JP2022123529A - Hot water storage type water heater - Google Patents

Abstract

To provide a hot water storage type water heater which is advantageous in suppressing increase of an inflow water temperature of a heat pump toward the end of a boiling operation.SOLUTION: A hot water storage type water heater includes control means for controlling a boiling operation which is an operation for accumulating hot water which has flowed out of a heat pump unit in a hot water storage tank. In the boiling operation, the control means executes: a stabilizing operation for stabilizing a hot water tapping temperature which is the temperature of the hot water which has flowed out of the heat pump unit substantially at a given temperature; and an after-start operation for lowering the hot water tapping temperature than the given temperature after the start of the heat pump unit and before the stabilizing operation. The control means can select a first mode in which the given temperature becomes a first temperature, and a second mode in which the given temperature becomes a second temperature lower than the first temperature. Regarding the hot water tapping temperature change rate which is a value in which the increase of the hot water tapping temperature during the after-start operation is divided by the time of the after-start operation, the hot water tapping temperature change rate of the second mode is larger than the hot water tapping temperature change rate of the first mode.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to a hot water storage type hot water supply apparatus.

A hot water supply apparatus disclosed in Patent Document 1 below includes a heat pump unit, a hot water storage tank, a circulation pump, a boiling circuit, an outlet hot water temperature sensor, a target outlet hot water temperature determination section, and a pump activation control section. When the target hot water temperature is equal to or lower than a predetermined threshold, the pump activation control unit controls the hot water temperature from the heat pump unit to a first stage temperature lower than the target hot water temperature for a predetermined time. After that, two-stage start-up for controlling to the target hot water temperature is performed, and when the target hot water temperature exceeds a predetermined threshold value, the hot water temperature from the heat pump unit is controlled to the target hot water temperature from the beginning. Perform a single start.

JP 2018-091517 A

In a hot water storage type hot water supply apparatus, the lower the outlet hot water temperature in the boiling operation, the lower the stored hot water temperature of the hot water storage tank. Therefore, in order to store the same amount of stored hot water heat in the hot water storage tank, the lower the outlet hot water temperature in the boiling operation, the larger the required amount of heated hot water. When the amount of hot water to be boiled increases, the remaining hot water in the upper part of the hot water storage tank reaches the lower part of the hot water storage tank and flows into the heat pump at the end of one heating operation, and the temperature of the water entering the heat pump rises. . As a result, the COP (coefficient of performance) is lowered.

The present disclosure has been made to solve the problems described above, and an object thereof is to provide a hot water storage type hot water supply apparatus that is advantageous in suppressing an increase in the temperature of water entering the heat pump at the end of the boiling operation. do.

A hot water storage type hot water supply apparatus according to the present disclosure includes a hot water storage tank, a heat pump unit that heats water, and a control means that controls a boiling operation that is an operation for accumulating hot water flowing out of the heat pump unit in the hot water storage tank, In the boiling operation, the control means performs a stable operation in which the outlet hot water temperature, which is the temperature of the hot water flowing out of the heat pump unit, is stabilized at a substantially constant temperature, and a stable operation in which the outlet hot water temperature is stabilized after the heat pump unit is started and before the stable operation. A first mode in which the constant temperature is the first temperature and a second mode in which the constant temperature is a second temperature lower than the first temperature are controlled. The means can be selected, and the outlet heated water temperature change rate of the second mode is higher than the outlet heated water temperature change rate of the first mode, which is the value obtained by dividing the rise in the outlet heated water temperature during operation after startup by the time of operation after startup. The outlet hot water temperature change rate is large.
Further, the hot water storage type hot water supply apparatus according to the present disclosure includes a hot water storage tank, a heat pump unit that heats water, and a heat pump unit that allows water flowing out of the hot water storage tank to flow into the heat pump unit and hot water flowing out of the heat pump unit to flow into the hot water storage tank. a circulation pump for circulating water in the heat pump unit; and a control means for controlling a boiling operation in which the hot water flowing out of the heat pump unit is accumulated in the hot water storage tank. A stable operation is performed to stabilize the temperature of the discharged hot water, which is the temperature of the heated hot water, at a substantially constant temperature, and a post-startup operation is performed to lower the temperature of the discharged hot water below a certain temperature after the start of the heat pump unit and before stable operation. The control means can select a first mode in which the constant temperature is the first temperature and a second mode in which the constant temperature is a second temperature lower than the first temperature. Regarding the pump rotation speed change rate, which is the value obtained by dividing the decrease in the rotation speed of the circulation pump by the operation time after startup, the pump rotation speed change rate in the second mode is larger than the pump rotation speed change rate in the first mode. is.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a hot water storage type hot water supply apparatus that is advantageous in suppressing an increase in the temperature of water entering the heat pump at the end of the boiling operation.

1 is a diagram showing a hot water storage type hot water supply apparatus according to Embodiment 1. FIG. 1 is a functional block diagram of a hot water storage type hot water supply apparatus according to Embodiment 1. FIG. 7 is a graph showing an example of the relationship between the heat pump outlet hot water temperature and time in operation after startup and in stable operation. 7 is a graph showing an example of the relationship between the number of revolutions of the circulation pump and time in operation after startup and in stable operation. 4 is a flow chart showing an example of processing executed when starting a boiling operation; FIG. 4 is a diagram schematically showing an example of temperature distribution in the hot water storage tank before the start of the boiling operation;

Embodiments will be described below with reference to the drawings. Elements that are common or correspond to each figure are denoted by the same reference numerals, and their explanations are simplified or omitted. In the following description, the terms "water", "hot water", and "hot water" basically mean liquid water, and can include low temperature water to high temperature water.

Embodiment 1.
FIG. 1 shows a hot water storage type hot water supply apparatus 1 according to Embodiment 1. As shown in FIG. As shown in FIG. 1, a hot water storage type hot water supply apparatus 1 of the present embodiment includes a heat pump unit 2 for heating water and a tank unit 3 having a hot water storage tank 11 . The heat pump unit 2 is arranged outdoors. The tank unit 3 is arranged outdoors or indoors. Although the heat pump unit 2 and the tank unit 3 are separated in the present embodiment, the hot water storage type hot water supply apparatus according to the present disclosure may have a structure in which the heat pump unit 2 and the tank unit 3 are integrated.

