Storage water heater

Abstract

To provide a storage water heater capable of suppressing deterioration of energy efficiency when performing a boiling-up operation at a relatively low boiling-up temperature.SOLUTION: A storage water heater includes: heating means for heating water; a hot water storage tank that stores the hot water heated by the heating means; a hot water storage circuit having a circulation pump for circulating water in the hot water storage tank to the heating means; a hot water storage temperature sensor that detects a water temperature in the hot water storage tank; water flow rate acquisition means for acquiring a water flow rate in the hot water storage circuit; prediction means for predicting an increase in an inflow water temperature that is a temperature of water flowing into the heating means on the basis of a detection value from the hot water storage temperature sensor and the water flow rate in the middle of a boiling-up operation for causing the hot water heated by the heating means to flow into the hot water storage tank; and heating capacity control means for lowering heating capacity of the heating means and the water flow rate when the increase of the inflow water temperature is predicted by the prediction means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The following Patent Document 1 discloses a storage-type water heater that changes the heating capacity to a second heating capacity lower than the first heating capacity when performing boiling operation during a frequent load period, which is a time period when the hot water load, which is the load generated by the hot water terminal, occurs multiple times during a set period. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-118315 Summary of the Invention [Problem to be solved by the invention]

[0004] The standard boiling temperature for storage-type hot water heaters is generally considered to be 60°C or higher to prevent Legionella infection, and 65°C or higher is desirable when considering heat dissipation from the piping. However, a new study on Legionella growth conditions using an actual water heater with a sealed hot water storage tank concluded that Legionella growth can be suppressed even when the lower limit of the standard boiling temperature is set to 55°C. Based on this, a low-temperature boiling operation, which boils hot water at a temperature lower than the previously established standard boiling temperature, could be considered. Low-temperature boiling operation, for example, with a boiling temperature of 55°C, increases the amount of medium-temperature water (approximately 30°C to 40°C) in the hot water storage tank. As a result, the inlet water temperature of the heat pump during boiling operation becomes higher than usual, resulting in reduced energy efficiency.

[0005] The present disclosure has been made to solve the above-mentioned problems. An object of the present disclosure is to provide a storage type hot water heater that can suppress a decrease in energy efficiency when performing heating operation at a relatively low heating temperature. [Means for solving the problem]

[0006] The hot water storage type water heater of the present disclosure comprises a heating means for heating water, a hot water storage tank for storing hot water heated by the heating means, a hot water storage circuit having a circulation pump for circulating the water in the hot water storage tank to the heating means, a hot water storage temperature sensor for detecting the water temperature in the hot water storage tank, a water flow rate acquisition means for acquiring the water flow rate of the hot water storage circuit, a prediction means for predicting a rise in the inlet water temperature, which is the temperature of the water flowing into the heating means, based on the detection value of the hot water storage temperature sensor and the water flow rate during boiling operation in which hot water heated by the heating means flows into the hot water storage tank, and a heating capacity control means for reducing the heating capacity and water flow rate of the heating means when a rise in the inlet water temperature is predicted by the prediction means. In addition, the hot water storage type water heater of the present disclosure comprises a heating means for heating water, a hot water storage tank for storing hot water heated by the heating means, a hot water storage circuit having a circulation pump for circulating the water in the hot water storage tank to the heating means, a learning means for learning the load concentration time period when the hot water supply load is concentrated, a differential time calculation means for calculating the differential time between the start time of the load concentration time period and the current time during the boiling operation in which the hot water heated by the heating means flows into the hot water storage tank, and a heating capacity control means for reducing the heating capacity of the heating means when the differential time becomes less than a reference time and for increasing the heating capacity of the heating means when the current time passes the start time of the load concentration time period. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a storage type hot water heater that can suppress a decrease in energy efficiency when performing boiling operation at a relatively low boiling temperature. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a diagram showing a storage type hot water heater according to a first embodiment. [Figure 2] FIG. 10 is a diagram for explaining a method by which the prediction means predicts an increase in the HP inlet water temperature. [Figure 3] 4 is a flowchart showing a control operation in the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of a configuration for realizing the functions of a control unit according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing a storage type water heater according to a second embodiment. [Figure 6] 10 is a flowchart showing a control operation in the second embodiment. [Figure 7] 10 is a graph showing an example of a change in heating capacity during low-temperature boiling operation. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. Common or corresponding elements in each drawing are designated by the same reference numerals, and descriptions thereof will be simplified or omitted. In the following description, terms such as "water," "hot water," "warm water," and "hot water" generally refer to liquid water, and may include anything from cold water to boiling water. Furthermore, the configurations shown in the following embodiments are examples of the technical ideas of the present disclosure, and may be combined with other known technologies, or multiple technical ideas described in the present disclosure may be combined. Furthermore, parts of the configurations may be omitted or modified without departing from the spirit of the present disclosure.

