Water heater

Abstract

To provide a water heater enabling defrosting with high efficiency when an outside air temperature is lower than 0°C.SOLUTION: A water heater 1 includes: a tank 2 storing hot water W2; a compressor 11 that compresses a refrigerant; a first heat exchanger 12 that exchanges heat between the compressed refrigerant and water W1; a decompression mechanism 13 that decompresses the refrigerant; a second heat exchanger 14 that exchanges heat between the decompressed refrigerant and outside air; piping 17 that connects the tank 2 and the first heat exchanger 12 so that a liquid heating medium to be heated by the refrigerant in the first heat exchanger 12 circulates between the tank 2 and the first heat exchanger 12 and that includes piping 43, 44 installed on the outdoor side; a pump 7 installed in the piping 17 to circulate the heating medium in the piping 17; and a control device 102 that suppresses freezing of the heating medium in the piping 17 during a defrosting operation that is performed when an outside air temperature is lower than 0°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to water heaters. [Background technology]

[0002] The abstract of Patent Document 1 states that "before defrosting operation, the heat pump water heater performs a high-temperature liquid introduction operation in which high-temperature liquid (including water) is introduced into the liquid-refrigerant heat exchanger 5, and during defrosting operation, a bypass circulation operation in which the liquid flowing out from the liquid-refrigerant heat exchanger 5 is circulated through the bypass piping 13. Furthermore, if the temperature of the liquid flowing into the liquid-refrigerant heat exchanger 5 is below a predetermined temperature for a predetermined period of time, an anti-freeze operation is performed in which the liquid flowing out from the liquid-refrigerant heat exchanger 5 is circulated through the bypass piping 13 at a lower flow rate than during boiling operation, to prevent freezing of the outbound piping 3A heading toward the liquid-refrigerant heat exchanger 5. Then, a defrosting operation is performed after the anti-freeze operation. As a result, even when the heat pump water heater is operated in an environment where the outside air condition is extremely low, freezing of the water in the piping can be prevented and stable boiling operation can be performed." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2010 / 109689 Summary of the Invention [Problem to be solved by the invention]

[0004] In the defrosting operation described in Patent Document 1, the pump 10 is driven to circulate the water discharged from the water-refrigerant heat exchanger 5 through the connection pipe 3 and the bypass pipe 13 (paragraph 0034). As a result, the amount of heat to be supplied to the evaporator 7 in the water-refrigerant heat exchanger 5 decreases, and the temperature of the refrigerant supplied to the evaporator 7 drops. As a result, the defrosting efficiency drops. The problem to be solved by the present disclosure is to provide a water heater that is capable of suppressing freezing and performing highly efficient defrosting when the outside air temperature is below 0°C. [Means for solving the problem]

[0005] The hot water heater of the present disclosure includes a tank for storing a liquid heat medium, a compressor for compressing the refrigerant, a first heat exchanger for exchanging heat between the compressed refrigerant and the heat medium, a decompression mechanism for decompressing the refrigerant, a second heat exchanger for exchanging heat between the decompressed refrigerant and outside air, a connection pipe including an outdoor pipe installed outdoors and connecting the tank and the first heat exchanger such that the heat medium heated by the refrigerant in the first heat exchanger circulates between the tank and the first heat exchanger, a pump installed on the connection pipe and circulating the heat medium through the connection pipe, and a freeze suppression unit for suppressing freezing of the heat medium in the connection pipe during a defrosting operation performed when the outside air temperature is below 0°C. The freeze suppression unit suppresses freezing of the heat medium in the connection pipe by driving the pump with the pressure reducing mechanism in an open state during the defrosting operation. . [Brief description of the drawings]

[0006] [Figure 1] 1 is a system diagram of a water heater according to an embodiment. [Diagram 2] 4 is a flowchart illustrating a defrosting method executed in the water heater of one embodiment. [Diagram 3] 3 is a flowchart illustrating a defrosting method executed in the water heater of one embodiment, the flowchart being executed following the control shown in FIG. 2. [Figure 4] 4 is a time chart in the water heater of one embodiment. [Diagram 5] 3 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment, the flowchart being executed following the control shown in FIG. [Figure 6] 10 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment. [Figure 7] 7 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment, which is executed following the control shown in FIG. 6. [Figure 8] 10 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment. [Figure 9] 9 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment, which is executed following the control shown in FIG. 8. [Figure 10] FIG. 11 is a system diagram of a water heater according to another embodiment. [Figure 11] 10 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment. [Figure 12] 12 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment, which is a flowchart executed following the control shown in FIG. [Figure 13] 10 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment. [Figure 14] FIG. 11 is a system diagram of a water heater according to another embodiment. [Figure 15] 10 is a flowchart illustrating a defrosting method executed in a water heater according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, a form for carrying out the present disclosure (referred to as an embodiment) will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the following embodiment, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. In addition, the same symbols will be used for the same members, and duplicate descriptions will be omitted. Furthermore, members having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, changes may be made from the actual configuration within a range that does not significantly impair the effects of the present disclosure, and some members may be omitted or modified between drawings.

[0008] 1 is a system diagram of a water heater 1 according to one embodiment. The water heater 1 includes a heat pump unit 100 and a hot water storage unit 101. The water heater 1 includes a refrigeration cycle 20 in the heat pump unit 100.

[0009] The water heater 1 is configured, for example, as a refrigeration cycle 20, in which a refrigerant circulates through a compressor 11, a first heat exchanger 12, a pressure reduction mechanism 13 (e.g., an expansion valve), and a second heat exchanger 14 that exchanges heat with outside air. These are connected by piping 16. The refrigerant flows through the piping 16, and the refrigerant leaving the compressor 11 returns to the compressor 11 via the first heat exchanger 12, the pressure reduction mechanism 13, and the second heat exchanger 14.

