Heat pump water heater units and their water circuit antifreeze control methods

Abstract

This invention discloses a heat pump water heater unit and its water circuit antifreeze control method. The water circuit system of the heat pump water heater unit includes: a battery, a control module, a first heat exchanger, a heat storage device, and branch lines with inlet and outlet water pipes connected to the heat exchanger at both ends and passing through the heat storage device. A water pump is installed on the branch lines. The exhaust gas of the heat pump water heater unit first exchanges heat through the heat storage device before entering the first heat exchanger to exchange heat with the water. The water system antifreeze control method proposed in this invention effectively solves the quality problem of freezing and cracking of pipes and components such as the shell-and-tube heat exchanger caused by prolonged low temperature exposure and water freezing due to sudden power outages in winter.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and in particular to a heat pump water heater unit and its water circuit antifreeze control method. Background Technology

[0002] The internal water system of a heat pump water heater unit includes components such as pipes and shell-and-tube heat exchangers. In cold winter weather, when the unit is shut down, the pipes and shell-and-tube heat exchangers placed outdoors are susceptible to damage from freezing and expansion of the water due to low temperatures. Existing technologies often use heating elements such as heating cables to heat the water system, or employ shutdown drainage methods to prevent pipe freezing and cracking in low-temperature environments.

[0003] The method of achieving freeze protection by adding heating tape involves laying electric heating tape on pipes or shell-and-tube heat exchangers. This utilizes electrical energy converted into heat energy to directly compensate for the heat loss in the pipes, maintaining the water temperature above freezing. In this method, the heating tape must be tightly fitted to the outer wall of the pipe or equipment (such as heat exchangers and pumps). For thinner pipes, a wrapping method can be used to increase the contact area; for thicker pipes or flat equipment, a straight laying method is usually used. Fixing is generally achieved using high-temperature resistant pressure-sensitive tape or aluminum foil tape to secure the heating tape tightly to the surface being heated. Aluminum foil tape also aids in heat conduction, resulting in more even heat distribution. It is highly recommended to use self-regulating heating tape. This type of tape automatically adjusts its output power as the temperature rises, preventing localized overheating and offering greater energy efficiency and safety. During use, when the pipe temperature is detected to be below the set value (e.g., 2℃-4℃), the power is automatically switched on to start heating the pipe; when the temperature rises back to a safe value (e.g., 6℃-8℃), the power is automatically switched off. Heat tracing tape can effectively prevent the risk of freezing and cracking caused by power outages or malfunctions of heat pump units.

[0004] Chinese patent application CN 103471242 A discloses a heat pump water heater with antifreeze function, such as Figure 2 As shown, the heat pump water heater proposed in this patent includes a compressor, a four-way reversing valve, a condenser, a liquid receiver, an expansion valve, an evaporator, a four-way reversing valve, a gas-liquid separator, and finally a working fluid circulation loop returning to the compressor, connected in sequence. The heat pump water heater also includes a heating water circulation loop consisting of a condenser, an insulated water tank, and a water pump. The condenser is equipped with a heating cable (reference numeral 11) that can heat the condenser. When the temperature is very low in winter, electrical energy is converted into heat energy to directly compensate for the heat in the pipeline, maintaining the water temperature in the pipeline above the freezing point.

[0005] However, in the event of a sudden power outage, traditional drainage and antifreeze operations cannot keep up with drainage in time due to the unpredictable nature of the power failure. Antifreeze measures utilizing heating cables also fail to replenish heat to the pipes during power outages. This greatly increases the risk of freezing and cracking damage to pipes and components such as shell-and-tube heat exchangers in the water system due to the expansion of ice. This prevents users from using hot water normally, and the replacement cost, maintenance expenses, and difficulty of repairing components like shell-and-tube heat exchangers are high. Therefore, it is essential to add antifreeze measures to cope with sudden power outages in heat pump water heaters used in cold regions. Summary of the Invention

[0006] This invention provides a heat pump water heater unit and its water circuit antifreeze control method to solve the technical problem of pipe freezing and cracking in the water system during severe winter caused by a sudden power outage from the external power grid.

[0007] The technical solution adopted by the invention is to design a heat pump water heater unit, including a water circuit system, wherein the water circuit system includes: a storage battery, a control module, a first heat exchanger, a heat storage device, and a branch line with inlet and outlet water pipes respectively connected to the first heat exchanger and passing through the heat storage device. A water pump is provided on the branch line. The exhaust gas of the heat pump water heater unit first passes through the heat storage device for heat exchange and then enters the heat exchanger to exchange heat with water.

