Storage water heater

Abstract

This hot water storage-type hot water supply unit comprises: a hot water storage tank; a water supply port which is located at the bottom of the hot water storage tank; a hot water supply port which is located at the top of the hot water storage tank; an evaporator which evaporates a refrigerant; a compressor which compresses the refrigerant discharged from the evaporator; a condenser which has a refrigerant passage located in the hot water storage tank and condenses the refrigerant by exchanging heat between the refrigerant compressed by the compressor and water in the hot water storage tank; an expansion valve which causes the refrigerant discharged from the condenser to expand; a control circuit which controls a hot water storage operation, which is an operation in which water in the hot water storage tank is heated by the refrigerant flowing through the refrigerant passage in the condenser; and a hot water supply detection sensor which is able to detect the start of a hot water supply operation, which is an operation in which hot water in the hot water storage tank is discharged from the hot water supply port and water flows from the water supply port into the hot water storage tank. When a hot water supply operation is started during the hot water storage operation, the control circuit increases the degree of opening of the expansion valve.

Description

[Technical field]

[0001] The present disclosure relates to a storage type water heater. [Background technology]

[0002] The heat pump water heater disclosed in the following Patent Document 1 includes a heat pump circuit, a water circulation circuit, a water supply pipe, and a hot water supply pipe, the water supply pipe branches and connects to the inlet side of the hot water tank and the inlet side of the water heater, the hot water supply pipe branches and connects to the outlet side of the hot water tank and the outlet side of the water heater, and is provided with a valve for switching between hot water supply from the hot water tank and hot water supply from the water heater. The water heat exchanger, which is composed of the water heater and the condenser, is spirally wound into a cylindrical shape and is installed to surround the hot water tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-314892 Summary of the Invention [Problem to be solved by the invention]

[0004] In a storage type hot water heater in which a condenser is disposed in a hot water storage tank, there is a demand for a higher coefficient of performance (COP) during hot water storage operation in order to further save energy.

[0005] The present disclosure has been made to solve the problems described above, and aims to provide a storage type water heater that is advantageous in increasing the COP during hot water storage operation. [Means for solving the problem]

[0006] The hot water storage type water heater of the present disclosure comprises a hot water storage tank, a water supply port located at the bottom of the hot water storage tank, a hot water supply port located at the top of the hot water storage tank, an evaporator that evaporates a refrigerant, a compressor that compresses the refrigerant flowing out of the evaporator, a condenser having a refrigerant passage located in the hot water storage tank and condensing the refrigerant by exchanging heat between the refrigerant compressed by the compressor and the water in the hot water storage tank, an expansion valve that expands the refrigerant flowing out of the condenser, a control circuit that controls a hot water storage operation in which water in the hot water storage tank is heated by refrigerant flowing through the refrigerant passage of the condenser, and a hot water supply detection sensor that can detect the start of a hot water supply operation in which hot water in the hot water storage tank flows out from the hot water supply port and water flows into the hot water storage tank from the water supply port, The refrigerant passage is arranged so that its position gradually decreases in the height direction of the hot water storage tank from the upstream to the downstream of the refrigerant flow, When the hot water supply operation is started during hot water storage operation, the control circuit increases the opening of the expansion valve. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a storage type water heater that is advantageous in increasing the COP during hot water storage operation. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a storage type hot water heater according to a first embodiment. [Diagram 2] 13 is a diagram for explaining the change in tank water temperature distribution along the vertical direction and the change in refrigerant temperature distribution in the condenser 17 when hot water supply operation is started during hot water storage operation. FIG. [Diagram 3] 4 is a flowchart showing an example of processing executed by the storage type hot water heater according to the first embodiment. [Figure 4] FIG. 11 is a diagram showing a storage type hot water heater according to a second embodiment. [Diagram 5] 10 is a flowchart showing an example of processing executed by the storage type hot water heater according to the second embodiment. [Figure 6] FIG. 11 is a diagram showing a storage type hot water heater according to a third embodiment. [Figure 7]11 is a flowchart showing an example of processing executed by the storage type hot water heater according to embodiment 3. [Figure 8] FIG. 11 is a diagram showing a storage type hot water heater according to a fourth embodiment. [Figure 9] 13 is a flowchart showing an example of processing executed by the storage type hot water heater according to embodiment 4. [Figure 10] FIG. 11 is a diagram showing a storage type hot water heater according to a fifth embodiment. [Figure 11] 13 is a flowchart showing an example of processing executed by the storage type hot water heater according to embodiment 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. The same reference numerals are used to designate common or corresponding elements in each drawing, and the description will be simplified or omitted. In the following description, the term "water" or "hot water" generally means liquid water, and can include anything from cold water to hot water.

[0010] Embodiment 1 FIG. 1 is a diagram showing a storage type water heater 1 according to embodiment 1. As shown in FIG. 1, the storage type water heater 1 according to embodiment 1 includes a heat source unit 2 and a tank unit 3. The heat source unit 2 is disposed outdoors. The tank unit 3 may be disposed outdoors or indoors. The heat source unit 2 and the tank unit 3 are connected via refrigerant pipes 4 and 5 and an electric cable (not shown). The storage type water heater 1 may be for home use or for commercial use.