[0010] The compressor 11 compresses the refrigerant. The compressor 11 is connected to the control device 102 by an electric signal line shown by a dashed line in FIG. 1. The compressor 11 includes, for example, an inverter (not shown), and the discharge pressure can be controlled by controlling the rotation speed of the inverter. The first heat exchanger 12 exchanges heat between the refrigerant (high-temperature refrigerant) compressed by the compressor 11 and water W1 (a liquid heat medium, described later). The pressure reducing mechanism 13 reduces the pressure of the refrigerant. The second heat exchanger 14 exchanges heat between the reduced-pressure refrigerant and outside air. The refrigeration cycle 20 is housed in a housing (not shown) that constitutes the heat pump unit 100. The heat pump unit 100 includes a fan 15, and the second heat exchanger 14 exchanges heat with the outside air when the fan 15 is driven.

[0011] The hot water heater 1 is equipped with sensors 31, 32, 33, and 34 in the heat pump unit 100. The sensor 31 measures the outside air temperature. The sensor 32 measures the temperature of the refrigerant discharged from the second heat exchanger 14. The sensor 33 measures the temperature (outlet temperature) of the heat medium (e.g., liquid water, etc., described later) discharged from the first heat exchanger 12. The sensor 34 measures the temperature (inlet temperature) of the heat medium supplied to the first heat exchanger 12. The sensors 31, 32, 33, and 34 are connected to the control device 102 by electric signal lines shown by dashed lines in FIG. 1.

[0012] The water heater 1 includes a tank 2 that stores hot water W2 (a liquid heat transfer medium). Hereinafter, when the term "heat transfer medium" is used simply, this refers to this "liquid heat transfer medium." The tank 2 stores the hot water W2 (a heat transfer medium heated by a high-temperature refrigerant) generated in the first heat exchanger 12. Inside the tank 2, due to the difference in specific gravity caused by temperature, high-temperature hot water W2 is stored in the upper part, and low-temperature water W1 (a concept that includes hot water having a lower temperature than hot water W2) is stored in the lower part.

[0013] The tank 2 contains a heat transfer tube (not shown) through which water W3 (e.g., tap water) flows, and the heat contained in hot water W2 is transferred to the water W3 via the heat transfer tube to generate hot water W4 to be supplied to the demand end. Meanwhile, the hot water W2 loses heat and is discharged from the tank 2 as water W1. In the tank 2, the hot water W3 is heated by the hot water W2 to generate hot water W4 to be supplied to the demand end (not shown, e.g., a faucet, a bath, etc.). The tank 2 is contained in a housing (not shown) that constitutes the hot water storage unit 101.

[0014] The water heater 1 includes a pipe 17 (connection pipe) that connects the first heat exchanger 12 and the tank 2. A liquid heat transfer medium flows through the pipe 17. The pipe 17 connects the tank 2 and the first heat exchanger 12 such that the liquid heat transfer medium circulates between the tank 2 and the first heat exchanger 12. The heat transfer medium is heated in the first heat exchanger 12 by a refrigerant flowing through a refrigeration cycle 20.

[0015] The piping 17 includes piping 3, 4, 42, 43, and 44. The piping 4 supplies hot water W2 (heated heat medium) generated by heating with the refrigerant in the first heat exchanger 12 to the tank 2. The piping 3 returns water W1, which has been used to generate hot water W4 in the tank 2 and has lost heat, to the first heat exchanger 12.

[0016] The pipes 3 and 4 include pipes 44 and 43 (outdoor pipes) that are installed outdoors. The pipe 3 includes the pipe 44, and the pipe 4 includes the pipe 43. In the illustrated example, the pipes 44 and 43 are disposed between the heat pump unit 100 and the hot water storage unit 101. Since the pipes 43 and 44 are installed outdoors, the heat medium inside the pipe 17 including the pipes 43 and 44 is easily affected by the outside air, and there is a possibility that the heat medium will freeze when the outside air temperature is low. Therefore, in the present disclosure, as will be described in detail later, highly efficient defrosting is performed when the outside air temperature is below 0°C (low temperature range), and freezing of the heat medium is suppressed.

[0017] The pipes 3 and 4 are connected by a pipe 42 (bypass pipe) so as to bypass the tank 2. The pipe 17 includes the pipe 42. The water heater 1 includes a three-way valve 41 that switches the flow path of the heat medium to either the tank 2 side or the pipe 42 side. The three-way valve 41 includes a motor M, and the flow path is switched by driving the motor M. Although details will be described later, when the pump 7 is driven during the defrosting operation, the heat medium is heated by the first heat exchanger 12, but the temperature of the hot water W2 at the outlet of the first heat exchanger 12 is not very high. Therefore, in order to prevent the low-temperature hot water W2 from being supplied to the tank 2, the flow path of the heat medium is switched to the pipe 42 side during the defrosting operation. In this case, the heat medium circulates between the first heat exchanger 12 and the pipe 42.

[0018] The water heater 1 includes a pump 7 connected to a pipe 17 and circulating a heat medium through the pipe 17. The pump 7 includes, for example, an inverter (not shown), and the discharge flow rate (discharge pressure) can be controlled by controlling the rotation speed of the inverter. The pump 7 is connected to the control device 102 by an electric signal line shown by a dashed line in FIG.

[0019] The water heater 1 includes a freeze suppression unit 21 that suppresses the freezing of the heat transfer medium in the pipe 17 during a defrosting operation performed when the outdoor air temperature is below 0° C. The outdoor air temperature is measured by, for example, a sensor 31. For example, the second heat exchanger 14 is defrosted by the defrosting operation in winter.

[0020] In the example of the present disclosure, the freeze suppression unit 21 includes a control device 102 that controls the pump 7 based on a predetermined temperature of the heat medium in the pipe 17. Control by the control device 102 makes it possible to suppress freezing of the heat medium in the pipe 17 using existing equipment. Although details will be described later, for example, when the outside air temperature is close to an extremely low temperature (e.g., -15°C), the heat medium is likely to freeze, so the pump 7 is driven. As a result, the heat medium flows through the pipe 17, making it difficult for the heat medium to freeze even at the same outside air temperature.