[0008] Furthermore, temperature sensors are respectively installed on the inlet and outlet pipes of the first heat exchanger.

[0009] Furthermore, a check valve is provided on the branch between the inlet pipe of the first heat exchanger and the water pump.

[0010] Furthermore, the heat storage device includes: One refrigerant coil has one end connected to the exhaust of the heat pump unit and the other end connected to the refrigerant inlet of the heat exchanger. One water coil has its two ends connected to the inlet and outlet water pipes of the heat exchanger, respectively. And heat storage medium, used to store and release heat.

[0011] Preferably, the heat storage medium is ethylene glycol.

[0012] Preferably, the first heat exchanger is a shell-and-tube heat exchanger.

[0013] Preferably, the battery is a rechargeable battery, which continuously stores heat for the heat storage device and charges the battery when the heat pump water heater is powered on normally.

[0014] The present invention also proposes an antifreeze control method for the above-mentioned heat pump water heater, comprising the following steps: When the heat pump water heater unit stops and the power grid is interrupted, switch to battery power supply. When the ambient temperature is detected to be lower than the first preset temperature and the inlet water temperature of the first heat exchanger is lower than the second preset temperature, the water pump is controlled to start, so that the water flows through the heat storage device to absorb heat. The system intermittently detects the ambient temperature and the inlet water temperature of the first heat exchanger. When the inlet water temperature is greater than or equal to the third preset temperature and the ambient temperature is greater than the first preset temperature, the system controls the water pump to stop working.

[0015] Preferably, the first preset temperature is 1-2℃, the second preset temperature is 1-2℃, and the third preset temperature is 4-5℃.

[0016] In one embodiment, the antifreeze control method for the heat pump water heater unit includes the following steps: Step S11: Determine whether the external network is disconnected when the heat pump water heater unit stops. If the external network is disconnected, automatically switch to battery power. Step S12: Detect the ambient temperature and the inlet water temperature of the first heat exchanger. If the ambient temperature is lower than the first preset temperature and the inlet water temperature is lower than the second preset temperature, start the antifreeze system. Step S13: Control the water pump to start, so that the water flows through the heat storage device to absorb the heat stored in the heat storage medium and provide heat for the water circuit inside the first heat exchanger. Step S14: Intermittently detect the inlet water temperature and ambient temperature. When the inlet water temperature is greater than or equal to the third preset temperature and the ambient temperature is greater than the first preset temperature, control the water pump to stop working.

[0017] In the above embodiments, the first preset temperature is 1-2℃, the second preset temperature is 1-2℃, and the third preset temperature is 4-5℃.

[0018] Furthermore, when the battery charge is less than or equal to 30% or the power outage time reaches any of the set durations, the control module sends a low battery signal to the user, reminding the user to drain the water in time.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: The water system antifreeze control method proposed in this invention effectively solves the quality problem of water freezing and cracking of pipes and components such as shell-and-tube heat exchangers caused by prolonged low temperature and water freezing due to sudden power outages in winter. This is achieved by adding a rechargeable battery and a heat storage device to the unit. This ensures the normal operation of the unit and effectively avoids the high maintenance and replacement costs caused by equipment freezing and cracking. Attached Figure Description

[0020] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of an existing heat pump water heater unit; Figure 2 This is a system diagram of a heat pump unit with antifreeze tracing tape in the existing technology; Figure 3 This is a system diagram of the heat pump water heater unit proposed in this invention; Figure 4 This is a schematic diagram of the heat storage device in this invention; Figure 5 This is a working block diagram of the antifreeze control method of the present invention; Figure 6 This is a flowchart of the first embodiment of the antifreeze control method of the present invention; Figure 7 This is a flowchart of the second embodiment of the antifreeze control method of the present invention.

[0021] The markings in the image are as follows: 1. Compressor; 2. First heat exchanger; 3. Four-way directional valve; 4. Throttling device; 5. Second heat exchanger; 6. Gas-liquid separator; 7. Heat storage device; 8 water pumps; 9. Check valve; 10 branch roads; 11 storage batteries; 12 control modules; 13 enclosures; 14 insulation layers; 15 refrigerant coil; 16 water coils; 17. Heat storage medium; T 大 Atmospheric temperature; T 进 —Inlet water temperature; T 出 —Outlet water temperature; T 环 —Ambient temperature; T1—First preset temperature; T2—Second preset temperature; T3—Third preset temperature. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and do not constitute any limitation on the invention.