[0010] Embodiment 1 FIG. 1 is a diagram showing a hot water storage type water heater 1 according to a first embodiment. As shown in FIG. 1, the hot water storage type water heater 1 includes a heating means 2 that utilizes a heat pump cycle and a hot water storage unit 3 that has a hot water storage tank 4. The heating means 2 consumes electricity to heat water. The heating means 2 is installed outdoors. The hot water storage unit 3 may be installed outdoors or indoors.

[0011] The heating means 2 has a refrigerant circuit including a compressor 5, a water-refrigerant heat exchanger 6, a pressure reducing device 7, an air-refrigerant heat exchanger 8, and an outdoor fan 9. The outdoor fan 9 blows outside air to the air-refrigerant heat exchanger 8.

[0012] The hot water storage type water heater 1 can perform a boiling operation. The boiling operation is an operation in which hot water heated by the heating means 2 flows into the hot water storage tank 4, thereby storing heat in the hot water storage tank 4. The hot water storage type water heater 1 in this embodiment performs a one-pass boiling operation in which water is heated to a target temperature by passing it through the heating means 2 only once.

[0013] The hot water storage unit 3 further includes a circulation pump 10, a hot water mixing valve 11, and a city water pressure reducing valve 12.

[0014] Pipe 13 connects the bottom of hot water storage tank 4 to the suction port of circulation pump 10. City water pressure reducing valve 12 is provided on water supply pipe 14. Water supply pipe 14 is connected to the bottom of hot water storage tank 4. Water supply pipe 15 branching off from water supply pipe 14 is connected to hot water supply mixing valve 11.

[0015] The HP supply pipe 16 connects the discharge port of the circulation pump 10 to the water inlet of the water-refrigerant heat exchanger 6. The HP return pipe 17 connects the water outlet of the water-refrigerant heat exchanger 6 to the top of the hot water storage tank 4.

[0016] The hot water outlet pipe 18 connects the top of the hot water storage tank 4 to the hot water mixing valve 11. The hot water mixing valve 11 mixes low-temperature water supplied from the water supply pipe 15 with hot water supplied from the hot water outlet pipe 18, and allows the mixture to flow into the hot water supply pipe 19. The hot water in the hot water supply pipe 19 is sent to a hot water supply terminal such as a bathtub, shower, or faucet.

[0017] In this embodiment, a hot water storage circuit is formed by the piping 13, the HP supply piping 16, the circulation pump 10, and the HP return piping 17. The temperature of the water flowing into the heating means 2 through the HP supply piping 16 is hereinafter referred to as the "HP inlet water temperature."

[0018] A hot water temperature sensor 20 is provided at the bottom of the hot water tank 4 to detect the water temperature inside the hot water tank 4. The hot water temperature sensor 20 may be configured as a thermistor. Hot water temperature sensors are also provided at the top and middle of the hot water tank 4, but are not shown in the figure.

[0019] The hot water storage type water heater 1 is equipped with a control unit 50 that controls the operation of the hot water storage type water heater 1. The control unit 50 has a water flow rate acquisition means 51 that acquires the water flow rate of the hot water storage circuit, a prediction means 52 that predicts an increase in the HP inlet water temperature, and a heating capacity control means 53 that controls the heating capacity of the heating means 2.