The heat pump unit 2 includes a compressor 4 for compressing refrigerant, a refrigerant-water heat exchanger 5, an expansion valve 6, an evaporator 7, and a heat pump controller 9 inside a housing. Substances used as refrigerants are not particularly limited, but CO ₂ , HFCs, HCs, HFOs, etc. can be used, for example. The refrigerant-water heat exchanger 5 comprises a refrigerant channel 5a and a water channel 5b. Heat is exchanged between the coolant passing through the coolant channel 5a and the water passing through the water channel 5b. A refrigerant circuit is formed by connecting the compressor 4, the refrigerant flow path 5a, the expansion valve 6, and the evaporator 7 via refrigerant pipes.

The expansion valve 6 corresponds to a decompression device that decompresses and expands the high-pressure refrigerant. The evaporator 7 exchanges heat between the refrigerant and outside air taken in from outside the heat pump unit 2 . The evaporator 7 evaporates the refrigerant with the heat of outside air. The heat pump unit 2 includes a blower 10 that blows outside air so that it flows to the evaporator 7 .

The tank unit 3 includes a hot water storage tank 11, a circulation pump 13, a hot water mixing valve 14, and a tank controller 16 inside a housing.

The hot water storage tank 11 stores hot water heated by the heat pump unit 2 . The hot water storage tank 11 is covered with a heat insulating material (not shown). In the hot water storage tank 11, temperature stratification is formed in which the upper layer side is a high temperature range and the lower layer side is a low temperature range due to the difference in the specific gravity of water due to the difference in temperature.

Hot water storage tank 11 in the present embodiment is configured by a single container. As a modification, the hot water storage tank 11 may have a structure in which a plurality of containers are connected in series via pipes. In the plurality of containers, the lower part of the container on the high temperature side, that is, the upper side, communicates with the upper part of the container that is on the lower temperature side, that is, the lower side with respect to the container.

A water supply end 17 provided in the tank unit 3 is connected to an external water supply pipe (not shown) through which water supplied from a water source such as tap water passes. The downstream side of the water supply end 17 branches into a first water supply pipe 18 and a second water supply pipe 19 . The first water supply pipe 18 is connected to the lower portion of the hot water storage tank 11 . The hot water mixing valve 14 has an inlet a, an inlet b, and an outlet c. The second water supply pipe 19 is connected to the inlet b of the hot water mixing valve 14 .

A hot water supply end 20 provided in the tank unit 3 is connected to an external hot water supply pipe (not shown) leading to a hot water supply destination such as a shower, a faucet, or a bathtub. The hot water pipe 21 connects the upper portion of the hot water storage tank 11 to the inlet a of the hot water mixing valve 14 . The hot water pipe 22 connects the outflow port c of the hot water mixing valve 14 to the hot water supply end 20 .

The hot water mixing valve 14 mixes high temperature water supplied from the upper part of the hot water storage tank 11 through the hot water supply pipe 21 and low temperature water supplied from the second water supply pipe 19 . The mixed hot water is sent to the hot water supply destination through the hot water supply pipe 22 and the external hot water supply pipe. By adjusting the mixing ratio of the high-temperature water and the low-temperature water with the hot water supply mixing valve 14, the temperature of the hot water supply can be adjusted. When the high temperature water stored in the upper part of the hot water storage tank 11 flows out to the hot water supply pipe 21 , the same amount of low temperature water flows into the lower part of the hot water storage tank 11 from the first water supply pipe 18 . In this way, the hot water storage tank 11 is kept full.

A lower portion of the hot water storage tank 11 is connected to an intake port of the circulation pump 13 via a tank lower passage 25 . The heat pump unit 2 and the tank unit 3 are connected to each other by a heat pump water inlet pipe 23 and a heat pump hot water outlet pipe 24 . The discharge port of the circulation pump 13 is connected to the inlet of the water flow path 5b of the refrigerant-water heat exchanger 5 via the heat pump water inlet pipe 23. As shown in FIG. The outlet of the water flow path 5b of the refrigerant-water heat exchanger 5 is connected to the upper part of the hot water storage tank 11 via the heat pump hot water supply pipe 24 and the tank upper passage 26 in the tank unit 3.

In the following description, the temperature of water flowing into the heat pump unit 2 will be referred to as "heat pump inlet water temperature", and the temperature of hot water flowing out of the heat pump unit 2 will be referred to as "heat pump hot water outlet temperature". The heat pump unit 2 includes a discharge temperature sensor 29 that detects the compressor discharge temperature, which is the temperature of the refrigerant discharged from the compressor 4, an inlet water temperature sensor 30 that detects the heat pump inlet water temperature, and a heat pump outlet hot water temperature. A temperature sensor 31 and an outside air temperature sensor 32 for detecting outside air temperature are installed. In the illustrated example, an inlet water temperature sensor 30 is arranged at the inlet of the water channel 5b, and an outlet hot water temperature sensor 31 is arranged at the outlet of the water channel 5b. Instead of this example, the incoming water temperature sensor 30 and the outgoing hot water temperature sensor 31 may be arranged in the tank unit 3, for example.

The hot water storage tank 11 is provided with a plurality of stored hot water temperature sensors 33 arranged at different height positions. These hot water temperature sensors 33 can detect the water temperature distribution in the hot water tank 11 in the vertical direction. Although four stored hot water temperature sensors 33 are provided in the illustrated example, the number of stored hot water temperature sensors 33 is not limited to this. The water supply temperature sensor 34 detects the water supply temperature, which is the temperature of the water supplied from the water source to the water supply end 17 .

The heat pump controller 9 and the tank controller 16 are connected by wire or wirelessly so as to be capable of bidirectional data communication. The heat pump controller 9 and the tank controller 16 correspond to control means for controlling the operation of the hot water storage type hot water supply apparatus 1 . At least one of the heat pump controller 9 and the tank controller 16 may have a timer function for managing time. At least one of the heat pump controller 9 and the tank controller 16 may have a calendar function for managing dates.

In the present embodiment, heat pump controller 9 and tank controller 16 cooperate to control the operation of hot water storage type hot water supply apparatus 1 . In the present embodiment, the processing described as being executed by the heat pump controller 9 may be executed by the tank controller 16 instead of the heat pump controller 9, or may be executed by the heat pump controller 9 and the tank controller 16 in cooperation. may Further, the processing described as executed by the tank controller 16 may be executed by the heat pump controller 9 instead of the tank controller 16, or may be executed by the heat pump controller 9 and the tank controller 16 in cooperation.