[0023] The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of protection of the invention.

[0024] While techniques, methods, and apparatus known to those skilled in the art are not discussed in detail herein, such techniques, methods, and apparatus should be considered part of this specification where appropriate. Any specific values ​​in this specification should be interpreted as merely exemplary and not as limiting the invention.

[0025] For ease of description, the terms used in the specification to describe position, such as "above", "to the left", "in front", etc., are only used to describe the spatial positional relationship between a component and other components in the embodiment shown in the figure. When the position of the component is different, the relative position will change. Therefore, the positional relationship of the embodiment in the figure should not be construed as limiting the present invention.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" in the specification is merely for distinguishing similar components and does not imply any order of precedence. Therefore, it should not be construed as limiting the scope of protection of this invention.

[0027] Figure 1 This is a schematic diagram of an existing heat pump water heater system. (For example...) Figure 1 As shown, the heat pump water heater unit includes a compressor 1, a four-way reversing valve 2, a first heat exchanger 3, a throttling device 4, a second heat exchanger 5, and a gas-liquid separator 6, all connected by pipelines. The first heat exchanger and the user-end heating system constitute a water circulation system. During cooling, the high-temperature, high-pressure gas compressed by the compressor 1 passes through the four-way reversing valve 2 to the first heat exchanger 3, where it condenses into a high-pressure, medium-temperature liquid refrigerant. Then, it passes through the throttling device 4 to become a low-temperature, low-pressure liquid refrigerant, which then evaporates into a low-pressure gas in the second heat exchanger 5 before returning to the compressor cycle.

[0028] In a heat pump water heater unit, the first heat exchanger 3 is a shell-and-tube heat exchanger. Water enters the shell-and-tube heat exchanger and exchanges heat with the refrigerant. After the temperature rises, it is introduced to the water consumption end through the outlet pipe, forming a hot water circulation system. As mentioned in the background technology, in cold winter weather, when the unit is shut down, the water temperature in the pipes and shell-and-tube heat exchanger placed outdoors will continuously drop under low ambient temperature. Without antifreeze measures, the water in the pipes is easily affected by the low temperature and will freeze and expand, leading to the risk of pipe freezing and cracking. Therefore, antifreeze control of the water circulation system is very important.

[0029] To solve the above problems, existing technologies generally adopt two methods to prevent pipes from freezing and cracking. One method is to drain the water in the water circulation system when the machine is shut down. The other method is to add a heating tape to the pipe wall to achieve the purpose of antifreeze. Specifically, an electric heating tape is laid on the pipe or shell-and-tube heat exchanger, and electrical energy is converted into heat energy to directly compensate for the heat of the pipeline, so as to maintain the water temperature in the pipeline above the freezing point.

[0030] Chinese patent application CN 103471242 A discloses a heat pump water heater with antifreeze function, such as Figure 2 As shown, the heat pump water heater proposed in this patent includes a compressor, a four-way reversing valve, a condenser, a liquid receiver, an expansion valve, an evaporator, a four-way reversing valve, a gas-liquid separator, and finally a working fluid circulation loop returning to the compressor, connected in sequence. The heat pump water heater unit also includes a heating water circulation loop consisting of a condenser, an insulated water tank, and a water pump. The condenser is equipped with a heating cable (reference numeral 11) that can heat the condenser. When the temperature is very low in winter, electrical energy is converted into heat energy to directly compensate for the heat in the pipeline, maintaining the water temperature in the pipeline above the freezing point. The technical solution disclosed in this patent requires mains power and will fail if the power is off.

[0031] However, in the event of a sudden power outage, traditional drainage and antifreeze operations cannot keep up with the sudden power failure due to the unpredictable nature of the outage. Antifreeze measures utilizing heating cables also fail to replenish heat to the pipes during power outages. This greatly increases the risk of freezing and cracking damage to pipes and components such as shell-and-tube heat exchangers in the water system, preventing users from using hot water normally. Furthermore, replacing components like shell-and-tube heat exchangers is costly, and repairs are difficult and expensive. Therefore, it is essential to incorporate appropriate antifreeze measures into heat pump water heaters used in cold regions.