[0011] A hot water tank 6 is provided in the tank unit 3. In this embodiment, the hot water tank 6 has a cylindrical outer shape. The central axis of the hot water tank 6 is substantially parallel to a vertical line. In the hot water tank 6, temperature stratification is formed, with the upper side being hotter and the lower side being colder, due to differences in water density caused by differences in temperature.

[0012] A water supply inlet 7 is disposed at the bottom of the hot water storage tank 6. A hot water supply inlet 8 is disposed at the top of the hot water storage tank 6. A water supply pipe 9 is connected to the water supply inlet 7. A hot water supply pipe 10 is connected to the hot water supply inlet 8. The downstream of the hot water supply pipe 10 is connected to a hot water supply terminal (not shown) inside the building. The hot water supply terminal may include, for example, at least one of a faucet, a shower, and a bathtub.

[0013] For example, water supplied from a water source such as a water supply flows into the bottom of hot water storage tank 6 through water supply pipe 9, thereby constantly keeping hot water storage tank 6 full. During hot water supply operation to supply hot water to a hot water supply terminal, water pressure from water supply pipe 9 causes hot water in hot water storage tank 6 to flow out from hot water supply outlet 8 to hot water supply pipe 10. Accordingly, an equal amount of water flows from water supply pipe 9 into the bottom of hot water storage tank 6 through water supply outlet 7. In this way, the hot water supply operation is an operation in which hot water in hot water storage tank 6 flows out from hot water supply outlet 8 and water flows into hot water storage tank 6 from water supply outlet 7. Hereinafter, the water supplied to hot water storage tank 6 from water supply pipe 9 may be referred to as "water supply."

[0014] The heat source unit 2 is provided with an evaporator 11 that evaporates a refrigerant, a compressor 12 that compresses the refrigerant flowing out from the evaporator 11, an expansion valve 13, and a control circuit 14. The evaporator 11 in this embodiment evaporates the refrigerant by exchanging heat between the outdoor air and the refrigerant. In the illustrated example, the heat source unit 2 further includes a blower 15 that blows the outdoor air to the evaporator 11.

[0015] The hot water storage type water heater 1 further includes a condenser 17. The condenser 17 condenses the refrigerant by exchanging heat between the refrigerant compressed by the compressor 12 and the water in the hot water storage tank 6. The condenser 17 has a refrigerant passage 18 arranged in the hot water storage tank 6. In this embodiment, the refrigerant passage 18 is formed by a refrigerant pipe wound in a spiral or coil shape around the outer periphery of the hot water storage tank 6. The refrigerant pipe forming the refrigerant passage 18 is in contact with the outer wall surface of the hot water storage tank 6. The heat of the refrigerant flowing through the refrigerant passage 18 is transferred to the peripheral wall of the hot water storage tank 6. The heat transferred to the peripheral wall of the hot water storage tank 6 is transferred to the water in the hot water storage tank 6, thereby heating the water in the hot water storage tank 6. The refrigerant passage 18 is arranged so that its position gradually decreases from the upstream to the downstream while going around the outer periphery of the hot water storage tank 6.

[0016] The refrigerant compressed by the compressor 12 moves from the heat source unit 2 through the refrigerant pipe 4 to the tank unit 3 and flows into the inlet of the condenser 17, i.e., the inlet of the refrigerant passage 18. The refrigerant flowing out from the outlet of the condenser 17, i.e., the outlet of the refrigerant passage 18, returns to the heat source unit 2 from the tank unit 3 through the refrigerant pipe 5 and flows into the expansion valve 13. The top of the condenser 17, i.e., the inlet of the refrigerant passage 18, is located lower than the hot water inlet 8. The bottom of the condenser 17, i.e., the outlet of the refrigerant passage 18, is located at the same height as the water inlet 7 or slightly higher than the water inlet 7. In the illustrated example, the refrigerant passage 18 is arranged in a part of the lower region of the body of the hot water storage tank 6. That is, the refrigerant passage 18 is not arranged in the upper region of the body of the hot water storage tank 6. The hot water storage tank 6 and the condenser 17 are covered with a heat insulating material (not shown) provided in the tank unit 3.

[0017] In this embodiment, the refrigerant passage 18 of the condenser 17 is provided outside the hot water storage tank 6. As a modified example, the refrigerant passage 18 of the condenser 17 may be provided inside the hot water storage tank 6. For example, a spiral or coiled refrigerant pipe forming the refrigerant passage 18 may be installed in contact with the inner wall surface of the hot water storage tank 6. Alternatively, the spiral or coiled refrigerant pipe forming the refrigerant passage 18 may be disposed inside the hot water storage tank 6 without contacting the inner wall surface of the hot water storage tank 6.