The present disclosure is not limited to a configuration in which a plurality of controllers cooperate to control the operation of the storage-type hot water supply apparatus 1 as in the illustrated example, and the operation of the storage-type hot water supply apparatus 1 is controlled by a single controller. It may be configured to be

The hot water storage type hot water supply apparatus 1 of the present embodiment includes a remote controller 50 . The remote control 50 and the tank controller 16 are connected by wire or wirelessly so as to be capable of bidirectional data communication. The remote control 50 may be installed in a room such as a kitchen or a bathroom, for example. The remote controller 50 has a function of receiving user's operations related to operation commands, setting value changes, and others. The remote control 50 corresponds to a user interface. Although not shown, the remote controller 50 may include a display for displaying information about the state of the storage-type hot water supply apparatus 1, an operation unit such as a user-operated switch, a speaker, a microphone, and the like. The hot water storage type hot water supply apparatus 1 may include a plurality of remote controllers 50 installed at different locations. Instead of remote control 50 or in addition to remote control 50 , other devices such as smart phones, tablet terminals, smart speakers, and televisions may be available as user interfaces for storage-type hot water supply apparatus 1 . The other device and tank controller 16 may communicate via a communication line such as the Internet or a local area network.

FIG. 2 is a functional block diagram of hot water storage type hot water supply apparatus 1 according to Embodiment 1. As shown in FIG. As shown in FIG. 2, each of the compressor 4, expansion valve 6, blower 10, discharge temperature sensor 29, incoming water temperature sensor 30, outgoing hot water temperature sensor 31, and outside air temperature sensor 32 is electrically connected to the heat pump controller 9. It is connected to the. Circulation pump 13 , hot water mixing valve 14 , stored hot water temperature sensor 33 , and feed water temperature sensor 34 are each electrically connected to tank controller 16 .

Each function of the heat pump controller 9 may be implemented by a processing circuit. The processing circuitry of the heat pump controller 9 may comprise at least one processor 9a and at least one memory 9b. At least one processor 9a may implement each function of heat pump controller 9 by reading and executing a program stored in at least one memory 9b. The processing circuitry of heat pump controller 9 may comprise at least one piece of dedicated hardware.

Each function of the tank controller 16 may be implemented by processing circuitry. The processing circuitry of tank controller 16 may include at least one processor 16a and at least one memory 16b. The at least one processor 16a may implement the respective functions of the tank controller 16 by reading and executing programs stored in the at least one memory 16b. The processing circuitry of tank controller 16 may comprise at least one piece of dedicated hardware.

The heat pump controller 9 can control the rotation speed of the compressor 4 to be variable, for example, by inverter control. The tank controller 16 can control the rotation speed of the circulation pump 13 to be variable, for example, by inverter control. In the present disclosure, "rotational speed" means the rotational speed per unit time, and corresponds to the rotational speed.

The hot water storage type hot water supply device 1 can perform the boiling operation. The boiling operation is an operation for accumulating hot water flowing out of the heat pump unit 2 in the hot water storage tank 11 . The heat pump controller 9 and tank controller 16 control the boiling operation. The heat pump controller 9 and the tank controller 16 control operations during the boiling operation, for example, as follows. Compressor 4 and circulation pump 13 are driven. The high-temperature and high-pressure refrigerant compressed by the compressor 4 flows into the refrigerant channel 5 a of the refrigerant-water heat exchanger 5 . The coolant flowing through the coolant channel 5a is cooled by the water flowing through the water channel 5b. The refrigerant that has passed through the refrigerant passage 5a is decompressed by the expansion valve 6 to become a low-temperature, low-pressure refrigerant. This low-temperature, low-pressure refrigerant flows into the evaporator 7 . In the evaporator 7, heat is exchanged between the outside air flowing by the blower 10 and the low-temperature, low-pressure refrigerant. The refrigerant is evaporated by being heated by the outside air in the evaporator 7 . The evaporated refrigerant is sucked into the compressor 4 . Thus, a refrigeration cycle is formed.

The water in the lower part of the hot water storage tank 11 flows through the tank lower passage 25, the circulation pump 13, and the heat pump water inlet pipe 23 into the water flow path 5b of the refrigerant-water heat exchanger 5. In the refrigerant-water heat exchanger 5, the water flowing through the water flow path 5b is heated by the refrigerant flowing through the refrigerant flow path 5a to become hot water. The heated high-temperature hot water flows into the upper portion of the hot water storage tank 11 through the heat pump hot water outlet pipe 24 and the tank upper passage 26 . With such a boiling operation, high-temperature water is gradually accumulated in the hot water storage tank 11 from top to bottom, thereby increasing the amount of hot water stored in the hot water storage tank 11 .

The flow rate of water passing through the heat pump unit 2 is hereinafter referred to as "boiling water flow rate". The boiling water flow rate corresponds to the volumetric flow rate of water flowing through the water flow path 5b. In this embodiment, the tank controller 16 adjusts the rotation speed of the circulation pump 13, thereby adjusting the boiling water flow rate. The higher the rotation speed of the circulation pump 13, the higher the boiling water flow rate and the lower the temperature of hot water discharged from the heat pump. The target value of the heat pump outlet hot water temperature during the boiling operation is hereinafter referred to as "target outlet hot water temperature". The tank controller 16 can feedback-control the rotational speed of the circulation pump 13 so that the temperature of the heat pump discharged hot water detected by the discharged hot water temperature sensor 31 becomes equal to the target discharged hot water temperature.

The heating capacity [W] of the heat pump unit 2 is the amount of heat given to water by the heat pump unit 2 per unit time. The heat pump controller 9 may adjust the rotational speed of the compressor 4 so that the heating capacity of the heat pump unit 2 becomes equal to the target value. The heat pump controller 9 may adjust the opening degree of the expansion valve 6 so that the compressor discharge temperature detected by the discharge temperature sensor 29 becomes equal to the target value. As the opening degree of the expansion valve 6 increases, the refrigerant flow rate increases and the compressor discharge temperature decreases.