[0032] The concept of this invention is to organically combine water circulation and heat release from the heat storage device. A rechargeable battery is added to the water circulation system. When the machine stops and the external power grid is disconnected, the battery drives the water pump to allow the water to flow slowly in the first heat exchanger, preventing the water in the pipes from freezing. At the same time, a heat storage device is added to the water circulation system. When the heat pump unit is running, the heat storage device stores heat. After the power is cut off, the heat storage device releases heat to heat the circulating water, raising the water temperature and preventing freezing.

[0033] The water system of the heat pump water heater unit proposed in the invention includes: a battery, a control module, a first heat exchanger, a heat storage device, and a branch line that is connected at both ends to the inlet and outlet water pipes of the first heat exchanger and passes through the heat storage device. The branch line is equipped with a water pump and a one-way valve. The exhaust gas of the heat pump water heater unit first passes through the heat storage device for heat exchange and then enters the first heat exchanger to exchange heat with the water.

[0034] Preferably, the battery is a rechargeable battery, which continuously heats and stores heat for the heat storage device while charging the battery when the heat pump water heater is powered on normally.

[0035] Specifically, the heat pump water heater unit proposed in this invention addresses the risk of freezing and cracking of the water system due to the unit's inability to supply heat as the water temperature gradually decreases during sudden power outages in winter. To address this, a rechargeable battery and a heat storage device are added to the water system. During unit operation, the rechargeable battery is charged, and the compressor exhaust is first introduced into the heat storage device for heat storage before being sent to the first heat exchanger. This method of heating the heat storage medium through heat pump operation is highly energy efficient. When the unit detects a sudden power outage, it automatically switches to battery power. When the water system temperature is low, the water pump is activated to allow water to flow at a low flow rate within the internal water system, while the heat storage device releases heat to ensure the water flowing in the pipes remains above freezing temperature, extending the anti-freezing time and providing reliable protection for subsequent drainage or short-term power outages.

[0036] Figure 3 This is a system diagram of the heat pump water heater unit proposed in this invention. (See diagram below.) Figure 3 As shown, the heat pump water heater unit proposed in this invention includes a compressor 1, a four-way reversing valve 2, a first heat exchanger 3, a throttling device 4, a second heat exchanger 5, and a gas-liquid separator 6, all connected by pipelines. During cooling, the high-temperature, high-pressure gas discharged from the compressor passes through the four-way reversing valve 2 to the heat storage device for heat storage. Then, it condenses into a high-pressure, medium-temperature liquid refrigerant in the first heat exchanger 3. Next, it is throttled by the throttling device 4 into a low-temperature, low-pressure liquid refrigerant, which then evaporates into a low-pressure gas in the second heat exchanger 5 before returning to the compressor for circulation.

[0037] The heat pump water heater unit includes a battery 11, a control module 12, a first heat exchanger 3, a heat storage device 7 connected in parallel with the first heat exchanger, and a branch line 10 connected at one end to the outlet pipe of the first heat exchanger and at the other end to the inlet pipe of the first heat exchanger. This branch line passes through a water coil inside the heat storage device, and a water pump 8 and a one-way valve 9 are installed on the branch line. Water drawn from the outlet pipe enters the heat storage device 7 to exchange heat with the heat storage medium, and then merges with the water in the inlet pipe into the first heat exchanger. The inlet pipe, the first heat exchanger, the outlet pipe, the branch line, the heat storage device, the water pump, and the one-way valve together constitute the water circulation system inside the heat pump unit.

[0038] When the heat pump water heater is cooling, the exhaust gas from compressor 1 first passes through four-way reversing valve 2 and then enters the heat storage device 7 for heat storage. It then enters the first heat exchanger 3 to exchange heat with water. After passing through throttling device 4 to reduce pressure, it enters the second heat exchanger 5 for cooling. Finally, it passes through four-way reversing valve 2 and gas-liquid separator 6 before returning to the compressor for circulation. When the heat pump water heater detects a sudden power outage, the unit controller automatically switches to battery power. When the water system temperature is low, water pump 8 is activated to allow water to flow at a low flow rate in the internal water system. Simultaneously, water flowing from the outlet pipe of the first heat exchanger 3 is introduced into the heat storage device 7 through branch 10. The water exchanges heat with the heat storage medium in the heat storage device, and after the water temperature rises, it returns to the first heat exchanger 3 through branch 10 for circulation. In this way, the water flowing in the pipes is always kept above the freezing temperature and will not freeze.