[0018] The expansion valve 13 expands the refrigerant that flows out from the condenser 17. The refrigerant is depressurized when it passes through the expansion valve 13. The expansion valve 13 may be a linear expansion valve whose opening degree can be continuously adjusted. The refrigerant that passes through the expansion valve 13 flows into the evaporator 11. The refrigerant that evaporates in the evaporator 11 flows into the compressor 12 and is compressed.

[0019] The control circuit 14 controls the hot water storage operation. The hot water storage operation is an operation in which the water in the hot water storage tank 6 is heated by the refrigerant flowing through the refrigerant passage 18 of the condenser 17. The control circuit 14 may include at least one processor and at least one memory. The at least one processor may achieve each function of the control circuit 14 by reading and executing a program stored in the at least one memory. The control circuit 14 may include at least one dedicated hardware. The control circuit 14 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these.

[0020] In the illustrated example, the control circuit 14 is disposed in the heat source machine 2, but as a modified example, the control circuit 14 may be disposed in the tank unit 3. Furthermore, the functions of the control circuit 14 may be achieved by a controller disposed in the heat source machine 2 and a controller disposed in the tank unit 3 communicating with each other and coordinating with each other. Furthermore, at least a part of the functions of the control circuit 14 may be achieved by a cloud server connected via a network such as the Internet.

[0021] During hot water storage operation, the control circuit 14 controls the operation of the compressor 12 and the opening degree of the expansion valve 13. The operating speed of the compressor 12 may be variable. The control circuit 14 may vary the operating speed of the compressor 12 by varying the operating frequency of the electric motor included in the compressor 12 through inverter control. The higher the operating frequency of the compressor 12, the higher the operating speed of the compressor 12. The higher the operating speed of the compressor 12, the greater the amount of refrigerant circulating, and the higher the heating capacity. The heating capacity is the amount of heat given from the refrigerant to the water in the hot water storage tank 6 per unit time, and is measured in watts.

[0022] The storage type hot water heater 1 further includes a hot water supply detection sensor 19 capable of detecting that a hot water supply operation has started. The control circuit 14 can receive a signal from the hot water supply detection sensor 19 by wired or wireless communication. The hot water supply detection sensor 19 may detect that a hot water supply operation has started by any method. For example, a hot water supply terminal connected downstream of the hot water supply pipe 10 may be provided with a hot water supply detection sensor 19 that detects whether the hot water supply terminal is open or not. When a user opens the hot water supply terminal, hot water flows out from the hot water supply terminal, and the hot water supply operation starts. Therefore, the hot water supply detection sensor 19 detects that the hot water supply terminal is opened, and thus it is possible to detect that the hot water supply operation has started. Other examples of the hot water supply detection sensor 19 will be described in the second embodiment and onwards.

[0023] As shown in the illustrated example, the hot water storage type water heater 1 may further include at least one sensor among a discharge temperature sensor 16, a hot water storage temperature sensor 20, a condensation temperature sensor 21, an evaporation temperature sensor 22, and an outside air temperature sensor 23. The discharge temperature sensor 16 detects the temperature of the refrigerant discharged from the compressor 12. In the following description, the temperature of the refrigerant discharged from the compressor 12 is referred to as the "compressor discharge temperature."

[0024] The hot water temperature sensor 20 is a sensor for detecting the temperature of the hot water. Hereinafter, the water temperature in the hot water tank 6 may be referred to as the "tank water temperature." In the illustrated example, the hot water temperature sensor 20 is attached to the hot water tank 6 at a position higher than the top of the condenser 17 and lower than the hot water supply port 8. The hot water temperature sensor 20 detects the tank water temperature at that position as the "hot water temperature."

[0025] The condensation temperature sensor 21 is a sensor for detecting the condensation temperature of the refrigerant in the condenser 17. In the illustrated example, the condensation temperature sensor 21 is attached to the refrigerant passage 18 at a position near the center of the entire length of the refrigerant passage 18.

[0026] The evaporation temperature sensor 22 is a sensor for detecting the evaporation temperature of the refrigerant in the evaporator 11. The outside air temperature sensor 23 is a sensor for detecting the temperature of the outside air before it is subjected to heat exchange in the evaporator 11.

[0027] During hot water storage operation, the control circuit 14 may determine a target discharge temperature based on the condensation temperature detected by the condensation temperature sensor 21 and the evaporation temperature detected by the evaporation temperature sensor 22, and adjust the opening of the expansion valve 13 so that the compressor discharge temperature detected by the discharge temperature sensor 16 becomes equal to the target discharge temperature.

[0028] In this embodiment, when the hot water supply detection sensor 19 detects that the hot water supply operation has started during the hot water storage operation, the control circuit 14 increases the opening degree of the expansion valve 13. This is advantageous in increasing the COP (Coefficient Of Performance) of the heat pump during the hot water storage operation. The reason for this will be explained below.