Here, the relationship between the rotation speed Fp of the circulation pump 13, the boiling water flow rate Gw [L/min], and the heat pump hot water temperature Two will be described. The rotational speed Fp of the circulation pump 13 and the boiling water flow rate Gw are in a proportional relationship. Further, when the heating capacity of the heat pump unit 2 is Qhp [kW] and the temperature of water entering the heat pump is Twi [°C], the following relationship holds. However, ρw [kg/m ³ ] is the density of water, and Cpw [kJ/kgK] is the specific heat of water.
Qhp=Gw/(60×1000)×ρw×Cpw×(Two−Twi)
Therefore, assuming that the heating capacity Qhp is constant, the boiling water flow rate Gw and the heat pump hot water temperature Two are in an inversely proportional relationship.

In the boiling operation, the heat pump controller 9 and the tank controller 16 first perform post-startup operation after the heat pump unit 2 is started, and then perform stable operation after the post-startup operation. The stable operation is an operation that stabilizes the temperature of the hot water discharged from the heat pump at a substantially constant temperature. Hereinafter, this "constant temperature" is referred to as "target stored hot water temperature". During stable operation, the tank controller 16 adjusts the rotational speed of the circulation pump 13 so that the temperature of the heat pump discharged hot water detected by the discharged hot water temperature sensor 31 becomes equal to the target stored hot water temperature. The post-startup operation is an operation in which the heat pump hot water outlet temperature is made lower than the target hot water storage temperature. During operation after startup, the tank controller 16 adjusts the rotation speed of the circulation pump 13 so that the temperature of the heat pump discharged hot water detected by the discharged hot water temperature sensor 31 becomes equal to the target discharged hot water temperature which is lower than the target stored hot water temperature.

Immediately after the heat pump unit 2 starts up, the compressor 4, the refrigerant-water heat exchanger 5, refrigerant pipes, etc. are not sufficiently warmed. If an attempt is made to raise the temperature of the hot water discharged from the heat pump in such a state, the rotation speed of the circulation pump 13 is rapidly lowered to lower the boiling water flow rate. As a result, the actual temperature of hot water discharged from the heat pump may overshoot the target temperature, or hunting may occur, thereby lowering the COP. On the other hand, in the present embodiment, by performing the post-startup operation in which the heat pump hot water output temperature is lower than the target hot water storage temperature before the stable operation, such a decrease in COP can be reliably suppressed.

The tank controller 16 can select a first mode in which the target stored hot water temperature is the first temperature and a second mode in which the target stored hot water temperature is a second temperature lower than the first temperature. In the present disclosure, the value obtained by dividing the rise in the heat pump outlet hot water temperature during operation after start-up by the time of operation after start-up is referred to as "outlet hot water temperature change rate." The heat pump controller 9 and the tank controller 16 perform control so that the outlet heated water temperature change rate in the second mode is greater than the outlet heated water temperature change rate in the first mode.

For example, in the first mode, the rate of change in outlet heated water temperature is ΔTwo1/t1, where ΔTwo1 is the rise in the outlet hot water temperature of the heat pump during the operation after startup, and t1 is the operation time after startup. In the second mode, the rate of change in outlet heated water temperature is .DELTA.Two2/t2, where .DELTA.Two2 is the amount of rise in the heat pump outlet hot water temperature during operation after startup, and t2 is the time of operation after startup. In this case, the heat pump controller 9 and the tank controller 16 perform control so that the following equation holds.
ΔTwo1/t1<ΔTwo2/t2

FIG. 3 is a graph showing an example of the relationship between the outlet hot water temperature of the heat pump and time during operation after start-up and stable operation. In FIG. 3, the dashed line graph indicates the target outlet heated water temperature in the first mode, and the solid line graph indicates the target outlet heated water temperature in the second mode. In the example of FIG. 3, the target stored hot water temperature in the first mode is 65°C, and the target stored hot water temperature in the second mode is 55°C. The example of FIG. 3 will be described below.

The temperature of hot water discharged from the heat pump immediately after the compressor 4 is started may be less than 40°C. In the example of FIG. 3, after the compressor 4 is started, the starting point of the post-startup operation is the time when the temperature of the hot water discharged from the heat pump reaches 40°C. The time of operation after start-up in the first mode is indicated by t1 in FIG. The target hot water outlet temperature in the first mode of operation after startup increases from 40° C. at the start of the operation after startup to 65° C. at the end of the operation after startup at a constant rate per hour. During the operation after start-up of the first mode, the tank controller 16 adjusts the rotation speed of the circulation pump 13 so that the temperature of the heat pump discharged hot water detected by the discharged hot water temperature sensor 31 rises in accordance with the rise of the target discharged hot water temperature. . The outlet heated water temperature change rate ΔTwo1/t1 in the first mode is expressed by (65° C.-40° C.)/t1, that is, 25° C./t1.

The time of operation after start-up in the second mode is indicated by t2 in FIG. t2<t1. The target hot water outlet temperature in the second mode of operation after startup increases from 40° C. at the start of the operation after startup to 55° C. at the end of the operation after startup at a constant rate per hour. The inclination of the rise of the target hot water temperature in the second mode of operation after startup is greater than the inclination of the rise of the target hot water temperature in the first mode of operation after startup. During the operation after startup in the second mode, the tank controller 16 causes the temperature of the heat pump discharged hot water detected by the discharged hot water temperature sensor 31 to follow the target discharged heated water temperature that rises at a greater slope than in the operation after startup in the first mode. The rotation speed of the circulating pump 13 is adjusted as follows. The outlet heated water temperature change rate ΔTwo2/t2 in the second mode is expressed by (55° C.-40° C.)/t2, that is, 15° C./t2.

The value of the heat pump discharged hot water temperature at which the tank controller 16 starts controlling the heat pump discharged hot water temperature is hereinafter referred to as the "starting point discharged hot water temperature". The origin outlet heated water temperature in the example of FIG. 3 is 40.degree. The starting hot water outlet temperature may be, for example, a low temperature within a range that can be used for hot water supply. The starting hot water outlet temperature is not limited to 40°C, and may be, for example, 38°C or 42°C.