[0021] In the example of the present disclosure, the predetermined temperature used in controlling the pump 7 is the temperature of the heat medium (water W1) at the inlet of the first heat exchanger 12. The inlet temperature can be measured by, for example, the sensor 34. During the defrosting operation, the refrigeration cycle 20 is driven, and the heat medium is heated in the first heat exchanger 12. Therefore, the possibility of the heat medium freezing can be grasped based on the inlet temperature of the first heat exchanger 12, which is the lowest temperature among the heat mediums flowing through the pipe 17.

[0022] The freezing suppression unit 21 includes a control device 102 that drives the pump 7 at predetermined time intervals to detect the temperature of the heat medium in the pipe 17. By driving the pump 7, the heat medium present in the outdoor pipes 43, 44 can be moved to the position of the sensor 34, and the temperature of the heat medium present in the pipes 43, 44 that are most likely to freeze can be detected. In addition, because the pump 7 is driven at predetermined time intervals, the heat medium in the pipe 17 circulates at predetermined time intervals, making it difficult for the heat medium in the pipe 17 to freeze. The predetermined time here is, for example, a second predetermined time t2, the details of which will be described later with reference to FIG. 2 etc.

[0023] The freeze suppression unit 21 includes a control device 102 that stops the operation of the pump 7 when the outside air temperature is equal to or higher than 0° C. When the outside air temperature is close to 0° C., the heat transfer medium is unlikely to freeze. Therefore, by stopping the operation of the pump 7, it is possible to improve the energy saving performance.

[0024] The freeze suppression unit 21 includes a control device 102 that performs a defrost preparatory operation before the above-mentioned defrost operation when the outside air temperature is −15° C. or lower. In the defrost preparatory operation, for example, the control device 102 connects the three-way valve 41 to the pipe 42 while driving the refrigeration cycle 20, and flows high-temperature hot water W2 (heat medium) into the pipe 17 including the pipe 42. This increases the temperature of the heat medium in the pipe 17. Therefore, by performing the defrost preparatory operation, it is possible to lengthen the time until the temperature of the heat medium in the pipe 17 reaches a predetermined temperature Tws (described later) during the defrost operation that is performed after the defrost preparatory operation.

[0025] In another embodiment, the control device 102 calculates the above-mentioned predetermined temperature based on the outdoor air temperature. The outdoor air temperature can be measured, for example, by the sensor 31. In this way, when the outdoor air temperature, which is an indicator of whether or not to perform a defrosting operation, is measured, the above-mentioned predetermined temperature can also be calculated based on the measured outdoor air temperature.

[0026] In yet another embodiment, the control device 102 calculates the above-mentioned predetermined temperature based on the temperature of the heat medium (hot water W2) at the outlet of the first heat exchanger 12 and the rotation speed of the compressor 11. The faster the rotation speed of the compressor 11, the higher the refrigerant temperature is, and the more heat can be supplied to the heat medium. As a result, the outlet temperature is higher. Therefore, the control device 102 holds in advance a first predetermined relationship that associates the rotation speed of the compressor 11 with the temperature rise in the first heat exchanger 12, and the control device 102 can calculate the inlet temperature from the outlet temperature based on the first predetermined relationship. The first predetermined relationship is, for example, a table or a formula, and can be determined by, for example, experiments in a factory or the like. By the control device 102 performing the calculation in this manner, freezing of the heat medium can be suppressed without directly measuring the inlet temperature.

[0027] The control device 102 is configured to include, for example, a CPU (Central Processing Unit) 1021, a RAM (Random Access Memory) 1022, and a ROM (Read Only Memory) 1023. The control device 102 is realized by developing a predetermined control program (for example, a program for executing a hot water storage method, a defrosting method, etc.) stored in the ROM 1023 into the RAM 1022 and executing the program by the CPU 1021.

[0028] Fig. 2 is a flowchart illustrating a defrosting method executed in the water heater 1 of one embodiment. Fig. 3 is a flowchart illustrating a defrosting method executed in the water heater 1 of one embodiment, which is a flowchart performed following the control shown in Fig. 2. "A" and "B" shown in Fig. 3 indicate that the method is performed following "A" and "B" shown in Fig. 2.

[0029] The control shown in Fig. 2 and Fig. 3 described later is executed by the control device 10 (Fig. 1) in the hot water heater 1 shown in Fig. 1. Therefore, the description of Fig. 2 and Fig. 3 will be made with appropriate reference to Fig. 1.

[0030] First, the control device 102 controls the three-way valve 41 to switch the flow path to the pipe 42 side (step S1) (at the start of operation and after defrosting operation is restored) while driving the refrigeration cycle 20 (heating operation). The control device 102 measures the temperature of the hot water W2 (outlet temperature Two) using the sensor 33 at predetermined time intervals and determines whether the outlet temperature Two is equal to or higher than a predetermined threshold value (step S2). The predetermined threshold value is, for example, a value indicating that the inside of the pipe 42 is sufficiently warm (high-temperature hot water is supplied to the tank 2).

[0031] If the outlet temperature Two becomes equal to or higher than a predetermined threshold (Yes), the control device 102 controls the three-way valve 41 to switch the flow path to the tank 2 side (step S3). This enables the tank 2 to be pumped up. The control device 102 judges whether a defrosting operation is necessary (step S4). If necessary (Yes), step S6 and subsequent steps are performed. In step S4, the control device 102 judges whether a predetermined start condition is satisfied. The start condition is, for example, when the inlet temperature and outlet temperature of the first heat exchanger 12 reach a predetermined temperature. If the start condition is satisfied, step S6 is performed. If the start condition is not satisfied (No), the control device 102 judges whether forced defrosting is necessary (step S5). If forced defrosting is necessary, for example, when the refrigeration cycle 20 has been stopped for a predetermined time. If not necessary (No), step S4 is performed again, and if necessary (Yes), step S6 is performed.