[0039] like Figure 4 As shown, the heat storage device 7 includes a housing 13, typically made of enamel or stainless steel, cylindrical or cuboid in shape. The housing is equipped with water coil connectors and refrigerant coil connectors, and an insulation layer 14 is provided outside the housing. The housing contains internal heat exchange tubes and a heat storage medium 19. The internal heat exchange tubes include: a refrigerant coil 15, one end of which is connected to the exhaust of the heat pump unit, and the other end is connected to the refrigerant inlet of the first heat exchanger 3; and a water coil 16, both ends of which are connected to the inlet and outlet water pipes of the first heat exchanger 3. The refrigerant coil 15 is connected to one interface of the four-way reversing valve 2 and the refrigerant inlet of the first heat exchanger 3 via refrigerant pipe connectors and pipes provided on the housing. The water coil 16 is connected to branch line 10 via water pipe connectors provided on the housing. The heat exchange tubes are generally made of copper, a material known for its high heat exchange efficiency.

[0040] The heat storage medium inside the tank is used to store and release heat. The heat storage medium is an antifreeze liquid, such as ethylene glycol. The freezing point of the selected ethylene glycol must be at least 5°C lower than the lowest ambient temperature at which the unit operates. For example, if the lowest ambient temperature at which the unit can operate is -35°C, then the freezing point of ethylene glycol should be at least -40°C. The heat storage capacity of the heat storage device is selected based on the set heat supply capacity required to maintain the unit's operation for 3-4 days after a power outage at low ambient temperatures. The stored heat capacity includes the heat supplied to the unit's internal water system and the heat loss of the heat storage device itself at low ambient temperatures. For example, when selecting ethylene glycol as the antifreeze medium, it is generally set according to the heat dissipation of the internal water system for approximately 3-4 days at the lowest ambient temperature at which the unit operates (design configuration is completed before delivery).

[0041] When the heat pump water heater is operating normally and producing hot water, the high-temperature and high-pressure gaseous refrigerant discharged from the compressor flows through the refrigerant coil inside the heat storage device after passing through the four-way reversing valve, providing heat to the heat storage device for heat storage, and then flows through the shell-and-tube type first heat exchanger to heat the hot water for the project.

[0042] During normal operation of the unit, the unit power supply charges the rechargeable battery 11, keeping it essentially fully charged. In the event of a sudden power outage from the external grid, the unit control module automatically switches the anti-freeze control system to rechargeable battery power and controls the temperature sensor to intermittently monitor the ambient temperature, typically every 15-20 minutes. When the ambient temperature is greater than or equal to a first preset value, the inlet water temperature sensor of the first heat exchanger does not activate, and the water pump 8 does not start circulating. When the ambient temperature is less than the first preset value, and the inlet water temperature in the inlet pipe section is less than a second preset value, the control module controls the battery to supply power to the low-flow circulating water pump 8, causing the water in the unit's internal water system to circulate. The low-temperature water in the unit's internal water system is heated by the heat storage device 7, circulating until the water temperature in the inlet pipe section of the first heat exchanger 3 is greater than or equal to the second preset value, at which point the water pump 8 is de-energized. In the event of a subsequent power outage, the control module will intermittently monitor the inlet water temperature of the first heat exchanger 3. By intermittently monitoring the ambient temperature and the inlet water temperature of the first heat exchanger, when both the ambient temperature and the inlet water temperature are below a first preset value and a second preset value, the water pump 8 will be activated to circulate the water system inside the unit. Simultaneously, the water flows through the heat storage device 7 on the high-temperature side, extracts heat from it, and supplies the heat to the water system. When the control module detects that the water temperature in the inlet pipe section is higher than the second preset value and the ambient temperature is greater than or equal to the first preset value, the control module will de-energize the water pump. This periodic cycle of monitoring and anti-freeze operation can extend the unit's anti-freeze duration under low-temperature conditions and prevent the unit from freezing in low ambient temperature environments, thereby improving the unit's reliability.

[0043] During antifreeze operation, if the battery 11's charge level is less than or equal to 30% or the power outage duration is up to 2 days, the control module will send a low charge signal to the user to remind the user to drain the battery in a timely manner.

[0044] After the external power grid is connected, the unit will automatically start the heat pump operation mode after detecting the external power source. The battery will switch to charging mode, and at the same time, the high-temperature refrigerant will flow through the heat storage device for heating and heat storage during the operation of the heat pump.

