Single-stage and two-stage low-temperature heat pump heating system and control method thereof

Abstract

The application relates to a single-double-stage low-temperature heat pump heating system and a control method thereof. The single-double-stage low-temperature heat pump heating system comprises a first air source heat pump circuit, a water source heat pump circuit, a terminal heating circuit and a pressure-bearing energy storage heat exchange water tank. The pressure-bearing energy storage heat exchange water tank comprises a pressure-bearing shell, at least two groups of heat exchange coils are arranged in the pressure-bearing shell, the heat exchange coils comprise first heat exchange coils and second heat exchange coils, and each group of heat exchange coils is arranged in a different temperature stratification area in the pressure-bearing shell. The first heat exchange coils are connected with the first air source heat pump circuit. The second heat exchange coils are connected with the water source heat pump circuit. First water inlets and first water outlets are arranged on the pressure-bearing shell. The first water outlets are connected with inlets of the terminal heating circuit. The first water inlets are connected with outlets of the terminal heating circuit. The system can realize automatic switching between single-stage and double-stage operation modes, and the efficiency of the whole machine is improved. The system also realizes frost-free defrosting by means of water tank heat storage, and the heating comfort during defrosting is improved.

Description

Technical Field

[0001] This invention relates to the field of heat pumps, and in particular to a single- or double-stage low-temperature heat pump heating system and its control method. Background Technology

[0002] Currently, the main type of heat pump system on the market is the cascade heat pump system. Existing cascade heat pumps have the following technical drawbacks: First, they have a single operating mode, supporting only two-stage heating operation and unable to switch to single-stage operation based on ambient temperature. This results in a low coefficient of performance (COP) when the ambient temperature is high, causing unnecessary energy waste. Second, they have a complex structure and low energy efficiency: the overall system size is large, often using external multi-plate heat exchangers, which not only increases heat loss from pipe connections but also requires a higher-powered circulating water pump, ultimately leading to low overall system energy efficiency. Third, they provide poor heating comfort: the conventional defrosting process requires absorbing heat from the heating terminals, causing indoor temperature fluctuations and reducing heating comfort.

[0003] Existing heat pump equipment generally suffers from rapid frosting and difficult defrosting during winter operation in frigid regions. Defrosting requires stopping heat pump heating, further exacerbating indoor temperature fluctuations. Furthermore, conventional defrosting methods rely on additional electric heating, increasing energy consumption and reducing overall system efficiency. In addition, most existing heating systems cannot effectively integrate renewable energy sources such as solar power, resulting in insufficient utilization of free environmental heat, further increasing energy consumption and operating costs, and failing to meet the actual needs of frigid regions for efficient, energy-saving, and comfortable heating. Summary of the Invention

[0004] The main objective of this invention is to provide a single- or double-stage low-temperature heat pump heating system that is highly energy efficient and provides high heating comfort during defrosting.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A single- or double-stage low-temperature heat pump heating system includes a first air-source heat pump circuit, a water-source heat pump circuit, a terminal heating circuit, and a pressurized energy storage and hot water exchange tank. The pressurized energy storage and hot water exchange tank includes a pressurized outer shell, and at least two sets of heat exchange coils are provided inside the pressurized outer shell, including a first heat exchange coil and a second heat exchange coil. Each set of heat exchange coils is respectively arranged in different temperature stratification areas inside the pressurized outer shell. The first heat exchange coil includes a first inlet and a first outlet. The first inlet is connected to the outlet of the first air source heat pump circuit, and the first outlet is connected to the inlet of the first air source heat pump circuit. The second heat exchange coil includes a second inlet and a second outlet. The second inlet is connected to the outlet of the water source heat pump circuit, and the second outlet is connected to the inlet of the water source heat pump circuit. The pressure-bearing outer shell is provided with a first water inlet and a first water outlet. The first water outlet is connected to the inlet of the terminal heating circuit through a first pipeline; the first water inlet is connected to the outlet of the terminal heating circuit through a second pipeline.

[0006] The first heat exchange coil is located below the second heat exchange coil, the first water inlet is located at the lower part of the pressure-bearing shell, and the first water outlet is located at the upper part of the pressure-bearing shell. The lower part of the pressure-bearing shell is provided with a second water outlet, and the upper part of the pressure-bearing shell is provided with a second water inlet. The second water outlet and the second water inlet are connected by a water pump.

[0007] The heat exchange coil is a spiral corrugated heat exchange coil, and the outer wall of the heat exchange coil is provided with continuous corrugated protrusions; the outer side of the pressure-bearing shell is provided with a heat insulation layer.

[0008] Furthermore, it also includes a third heat exchange coil disposed within the pressure-bearing outer casing, the third heat exchange coil being located below the first heat exchange coil, the third heat exchange coil including a third inlet and a third outlet; the third inlet is connected to the outlet of the second air source heat pump circuit, the outlet of the multi-energy recovery heat exchange circuit, or the outlet of the domestic hot water heat extraction circuit, and the third outlet is connected to the inlet of the second air source heat pump circuit, the inlet of the multi-energy recovery heat exchange circuit, or the inlet of the domestic hot water heat extraction circuit.

