-to-water heat exchanger 2 is decompressed by the decompression device 3 and flows into the evaporator 4, where it absorbs atmospheric heat to evaporate and returns to the compressor 1. On the other hand, hot water heated by the refrigerant-to-water heat exchanger 2 flows into the upper part of the hot water storage tank 5 and is gradually stored from above. When the inlet water temperature of the refrigerant-to-water heat exchanger 2 reaches a set value, the water temperature detecting means 8 detects it, stops the heat pump operation by the compressor 1, and switches to the independent operation of the auxiliary heater 7. .
JP 60-164157 A

  In the conventional heat pump water heater shown in FIG. 16, a capillary tube or a temperature type expansion valve is used as the decompression device 3. When a capillary tube is used as the decompression device 3, the specification of the capillary tube is generally designed based on the summer temperature conditions in which the refrigerant circulation amount is large. For this reason, there is a problem that the operation efficiency is deteriorated in the winter season when the hot water supply load is particularly large except the summer season. Similarly, during the winter when the outside air temperature is low except in summer, excessive refrigerant circulates in the refrigerant circuit, so that the liquid refrigerant is sucked into the compressor 1, resulting in liquid compression and the durability of the compressor. Had the problem of getting worse.

  On the other hand, when a temperature expansion valve is used as the decompression device 3, generally, the specification of the temperature expansion valve as the decompression device 3 is such that the refrigerant at the outlet of the evaporator 4 is in a superheated gas state with a superheat degree. To design. Therefore, depending on the outside air temperature condition, there is a problem that the discharge pressure increases or the discharge temperature increases, and the durability of the compressor deteriorates. And if it designed to avoid this subject, it had the subject that the boiling temperature which is the exit water temperature of the refrigerant | coolant versus water heat exchanger 2 cannot be made high. Furthermore, even when the evaporator 4 is frosted in winter, the refrigerant state at the outlet of the evaporator 4 is controlled so that the degree of superheat can be obtained, so that frosting further proceeds and the efficiency of operation is deteriorated. It was. In particular, since the refrigerant state at the outlet of the evaporator 4 is unnecessarily controlled so that the degree of superheat can be taken when the outside air temperature suddenly drops during the day, such as at dawn, there is a problem that the efficiency of the operation further deteriorates. Had.

  An object of the present invention is to realize an efficient hot water supply heating operation without an abnormal temperature rise and abnormal pressure rise of a compressor.

  In order to solve the above problems, the present invention provides a refrigeration cycle including a compressor, a refrigerant-to-water heat exchanger, and a pressure reducing device, a hot water storage tank, a hot water supply circuit having the refrigerant-to-water heat exchanger, and a circulation pump. Supply water temperature detection means for detecting the supply water temperature, discharge temperature detection means for detecting the discharge temperature of the compressor, and a pressure reducing device so that the temperature detected by the discharge temperature detection means becomes a preset target discharge temperature Control means for controlling the opening degree of the refrigerant, and controlling the number of revolutions of the circulation pump so that the outlet water temperature of the refrigerant-to-water heat exchanger is substantially constant, and the higher the feed water temperature, the higher the target discharge temperature. A heat pump water heater that lowers the temperature.

  Further, a refrigeration cycle including a compressor, a refrigerant-to-water heat exchanger, and a pressure reducing device, a hot water storage tank, a hot water supply circuit having the refrigerant-to-water heat exchanger and a circulation pump, and the refrigerant-to-water in the hot water supply circuit. Water temperature detection means for detecting the inlet water temperature of the heat exchanger, discharge temperature detection means for detecting the discharge temperature of the compressor, and the temperature detected by the discharge temperature detection means become a preset target discharge temperature. Control means for controlling the opening degree of the pressure reducing device, and controlling the number of revolutions of the circulation pump so as to make the outlet water temperature of the refrigerant-to-water heat exchanger substantially constant, A heat pump water heater that lowers the target discharge temperature as the detected temperature increases.

  In the above invention, a discharge temperature with the highest efficiency of the hot water supply operation with respect to the water supply temperature is obtained in advance, and this is set as the target discharge temperature. And when performing hot water supply operation, the feed water temperature and the discharge temperature of the compressor are detected, and the opening of the pressure reducing device is controlled so as to reach this target discharge temperature. it can.