[0045] The antifreeze control system proposed in this invention adds a control module (containing a 4G communication network), a rechargeable battery, a heat storage device, and a branch line connected in parallel with the first heat exchanger to the internal water system of the heat pump water heater. This branch line passes through the heat storage device and is equipped with a water pump and a one-way valve. After the antifreeze water circulation is turned on, the internal water flow sequence is as follows: outlet pipe of the first heat exchanger → branch line → heat storage device → small flow circulation water pump → one-way valve → branch line → inlet pipe of the first heat exchanger → shell-and-tube heat exchanger → outlet pipe section. The inlet water temperature sensor is located in the inlet pipe section, and the outlet water temperature sensor is located in the outlet pipe section, both within the pipe sections through which the antifreeze water system flows.

[0046] Figure 5 This is a block diagram of the antifreeze control proposed in this invention. (See diagram below.) Figure 5 As shown, the antifreeze control method proposed in this invention includes: When the heat pump water heater unit is detected to be shut down and the power grid is interrupted, switch to battery power supply. The system detects the inlet water temperature of the first heat exchanger. When the detected inlet water temperature of the first heat exchanger is less than or equal to the second preset temperature, the system controls the water pump to start, allowing circulating water to enter the heat storage device through the branch to absorb heat, and then return to the first heat exchanger for circulation. When the detected inlet water temperature of the first heat exchanger is greater than or equal to the third preset temperature, it indicates that there is no risk of pipe freezing and cracking, and the system controls the water pump to stop working.

[0047] After the water system antifreeze operation stops, the antifreeze control method also includes intermittent detection of ambient temperature. When the ambient temperature is greater than or equal to the first preset temperature, the antifreeze system is not activated; when the ambient temperature is less than the first preset temperature and the inlet water temperature is less than the second preset temperature, the antifreeze system is activated.

[0048] Figure 6 This is a flowchart of the first embodiment of the water system antifreeze control method of the present invention. The antifreeze control method of the heat pump water heater unit includes the following steps: Step S11: When the heat pump water heater unit stops, check whether the external network is supplying power. If not, automatically switch to battery power. Step S12: Detect the ambient temperature and the inlet water temperature of the first heat exchanger, and determine whether the ambient temperature is lower than the first preset temperature and whether the inlet water temperature is lower than the second preset temperature. If yes, proceed to step S13; otherwise, the antifreeze system will not start. Step S13: Control the water pump to start, so that the water flows through the heat storage device to absorb the heat stored in the heat storage medium and provide heat for the water circuit inside the first heat exchanger. Step S14: Intermittently detect the inlet water temperature and ambient temperature, and determine whether the inlet water temperature is greater than or equal to the third preset temperature and whether the ambient temperature is greater than the first preset temperature. If yes, control the water pump to stop working; otherwise, control the water pump to continue running.

[0049] In the above embodiments, the first preset temperature is 1-2℃, the second preset temperature is 1-2℃, and the third preset temperature is 4-5℃.

[0050] Figure 7 This is a flowchart of the second embodiment of the water system antifreeze control of the present invention. This embodiment is the operation procedure when a sudden power outage occurs during unit operation. When the external power grid suddenly fails and the entire unit stops operating, the following steps are performed: Step S21: The control module automatically switches to battery power; Step S22: Determine whether the battery charge is less than 30% or whether the battery has been continuously supplying power for more than 45 hours. If yes, send a message to the user to remind them to drain the battery in time; otherwise, proceed to step S23. Step S23: Read the weather forecast for the day. If the forecast temperature is greater than or equal to 5℃, the water circuit antifreeze control will not be activated. If the temperature is less than 5℃, the ambient temperature will be detected to determine if it is greater than or equal to 1℃. If it is, the antifreeze system will not be activated. If not, proceed to step S24. Step S24: Detect the inlet water temperature of the first heat exchanger and determine whether the inlet water temperature is greater than or equal to 1℃. If yes, the antifreeze system will not be started; otherwise, proceed to step S25. Step S25: Start the antifreeze control, turn on the water pump, and make the water circulate through the heat storage device to absorb the heat stored in the heat storage medium and provide heat to the water circuit inside the first heat exchanger. Step S26: When the inlet water temperature is detected to be greater than or equal to 5°C, control the water pump to stop working, and the antifreeze operation ends.