[0029] Fig. 2 is a diagram for explaining the change in tank water temperature distribution along the vertical direction and the change in refrigerant temperature distribution in condenser 17 when hot water supply operation is started during hot water storage operation. In each graph of Fig. 2(1) to Fig. 2(6), the horizontal axis indicates the tank water temperature and the refrigerant temperature, and the vertical axis indicates the position along the vertical direction. Hereinafter, the temperature of the refrigerant flowing out from condenser 17 is referred to as the "condenser outlet temperature."

[0030] The graph in FIG. 2(1) shows an example of temperature distribution when hot water supply operation is not started during hot water storage operation. In this graph, the refrigerant temperature in the portion where the refrigerant temperature is constant along the vertical direction corresponds to the condensation temperature. The difference between the refrigerant temperature at the inlet of the condenser 17 and the condensation temperature is called the degree of superheat. The refrigerant temperature at the inlet of the condenser 17 can be considered to be substantially equal to the compressor discharge temperature. The difference between the condensation temperature and the condenser outlet temperature is called the degree of supercooling. The degree of supercooling is also generally called subcooling.

[0031] During hot water storage operation, the water whose temperature has risen due to the heat of the refrigerant passing through the refrigerant passage 18 decreases in density, and moves upward in the hot water storage tank 6 due to buoyancy. This causes convection. When the hot water supply operation has not started, the tank water temperature is distributed almost uniformly from a position close to the bottom of the condenser 17 to a position close to the top of the hot water storage tank 6, as shown in the water temperature distribution of the graph in FIG. 2(1). This almost uniform tank water temperature distribution is detected as the hot water temperature by the hot water storage temperature sensor 20. The hot water temperature gradually rises while maintaining this temperature distribution. As the hot water temperature gradually rises, the condensation temperature also gradually rises. As the hot water temperature and the condensation temperature gradually rise, the control circuit 14 may gradually decrease the opening of the expansion valve 13 so that the compressor discharge temperature gradually rises.

[0032] The graphs in Figures 2(2) to 2(6) explain the change in temperature distribution when the hot water supply operation is started during the hot water storage operation. The graphs of the refrigerant temperature distribution in Figures 2(3) to 2(6) show the change in the refrigerant temperature distribution when the control circuit 14 does not increase the opening of the expansion valve 13. In other words, Figures 2(3) to 2(6) correspond to comparative examples for this embodiment.

[0033] The graph in FIG. 2(2) shows the temperature distribution immediately after the hot water supply operation starts. When the hot water supply operation starts, water with a temperature lower than the hot water temperature flows from the water supply port 7 into the lower part of the hot water storage tank 6. As a result, the tank water temperature in the lower part of the hot water storage tank 6 drops. As a result, the condenser outlet temperature drops, and the degree of supercooling increases. On the other hand, since the tank water temperature at the position of the condensation temperature sensor 21 has not yet dropped, the temperature detected by the condensation temperature sensor 21 has not yet started to drop. The hot water temperature detected by the hot water storage temperature sensor 20 has not yet started to drop either. In this way, when the hot water supply operation starts, the degree of supercooling increases, but the temperature detected by the condensation temperature sensor 21 does not change, and the temperature detected by the hot water storage temperature sensor 20 does not change either. For this reason, if the hot water supply detection sensor 19 did not exist, the control circuit 14 would not be able to immediately detect that the hot water supply operation has started.

[0034] Hereinafter, the temperature boundary layer between the low-temperature water supply flowing into the hot water storage tank 6 and the hot water in the hot water storage tank 6 is referred to as the "temperature boundary layer 24". When the hot water supply operation continues from the state of FIG. 2(2), water further flows into the hot water storage tank 6, and the position of the temperature boundary layer 24 further rises, the state of FIG. 2(3) is reached. FIG. 2(3) shows the temperature distribution at the time when the temperature boundary layer 24 reaches the position of the condensation temperature sensor 21. From this point, the detected temperature of the condensation temperature sensor 21 starts to drop. At this point, the refrigerant temperature in the refrigerant passage 18 below the position of the condensation temperature sensor 21 is lower than the condensation temperature. That is, the refrigerant passage 18 below the position of the condensation temperature sensor 21 is filled with liquid refrigerant, which is a liquefied refrigerant. In this way, when a large amount of liquid refrigerant accumulates in the condenser 17, which is the high-pressure part of the refrigerant circuit, the amount of refrigerant in the evaporator 11, which is the low-pressure part of the refrigerant circuit, decreases. As a result, the evaporation temperature decreases, the evaporation pressure decreases, and the degree of refrigerant superheat at the outlet of the evaporator 11 increases. Therefore, the amount of heat absorbed by the refrigerant from the outside air in the evaporator 11 decreases, and the COP of the heat pump decreases.

[0035] As the hot water supply operation continues from the state shown in Fig. 2(3), more water flows into the hot water storage tank 6, and the position of the temperature boundary layer 24 rises further, resulting in the state shown in Fig. 2(4). Fig. 2(4) shows the temperature distribution at the time when the temperature boundary layer 24 reaches a position above the condensation temperature sensor 21. At this time, the temperature detected by the condensation temperature sensor 21 is lower than the actual condensation temperature. In this way, it is only after the temperature boundary layer 24 rises above the position of the condensation temperature sensor 21 that the temperature detected by the condensation temperature sensor 21 begins to decrease.