After the compressor 4 is started, the heat pump controller 9 and the tank controller 16 control the rotation speed of the compressor 4 and the rotation of the circulation pump 13 until the temperature of the hot water discharged from the heat pump reaches the starting hot water temperature. The numbers may be fixed at predetermined values for operation. After the heat pump discharged hot water temperature reaches the starting point discharged hot water temperature, the tank controller 16 may start feedback control to adjust the rotational speed of the circulation pump 13 so that the heat pump discharged hot water temperature becomes equal to the target discharged hot water temperature.

In the above example, the time at which the hot water outlet temperature of the heat pump reaches the starting point hot water temperature has been described as the start time of the post-startup operation. good.

At the end of the boiling operation, there is a possibility that residual hot water in the upper part of the hot water storage tank 11 before the start of the boiling operation moves to the lower part of the hot water storage tank 11 and flows into the heat pump unit 2 . When the remaining hot water flows into the heat pump unit 2 in this way, the heat pump inlet water temperature rises and becomes higher than the feed water temperature. The COP (coefficient of performance) of the heat pump unit 2 decreases as the heat pump inlet water temperature increases.

In the present disclosure, the total volume of water that passes through the heat pump unit 2 during boiling operation is referred to as "boiling amount of hot water". The amount of hot water to be boiled corresponds to the volume of hot water flowing from the heat pump unit 2 to the upper portion of the hot water storage tank 11 during the boiling operation. Assuming that the amount of heat to be added to the hot water storage tank 11 during the boiling operation is the same, the lower the target stored hot water temperature, the greater the required amount of hot water to be boiled. As the amount of hot water to be boiled increases, the downward movement amount of the remaining hot water in the hot water storage tank 11 increases, so that the heat pump inlet water temperature tends to increase and the COP tends to decrease at the end of the boiling operation.

According to the present embodiment, the second mode can be selected when the target stored hot water temperature is low. In the second mode, the outlet heated water temperature change rate is higher than in the first mode, so the outlet heated water temperature of the heat pump can be raised in a shorter period of time than in the first mode. Therefore, in the second mode, it is possible to shorten the time for hot water having a temperature lower than the target hot water storage temperature to flow into the hot water storage tank 11, thereby reducing an increase in the amount of hot water to be boiled. Therefore, in the present embodiment, even when the target stored hot water temperature is low, the heat pump inlet water temperature is less likely to rise in the final stage of the boiling operation, which is advantageous in preventing the COP from lowering.

If the target stored hot water temperature is set low, the amount of stored hot water heat that can be stored in the hot water storage tank 11 becomes small, so there is a possibility that the number of boiling operations per day will increase. In the present embodiment, even if the target hot water storage temperature is low and the number of times the boiling operation is performed per day is large, the boiling operation in the second mode is performed to ensure an increase in the amount of hot water to be boiled. can be suppressed to

Further, according to the present embodiment, when the target stored hot water temperature is high, the first mode can be selected. When the target stored hot water temperature is high, overshooting or hunting of the heat pump discharged hot water temperature is more likely to occur during the period from when the heat pump unit 2 is started until it warms up, compared to when the target stored hot water temperature is low. On the other hand, in the first mode, the rate of change in outlet hot water temperature during operation after startup is smaller than in the second mode, and the change in the outlet hot water temperature of the heat pump is gentle. Therefore, in the first mode, it is possible to reliably suppress the occurrence of overshooting or hunting of the temperature of the hot water discharged from the heat pump, which is advantageous for improving the COP. Therefore, even if the amount of hot water to be boiled increases due to a longer operation time after startup, highly efficient operation can be performed in total.

FIG. 4 is a graph showing an example of the relationship between the number of revolutions of the circulation pump 13 and time in operation after startup and in stable operation. Hereinafter, the rotation speed of the circulation pump 13 may be referred to as "pump rotation speed". In FIG. 4, the dashed-dotted line graph indicates the pump rotation speed in the first mode, and the solid line graph indicates the pump rotation speed in the second mode. In the post-startup operation, the tank controller 16 gradually lowers the pump rotation speed, thereby gradually raising the temperature of the hot water discharged from the heat pump. In stable operation, the tank controller 16 keeps the pump rotation speed substantially constant so that the heat pump outlet hot water temperature is kept equal to the target hot water storage temperature.

In the present disclosure, the value obtained by dividing the decrease in the pump rotation speed during operation after start-up by the time of operation after start-up is referred to as "pump rotation speed change rate." The heat pump controller 9 and the tank controller 16 perform control so that the pump rotation speed change rate in the second mode is greater than the pump rotation speed change rate in the first mode.

In the example of FIG. 4, the pump rotation speed during stable operation in the first mode is the stable rotation speed Fp1. The pump rotation speed during the operation after startup in the first mode decreases at a constant rate per hour from the initial rotation speed Fps at the start of the operation after startup to the stable rotation speed Fp1 at the end of the operation after startup. . The pump rotation speed during stable operation in the second mode is the stable rotation speed Fp2. Here, Fp2>Fp1. The pump rotation speed during the operation after startup in the second mode decreases at a constant rate per hour from the initial rotation speed Fps at the start of the operation after startup to the stable rotation speed Fp2 at the end of the operation after startup. . In the example of FIG. 4, the second mode pump rotation speed change rate represented by (Fps−Fp2)/t2 is the first mode pump rotation speed change represented by (Fps−Fp1)/t1. Greater than rate.

In the present embodiment, since the second mode has a higher rate of change in the pump rotation speed than the first mode, the pump rotation speed can be changed to a stable rotation speed in a shorter time than in the first mode. Therefore, in the second mode, it is possible to shorten the time for hot water having a temperature lower than the target hot water storage temperature to flow into the hot water storage tank 11, thereby reducing an increase in the amount of hot water to be boiled. Therefore, in the present embodiment, even when the target stored hot water temperature is low, the heat pump inlet water temperature is less likely to rise in the final stage of the boiling operation, which is advantageous in preventing the COP from lowering.

The tank controller 16 may select the first mode of boiling operation when the target stored hot water temperature is equal to or higher than the threshold, and may select the second mode of boiling operation when the target stored hot water temperature is lower than the threshold. . In this case, the temperature equal to or higher than the threshold corresponds to the first temperature, and the temperature lower than the threshold corresponds to the second temperature. The threshold may be 65°C. In the present disclosure, the threshold is not limited to 65°C, and may be 60°C or 70°C, for example.