[0051] The water system antifreeze control method proposed in this invention effectively solves the quality problem of water freezing and cracking of pipes and components such as shell-and-tube heat exchangers caused by prolonged low temperature when the water system inside the heat pump water heater is subjected to prolonged low temperature due to a sudden power outage in winter. This ensures the normal operation of the unit and effectively avoids the high maintenance and replacement costs caused by equipment freezing and cracking.

[0052] The water system antifreeze control method proposed in this invention organically combines a storage battery, control module, small flow water pump, one-way check valve and heat storage device in the system architecture; the power supply mechanism is independent of the mains power, and automatically switches to battery power supply when the power is interrupted; in terms of heat source utilization, it makes full use of the residual heat stored in the heat storage medium during normal operation of the unit; the control logic adopts dual temperature condition judgment plus threshold control, which can accurately start and stop and extend the antifreeze time.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat pump water heater unit, comprising a water circuit system, characterized in that, The water system includes: a battery, a control module, a first heat exchanger, a heat storage device, and a branch line with inlet and outlet water pipes connected to the first heat exchanger at both ends and passing through the heat storage device. A water pump is installed on the branch line. The exhaust gas of the heat pump water heater unit first exchanges heat through the heat storage device and then enters the first heat exchanger to exchange heat with the water.

2. The heat pump water heater unit according to claim 1, characterized in that, Temperature sensors are installed on the inlet and outlet pipes of the first heat exchanger.

3. The heat pump water heater unit according to claim 1, characterized in that, In the inlet pipe of the first heat exchanger and One-way valves are installed on the branch lines between the water pumps.

4. The heat pump water heater unit according to claim 1, characterized in that, The heat storage device includes: One refrigerant coil has one end connected to the exhaust of the heat pump unit and the other end connected to the refrigerant inlet of the first heat exchanger. One water coil has its two ends connected to the inlet and outlet water pipes of the first heat exchanger, respectively. And heat storage medium, used to store and release heat.

5. The heat pump water heater unit according to claim 4, characterized in that, The heat storage medium is ethylene glycol.

6. The heat pump water heater unit according to claim 1, characterized in that, The first heat exchanger is a shell-and-tube heat exchanger.

7. The heat pump water heater unit according to claim 1, characterized in that, When the heat pump water heater is powered on normally, it continuously stores heat for the heat storage device and charges the battery at the same time.

8. The antifreeze control method for the heat pump water heater unit according to any one of claims 1-7, characterized in that, The following steps are included: automatically switching to battery power when the external power grid fails and the heat pump water heater unit stops; When the inlet water temperature of the first heat exchanger is detected to be less than or equal to the second preset temperature, the antifreeze system is activated to control the water pump to work, so that the water circulates through the heat storage device to absorb heat. When the inlet water temperature of the first heat exchanger is detected to be greater than or equal to the third preset temperature, the water pump is controlled to stop working.

9. The antifreeze control method according to claim 8, characterized in that, Also includes: The system detects the ambient temperature and activates the antifreeze system when the ambient temperature is lower than the first preset temperature and the inlet water temperature is lower than the second preset temperature.

10. The antifreeze control method according to claim 9, characterized in that, The first preset temperature is 1-2℃, the second preset temperature is 1-2℃, and the third preset temperature is 4-5℃.

11. The antifreeze control method for a heat pump water heater unit according to any one of claims 1-7, characterized in that, Includes the following steps: Step S11: When the heat pump water heater unit is detected to be shut down and the power grid is interrupted, automatically switch to battery power supply; Step S12: Detect the ambient temperature and the inlet water temperature of the first heat exchanger. When the ambient temperature is lower than the first preset temperature and the inlet water temperature is lower than the second preset temperature, start the antifreeze system. Step S13: Control the water pump to start, so that the water flows through the heat storage device to absorb the heat stored in the heat storage medium and provide heat to the water circuit inside the heat exchanger. Step S14: Intermittently detect the inlet water temperature and ambient temperature. When the inlet water temperature is greater than or equal to the third preset temperature and the ambient temperature is greater than the first preset temperature, control the water pump to stop working.

12. The antifreeze control method according to claim 11, characterized in that, The first preset temperature is 1-2℃, the second preset temperature is 1-2℃, and the third preset temperature is 4-5℃.

13. The antifreeze control method according to claim 11, characterized in that, When either the battery charge is less than or equal to 30% or the power outage time reaches the set duration, the control module sends a low battery signal to the user, reminding the user to drain the battery in time.

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