  According to the present invention, there is an effect that an efficient hot water supply heating operation can be performed. In particular, when controlling using the feed water temperature, in order not to take the refrigerant superheat degree at the outlet of the evaporator unnecessarily even when the outside air temperature suddenly drops, such as at dawn, during the day, Stable operation control can be performed and the efficiency is improved.

  Moreover, when detecting the inlet water temperature of a refrigerant | coolant versus water heat exchanger, it can respond also to the rapid temperature rise of the inlet water temperature of a refrigerant | coolant versus water heat exchanger by the mixed layer detection in boiling operation.

  The present invention can be implemented in the form described in each claim. As described in claim 1, a refrigerant circulation circuit in which a compressor, a refrigerant-to-water heat exchanger, a decompression device, and an evaporator are sequentially connected, and hot water storage A hot water supply circuit in which a tank, a circulation pump, a refrigerant-to-water heat exchanger are sequentially connected, a feed water temperature detecting means for detecting the feed water temperature, a discharge temperature detecting means for detecting the discharge temperature of the compressor, and a water supply temperature in advance. By providing a control means for controlling the opening of the pressure reducing device so as to reach the set target discharge temperature, a discharge temperature with the highest efficiency of the hot water supply operation is obtained in advance with respect to the water supply temperature. Since this is set as the target discharge temperature, efficient hot water heating operation can be performed throughout the year. Further, since the feed water temperature is used, since there is no great change in the day like the outside air temperature, stable operation control can be performed and efficiency is improved.

  Further, as described in claim 2, a refrigeration cycle provided with a compressor, a refrigerant-to-water heat exchanger, and a pressure reducing device, a hot water storage tank, a hot water supply circuit having the refrigerant-to-water heat exchanger, and a circulation pump, In the hot water supply circuit, water temperature detection means for detecting the inlet water temperature of the refrigerant-to-water heat exchanger, discharge temperature detection means for detecting the discharge temperature of the compressor, and the temperature detected by the discharge temperature detection means in advance. Control means for controlling the opening of the pressure reducing device so as to reach a set target discharge temperature, and controlling the rotation speed of the circulation pump so as to make the outlet water temperature of the refrigerant-to-water heat exchanger substantially constant In addition, a hot water supply operation with respect to the water temperature detecting means for detecting the inlet water temperature of the refrigerant-to-water heat exchanger is also achieved by using a heat pump water heater that lowers the target discharge temperature as the detected temperature of the water temperature detecting means increases. of The rate is determined in advance for best discharge temperature, since the set as a target discharge temperature, throughout the year, it is good hot water heating operation efficiency. Since the inlet water temperature of the refrigerant-to-water heat exchanger is detected, it is possible to cope with an abrupt increase in the inlet water temperature of the refrigerant-to-water heat exchanger due to the mixed layer detection in the boiling operation.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a configuration diagram of a heat pump water heater according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram showing discharge temperature, discharge pressure, and efficiency with respect to the opening of a pressure reducing device of the heat pump water heater, and FIG. 3 is the heat pump water heater. FIG. 4 is an explanatory diagram showing a target discharge temperature with respect to a feed water temperature of the heat pump water heater. In addition, the same code | symbol is used for the same component as FIG. 16 demonstrated in the prior art example, and description is abbreviate | omitted.

  In FIG. 1, the rotation speed control means 10 controls the rotation speed of the circulation pump 6 by a signal from the boiling temperature detection means 9 provided at the water-side outlet of the refrigerant-to-water heat exchanger 2, and the refrigerant-to-water heat The outlet water temperature (boiling temperature) of the exchanger 2 is boiled so as to be substantially constant. Further, the control means 11 controls the decompression device 3 with signals from the feed water temperature detection means 12 for detecting the feed water temperature and the discharge temperature detection means 13 for detecting the discharge temperature of the compressor 1. Reference numeral 14 denotes first storage means for storing a target discharge temperature with respect to the water supply temperature. The decompression device 3 includes an electric expansion valve (not shown).