[0036] As the hot water supply operation continues from the state shown in Fig. 2(4), more water flows into the hot water tank 6, and the position of the temperature boundary layer 24 rises further, resulting in the state shown in Fig. 2(5). Fig. 2(5) shows the temperature distribution at the point when the temperature boundary layer 24 reaches a position directly below the hot water temperature sensor 20. From this point, the temperature detected by the hot water temperature sensor 20 begins to decrease.

[0037] As the hot water supply operation continues from the state shown in Fig. 2(5), more water flows into the hot water tank 6, and the position of the temperature boundary layer 24 rises further, resulting in the state shown in Fig. 2(6). Fig. 2(6) shows the temperature distribution at the point when the temperature boundary layer 24 reaches a position higher than the hot water temperature sensor 20. At this point, the value of the temperature detected by the hot water temperature sensor 20 is substantially equal to the temperature of the water supply.

[0038] 2(6) from the state of FIG. 2(3), a larger amount of liquid refrigerant accumulates in the condenser 17. As a result, the amount of refrigerant in the evaporator 11 becomes even more insufficient, and the COP decreases further.

[0039] In contrast, in this embodiment, when the hot water supply detection sensor 19 detects that the hot water supply operation has started, the control circuit 14 increases the opening of the expansion valve 13. For example, the control circuit 14 may increase the opening of the expansion valve 13 at the time of FIG. 2(2). When the opening of the expansion valve 13 increases, the flow rate of the refrigerant flowing from the condenser 17 to the evaporator 11 increases. As a result, the amount of refrigerant in the evaporator 11 becomes larger than that in the comparative example, and the decrease in the evaporation temperature and evaporation pressure can be reliably avoided. Therefore, the amount of heat absorbed by the refrigerant from the outside air in the evaporator 11 becomes larger than that in the comparative example, and the COP becomes higher than that in the comparative example. In this way, in this embodiment, it is possible to reliably prevent a large amount of liquid refrigerant from accumulating in the condenser 17, and therefore it is possible to reliably prevent a transition from the state of FIG. 2(2) to the state of FIG. 2(3) and subsequent states. This is advantageous in increasing the COP.

[0040] Fig. 3 is a flow chart showing an example of processing executed by the storage type hot water heater 1 according to the first embodiment. As step S1 in Fig. 3, the control circuit 14 starts a hot water storage operation. Next, as step S2, the control circuit 14 judges whether or not the hot water supply detection sensor 19 detects that a hot water supply operation has started while the hot water storage operation is being performed. If the hot water supply detection sensor 19 detects that a hot water supply operation has started, as step S3, the control circuit 14 increases the opening degree of the expansion valve 13. Thereafter, the control circuit 14 continues the hot water storage operation as step S4.

[0041] On the other hand, if hot water supply detection sensor 19 does not detect the start of the hot water supply operation in step S2, control circuit 14 skips step S3 and proceeds to step S4, where it continues the hot water storage operation.

[0042] Embodiment 2 Next, a second embodiment will be described with reference to Figures 4 and 5. The differences from the first embodiment will be mainly described, and the description of the commonalities will be simplified or omitted. Also, the same reference numerals will be used to denote the common or corresponding elements to the elements described above.

[0043] FIG. 4 is a diagram showing a storage type hot water heater 25 according to the second embodiment. As shown in FIG. 4, the storage type hot water heater 25 according to the second embodiment includes a condenser outlet temperature sensor 26. The condenser outlet temperature sensor 26 is attached to the outlet of the condenser 17, i.e., the outlet of the refrigerant passage 18. The condenser outlet temperature sensor 26 in this embodiment corresponds to the hot water supply detection sensor 19. In this embodiment, when the condenser outlet temperature sensor 26 detects that the hot water supply operation has started during the hot water storage operation, the control circuit 14 increases the opening degree of the expansion valve 13. This provides the same effect as in the first embodiment.

[0044] Condenser outlet temperature sensor 26 is located at the bottom of hot water storage tank 6, and is therefore susceptible to temperature changes in the tank water at the bottom of hot water storage tank 6. For this reason, when hot water supply operation is started during hot water storage operation and water starts to flow into the bottom of hot water storage tank 6, the condenser outlet temperature immediately drops. For this reason, condenser outlet temperature sensor 26 makes it possible to quickly detect that hot water supply operation has started.

[0045] FIG. 5 is a flowchart showing an example of processing executed by the storage type hot water heater 25 according to the second embodiment. In step S11 of FIG. 5, the control circuit 14 starts a hot water storage operation. Next, in step S12, the control circuit 14 judges whether or not the condenser outlet temperature sensor 26 detects that a hot water supply operation has started while the hot water storage operation is being executed. For example, the control circuit 14 may determine that a hot water supply operation has started when the amount of decrease in the temperature detected by the condenser outlet temperature sensor 26 exceeds a reference value. Alternatively, the control circuit 14 may determine that a hot water supply operation has started when the amount of increase in the difference between the temperature detected by the condenser outlet temperature sensor 26 and the temperature detected by the condensation temperature sensor 21 exceeds a reference value.