[0009] The first air source heat pump circuit and the second air source heat pump circuit have the same structure. The first air source heat pump circuit includes a first-stage evaporator. The outlet of the first-stage evaporator is connected to the first inlet of a first-stage four-way valve. The outlet of the first-stage four-way valve is connected to a first-stage compressor. The first outlet of the first-stage compressor is connected to the second inlet of the first-stage four-way valve through a gas-liquid separator. The second outlet of the first-stage compressor is connected to the inlet of the first-stage evaporator through an expansion valve, thus forming the first air source heat pump circuit. The third inlet of the first-stage four-way valve is connected to the first outlet of the first heat exchange coil, and the first inlet of the first heat exchange coil is connected to the second outlet of the first-stage compressor through a liquid receiver. The water source heat pump circuit includes a condenser. The first outlet of the condenser is connected to the second inlet of the second heat exchange coil through a liquid receiver and an expansion valve. The second outlet of the second heat exchange coil is connected to the inlet of the secondary compressor through a gas-liquid separator. The outlet of the secondary compressor is connected to the first inlet of the condenser, thus forming a water source heat pump circuit. The second outlet of the condenser is connected to the inlet of the terminal heating circuit via a third pipeline, and the first pipeline is connected to the third pipeline. The second inlet of the condenser is connected to the outlet of the terminal heating circuit via a fourth pipeline, and the second pipeline is connected to the fourth pipeline.

[0010] Furthermore, it also includes a fourth heat exchange coil disposed within the pressure-bearing housing; The inlet of the fourth heat exchange coil is connected to the outlet pipe of tap water, and the outlet of the fourth heat exchange coil is connected to the outlet pipe of hot water. The fourth heat exchange coil is located below or above the second heat exchange coil; The multiple energy sources in the multi-energy recovery heat exchange circuit include solar energy or industrial waste heat.

[0011] The first pipeline is equipped with a one-way check valve, the second pipeline is equipped with a first valve, the third pipeline is equipped with a second valve and a third valve, the first pipeline is connected to the third pipeline between the second valve and the third valve, the fourth pipeline is equipped with a fourth valve and a fifth valve, and the second pipeline is connected to the fourth pipeline between the fourth valve and the fifth valve. The industrial waste heat is selected from one of the following: high-temperature flue gas waste heat, cooling medium waste heat, wastewater and waste gas waste heat, chemical reaction waste heat, high-temperature products and slag waste heat, and combustible waste gas, waste liquid and waste material waste heat. When the waste heat end is a pressurized device, the water from the waste heat end is directly connected to the pressurized energy storage hot water exchange tank to complete the circulating heat exchange.

[0012] The present invention also provides a control method for the single- or double-stage low-temperature heat pump heating system, comprising the following steps: The system detects the ambient temperature. When the ambient temperature is higher than the set value, the control system enters a single-stage operation mode: the first air source heat pump or / and the first air source heat pump operate, while the water source heat pump remains off. The one-way check valve, the second valve, the fourth valve, and the sixth valve are opened to start the water pump. The water is heated through the first heat exchange coil. The terminal heating circuit draws water from the pressurized energy storage hot water tank through the first pipeline, and the return water flows back through the second pipeline and then through the first inlet to the pressurized energy storage hot water tank, thus achieving heat extraction and heating. When the ambient temperature is lower than the set value, the control system enters a two-stage operation mode: the first air source heat pump or / and the first air source heat pump operate simultaneously, while the water source heat pump remains off; the one-way check valve and the first valve are closed, and the second, third, fourth, and fifth valves are opened to start the water pump. The heat generated by the air source heat pump is transferred to the water in the tank through the heat exchange coils in the lower layer of the pressurized energy storage water exchange tank. The water source heat pump absorbs heat from the heat exchange coils in the upper layer of the pressurized energy storage water exchange tank to complete the secondary heating, and then delivers it to the terminal heating circuit through the condenser for heating. When the system needs to defrost, the heat stored in the pressurized energy storage hot water tank is used to transfer the heat back to the first-stage evaporator of the air source heat pump through the forced water circulation system to complete the defrosting. When there is sufficient solar energy during the day, the system controls the solar energy recovery and heat exchange circuit to start, collecting solar heat through the solar collector and then transporting it to the pressurized energy storage and heat exchange tank for storage. When there is sufficient solar heat and the heating demand is met, the solar heat stored in the pressurized energy storage and heat exchange tank is used directly to heat the terminal heating circuit, and the air source heat pump and water source heat pump are turned off.

[0013] The set value is -12℃ to -7℃; the set temperature difference value is 3-5℃.