  Next, the operation and action will be described. In FIG. 2, the opening of the decompression device 3 is taken on the horizontal axis, and the discharge temperature, the discharge pressure, and the efficiency are taken on the vertical axis, and the discharge temperature and the discharge pressure with respect to the opening of the decompression device 3 at a certain outside air temperature and feed water temperature. It shows the relationship of efficiency. FIG. 3 shows the relationship between the water supply temperature and the average outside air temperature, with the water supply temperature on the horizontal axis and the average outside air temperature on the vertical axis. As the average outside air temperature at this time, for example, an average outside air temperature of several days to one week is used. Then, if the relationship between the feed water temperature and the average outside air temperature paper is obtained in advance, the average outside air temperature can be estimated if the feed water temperature is known as can be seen from FIG. In FIG. 2, the efficiency has a maximum value with respect to the opening of the decompression device 3. Moreover, in the same figure, a dashed-dotted line is the maximum temperature at the time of normal use of a compressor (normal maximum discharge temperature), and a dashed-two dotted line is the maximum pressure at the time of normal use of a compressor (normal maximum discharge pressure). Here, the discharge temperature with respect to the opening degree X of the pressure reducing device 3 at which the efficiency is maximized is defined as a target discharge temperature Y. And when this target discharge temperature Y is calculated | required with respect to each feed water temperature, it will become like FIG. The relationship between the target discharge temperature and the water supply temperature is stored in the first storage unit 14 in advance.

  That is, when the hot water supply operation is started and the compressor 1 is started, the control unit 11 detects the feed water temperature and the discharge temperature by signals from the feed water temperature detection unit 12 and the discharge temperature detection unit 13. If the current discharge temperature is higher than the target discharge temperature in the information from the first storage unit 14 storing the relationship between the feed water temperature and the target discharge temperature, the control unit 11 opens the opening of the decompression device 3. Is controlled to increase (open). Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  As described above, if the discharge temperature control by the control means 11 is performed every certain time, an efficient hot water supply operation can always be performed even if the water supply temperature (average outside air temperature) changes. Furthermore, since the feed water temperature is used, since there is no significant change during the day, stable operation control can be performed and efficiency is improved. Moreover, since the discharge temperature of the compressor 1 is controlled so as to reach the target discharge temperature instead of the course, a high boiling temperature can be obtained.

  In addition, it can implement similarly even if it uses the water temperature detection means 8 as a feed water temperature detection means.

(Example 2)
FIG. 5 is a configuration diagram of a heat pump water heater according to a second embodiment of the present invention, FIG. 6 is an explanatory diagram showing discharge temperature, discharge pressure, and efficiency with respect to the opening of the pressure reducing device of the heat pump water heater, and FIG. 7 is the heat pump water heater. It is explanatory drawing which shows the discharge pressure with respect to the water supply temperature, and the opening degree of a pressure reduction device.

  The present embodiment is different from the first embodiment in that the pressure detection means 15 is provided on the discharge side of the compressor 1. In addition, the part of the same code | symbol as Example 1 has the same structure, and abbreviate | omits description.

  Next, the operation and action will be described. In FIG. 6, the opening of the decompression device 3 is taken on the horizontal axis, and the discharge temperature, the discharge pressure, and the efficiency are taken on the vertical axis, with respect to the opening of the decompression device 3 when a certain feed water temperature is high (when the outside air temperature is high). The relationship between discharge temperature, discharge pressure, and efficiency is shown. As shown in the figure, when the feed water temperature becomes considerably high, the discharge pressure sometimes exceeds the normal maximum discharge pressure at the opening of the pressure reducing device 3 at which the efficiency reaches a maximum value. In this case, when the opening degree of the decompression device 3 is changed from A to B, the discharge pressure decreases from C to D.

  That is, when the hot water supply operation is started and the compressor 1 is started, the control means 11 detects the discharge pressure by the signal from the pressure detection means 15. If this discharge pressure is lower than the normal maximum discharge pressure, the control means 11 detects the feed water temperature and the discharge temperature by signals from the feed water temperature detection means 12 and the discharge temperature detection means 13, and the feed water temperature and the target discharge temperature. If the current discharge temperature is higher than the target discharge temperature with the information from the first storage means 14 storing the relationship, the control means 11 controls to increase (open) the opening of the decompression device 3. To do. Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  On the other hand, if the discharge pressure detected by the signal from the pressure detection means 15 is higher than the normal maximum discharge pressure, the control means 11 controls to increase (open) the opening of the decompression device 3.

  FIG. 7 shows changes in the discharge pressure and the opening of the pressure reducing device 3 with respect to the water supply temperature, with the water supply temperature on the horizontal axis and the discharge pressure and the opening of the pressure reducing device 3 on the vertical axis. In the figure, if the feed water temperature is high, the discharge pressure can be controlled so as not to exceed the normal maximum discharge pressure by performing the control by the discharge pressure as described above. In this way, a hot water supply operation without an abnormal pressure increase is possible. In addition, the dotted line in a figure is the case of control by the discharge temperature demonstrated in Example 1, and symbol A, B, C, D respond | corresponds to the same symbol of FIG.