[0046] When the condenser outlet temperature sensor 26 detects that the hot water supply operation has started in Step S12, the control circuit 14 increases the opening degree of the expansion valve 13 in Step S13. After that, the control circuit 14 continues the hot water storage operation in Step S14.

[0047] On the other hand, if the condenser outlet temperature sensor 26 does not detect in step S12 that the hot water supply operation has started, the control circuit 14 skips step S13 and proceeds to step S14, where it continues the hot water storage operation.

[0048] This embodiment has the advantage that there is no need to attach the hot water supply detection sensor 19 to the hot water supply terminal inside the building.

[0049] Embodiment 3 Next, a third embodiment will be described with reference to Fig. 6 and Fig. 7, focusing on the differences from the first embodiment and simplifying or omitting the description of the commonalities. Also, the same reference numerals are used to denote the common or corresponding elements to the elements described above.

[0050] FIG. 6 is a diagram showing a storage type hot water heater 27 according to the third embodiment. As shown in FIG. 6, the storage type hot water heater 27 according to the third embodiment includes a feed water temperature sensor 28. The feed water temperature sensor 28 detects the temperature of the feed water that flows into the hot water storage tank 6 from the feed water inlet 7. The feed water temperature sensor 28 is attached to the lower part of the hot water storage tank 6. For example, the feed water temperature sensor 28 may be disposed at a position equivalent to the height of the feed water inlet 7. The feed water temperature sensor 28 may also be disposed at a position lower than the feed water inlet 7. Alternatively, the feed water temperature sensor 28 may be disposed at a position slightly higher than the feed water inlet 7.

[0051] The water supply temperature sensor 28 in this embodiment corresponds to the hot water supply detection sensor 19. In this embodiment, when the water supply temperature sensor 28 detects that the hot water supply operation has started during the hot water storage operation, the control circuit 14 increases the opening degree of the expansion valve 13. This provides the same effect as in the first embodiment.

[0052] During hot water storage operation, when the hot water supply operation is started and the supply water starts to flow into the lower part of the hot water storage tank 6, the temperature detected by the supply water temperature sensor 28 immediately drops. Therefore, the supply water temperature sensor 28 can quickly detect that the hot water supply operation has started.

[0053] Fig. 7 is a flow chart showing an example of processing executed by storage type hot water heater 27 according to embodiment 3. In step S21 of Fig. 7, control circuit 14 starts a hot water storage operation. Next, in step S22, control circuit 14 determines whether or not feed water temperature sensor 28 has detected that a hot water supply operation has started while the hot water storage operation is being performed. For example, control circuit 14 may determine that a hot water supply operation has started when an amount of decrease in the temperature detected by feed water temperature sensor 28 exceeds a reference value.

[0054] When the supply water temperature sensor 28 detects that the hot water supply operation has started in Step S22, the control circuit 14 increases the opening degree of the expansion valve 13 in Step S23. After that, the control circuit 14 continues the hot water storage operation in Step S24.

[0055] On the other hand, if the supply water temperature sensor 28 does not detect in step S22 that the hot water supply operation has started, the control circuit 14 skips step S23 and proceeds to step S24, where the hot water storage operation continues as is.

[0056] This embodiment has the advantage that there is no need to attach the hot water supply detection sensor 19 to the hot water supply terminal inside the building.

[0057] In step S23, the control circuit 14 may increase the opening degree of the expansion valve 13 as the temperature of the feed water flowing into the hot water storage tank 6 decreases. For example, the control circuit 14 may increase the opening degree of the expansion valve 13 as the value of the temperature detected by the feed water temperature sensor 28 decreases. Alternatively, the control circuit 14 may increase the opening degree of the expansion valve 13 as the decrease in the temperature detected by the feed water temperature sensor 28 increases. If the opening degree of the expansion valve 13 is the same, the lower the temperature of the feed water flowing into the hot water storage tank 6, the more likely the liquid refrigerant that accumulates in the condenser 17 will increase. In contrast, the lower the temperature of the feed water flowing into the hot water storage tank 6, the greater the opening degree of the expansion valve 13, thereby making it possible to more reliably prevent an increase in the amount of liquid refrigerant in the condenser 17.

[0058] Embodiment 4 Next, a fourth embodiment will be described with reference to Figures 8 and 9. The differences from the first embodiment will be mainly described, and the description of the common parts will be simplified or omitted. The same reference numerals will be used to denote the common parts or parts corresponding to the above-described first embodiment.

[0059] Fig. 8 is a diagram showing a storage type hot water heater 29 according to embodiment 4. As shown in Fig. 8, storage type hot water heater 29 according to embodiment 4 includes a hot water temperature sensor 30. Hot water temperature sensor 30 detects the temperature of hot water flowing out from hot water outlet 8. Hot water temperature sensor 30 is attached to hot water pipe 10.