[0032] In step S6, the control device 102 controls the three-way valve 41 to switch the flow path to the pipe 42 side. The control device 102 determines whether the outside air temperature Ta is higher than an extremely low temperature (e.g., -15°C) (step S7). If it is (Yes), step S9 is performed. If it is not (No, -15°C or lower), the control device 102 performs a defrost preparatory operation (step S8). The defrost preparatory operation can be performed, for example, by the method described above. After the defrost preparatory operation, step S9 is performed.

[0033] In step S9, the control device 102 judges whether the outdoor air temperature Ta is less than 0°C. If so (Yes), the defrosting operation is started as follows (step S13). If the outdoor air temperature Ta is not less than 0°C (No in step S9), the control device 102 stops the pump 7 (step S10. The load is 0) and starts the defrosting operation (step S11). The defrosting operation can be performed by driving the refrigeration cycle 20. The defrosting operation is performed until a termination condition is satisfied (No), and when the termination condition is satisfied (Yes in step S12), the control is terminated. The termination condition is, for example, when at least one of the following is satisfied: when the temperature of the refrigerant flowing into the first heat exchanger 12 (or the refrigerant temperature at the outlet of the second heat exchanger 14) reaches a predetermined temperature, or when a predetermined time has elapsed since the start of the defrosting operation.

[0034] In step S13, the defrosting operation is started in the same manner as in step S12. At the start, the pump 7 is driven. After the defrosting operation is started by starting the operation of the refrigeration cycle 20, the control device 102 sets a timer (step S14). Next, the control device 102 drives the pump 7 at a load of, for example, 10% to 15% (low speed) of the rated load (step S15). Note that, in the example of the present disclosure, the rotation speed of the pump 7 during the defrosting operation is fixed to 10% to 15% (low speed) of the rated load, but may be changed as appropriate. In the first heat exchanger 12, the heat of the refrigerant that has become high temperature due to the operation of the refrigeration cycle 20 is transferred to the heat medium flowing through the pipe 17.

[0035] The control device 102 judges whether the elapsed time t, which is the timer set in step S14, exceeds the first predetermined time t1 (step S16). The first predetermined time t1 is a set value related to the drive timing of the pump 7 during the defrosting operation of the second heat exchanger 14. The first predetermined time t1 is a time for the heat medium in the pipe 44 installed outdoors to flow to the sensor 34 installed in the heat pump unit 100, for example, in order to measure the heat medium temperature in the pipe 44 installed outdoors by the sensor 34 installed in the heat pump unit 100, for example. The first predetermined time t1 is determined based on the distance between the pipe 44 (or the pipe 43) and the sensor 34, for example. This allows the temperature of the heat medium inside the pipe 44 installed outdoors to be measured by the sensor 34 installed in the heat pump unit 100, for example. However, the heat medium is mixed to some extent in the pipe 17 by driving the pump 7. For this reason, the sensor 34 cannot necessarily measure the temperature of the heat transfer medium present in the pipe 44 when the first predetermined time t1 is reached. However, once the first predetermined time t1 is exceeded, the heat transfer medium is mixed to a certain extent in the pipe 17, and the temperature can be measured stably.

[0036] In step S16, until the temperature exceeds the threshold (No), it is determined whether the defrost end condition is satisfied (step S17) in the same manner as in step S12, and until the condition is satisfied (No), step S16 is performed. On the other hand, if the condition is satisfied (Yes), the control ends.

[0037] If it is exceeded in step S16 (Yes), the control device 102 judges whether the inlet temperature Twi of the heat transfer medium measured by, for example, the sensor 34 exceeds a predetermined temperature Tws (step S18). The predetermined temperature Tws is a threshold value for switching between driving and stopping the pump 7, and is a fixed value determined, for example, by experiments in a factory or the like. The predetermined temperature Tws is also a temperature at which the heat transfer medium is unlikely to freeze even if the pump 7 is stopped. The predetermined temperature Tws can be set to a value, for example, between 0°C and 5°C. If it is exceeded in step S18 (Yes), the control device 102 stops the pump 7 (step S19. Load is 0).

[0038] Next, the control device 102 judges whether the elapsed time t exceeds a second predetermined time t2 (step S20). The second predetermined time t2 is a set value related to the timing of driving the pump 7 during the defrosting operation of the second heat exchanger 14. The second predetermined time t2 is a time during which the possibility of the heat medium freezing is low even if the pump 7 is stopped, and is, for example, a fixed value determined in advance by experiments in a factory or the like. The second predetermined time t2 is also a waiting time until the next temperature measurement. On the other hand, if the elapsed time t does not exceed the second predetermined time t2 in step S18 (No), step S20 is performed. As a result, the pump 7 continues to be driven, and the heat medium temperature in the pipe 17 increases.

[0039] In step S20, if the elapsed time t exceeds the second predetermined time t2 (Yes), the timer is reset (step S21), and steps S15 and after are performed again. On the other hand, if the elapsed time t does not exceed the second predetermined time t2 (No), the control device 102 judges whether the end condition is satisfied (step S22) in the same manner as in step S17 above. If the condition is satisfied (Yes), the control ends, and if the condition is not satisfied (No), step S20 is performed again.

[0040] FIG. 4 is a time chart of the water heater 1 of one embodiment. The horizontal axis represents time, and the vertical axis represents, from the top, the rotation speed of the compressor 11, the opening degree of the pressure reducing mechanism 13, the outlet refrigerant temperature of the second heat exchanger 14, the inlet heat medium temperature of the first heat exchanger 12, and the rotation speed of the pump 7. On the horizontal axis, the boiling operation is an operation in which hot water is stored in the tank 2 by using the refrigeration cycle 20. At this time, the three-way valve 41 connects the tank 2 to the piping 17. On the other hand, the defrosting operation is an operation in which the second heat exchanger 14 is defrosted by using the refrigeration cycle 20 as described above. At this time, the three-way valve 41 connects the piping 17 including the piping 42 so as to bypass the tank 2.