[0020] The control unit 50 controls the boiling operation by controlling the operation of the compressor 5, the pressure reducing device 7, the outdoor fan 9, and the circulation pump 10. The temperature of the hot water flowing out from the heating means 2 during the boiling operation is hereinafter referred to as the "boiling temperature."

[0021] The control unit 50 can control the boiling temperature by controlling the rotation speed of the circulation pump 10. The control unit 50 may control the boiling temperature to be between 50°C and 60°C. If the boiling temperature is 50°C or higher, the growth of Legionella bacteria can be suppressed. The lower the boiling temperature, the higher the energy efficiency, so by keeping the boiling temperature as low as possible within the range that can suppress the growth of Legionella bacteria, it is possible to increase energy efficiency. Boiling operation in which the boiling temperature is between 50°C and 60°C is referred to as "low-temperature boiling operation" below.

[0022] The water flow rate acquisition means 51 stores the relationship between the rotation speed of the circulation pump 10 and the water flow rate, and estimates the water flow rate from the rotation speed of the circulation pump 10. This configuration is not limited to this, and a flow rate sensor may be provided in the hot water storage circuit to directly detect the water flow rate.

[0023] The heating capacity of the heating means 2 is the amount of heat that the heating means 2 gives to water per unit time, and is expressed in watts. The heating capacity control means 53 can change the heating capacity of the heating means 2 by changing the operating frequency of the compressor 5 through inverter control. The higher the heating capacity, the lower the energy efficiency of the boiling operation tends to be.

[0024] When storing the same amount of hot water heat energy in the hot water storage tank 4 using low-temperature heating operation as in normal heating operation, which sets the heating temperature at 65°C or higher, the water temperature at the bottom of the hot water storage tank 4 tends to be high. The HP inlet water temperature is approximately equal to the water temperature at the bottom of the hot water storage tank 4. The higher the HP inlet water temperature, the lower the energy efficiency of the heating operation tends to be.

[0025] During the heating operation, the prediction means 52 predicts a rise in the HP inlet water temperature based on the detection value of the hot water temperature sensor 20 and the water flow rate. FIG. 2 is a diagram for explaining how the prediction means 52 predicts a rise in the HP inlet water temperature. In this embodiment, the volume of the hot water tank 4 is assumed to be 370 L. In the example of FIG. 2, the water temperature at a position 330 L from the top of the hot water tank 4 is 45°C, and the water flow rate is 1.4 L / min. In this case, the time until the 45°C hot water flows into the heating means 2 can be calculated using the following equation: (370L-330L) / (1.4L / min)≒28 minutes

[0026] As described above, prediction means 52 can predict that the HP inlet water temperature will rise to 45°C after 28 minutes. In other words, prediction means 52 can predict that water at the temperature detected by hot water temperature sensor 20 will flow into heating means 2 after the time calculated by dividing the volume from the position of hot water temperature sensor 20 to the bottom of hot water tank 4 by the water flow rate. This makes it possible to accurately predict the rise in the HP inlet water temperature.

[0027] When a rise in the HP inlet water temperature is predicted by the prediction means 52, the heating capacity control means 53 reduces the heating capacity and water flow rate of the heating means 2. This makes it possible to reliably reduce or suppress a decrease in energy efficiency due to a rise in the HP inlet water temperature.

[0028] Figure 3 is a flowchart showing the control operation in embodiment 1. In step S1 of Figure 3, the control unit 50 starts low-temperature boiling operation. The hot water storage type water heater 1 constantly detects the hot water temperature using the hot water storage temperature sensor, and when the amount of heat stored in the hot water storage tank 4 falls below a threshold, the low-temperature boiling operation starts.

[0029] Next, in step S2, the water flow rate obtaining means 51 performs a process of estimating the water flow rate from the rotation speed of the circulation pump 10.

[0030] Next, in step S3, the volume from the hot water storage position where the hot water storage temperature sensor 20 is located to the bottom of the hot water storage tank 4 is divided by the water flow rate to calculate the time x required for the hot water at that hot water storage position to reach the bottom of the hot water storage tank 4. The prediction means 52 can predict that the temperature detected by the hot water storage temperature sensor 20 at this time will correspond to the HP inlet water temperature x minutes later.