Example 3
FIG. 8 is a configuration diagram of a heat pump water heater according to a third embodiment of the present invention, FIG. 9 is an explanatory diagram showing discharge temperature, discharge pressure, and efficiency with respect to the opening of the decompression device of the heat pump water heater, and FIG. 10 is the heat pump water heater. It is explanatory drawing which shows the target discharge temperature with respect to the feed water temperature.

  This embodiment is different from the second embodiment in that the feed water temperature detecting means 12 and the discharge temperature detecting means 13 are used as the pressure detecting means, and the second storage means 16 is further provided. In addition, the part of the same code | symbol as Example 2 has the same structure, and description is abbreviate | omitted.

  Next, the operation and action will be described. In FIG. 9, the opening of the decompression device 3 is taken on the horizontal axis, and the discharge temperature, the discharge pressure, and the efficiency are taken on the vertical axis, with respect to the opening of the decompression device 3 when a certain feed water temperature is high (when the outside air temperature is high). The relationship between discharge temperature, discharge pressure, and efficiency is shown. As shown in the figure, when the feed water temperature becomes considerably high, the discharge pressure sometimes exceeds the normal maximum discharge pressure (for example, 2.4 MPa) at the opening of the decompression device 3 at which the efficiency reaches a maximum value. In this case, when the opening degree of the decompression device 3 is changed from A to B, the discharge pressure decreases from C to D, and the discharge temperature decreases from E to F. Eventually, in the case of the water supply temperature shown in the figure, the discharge temperature may be set to F in order to set the discharge pressure to D. The discharge temperature with respect to the opening degree B of the decompression device 3 is set as a target discharge temperature Z. And when this target discharge temperature Z is calculated | required with respect to each feed water temperature, it will become like the continuous line of FIG. The relationship between the target discharge temperature Z and the water supply temperature is stored in advance in the second storage unit 16. In the figure, a dotted line is the case of control by the discharge temperature demonstrated in Example 1, and let the water supply temperature of the intersection of a solid line and a dotted line be the high temperature side limit water supply temperature Tu.

  That is, when the hot water supply operation is started and the compressor 1 is started, the control unit 11 detects the feed water temperature by a signal from the feed water temperature detection unit 12. If the feed water temperature is lower than the high temperature side limit feed water temperature Tu, the control means 11 further detects the feed water temperature and the discharge temperature by signals from the feed water temperature detection means 12 and the discharge temperature detection means 13, and If the current discharge temperature is higher than the target discharge temperature based on information from the first storage unit 14 storing the relationship with the target discharge temperature, the control unit 11 increases (opens) the opening of the decompression device 3. ) To control. Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  On the other hand, if the feed water temperature detected by the signal from the feed water temperature detecting means 12 is higher than the high temperature side limit feed water temperature Tu, the discharge temperature is detected by the signal from the discharge temperature detecting means 13, and the second storage means 16 If the current discharge temperature is higher than the target discharge temperature, the control means 11 performs control to increase (open) the opening of the decompression device 3. Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  If the discharge temperature control by the control means 11 is performed at a certain time as described above, it is possible to prevent the discharge pressure from exceeding the normal maximum discharge pressure by performing the control based on the discharge temperature, so there is no abnormal pressure increase. Hot water supply operation is possible.

Example 4
FIG. 11 is a configuration diagram of a heat pump water heater according to a fourth embodiment of the present invention, FIG. 12 is an explanatory diagram showing discharge temperature, discharge pressure, and efficiency with respect to the opening of the decompression device of the heat pump water heater, and FIG. 13 is the heat pump water heater. It is explanatory drawing which shows the target discharge temperature with respect to the feed water temperature.

  The present embodiment is different from the first embodiment in that the third storage means 17 is provided. In addition, the part of the same code | symbol as Example 1 has the same structure, and abbreviate | omits description.