[0041] In the boiling operation, the rotation speed of the compressor 11 is set to a predetermined value greater than 0, and the opening degree of the pressure reducing mechanism 13 is also set to a predetermined value greater than 0. In the boiling operation, hot water W4 is generated in the tank 2 by utilizing heat from the outside air. Therefore, in the second heat exchanger 14 which exchanges heat with the outside air, for example in winter, the heat exchange capacity decreases due to frosting, and the outlet refrigerant temperature of the second heat exchanger 14 gradually decreases. In addition, the inlet heat medium temperature of the first heat exchanger 12 is maintained at a temperature at which it does not freeze, and the rotation speed of the pump 7 is also high.

[0042] For example, when the outlet refrigerant temperature of the second heat exchanger 14 reaches temperature Ts, a defrosting operation is started. In the defrosting operation, as described in the above step S6 (FIG. 2) and thereafter, the three-way valve 41 is connected to the pipe 42. In addition, the rotation speed of the compressor 11 is set to, for example, the maximum speed that can be set for the compressor 11, and the opening degree of the pressure reduction mechanism 13 is set to, for example, the maximum opening degree that can be set for the pressure reduction mechanism 13. Therefore, the refrigeration cycle 20 is operated at the maximum operable capacity, and as a result, a particularly high-temperature heat medium is supplied to the second heat exchanger 14, so that the outlet refrigerant temperature of the second heat exchanger 14 rises significantly. Note that when liquid water and frost (ice) coexist on the surface of the second heat exchanger 14, the outlet refrigerant temperature is constant.

[0043] After the defrosting operation starts, the rotation speed of the pump 7 decreases as described in steps S15, S19 (FIG. 2) and the like above, and then stops. Therefore, the amount of heat exchanged in the first heat exchanger 12 decreases due to the decrease in rotation speed, and the amount of heat exchanged becomes zero when the pump is stopped. Therefore, the inlet heat medium temperature of the first heat exchanger 12 gradually decreases during the defrosting operation. However, the pump 7 is driven only for a first predetermined time t1 to measure the temperature of the heat medium. When the pump 7 is driven, the heat medium is heated by the high-temperature refrigerant flowing through the refrigeration cycle 20, so the decrease in the inlet refrigerant temperature becomes smaller.

[0044] As the inlet refrigerant temperature of the first heat exchanger 12 drops, the inlet refrigerant temperature reaches temperature Tws. As described above, temperature Tws is the temperature at which the heat medium may freeze in the pipe 17. When the inlet refrigerant temperature reaches temperature Tws, the pump 7 is driven for the second predetermined time t2. This heats the heat medium in the first heat exchanger 12, and the temperature of the heat medium in the pipe 17 increases. After the second predetermined time t2 has elapsed, the pump 7 stops again. For example, when the outlet refrigerant temperature of the second heat exchanger 14 reaches temperature Te, the defrosting operation ends. After the defrosting operation, the boiling operation is performed again.

[0045] Fig. 5 is a flowchart for explaining a defrosting method executed in the hot water heater 1 of another embodiment, which is a flowchart executed following the control shown in Fig. 2. The same step numbers are used for the same steps as those shown in Fig. 2 and Fig. 3 above, and duplicated explanations are omitted. This is the same below.

[0046] The flow shown in FIG. 5 is executed by the control device 102. In the embodiment shown in FIG. 5, the control device 102 controls the pump 7 based on a temperature change of the heat medium at the inlet of the first heat exchanger 12 after the defrosting operation is started. Specifically, after the defrosting operation is started, a change in the inlet temperature of the heat medium to the first heat exchanger 12 (for example, a difference between a previous measured temperature and a current measured temperature) is calculated, and the pump 7 is driven based on the change. In this way, the pump 7 can be driven according to the actual environment in which the water heater 1 is installed, thereby further improving the energy saving performance and the prevention of freezing of the pipe 17. In the flow shown in FIG. 5, the pump 7 is driven based on the second predetermined time t2 set based on the temperature change.

[0047] In step S30, the timer is set in step S14 (FIG. 2). The timer is a time measurement function that the control device 102 has in advance. Furthermore, in step S30, the control device 102 sets the inlet temperature Twi of the heat medium to the first heat exchanger 12 that is measured first after the defrosting operation starts as the previous inlet temperature Twi0 (step S30). Next, steps S15 and the like are performed, and step S16 is followed by step S31.

[0048] In step S31, the control device 102 measures the inlet temperature Twi of the heat medium and calculates the difference ΔTwi (=Twi0-Twi). At the same time, the control device 102 sets the second predetermined time t2 according to the difference ΔTwi. The second predetermined time t2 is different from the embodiment shown in FIG. 3 in that the second predetermined time t2 is a value that can change for each difference ΔTwi. Therefore, the control device 102 sets the second predetermined time t2 based on the second predetermined relationship that associates the difference ΔTwi with the second predetermined time t2 and the calculated difference ΔTwi. The second predetermined relationship is, for example, a table, a formula, or the like, and can be determined by experiments in a factory, for example. The second predetermined relationship is, for example, held in advance by the control device 102.

[0049] After step S31, the inlet temperature Twi measured in step S31 is set as the previous inlet temperature Twi0 in the same manner as in step S30 (step S32). After that, the pump 7 is driven in the same manner as in the embodiment shown in FIG.

[0050] Fig. 6 is a flowchart illustrating a defrosting method executed in the water heater 1 of another embodiment. Fig. 7 is a flowchart illustrating a defrosting method executed in the water heater 1 of another embodiment, and is a flowchart performed following the control shown in Fig. 6. "C" and "D" shown in Fig. 7 indicate that the method is performed following "C" and "D" shown in Fig. 2.