[0060] The hot water temperature sensor 30 in this embodiment corresponds to the hot water detection sensor 19. In this embodiment, when the hot water temperature sensor 30 detects that the hot water supply operation has started during the hot water storage operation, the control circuit 14 increases the opening degree of the expansion valve 13. This provides the same effect as in the first embodiment.

[0061] When the hot water supply operation is started during the hot water storage operation, the temperature detected by the hot water supply temperature sensor 30 immediately rises. Therefore, the hot water supply temperature sensor 30 can quickly detect that the hot water supply operation has started.

[0062] Fig. 9 is a flowchart showing an example of processing executed by storage type hot water heater 29 according to embodiment 4. In step S31 of Fig. 9, control circuit 14 starts a hot water storage operation. Next, in step S32, control circuit 14 determines whether or not hot water supply temperature sensor 30 has detected that a hot water supply operation has started while the hot water storage operation is being performed. For example, control circuit 14 may determine that a hot water supply operation has started when the amount of increase in the temperature detected by hot water supply temperature sensor 30 exceeds a reference value.

[0063] When the hot water supply temperature sensor 30 detects that the hot water supply operation has started in Step S32, the control circuit 14 increases the opening degree of the expansion valve 13 in Step S33. After that, the control circuit 14 continues the hot water storage operation in Step S34.

[0064] On the other hand, if the hot water temperature sensor 30 does not detect the start of the hot water supply operation in step S32, the control circuit 14 skips step S33 and proceeds to step S34, where the hot water storage operation continues as is.

[0065] This embodiment has the advantage that there is no need to attach the hot water supply detection sensor 19 to the hot water supply terminal inside the building.

[0066] Embodiment 5. Next, a fifth embodiment will be described with reference to Fig. 10 and Fig. 11. The differences from the first embodiment will be mainly described, and the description of the common parts will be simplified or omitted. The same reference numerals will be used to denote the common parts or parts corresponding to the above-described first embodiment.

[0067] FIG. 10 is a diagram showing a storage type hot water heater 31 according to embodiment 5. As shown in FIG. 10, storage type hot water heater 31 according to embodiment 5 includes a flow sensor 32. Flow sensor 32 detects the presence or absence of water flow at water supply inlet 7. In the example shown, flow sensor 32 is attached to water supply pipe 9. As an alternative to the example shown, flow sensor 32 may be attached to water supply inlet 7. As a modified example, flow sensor 32 may be attached to hot water supply inlet 8 or hot water supply pipe 10, and configured so that flow sensor 32 detects the presence or absence of water flow at hot water supply inlet 8 or hot water supply pipe 10.

[0068] The flow sensor 32 in this embodiment corresponds to the hot water supply detection sensor 19. In this embodiment, when the flow sensor 32 detects that the hot water supply operation has started during the hot water storage operation, the control circuit 14 increases the opening degree of the expansion valve 13. This provides the same effect as in the first embodiment.

[0069] When the hot water supply operation starts during the hot water storage operation, the flow sensor 32 detects the water flow immediately. Therefore, the flow sensor 32 makes it possible to quickly detect that the hot water supply operation has started.

[0070] The flow sensor 32 may be capable of detecting only the presence or absence of water flow. Alternatively, the flow sensor 32 may be capable of detecting the flow rate of water passing through the water supply port 7 or the hot water supply port 8. The flow rate of water passing through the water supply port 7 is equal to the flow rate of water passing through the hot water supply port 8.

[0071] Fig. 11 is a flow chart showing an example of processing executed by storage type hot water heater 31 according to embodiment 5. In step S41 of Fig. 11, control circuit 14 starts a hot water storage operation. Next, in step S42, control circuit 14 determines whether or not flow sensor 32 has detected that a hot water supply operation has started while the hot water storage operation is being performed. For example, control circuit 14 may determine that a hot water supply operation has started when the flow rate detected by flow sensor 32 exceeds a reference value.

[0072] When the flow sensor 32 detects that the hot water supply operation has started in Step S42, the control circuit 14 increases the opening degree of the expansion valve 13 in Step S43. After that, the control circuit 14 continues the hot water storage operation in Step S44.

[0073] On the other hand, if the flow sensor 32 does not detect in step S42 that the hot water supply operation has started, the control circuit 14 skips step S43 and proceeds to step S44, where it continues the hot water storage operation.

[0074] This embodiment has the advantage that there is no need to attach the hot water supply detection sensor 19 to the hot water supply terminal inside the building.

[0075] In step S43, the control circuit 14 may increase the opening of the expansion valve 13 as the flow rate detected by the flow sensor 32 increases. If the opening of the expansion valve 13 is the same, the greater the flow rate of water flowing into the hot water storage tank 6 from the water supply port 7, the faster the water temperature at the bottom of the hot water storage tank 6 drops, and the more likely it is that the amount of liquid refrigerant that accumulates in the condenser 17 will increase. In contrast, by increasing the opening of the expansion valve 13 as the flow rate detected by the flow sensor 32 increases, it becomes possible to more reliably prevent the amount of liquid refrigerant in the condenser 17 from increasing.