  Next, the operation and action will be described. In FIG. 12, the horizontal axis represents the opening of the decompression device 3, and the vertical axis represents the discharge temperature, discharge pressure, and efficiency, and the opening of the decompression device 3 when the water supply temperature is low (when the outside air temperature is low). The relationship between discharge temperature, discharge pressure, and efficiency is shown. As shown in the figure, when the feed water temperature becomes considerably low, the discharge temperature sometimes exceeds the normal maximum discharge temperature (for example, 105 ° C.) at the opening of the pressure reducing device 3 at which the efficiency reaches a maximum value. In this case, when the opening degree of the decompression device 3 is changed from A to B, the discharge temperature decreases from C to D. FIG. 13 shows the relationship of the target discharge temperature W with respect to the water supply temperature, with the water supply temperature on the horizontal axis and the target discharge temperature on the vertical axis. As shown by the solid line in the figure, the target discharge temperature W in the case of the low water supply temperature is constant at the normal maximum discharge temperature (for example, 105 ° C.). The relationship between the target discharge temperature W and the water supply temperature is stored in the third storage unit 17 in advance. Further, the dotted line in the figure is the case of the control based on the discharge temperature described in the first embodiment, and the water supply temperature at the intersection of the solid line and the dotted line is the low limit side water supply temperature Tl.

  That is, when the hot water supply operation is started and the compressor 1 is started, the control unit 11 detects the feed water temperature by a signal from the feed water temperature detection unit 12. If the feed water temperature is higher than the low limit side limit feed water temperature Tl, the control means 11 detects the discharge temperature by a signal from the discharge temperature detection means 13, and stores the relationship between the feed water temperature and the target discharge temperature. If the current discharge temperature is higher than the target discharge temperature based on the information from the first storage unit 14, the control unit 11 performs control so as to increase (open) the opening of the decompression device 3. Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  On the other hand, if the feed water temperature detected by the signal from the feed water temperature detection means 12 is lower than the low limit side limit feed water temperature Tl, the control means 11 detects the discharge temperature by the signal from the discharge temperature detection means 13, and the feed water temperature If the current discharge temperature is higher than the target discharge temperature by the information from the third storage means 17 storing the relationship between the target discharge temperature and the target discharge temperature, the control means 11 increases the opening of the decompression device 3 ( Control). Conversely, if the current discharge temperature is lower than the target discharge temperature, the control means 11 performs control so as to reduce (close) the opening of the decompression device 3.

  If the discharge temperature control by the control means 11 is performed at certain intervals as described above, the discharge temperature can be prevented from exceeding the normal maximum discharge temperature, so that a hot water supply operation without an abnormal temperature rise is possible.

(Example 5)
FIG. 14 is a configuration diagram of a heat pump water heater according to a fifth embodiment of the present invention.

  In this embodiment, the difference from the first embodiment is that a minimum opening degree storage means 18 for storing the minimum opening degree of the decompression device 3 is provided. In addition, the part of the same code | symbol as Example 1 has the same structure, and abbreviate | omits description.

  Next, the operation and action will be described. When the hot water supply operation is started and the compressor 1 is started, the control unit 11 detects the feed water temperature and the discharge temperature by signals from the feed water temperature detection unit 12 and the discharge temperature detection unit 13. If the current discharge temperature is higher than the target discharge temperature in the information from the first storage unit 14 storing the relationship between the feed water temperature and the target discharge temperature, the control unit 11 opens the opening of the decompression device 3. Is controlled to increase (open). On the contrary, if the current discharge temperature is lower than the target discharge temperature, the control means 11 determines the minimum opening degree of the decompression device 3 and the current opening degree of the decompression device 3 obtained from the signal from the minimum opening degree storage means 18. Compare. And if the opening degree of the present decompression device 3 is larger than the minimum opening degree, the opening degree of the decompression device 3 is controlled to be reduced (closed) within a range not lowering the minimum opening degree. Further, if the current opening of the decompression device 3 is smaller than or equal to the minimum opening, the opening of the decompression device 3 is controlled to be the minimum opening.

  In this way, when the feed water temperature is low (the outside air temperature is low), even if frost adheres to the evaporator 4 and the discharge temperature or the evaporation temperature decreases, the opening of the decompression device 3 is made smaller than necessary. Therefore, efficient hot water heating operation can be maintained.

(Example 6)
The refrigeration cycle of the heat pump water heater of Example 6 of the present invention is a supercritical refrigeration cycle in which the discharge pressure of the compressor 1 becomes a supercritical pressure.

  FIG. 15 shows the operating point of the refrigeration cycle with the enthalpy of the refrigerant on the horizontal axis and the pressure on the vertical axis. In the figure, a dotted line shows an isotherm, and becomes high temperature in the direction where enthalpy increases.