[0051] The flow shown in FIG. 6 and FIG. 7 is for determining the set value for driving the pump 7 during the defrosting operation by a trial operation. Specifically, the control device 102 determines the third predetermined time t3 from the start of the defrosting operation to the start of driving the pump 7 based on the temperature difference of the heat medium between the inlet and the outlet of the first heat exchanger 12. In this way, for example, the third predetermined time t3 can be controlled according to the laying condition of the insulation material, etc., in the pipes 44, 43 installed outdoors, and the driving stop time of the pump 7 can be extended. That is, after the start of the defrosting operation, for example, if sufficient insulation performance is ensured in the pipes 44, 43, the heat medium is unlikely to freeze even if the pump 7 is stopped for a long time. On the other hand, if the insulation performance of the pipes 44, 43 is poor, the heat medium is likely to freeze, so it is preferable to shorten the time until the start of driving the pump 7. This makes it possible to achieve both highly efficient defrosting and suppression of freezing of the heat medium. In the embodiment shown in Figures 6 and 7, a third predetermined time t3 is determined, which is the time from the start of the defrosting operation, which is started with the pump 7 stopped, to the drive start time when the pump 7 is driven again.

[0052] After step S1, the control device 102 sets a difference ΔTw between the outlet temperature Two and the inlet temperature Twi of the first heat exchanger 12 (step S40). The difference ΔTw set here is a value calculated based on the outlet temperature Two and the inlet temperature Twi measured after step S1.

[0053] After step S2, the control device 102 sets a third predetermined time t3 in accordance with the difference ΔTw (step S41). The third predetermined time t3 is the time from the start of the defrosting operation with the pump 7 stopped (step S42) until the pump 7 starts to be driven. Therefore, the control device 102 sets the third predetermined time t3 to a time determined based on a third predetermined relationship that associates the difference ΔTw with the third predetermined time t3 and the calculated difference ΔTw. The third predetermined relationship is, for example, a table or a formula, and can be determined, for example, by experiments in a factory or the like. The third predetermined relationship is, for example, held in advance by the control device 102.

[0054] After step S41, steps S3 to S8 are performed. After step S7 or step S8, the control device 102 stops the pump 7 (step S42. Load is 0). Then, steps S9 and the like are performed. After step S13, the control device 102 sets a first timer (step S43) in the same manner as in step S14 (FIG. 2) described above. The first timer is a time measurement function that the control device 102 has in advance.

[0055] The control device 102 judges whether the elapsed time t from the setting of the first timer has passed the third predetermined time t3 (step S44). Until the third predetermined time t3 has passed (No), it is judged whether the defrosting end condition is satisfied as in step S12 (step S45), and after the third predetermined time t3 has passed (Yes), the control device 102 sets a second timer (step 46). The second timer is a time measurement function that the control device 102 has in advance.

[0056] Next, steps S15 to S22 are performed, but in the embodiment shown in Fig. 6 and Fig. 7, instead of step S21 (Fig. 3), the control device 102 resets the second timer (step S47). After step S22, the control device 102 resets the first timer (step S48).

[0057] Fig. 8 is a flowchart illustrating a defrosting method executed in a water heater 1 of another embodiment. Fig. 9 is a flowchart illustrating a defrosting method executed in a water heater 1 of another embodiment, and is a flowchart performed following the control shown in Fig. 8. "E" and "F" shown in Fig. 9 indicate that they are performed following "E" and "F" shown in Fig. 8.

[0058] The flow shown in Fig. 8 and Fig. 9 is similar to the embodiment shown in Fig. 6 and Fig. 7, in which the set value for driving the pump 7 during the defrosting operation is determined by a trial run. However, in the embodiment shown in Fig. 8 and Fig. 9, the control device 102 determines the first predetermined time t1 and the second predetermined time t2 based on the difference ΔTw, which is the temperature difference of the heat medium between the inlet and the outlet of the first heat exchanger 12. In this way, the number of set values ​​can be reduced, and the calculation process can be speeded up. As described above, the first predetermined time t1 and the second predetermined time t2 are both set values ​​related to the drive timing of the pump 7 during the defrosting operation of the second heat exchanger 14.

[0059] After steps S1, S40, and S2 are performed, the control device 102 sets the first predetermined time t1 and the second predetermined time t2 according to the difference ΔTw (step S50). The setting can be performed, for example, based on a fourth predetermined relationship that associates the difference ΔTw with the first predetermined time t1, and a fifth predetermined relationship that associates the difference ΔTw with the second predetermined time t2. The fourth predetermined relationship and the fifth predetermined relationship are, for example, tables, formulas, etc., and can be determined independently, for example, by experiments in a factory, etc. The fourth predetermined relationship and the fifth predetermined relationship are, for example, held in advance by the control device 102. After step S50, steps up to step S43 (setting the first timer) are performed in the same manner as in each of the above embodiments.

[0060] After step S43, the pump 7 is stopped (step S51; load is 0). Therefore, in the embodiment shown in Figs. 8 and 9, unlike the above-described embodiments, the pump 7 is operated until step S43. Next, it is determined whether or not the second predetermined time t2 has elapsed from the first timer set (step S20). The second predetermined time t2 used here is the set value set in step S50, as described above. Until it is exceeded (No), the control device 102 determines whether or not the defrost termination condition is satisfied (step S52) in the same manner as step S12, etc. If it is satisfied (Yes), the defrost operation is terminated. If it is not satisfied (No), step S20 is performed again.

[0061] After the second predetermined time t2 has elapsed in step S20, steps up to step S22 are performed in the same manner as in each of the above-described embodiments. In step S22, if the defrosting end condition is not satisfied (No), the control device 102 resets the first timer and the second timer (step S53). If the defrosting end condition is satisfied (Yes), the defrosting operation is ended.