The target stored hot water temperature corresponds to the main temperature of the hot water stored in the hot water storage tank 11 by the boiling operation. In the present embodiment, the compressor 4, the refrigerant-water heat exchanger 5, the refrigerant pipes, etc. are sufficiently heated during operation after startup, and their temperatures rise. This makes it possible to stably maintain the temperature of hot water discharged from the heat pump at the target stored hot water temperature during stable operation.

The temperature of the hot water flowing into the hot water storage tank 11 may be slightly lower than the temperature of the hot water discharged from the heat pump due to heat radiation from the heat pump hot water discharge pipe 24 or the like. If this temperature drop is taken into consideration, the tank controller 16 may control the rotation speed of the circulation pump 13 so that the temperature of the hot water discharged from the heat pump stabilizes at a temperature higher than the target hot water storage temperature by a predetermined temperature. good.

The tank controller 16 can calculate the heat quantity of hot water stored in the hot water storage tank 11 using the temperature distribution along the vertical direction in the hot water storage tank 11 detected by the hot water storage temperature sensor 33 . The tank controller 16 calculates the current hot water heat quantity at regular intervals. The stored hot water heat quantity corresponds to the heat quantity that can be used for hot water supply. When the current stored hot water heat amount falls below the boiling start threshold, the heat pump controller 9 and the tank controller 16 start the boiling operation. When the hot water heat quantity in the hot water storage tank 11 reaches the target hot water heat quantity, the heat pump controller 9 and the tank controller 16 terminate the boiling operation.

The tank controller 16 may detect the hot water supply load by detecting the temperature and amount of hot water flowing through the hot water supply pipe 21 or the hot water supply pipe 22 with a sensor (not shown). The tank controller 16 may determine the target hot water storage heat amount based on the learning result obtained by statistically processing the hot water supply load for the past several days. For example, the tank controller 16 may calculate the target hot water storage heat amount as the heat amount required for the hot water supply load predicted from now until a certain time.

In the example shown in FIG. 3, it is assumed that the target outlet heated water temperature during the operation after starting rises at a constant rate per hour. As a modification, the target outlet heated water temperature may be increased stepwise in one or more steps during operation after startup.

In the example shown in FIG. 4, it is assumed that the pump rotation speed during operation after startup decreases at a constant rate per hour. Alternatively, the pump speed may be stepped down in one or more steps during post-startup operation.

The tank controller 16 may further select a third mode. The target stored hot water temperature in the third mode is the same as in the second mode, which is the relatively low second temperature. The outlet heated water temperature change rate in the third mode is smaller than the outlet heated water temperature change rate in the second mode. The outlet heated water temperature change rate value in the third mode may be equal to the outlet heated water temperature change rate value in the first mode. The pump rotation speed change rate in the third mode is smaller than the pump rotation speed change rate in the second mode. The pump speed change rate value for the third mode may be equal to the pump speed change rate value for the first mode.

The amount of heat added to the hot water storage tank 11 in one boiling operation is hereinafter referred to as "boiling heat amount". The boiling heat amount corresponds to the difference between the target stored hot water heat amount and the stored hot water heat amount in the hot water storage tank 11 before the start of the boiling operation.

The tank controller 16 may select the third mode instead of the second mode when the target stored hot water temperature corresponds to the second temperature and the target stored hot water heat amount or boiling heat amount is relatively small. When the target hot water storage heat quantity or boiling heat quantity is relatively small, the amount of hot water to be boiled is small, so the amount of downward movement of the remaining hot water in the hot water storage tank 11 is small. Therefore, even in the final stage of the boiling operation, the temperature of water entering the heat pump is less likely to increase, and the COP is less likely to decrease. Therefore, even if the boiling operation in the third mode is executed instead of the second mode, it is possible to prevent the temperature of the water entering the heat pump from rising at the end of the boiling operation. The third mode has a higher COP during operation after startup than the second mode. Therefore, by selecting the third mode instead of the second mode, the COP during operation after startup is improved.

FIG. 5 is a flowchart showing an example of processing executed when starting the boiling operation. The flowchart of FIG. 5 will be described below. Before starting the boiling operation, in step S101, the tank controller 16 sets a target stored hot water temperature. The tank controller 16 may change the target stored hot water temperature according to at least one of the hot water supply set temperature set by the user using the remote control 50 and the amount of heat to be boiled in one boiling operation.

The late-night time zone is a time zone in which the power rate unit price is low. A tank controller 16 sets a target stored hot water temperature to a relatively high value to increase the amount of heating heat when the amount of heat to cover most of the hot water supply load for one day is stored in the hot water storage tank 11 by the boiling operation in the midnight hours. The target stored hot water temperature at this time is, for example, 65°C. On the other hand, the tank controller 16, for example, performs a heating operation during the day using electric power such as solar power generation, and together with the heating operation in the late-night time zone, the amount of heat to cover the hot water supply load for the day is reduced. may be generated. In this way, when the amount of heat to cover the daily hot water supply load is generated by distributing it over a plurality of boiling operations, the amount of heat to be boiled per one boiling operation is reduced. Set the target hot water storage temperature relatively low. The target stored hot water temperature at this time is, for example, 55°C.

Since the capacity of the hot water tank 11 is constant, when the target hot water temperature is lowered, the amount of hot water heat that can be stored in the hot water tank 11 decreases. On the other hand, if the target hot water storage temperature is lowered, the heat pump hot water outlet temperature during stable operation can be lowered, so the discharge pressure of the compressor 4 is lowered, thereby improving the COP during stable boiling operation. . Therefore, when the amount of heat to be boiled at one time is small, the power consumption of the boiling operation can be reduced by lowering the target stored hot water temperature.

When the target stored hot water temperature is determined, in step S102, the tank controller 16 determines whether the target stored hot water temperature is equal to or higher than a threshold. As previously mentioned, this threshold may be, for example, 65°C. When the target stored hot water temperature is equal to or higher than the threshold, the process proceeds to step S103, and the heat pump controller 9 and the tank controller 16 perform the boiling operation in the first mode.

On the other hand, when the target hot water storage temperature is lower than the threshold, the tank controller 16 proceeds to step S104 and calculates the low temperature water amount Vcw [L] of the hot water storage tank 11 . The low-temperature water volume Vcw is the volume of water on the lower layer side in the hot water storage tank 11 . Here, an example of a method for calculating the low-temperature water amount Vcw will be described with reference to FIG.