[0031] Next, in step S4, prediction means 52 determines whether the HP inlet water temperature after x minutes will be equal to or higher than z°C. z°C may be a value within the range of 30°C to 50°C, for example. If the HP inlet water temperature after x minutes is equal to or higher than z°C, it is predicted that the HP inlet water temperature will rise, so the process proceeds to step S6, and heating capacity control means 53 reduces the heating capacity and water flow rate of heating means 2.

[0032] If in step S4 the HP inlet water temperature after x minutes is less than z°C, the process proceeds to step S5. In step S5, prediction means 52 determines whether the HP inlet water temperature after x minutes is equal to or greater than the HP inlet water temperature at the start of boiling + y°C. y°C may be a value within the range of 10°C to 20°C, for example. If the HP inlet water temperature after x minutes is equal to or greater than the HP inlet water temperature at the start of boiling + y°C, it is predicted that the HP inlet water temperature will rise, so the process proceeds to step S6, and heating capacity control means 53 reduces the heating capacity and water flow rate of heating means 2.

[0033] FIG. 4 is a diagram showing an example of a configuration for realizing the functions of the control unit 50 in the first embodiment. Each function of the control unit 50 is realized by, for example, a processing circuit. The processing circuit may be dedicated hardware 600. The processing circuit may include a processor 601 and a memory 602. A part of the processing circuit may be formed as the dedicated hardware 600, and the processing circuit may further include the processor 601 and the memory 602. In the example shown in FIG. 4, a part of the processing circuit is formed as the dedicated hardware 600. Furthermore, in the example shown in FIG. 4, the processing circuit further includes the processor 601 and the memory 602 in addition to the dedicated hardware 600.

[0034] The processing circuitry of which at least one portion is dedicated hardware 600 may be, for example, a single circuit, a multiple circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0035] When the processing circuit includes at least one processor 601 and at least one memory 602, the functions of each part of the control unit 50 are realized by software, firmware, or a combination of software and firmware.

[0036] The software and firmware are written as programs and stored in memory 602. The programs may be recorded on a computer-readable recording medium. The processor 601 realizes the functions of each unit by reading and executing the programs stored in memory 602. The processor 601 is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 602 may be, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM, or a magnetic disk, flexible disk, optical disk, compact disk, minidisk, DVD, etc.

[0037] In this way, the processing circuit can realize the functions of the control unit 50 by hardware, software, firmware, or a combination of these. Note that each function of the control unit 50 may be realized by multiple devices working together, or by a single device. Furthermore, at least some of the functions of the control unit 50 may be implemented in a server or the like on an external network.

[0038] Embodiment 2 Next, a second embodiment will be described with reference to Figures 5 to 7. The description will focus on differences from the first embodiment, and common explanations will be simplified or omitted. Elements that are common to or correspond to the elements described above will be denoted by the same reference numerals.

[0039] Fig. 5 is a diagram showing a hot water storage type water heater 21 according to embodiment 2. As shown in Fig. 5, a control unit 50 of the hot water storage type water heater 21 of the present embodiment includes a learning means 54 and a difference time calculation means 55.

[0040] Hot water supply pipe 19 is provided with hot water supply temperature sensor 22 and hot water supply flow rate sensor 23. Learning means 54 learns the hot water supply load detected by hot water supply temperature sensor 22 and hot water supply flow rate sensor 23, thereby learning the load concentration time periods when the hot water supply load is concentrated. The load concentration time periods correspond to, for example, the time periods when the bathtub is filled with water.

[0041] The differential time calculation means 55 calculates the differential time x between the start time of the load concentration time period and the current time during the heating operation.

[0042] The heating capacity control means 53 reduces the heating capacity of the heating means 2 when the differential time x becomes less than an arbitrary reference time y, and increases the heating capacity of the heating means 2 when the current time passes the start time of the load concentration period.