[0062] FIG. 10 is a system diagram of the water heater 1 of another embodiment. In the embodiment shown in FIG. 10, the freeze suppression unit 21 is a heater 51 installed at least in the pipes 43, 44 (outdoor pipes). The heater 51 is executed by a control device 102 connected through an electric signal line shown by a dashed line in FIG. 10. In the illustrated example, the heater 51 is installed only in the pipes 43, 44 installed outdoors, but it may be installed in a part or all of the remaining part of the pipe 17. In this way, the part of the pipes 43, 44 that is most susceptible to the influence of the outside air can be directly heated, and the freezing of the heat transfer medium in the pipe 17 can be suppressed. The heater 51 is, for example, an electric heating wire that generates heat when electricity is applied, but is not limited to this.

[0063] Fig. 11 is a flowchart illustrating a defrosting method executed in a water heater of another embodiment. Fig. 12 is a flowchart illustrating a defrosting method executed in a water heater of another embodiment, which is a flowchart performed following the control shown in Fig. 11. "G" and "H" shown in Fig. 12 indicate that the method is performed following "G" and "H" shown in Fig. 11.

[0064] Similar to the embodiment shown in Figs. 2 and 3, the process is performed up to step S14. However, unlike the embodiment shown in Figs. 2 and 3, if the determination in step S7 is Yes, the pump 7 is stopped (step S10; load is 0). Therefore, the defrosting operation is started in a state in which the pump 7 is stopped (step S13). After the timer is set in step S14, the control device 102 turns on the heater 51 (step S60). As a result, the heater 51 is driven during the defrosting operation performed when the outside air temperature is below 0°C, and the heat transfer medium in the pipe 17 is heated. This prevents the heat transfer medium in the pipe 17 from freezing.

[0065] Next, steps S16, S18, etc. are performed, and if it is determined that "Yes" in step S18, the control device 102 turns off the heater 51 (step S61). This stops the temperature rise of the heat medium in the pipe 17. Next, steps S20 and after are performed, and the defrosting operation ends. In this way, the heat medium in the pipe 17 can be prevented from freezing even when the pump 7 is stopped during the defrosting operation.

[0066] FIG. 13 is a flow chart for explaining a defrosting method executed in the hot water heater 1 of another embodiment. As in the embodiment shown in FIG. 11 and FIG. 12, when the defrosting operation is started (step S13), the control device 102 drives the heater 51 (step S60). However, unlike the embodiment shown in FIG. 11 and FIG. 12, in the embodiment shown in FIG. 13, the control device 102 does not control to stop the heater 51 thereafter. Therefore, when the defrosting end condition is satisfied (Yes in step S22), the heater 51 is stopped and the defrosting operation is ended. In this way, the heat transfer medium in the pipe 17 can be prevented from freezing even when the pump 7 is stopped during the defrosting operation.

[0067] Fig. 14 is a system diagram of the water heater 1 in another embodiment. In the embodiment shown in Fig. 14, the freeze prevention unit 21 includes a drain plug 61 that drains the heat medium inside at least the pipes 43, 44 (outdoor pipes) to the outside. In this manner, freezing of the heat medium can be prevented in the pipes 43, 44 that are installed outdoors and therefore subject to the influence of outside air. In the illustrated example, the entire heat medium in the pipe 17 on the pipe 42 side of the pipe 17 including the pipes 43, 44 is drained through the drain plug 61. This makes it possible to prevent the heat medium from freezing inside the pipe 17.

[0068] The water heater 1 is equipped with a drain plug 61 and a relief valve 62. Opening and closing control of the drain plug 61 and the relief valve 62 is executed by a control device 102 connected through an electric signal line shown by a dashed line in Fig. 14. The drain plug 61 is installed at the lowest part of the piping 17. The drain plug 61 is installed, for example, outdoors so as to facilitate draining of water to the outside. The relief valve 62 is opened together with the drain plug 61, and is installed, for example, at the highest part of the piping 17. By opening the relief valve 62 together with the drain plug 61, air flows into the piping 17 through the relief valve 62 as the heat medium is drained, making it easier for the heat medium to flow out through the drain plug 61.

[0069] FIG. 15 is a flow chart for explaining a defrosting method executed in a hot water heater 1 of another embodiment. When a defrosting operation is started by the same flow as that of the embodiment shown in FIG. 13 above (step S13), the controller 102 fully closes the three-way valve 41 to cut off the connection of the pipe 17 (step S70). Next, the controller 102 opens the relief valve 62 and the drain plug 61 (step S71). As a result, the heat medium inside the pipe 17 is drained to the outside through the drain plug 61. Then, when the defrosting end condition is satisfied (Yes in step S22), the defrosting operation ends. In this manner, freezing of the heat medium in the pipe 17 can be suppressed.

[0070] Although not shown in the figures, when performing a heating operation after a defrosting operation, the control device 102 closes the drain valve 61 and then switches the piping 17 to the tank 2. This allows the air in the piping 17 to flow out through the relief valve 62, and instead allows the heat medium to flow in through the tank 2. After the air in the piping 17 has been discharged through the relief valve 62, the relief valve 62 is closed. The heat medium can be carried out, for example, through an inlet valve (not shown) provided in the piping 17.