  First, the case where the discharge temperature is not controlled will be described. In this case, when the feed water temperature is low, the refrigeration cycle is indicated by a solid line, and the discharge refrigerant is in the state indicated by point A, so the discharge temperature is T1. On the other hand, when the feed water temperature is high, the refrigeration cycle indicated by the alternate long and short dash line is established, and the discharge refrigerant is in the state indicated by point B. Therefore, the discharge temperature is T2 (T1> T2). As described above, when the feed water temperature is increased, the discharge temperature is lowered, and it is sometimes difficult to increase the boiling temperature.

  Therefore, in this embodiment, the opening degree of the decompression device 3 is controlled so that the discharge temperature becomes the target discharge temperature (in this case, T1). As a result, the refrigeration cycle indicated by the two-dot chain line is obtained, and the discharge refrigerant becomes the point B ', and thus the discharge temperature becomes T1.

  As described above, even when the feed water temperature is high in the supercritical refrigeration cycle, since the discharge temperature is controlled to the target discharge temperature, a high boiling temperature can be obtained.

(Example 7)
The refrigerant used in the refrigeration cycle of the heat pump water heater of Example 7 of the present invention is carbon dioxide. Since the operations and effects in this case are the same as those in the sixth embodiment, the description thereof will be omitted.

The block diagram which shows the heat pump water heater of Example 1 of this invention Characteristic chart showing discharge temperature, discharge pressure and efficiency with respect to the opening of the decompression device of the heat pump water heater Characteristic diagram showing the relationship between the feed water temperature and average outside air temperature of the heat pump water heater The characteristic diagram which shows the target discharge temperature with respect to the feed water temperature of the heat pump water heater The block diagram of the heat pump water heater of Example 2 of this invention Characteristic chart showing discharge temperature, discharge pressure and efficiency with respect to the opening of the decompression device of the heat pump water heater The characteristic diagram which shows the discharge pressure with respect to the feed water temperature of the heat pump water heater and the opening of the decompression device The block diagram of the heat pump water heater of Example 3 of this invention Characteristic chart showing discharge temperature, discharge pressure and efficiency with respect to the opening of the decompression device of the heat pump water heater The characteristic diagram which shows the target discharge temperature with respect to the feed water temperature of the heat pump water heater The block diagram of the heat pump water heater of Example 4 of this invention Characteristic chart showing discharge temperature, discharge pressure and efficiency with respect to the opening of the decompression device of the heat pump water heater The characteristic diagram which shows the target discharge temperature with respect to the feed water temperature of the heat pump water heater The block diagram of the heat pump water heater of Example 5 of this invention Explanatory drawing which shows the operating point of the refrigerating cycle of the heat pump water heater of Example 6 of this invention. Configuration diagram of heat pump water heater in conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Refrigerant to water heat exchanger 3 Pressure reducing device 4 Evaporator 5 Hot water storage tank 6 Circulating pump 11 Control means 12 Feed water temperature detection means 13 Discharge temperature detection means

Claims (2)

A refrigeration cycle comprising a compressor, a refrigerant-to-water heat exchanger, and a pressure reducing device; a hot water storage tank; a hot water supply circuit having the refrigerant-to-water heat exchanger and a circulation pump; and a feed water temperature detecting means for detecting a feed water temperature; Discharge temperature detection means for detecting the discharge temperature of the compressor; and control means for controlling the opening of the decompression device so that the temperature detected by the discharge temperature detection means becomes a preset target discharge temperature. A heat pump water heater that controls the number of revolutions of the circulation pump so that the outlet water temperature of the refrigerant-to-water heat exchanger is substantially constant, and lowers the target discharge temperature as the feed water temperature increases. A refrigeration cycle comprising a compressor, a refrigerant-to-water heat exchanger, and a pressure reducing device, a hot water storage tank, a hot water supply circuit having the refrigerant-to-water heat exchanger and a circulation pump, and the refrigerant-to-water heat exchange in the hot water supply circuit A water temperature detecting means for detecting the inlet water temperature of the compressor, a discharge temperature detecting means for detecting the discharge temperature of the compressor, and a temperature detected by the discharge temperature detecting means so as to become a preset target discharge temperature. Control means for controlling the opening degree of the decompression device, and controls the number of revolutions of the circulation pump so as to make the outlet water temperature of the refrigerant-to-water heat exchanger substantially constant, and the detected temperature of the water temperature detecting means A heat pump water heater that lowers the target discharge temperature as the temperature increases.

Images