[0043] During the concentrated load time period, hot water from the upper part of the hot water storage tank 4 flows out into the hot water outlet pipe 18, and low-temperature water from the water supply pipe 14 flows into the lower part of the hot water storage tank 4, so the HP inlet water temperature drops. As a result, energy efficiency increases. In this embodiment, when the differential time x is equal to or less than the reference time y, that is, when the boiling operation is being performed near the concentrated load time period, the amount of heat generated by the heating means 2 can be reduced by lowering the heating capacity. Since the amount of heat generated during the concentrated load time period increases accordingly, it is possible to improve energy efficiency.

[0044] Figure 6 is a flowchart showing the control operation in embodiment 2. In step S11 of Figure 6, control unit 50 starts low-temperature boiling operation. Next, in step S12, difference time calculation means 55 calculates the difference time x between the start time of the load concentration period and the current time.

[0045] Next, in step S13, the heating capacity control means 53 determines whether the difference time x is less than an arbitrary reference time y. If the difference time x is less than the reference time y, the process proceeds to step S14, and the heating capacity control means 53 reduces the heating capacity and the water flow rate.

[0046] Next, in step S15, the heating capacity control means 53 determines whether the current time has passed the start time of the concentrated load time period. If the current time has passed the start time of the concentrated load time period, the process proceeds to step S16, where the heating capacity control means 53 increases the heating capacity to the rated value.

[0047] Figure 7 is a graph showing an example of changes in heating capacity during low-temperature boiling operation. In the example shown in Figure 7, the start time of the concentrated load period is 7:40 PM, and the arbitrary reference time y is 40 minutes. In case 1, when the current time is 6 PM, there is still 100 minutes of difference time x until the start time of the concentrated load period, so operation continues without reducing heating capacity. In case 2, when the current time is 7 PM, there is 40 minutes of difference time x until the start time of the concentrated load period, so heating capacity is reduced and operation continues.

[0048] The reference time y may be the time required for the heating means 2 to generate the amount of hot water required for one hot water supply or shower when the heating means 2 is operated at rated capacity. The amount of hot water required for one hot water supply or shower may be the amount of hot water specified by JIS, for example, 50 L at 40°C. By setting the reference time y in this way, it becomes possible to more reliably prevent running out of hot water. The value of the reference time y may be about 5 to 10 minutes.

[0049] Of the features of the above-described multiple embodiments, two or more features that can be combined may be combined and implemented.

[0050] Various aspects of the present disclosure are summarized below as appendices.

[0051] (Appendix 1) a heating means for heating water; a hot water storage tank for storing hot water heated by the heating means; a hot water storage circuit having a circulation pump that circulates water in the hot water storage tank to the heating means; a hot water temperature sensor that detects the water temperature in the hot water tank; a water flow rate acquiring means for acquiring a water flow rate of the hot water storage circuit; a prediction means for predicting a rise in an inlet water temperature, which is the temperature of the water flowing into the heating means, based on a detection value of the stored hot water temperature sensor and the water flow rate during a boiling operation in which the hot water heated by the heating means flows into the hot water storage tank; a heating capacity control means for reducing the heating capacity of the heating means and the water flow rate when the prediction means predicts an increase in the inlet water temperature; A storage type water heater equipped with (Appendix 2) A hot water storage type water heater as described in Appendix 1, wherein the prediction means predicts that water at the temperature detected by the hot water storage temperature sensor will flow into the heating means after a time equal to the volume from the position of the hot water storage temperature sensor to the bottom of the hot water storage tank divided by the water flow rate. (Appendix 3) A hot water storage type water heater as described in Appendix 1 or Appendix 2, wherein the heating capacity control means reduces the heating capacity of the heating means and the water flow rate when the temperature of the water predicted to flow into the heating means is higher than a reference temperature, or when the temperature of the water predicted to flow into the heating means is lower than the reference temperature and higher by a predetermined temperature or more than the inlet water temperature at the start of the boiling operation. (Appendix 4) a heating means for heating water; a hot water storage tank for storing hot water heated by the heating means; a hot water storage circuit having a circulation pump that circulates water in the hot water storage tank to the heating means; a learning means for learning a load concentration time period during which hot water supply load is concentrated; a time difference calculation means for calculating a time difference between a start time of the load concentration period and a current time during a boiling operation in which hot water heated by the heating means flows into the hot water storage tank; a heating capacity control means for reducing the heating capacity of the heating means when the difference time becomes less than a reference time, and for increasing the heating capacity of the heating means when the current time passes the start time of the load concentration period; A storage type water heater equipped with (Appendix 5) A hot water storage type water heater as described in Appendix 4, wherein the reference time is the time required for the heating means to generate the amount of hot water required for one hot water supply or shower when the heating means is operated at rated capacity. (Appendix 6) A hot water storage type water heater according to any one of appendices 1 to 5, wherein the temperature of the hot water flowing into the hot water storage tank during the heating operation is 50°C or higher and 60°C or lower. [Explanation of symbols]