FIG. 6 is a diagram schematically showing an example of temperature distribution in the hot water storage tank 11 before starting the boiling operation. As shown in the diagram on the left side of FIG. 6, in the hot water storage tank 11 before the start of the boiling operation, there is residual hot water on the upper layer side, low-temperature water on the lower layer side, and a temperature boundary layer between them. is formed. The graph on the right side of FIG. 6 shows the relationship between the water temperature detected by the four stored hot water temperature sensors 33 and the capacity of the hot water storage tank 11 . In FIG. 6, the four stored hot water temperature sensors 33 are identified as a, b, c, and d in descending order of position.

Low-temperature water is water that is located in the lower part of the hot water storage tank 11 and has a temperature sufficiently lower than that of the hot water supplied from the upper part of the hot water storage tank 11 . The tank controller 16 may regard water having a water temperature equal to or lower than the threshold temperature Tcw as low-temperature water. The threshold temperature Tcw may be, for example, a value that is higher than the feed water temperature detected by the feed water temperature sensor 34 by a predetermined temperature (for example, about 5 degrees). The tank controller 16 may calculate, as the threshold temperature Tcw, a value obtained by adding the predetermined temperature to the feed water temperature obtained by averaging the feed water temperatures detected by the feed water temperature sensor 34 for a predetermined period in the past. The tank controller 16 stores in advance the relationship between the position of each stored hot water temperature sensor 33 and the capacity of the hot water storage tank 11 . Based on the temperature detected by each hot water temperature sensor 33, the tank controller 16 creates a temperature distribution with respect to the capacity of the hot water tank 11, as shown in the graph of FIG. At this time, the tank controller 16 may calculate the water temperature between the vertically adjacent stored hot water temperature sensors 33 by linear interpolation. The tank controller 16 estimates the capacity of the hot water storage tank 11 at the position where this temperature distribution and the threshold temperature Tcw intersect, and calculates the low-temperature water amount Vcw. In this embodiment, the tank controller 16 and the stored hot water temperature sensor 33 correspond to means for calculating the low-temperature water amount Vcw of the hot water storage tank 11 .

After calculating the low-temperature water amount Vcw of the hot water storage tank 11, in step S105, the tank controller 16 calculates a predicted value of the boiling water amount Vhw [L] in the current boiling operation using the following equation (1).
Vhw=Qhw/[ρw×Cpw×(Two−Twi_ave)]×10 ⁶

Here, Qhw [MJ] is the amount of heat to be heated, Two [°C] is the hot water outlet temperature of the heat pump, and Twi_ave [°C] is the average value of the heat pump inlet water temperature. The tank controller 16 can calculate the average value Twi_ave of the heat pump inlet water temperature, for example, by averaging the temperature distribution in the region of the low-temperature water amount Vcw detected in step S104. The tank controller 16 may use the value of the target stored hot water temperature as the heat pump hot water outlet temperature Two. Alternatively, the tank controller 16 divides the amount of hot water to be boiled for each outlet hot water temperature in consideration of the value of the heat pump outlet hot water temperature (40° C. in the example of FIG. 3) at the start of the operation after startup and the value of the target hot water storage temperature. , and summing them up to calculate the boiling water amount Vhw. In this embodiment, the tank controller 16 corresponds to means for predicting the boiling water amount Vhw.

After predicting the boiling water amount Vhw in step S105, the tank controller 16 determines whether the boiling water amount Vhw is smaller than the low-temperature water amount Vcw of the hot water storage tank 11 in step S106. When the boiling water amount Vhw is smaller than the low-temperature water amount Vcw in the hot water storage tank 11, it can be expected that the heat pump inlet water temperature will not rise at the end of the boiling operation even if the third mode boiling operation is performed. Therefore, in this case, the process proceeds to step S107, and the heat pump controller 9 and the tank controller 16 perform the boiling operation in the third mode.

On the other hand, if the boiling water amount Vhw is equal to or higher than the low-temperature water amount Vcw in the hot water storage tank 11, it can be expected that the heat pump inlet water temperature will rise at the end of the boiling operation when the third mode boiling operation is executed. Therefore, in this case, the process proceeds to step S108, and the heat pump controller 9 and the tank controller 16 perform the boiling operation in the second mode. As in the above example, when the target stored hot water temperature is the second temperature, the second mode is selected when the boiling water amount Vhw is larger than the low-temperature water amount Vcw, and the boiling water amount Vhw is higher than the low-temperature water amount Vcw. Selecting the third mode when the amount is small is more advantageous in improving the COP.

The tank controller 16 counts the number of times the boiling operation is performed in one day when the target stored hot water temperature is the second temperature. If the standard is exceeded, a second mode of boiling operation may be performed. For example, the tank controller 16 executes the boiling operation in the third mode if the number of times of the boiling operation at which the target stored hot water temperature is the second temperature is the second one in a day, and the target stored hot water temperature is the second temperature. The second mode of boiling operation may be performed when the number of times of the boiling operation with two temperatures reaches the third time. In the case described above, if the number of times of the boiling operation in which the target hot water storage temperature is the second temperature is small in one day, the boiling operation in the third mode is executed to reduce the COP in the post-startup operation. can be higher than in the second mode. When the number of times of the heating operation in which the target stored hot water temperature reaches the second temperature increases in one day, the increase in the amount of hot water to be boiled in one day may increase the temperature of the water entering the heat pump at the end of the heating operation. growing. In this case, by executing the boiling operation in the second mode, the amount of hot water to be boiled can be suppressed, and an increase in the temperature of water entering the heat pump at the final stage of the boiling operation can be suppressed.

When the tank controller 16 counts the number of boiling operations in which the target stored hot water temperature reaches the second temperature in one day, the counted number of times is reset after 24 hours. The tank controller 16 resets the counted number at a specific time every day. The specific time may be the end time of the midnight hours (eg, 7:00 am).

In the present disclosure, a value obtained by dividing the increase in the rotation speed of the compressor 4 of the heat pump unit 2 during operation after startup by the time of operation after startup is referred to as a "compressor rotation speed change rate." The heat pump controller 9 and the tank controller 16 may change the rotation speed of the compressor 4 so that the compressor rotation speed change rate in the second mode is larger than the compressor rotation speed change rate in the first mode. As a result, the amount of increase per hour in the rotation speed of the compressor 4 in the operation after startup in the second mode is higher than the amount of increase in the rotation speed of the compressor 4 per hour in the operation after startup in the first mode. will also grow. As a result, the increase in the refrigerant flow rate per hour during the second mode of operation after startup becomes greater than the increase in the refrigerant flow rate per hour during the first mode of operation after startup. Therefore, the temperature of the heat pump discharged hot water can be increased more quickly during the operation after startup in the second mode.