[0076] Although each embodiment has been described above, the hot water storage type hot water heater according to the present disclosure is not limited to the embodiment. For example, the hot water supply detection sensor 19 is not limited to the configuration described in each embodiment. In the present disclosure, the hot water supply detection sensor 19 may be, for example, a sensor that detects sound or vibration generated from the water supply inlet 7, the hot water supply inlet 8, the water supply pipe 9, or the hot water supply pipe 10. When the hot water supply operation is started, a water flow is generated in the water supply inlet 7, the hot water supply inlet 8, the water supply pipe 9, and the hot water supply pipe 10, and sound or vibration is generated from the water supply inlet 7, the hot water supply inlet 8, the water supply pipe 9, and the hot water supply pipe 10. Therefore, by detecting the sound or vibration generated from the water supply inlet 7, the hot water supply inlet 8, the water supply pipe 9, or the hot water supply pipe 10 by the hot water supply detection sensor 19, it is possible to detect that the hot water supply operation has started. [Explanation of symbols]

[0077] 1 storage type water heater, 2 heat source unit, 3 tank unit, 4 refrigerant pipe, 5 refrigerant pipe, 6 hot water tank, 7 water inlet, 8 hot water inlet, 9 water supply pipe, 10 hot water pipe, 11 evaporator, 12 compressor, 13 expansion valve, 14 control circuit, 15 blower, 16 discharge temperature sensor, 17 condenser, 18 refrigerant passage, 19 hot water detection sensor, 20 storage water temperature sensor, 21 condensation temperature sensor, 22 evaporation temperature sensor, 23 outside air temperature sensor, 24 temperature boundary layer, 25 storage type water heater, 26 condenser outlet temperature sensor, 27 storage type water heater, 28 water supply temperature sensor, 29 storage type water heater, 30 hot water temperature sensor, 31 Storage water heater, 32 Flow sensor

Claims

1. A hot water tank and A water supply port disposed at a lower portion of the hot water storage tank; A hot water supply port disposed at an upper portion of the hot water storage tank; an evaporator that evaporates a refrigerant; a compressor that compresses the refrigerant flowing out from the evaporator; a condenser having a refrigerant passage disposed in the hot water storage tank, the condenser exchanging heat between the refrigerant compressed by the compressor and water in the hot water storage tank to condense the refrigerant; an expansion valve for expanding the refrigerant flowing out from the condenser; a control circuit for controlling a hot water storage operation in which water in the hot water storage tank is heated by the refrigerant flowing through the refrigerant passage of the condenser; a hot water supply detection sensor capable of detecting the start of a hot water supply operation in which hot water in the hot water storage tank flows out from the hot water supply port and water flows into the hot water storage tank from the water supply port; Equipped with The refrigerant passage is disposed so that its position gradually decreases in a height direction of the hot water storage tank from an upstream side to a downstream side of the flow of the refrigerant, When the hot water supply operation is started during the hot water storage operation, the control circuit increases the opening degree of the expansion valve.

2. A condenser outlet temperature sensor that detects the temperature of the refrigerant flowing out from the condenser is provided as the hot water supply detection sensor, 2. The hot water storage type hot water heater according to claim 1, wherein when the condenser outlet temperature sensor detects that the hot water supply operation has started during the hot water storage operation, the control circuit increases the opening of the expansion valve.

3. a water supply temperature sensor that detects the temperature of the water that flows into the hot water storage tank from the water supply port is provided as the hot water supply detection sensor; 2. The storage type hot water heater according to claim 1, wherein when the supply water temperature sensor detects that the hot water supply operation has started during the hot water storage operation, the control circuit increases the opening of the expansion valve.

4. A hot water storage type water heater as described in claim 3, wherein when the hot water supply operation is started during the hot water storage operation, the control circuit increases the opening degree of the expansion valve the lower the temperature of the supply water flowing into the hot water storage tank.

5. A hot water temperature sensor that detects the temperature of hot water flowing out from the hot water outlet is provided as the hot water detection sensor, 2. The storage type hot water heater according to claim 1, wherein when the hot water supply temperature sensor detects that the hot water supply operation has started during the hot water storage operation, the control circuit increases the opening of the expansion valve.

6. A flow sensor that detects the water flow of the water supply port or the water flow of the hot water supply port is provided as the hot water supply detection sensor, 2. The storage type hot water heater according to claim 1, wherein when the flow sensor detects that the hot water supply operation has started during the hot water storage operation, the control circuit increases the opening of the expansion valve.

7. The flow sensor is capable of detecting a flow rate of water passing through the water supply port or the hot water supply port, The storage type hot water heater according to claim 6, wherein when the hot water supply operation is started during the hot water storage operation, the control circuit increases the opening degree of the expansion valve as the flow rate increases.

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