[0052] 1 storage type water heater, 2 heating means, 3 water storage unit, 4 water storage tank, 5 compressor, 6 water-refrigerant heat exchanger, 7 pressure reducing device, 8 air-refrigerant heat exchanger, 9 outdoor fan, 10 circulation pump, 11 water supply mixing valve, 12 city water pressure reducing valve, 13 piping, 14 water supply piping, 15 water supply piping, 16 HP forward piping, 17 HP return piping, 18 hot water outlet piping, 19 hot water supply piping, 20 hot water storage temperature sensor, 21 storage type water heater, 22 hot water supply temperature sensor, 23 hot water supply flow rate sensor, 50 control unit, 51 water flow rate acquisition means, 52 prediction means, 53 heating capacity control means, 54 learning means, 55 difference time calculation means, 600 dedicated hardware, 601 Processor, 602 memory

Claims

1. a heating means for heating water; a hot water storage tank for storing hot water heated by the heating means; a hot water storage circuit having a circulation pump that circulates water in the hot water storage tank to the heating means; a hot water temperature sensor that detects the water temperature in the hot water tank; a water flow rate acquiring means for acquiring a water flow rate of the hot water storage circuit; a prediction means for predicting a rise in an inlet water temperature, which is the temperature of the water flowing into the heating means, based on a detection value of the stored hot water temperature sensor and the water flow rate during a boiling operation in which the hot water heated by the heating means flows into the hot water storage tank; a heating capacity control means for reducing the heating capacity of the heating means and the water flow rate when the prediction means predicts an increase in the inlet water temperature; A storage type water heater equipped with

2. A hot water storage type water heater as described in claim 1, wherein the prediction means predicts that water at the temperature detected by the hot water storage temperature sensor will flow into the heating means after a time calculated by dividing the volume from the position of the hot water storage temperature sensor to the bottom of the hot water storage tank by the water flow rate.

3. A hot water storage type water heater as described in claim 1 or claim 2, wherein the heating capacity control means reduces the heating capacity of the heating means and the water flow rate when the temperature of the water predicted to flow into the heating means is higher than a reference temperature, or when the temperature of the water predicted to flow into the heating means is lower than the reference temperature and higher by a predetermined temperature or more than the inlet water temperature at the start of the boiling operation.

4. a heating means for heating water; a hot water storage tank for storing hot water heated by the heating means; a hot water storage circuit having a circulation pump that circulates water in the hot water storage tank to the heating means; a learning means for learning a load concentration time period during which hot water supply load is concentrated; a time difference calculation means for calculating a time difference between a start time of the load concentration period and a current time during a boiling operation in which hot water heated by the heating means flows into the hot water storage tank; a heating capacity control means for reducing the heating capacity of the heating means when the difference time becomes less than a reference time, and for increasing the heating capacity of the heating means when the current time passes the start time of the load concentration period; A storage type water heater equipped with

5. The hot water storage type water heater according to claim 4, wherein the reference time is the time required for the heating means to generate the amount of hot water required for one hot water supply or shower when the heating means is operated at rated capacity.

6. 5. The hot water storage type water heater according to claim 1, wherein the temperature of the hot water flowing into the hot water storage tank during the boiling operation is 50°C or higher and 60°C or lower.

Images