In the present disclosure, the value obtained by dividing the amount of decrease in the opening degree of the expansion valve 6 of the heat pump unit 2 during operation after start-up by the time of operation after start-up is referred to as "expansion valve opening change rate". The heat pump controller 9 and the tank controller 16 may change the opening degree of the expansion valve 6 so that the expansion valve opening degree change rate in the second mode is larger than the expansion valve opening degree change rate in the first mode. During operation after startup, the degree of opening of the expansion valve 6 is greater than during stable operation. During operation after startup, the heat pump controller 9 reduces the degree of opening of the expansion valve 6 to increase the compressor discharge temperature in accordance with the increase in the target hot water temperature. By reducing the opening degree of the expansion valve 6 faster than in the first mode during the operation after startup in the second mode, the rise in the compressor discharge temperature per hour becomes greater than in the first mode. Therefore, the temperature of the heat pump discharged hot water can be increased more quickly during the operation after startup in the second mode.

1 hot water storage type water heater 2 heat pump unit 3 tank unit 4 compressor 5 refrigerant-water heat exchanger 5a refrigerant flow path 5b water flow path 6 expansion valve 7 evaporator 9 heat pump controller 9a processor 9b memory 10 blower 11 hot water storage tank 13 circulation pump 14 hot water mixing valve 16 tank controller 16a processor 16b memory 17 water supply end 18 first water supply pipe 19 second water supply pipe 20 hot water supply end 21 Hot water supply pipe 22 Hot water supply pipe 23 Heat pump water inlet pipe 24 Heat pump hot water outlet pipe 25 Tank lower passage 26 Tank upper passage 29 Discharge temperature sensor 30 Water inlet temperature sensor 31 Hot water outlet temperature sensor 32 Outside air temperature sensor 33 Hot water storage temperature sensor, 34 feed water temperature sensor, 50 remote control

Claims (8)

a water storage tank;
a heat pump unit for heating water;
a control means for controlling a boiling operation in which the hot water flowing out from the heat pump unit is stored in the hot water storage tank;
with
In the boiling operation, the control means includes a stable operation for stabilizing the outlet hot water temperature, which is the temperature of the hot water discharged from the heat pump unit, at a substantially constant temperature, and a stable operation after starting the heat pump unit and before the stable operation. and performing a post-startup operation in which the outlet heated water temperature is made lower than the constant temperature,
The control means can select a first mode in which the constant temperature is the first temperature and a second mode in which the constant temperature is a second temperature lower than the first temperature,
Regarding the outlet heated water temperature change rate, which is a value obtained by dividing the rise in the outlet heated water temperature during the operation after startup by the time of the operation after startup, the outlet heated water temperature change rate in the second mode is higher than the outlet heated water temperature change rate in the first mode. A hot water storage type hot water supply device with a large rate of change in outlet hot water temperature. 2. The hot water storage type hot water supply apparatus according to claim 1, wherein said constant temperature is said second temperature, and said control means can further select a third mode in which said outlet hot water temperature change rate is smaller than said second mode. a water storage tank;
a heat pump unit for heating water;
a circulation pump for circulating water so that water flowing out of the hot water storage tank flows into the heat pump unit and hot water flowing out of the heat pump unit flows into the hot water storage tank;
a control means for controlling a boiling operation in which the hot water flowing out from the heat pump unit is accumulated in the hot water storage tank;
with
In the boiling operation, the control means includes a stable operation for stabilizing the outlet hot water temperature, which is the temperature of the hot water discharged from the heat pump unit, at a substantially constant temperature, and a stable operation after starting the heat pump unit and before the stable operation. and performing a post-startup operation in which the outlet heated water temperature is made lower than the constant temperature,
The control means can select a first mode in which the constant temperature is the first temperature and a second mode in which the constant temperature is a second temperature lower than the first temperature,
Regarding the pump rotation speed change rate, which is a value obtained by dividing the decrease in the rotation speed of the circulation pump during the operation after startup by the time of the operation after startup, the pump rotation speed change rate is higher than the pump rotation speed change rate in the first mode. A hot water storage type hot water supply apparatus in which the rate of change of the pump rotation speed in the second mode is large. 4. The hot water storage type hot water supply apparatus according to claim 3, wherein the constant temperature is the second temperature, and the control means can further select a third mode in which the rate of change in the pump rotation speed is smaller than that in the second mode. . means for calculating a low-temperature water volume, which is the volume of water on the lower layer side in the hot water storage tank;
means for estimating a boiling water quantity, which is the volume of water passing through the heat pump unit during the boiling operation;
further comprising
When the constant temperature is the second temperature, the second mode is selected when the amount of hot water to be boiled is larger than the amount of low-temperature water, and the second mode is selected when the amount of hot water to be boiled is smaller than the amount of low-temperature water. The hot water storage type hot water supply apparatus according to claim 2 or 4, wherein three modes are selected. The control means counts the number of times of the boiling operation at which the constant temperature becomes the second temperature in one day,
6. The method according to any one of claims 2, 4, and 5, wherein the third mode is selected if the number of times is less than a reference, and the second mode is selected if the number of times exceeds the reference. The hot water storage type hot water supply device described. Regarding the compressor rotation speed change rate, which is a value obtained by dividing the increase in the rotation speed of the compressor of the heat pump unit during the operation after startup by the time of the operation after startup, the compressor rotation speed in the first mode The hot water storage type hot water supply apparatus according to any one of claims 1 to 6, wherein the compressor rotational speed change rate in the second mode is larger than the change rate. The expansion valve opening degree in the first mode with respect to an expansion valve opening change rate, which is a value obtained by dividing the decrease in the opening degree of the expansion valve of the heat pump unit during the operation after startup by the time of the operation after startup. The hot water storage type hot water supply apparatus according to any one of claims 1 to 7, wherein the expansion valve opening change rate in the second mode is larger than the change rate.

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