[0071] In the above embodiments, the tank 2 is provided with a heat transfer tube (not shown) through which the water W3 flows. However, the tank 2 may be provided with a heat exchanger (not shown) for heating the water W3 (tap water, etc.). In this case, the hot water W2 extracted from the upper part of the tank 2 is heated by heat exchange with the water W3, and the heated water W3 can be supplied to the demand end as hot water W4. The present disclosure can also be applied to a water heater (direct water pressure type, not shown) of a type in which the hot water W1, which is the hot water W2 that has lost heat through heat exchange with the water W3, is returned to the lower part of the tank 2. The present disclosure can also be applied to a water heater (not shown) of a type in which the hot water W2 stored inside the tank 2 is directly supplied to a demand unit (mixer faucet) and the water W3 is supplied to the lower part of the tank 2. In this case, the water heater is a pressure reducing valve type that supplies the hot water W2 in the tank 2 to the supply end with the water pressure of the water W3. Therefore, the present disclosure is not limited to the above embodiments and can be applied to various types of water heaters. [Explanation of symbols]

[0072] 1. Water heater 10 Control device 100 Heat Pump Unit 101 Hot water storage unit 102 Control device 1021 CPU 1022 RAM 1023 ROM 11 Compressor 12 1st heat exchanger 13 Pressure reducing mechanism 14 Second heat exchanger 15 Fan 16 Piping 17 Piping 2 Tank 20 Refrigeration Cycle 21 Freeze suppression part 3 Piping 31 Sensors 32 Sensors 33 Sensors 34 Sensors 4 Piping 41 Three-way valve 42 Piping 43 Piping 44 Piping 46 Steps 51 Heater 61 Drain plug 62 Relief valve 7. Pump Medium motor t Elapsed time t1 First specified time t2 Second specified time t3 Third specified time Ta Outside air temperature Temperature Ts temperature Twi inlet temperature Twi0 Previous inlet temperature Two outlet temperature Tws temperature W1 Water W2 Hot water W3 Water W4 Hot water ΔTw difference ΔTwi difference

Claims

1. A tank for storing a liquid heat transfer medium; A compressor that compresses a refrigerant; a first heat exchanger for exchanging heat between the compressed refrigerant and a heat medium; a pressure reducing mechanism for reducing the pressure of the refrigerant; a second heat exchanger for exchanging heat between the decompressed refrigerant and outside air; a connecting pipe that connects the tank and the first heat exchanger so that the heat medium heated by the refrigerant in the first heat exchanger circulates between the tank and the first heat exchanger, and includes an outdoor pipe that is installed outdoors; a pump that is installed in the connecting pipe and circulates the heat medium through the connecting pipe; A freeze suppression unit that suppresses freezing of the heat medium in the connection pipe during a defrosting operation performed when the outside air temperature is lower than 0 ° C., The freeze suppression unit suppresses freezing of the heat medium in the connection pipe by driving the pump with the pressure reducing mechanism in an open state during the defrosting operation. A water heater characterized by the above.

2. The freeze suppression unit includes a control device that drives the pump at predetermined time intervals and detects the temperature of the heat medium in the connecting pipe. The water heater according to claim 1 .

3. The freeze suppression unit includes a control device that controls the pump based on a predetermined temperature of the heat medium in the connection pipe. The water heater according to claim 1 .

4. The predetermined temperature is the temperature of the heat medium at the inlet of the first heat exchanger. The water heater according to claim 3 .

5. The control device calculates the predetermined temperature based on an outside air temperature. The water heater according to claim 3 .

6. The control device calculates the predetermined temperature based on the temperature of the heat medium at the outlet of the first heat exchanger and the rotation speed of the compressor. The water heater according to claim 3 .

7. The control device controls the pump based on a temperature change of the heat medium at an inlet of the first heat exchanger after the defrosting operation is started. The water heater according to claim 2 .

8. A tank for storing a liquid heat transfer medium; A compressor that compresses a refrigerant; a first heat exchanger for exchanging heat between the compressed refrigerant and a heat medium; a pressure reducing mechanism for reducing the pressure of the refrigerant; a second heat exchanger for exchanging heat between the decompressed refrigerant and outside air; a connecting pipe that connects the tank and the first heat exchanger so that the heat medium heated by the refrigerant in the first heat exchanger circulates between the tank and the first heat exchanger, and includes an outdoor pipe that is installed outdoors; a pump that is installed in the connecting pipe and circulates the heat medium through the connecting pipe; A freeze suppression unit that suppresses freezing of the heat medium in the connection pipe during a defrosting operation performed when the outside air temperature is lower than 0 ° C., The freeze suppression unit includes a control device that drives the pump at predetermined time intervals and detects the temperature of the heat medium in the connection pipe, The control device determines a time from a start of a defrosting operation to a start time of driving the pump based on a temperature difference of the heat medium between an inlet and an outlet of the first heat exchanger. A water heater characterized by the above.

9. A tank for storing a liquid heat transfer medium; A compressor that compresses a refrigerant; a first heat exchanger for exchanging heat between the compressed refrigerant and a heat medium; a pressure reducing mechanism for reducing the pressure of the refrigerant; a second heat exchanger for exchanging heat between the decompressed refrigerant and outside air; a connecting pipe that connects the tank and the first heat exchanger so that the heat medium heated by the refrigerant in the first heat exchanger circulates between the tank and the first heat exchanger, and includes an outdoor pipe that is installed outdoors; a pump that is installed in the connecting pipe and circulates the heat medium through the connecting pipe; A freeze suppression unit that suppresses freezing of the heat medium in the connection pipe during a defrosting operation performed when the outside air temperature is lower than 0 ° C., The freeze suppression unit includes a control device that drives the pump at predetermined time intervals and detects the temperature of the heat medium in the connection pipe, The control device determines a set value related to a drive timing of the pump during a defrosting operation of the second heat exchanger based on a temperature difference of the heat medium between an inlet and an outlet of the first heat exchanger. A water heater characterized by the above.

10. The freeze suppression unit includes a control device that stops driving the pump when the outside air temperature is 0° C. or higher. The water heater according to claim 1 .

11. When the outside air temperature is −15° C. or lower, the freeze suppression unit performs a defrost preparation before the defrosting operation. Includes a control device that operates the device The water heater according to claim 1 .

12. During the defrosting operation, the pump is driven to suppress freezing of the heat transfer medium at predetermined intervals that are set to a value at which the possibility of freezing of the heat transfer medium is low even if the pump is stopped. The water heater according to claim 1 .

13. The freeze suppression unit performs the defrosting operation by increasing the opening degree of the pressure reducing mechanism to a value greater than the opening degree during the heating operation. The water heater according to claim 1 .

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