[0014] By employing the above technical solution, the present invention has at least the following advantages: This invention integrates the primary air-source heat pump heat exchange and the secondary water-source heat pump heat exchange into a single water tank. Utilizing the temperature stratification characteristics within the tank, each heat exchange coil is adapted to different water temperature zones, effectively avoiding the temperature difference losses caused by cross-temperature range heat exchange in traditional external heat exchange schemes. The heat exchange coils are housed within the water tank, and the integrated water circuit design of the internal heat exchange coils reduces the use of external piping and independent heat exchangers, saving installation space, reducing material costs, and minimizing heat loss at pipe connections, further improving the overall heating efficiency of the system. The addition of a forced water circulation active heat exchange system actively drives the water flow within the tank, improving heat exchange efficiency and reducing the temperature difference. The system can automatically switch between single-stage and dual-stage operation modes. Single-stage operation is used to save energy when the ambient temperature is high, while dual-stage operation is used to ensure heating capacity when the ambient temperature is low, thereby improving the overall energy efficiency (COP). This invention also utilizes water tank heat storage for uninterrupted defrosting. The defrosting process is completed using the heat stored in the water tank, eliminating the need to absorb heat from the heating terminals and completely solving the problem of indoor temperature drop during defrosting, thus improving heating comfort during defrosting. This invention addresses the problems of low energy efficiency, impact on heating comfort during defrosting, and difficulty in preventing equipment freezing in heat pump heating systems in extremely cold regions. Through structural integration and control logic optimization, this invention simplifies the system structure while ensuring heat exchange efficiency, reducing equipment manufacturing and installation costs, and maintaining the system COP in line with design requirements. This invention can operate stably in extreme low-temperature environments of -35℃ and above, continuously outputting high-temperature hot water to meet heating needs. The temperature of the high-temperature hot water can reach above 70℃, effectively solving the problems of energy efficiency degradation and reliability in heat pump heating systems in extremely cold regions.

[0015] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a single- or double-stage low-temperature heat pump heating system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another single- or double-stage low-temperature heat pump heating system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of another single- or double-stage low-temperature heat pump heating system provided in an embodiment of the present invention.

[0017] In the picture: 1. First air source heat pump circuit; 2. Water source heat pump circuit; 3. Terminal heating circuit; 4. Pressurized energy storage and hot water exchange tank; 5. Pressurized shell; 6. First heat exchange coil; 7. Second heat exchange coil; 8. First inlet; 9. First outlet; 10. Second inlet; 11. Second outlet; 12. First water inlet; 13. First water outlet; 14. First pipeline; 15. Second pipeline; 16. Second water outlet; 17. Second water inlet; 18. Water pump; 19. Third heat exchange coil; 20. Third inlet; 21. Third outlet; 22. Second air source heat pump circuit; 23. Solar collector; 24. First-stage evaporator; 25. First-stage four-way valve; 26. First-stage compressor; 27. Gas-liquid separator; 28. Expansion valve; 29. ​​Liquid receiver; 30. Condenser; 31. Second-stage compressor; 32. Third pipeline; 33. Fourth pipeline; 34. One-way check valve; 35. First valve; 36. Second valve; 37. Third valve; 38. Fourth valve; 39. Fifth valve. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, structures, features, and effects of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] like Figure 1 As shown, a single- or double-stage low-temperature heat pump heating system includes a first air source heat pump circuit 1, a water source heat pump circuit 2, a terminal heating circuit 3, and a pressurized energy storage and hot water exchange tank 4. The pressurized energy storage and hot water exchange tank 4 includes a pressurized outer shell 5. The pressurized outer shell 5 is equipped with at least two sets of heat exchange coils, including a first heat exchange coil 6 and a second heat exchange coil 7. Each set of heat exchange coils is respectively arranged in different temperature stratification areas inside the pressurized outer shell. The first heat exchange coil 6 includes a first inlet 8 and a first outlet 9. The first inlet 8 is connected to the outlet of the first air source heat pump circuit 1, and the first outlet 9 is connected to the inlet of the first air source heat pump circuit 1. The second heat exchange coil 7 includes a second inlet 10 and a second outlet 11. The second inlet 10 is connected to the outlet of the water source heat pump circuit 2, and the second outlet 11 is connected to the inlet of the water source heat pump circuit 2. The pressure-bearing outer shell 5 is provided with a first inlet 12 and a first outlet 13. The first outlet 13 is connected to the inlet of the terminal heating circuit 3 through a first pipeline 14; the first inlet 12 is connected to the outlet of the terminal heating circuit 3 through a second pipeline 15.

[0020] In this invention, both the primary heat exchange from the air-source heat pump and the secondary heat exchange from the water-source heat pump are completed within the same pressurized energy storage water exchange tank. During defrosting, the heat stored in the pressurized energy storage water exchange tank is utilized, eliminating the need to absorb heat from the heating terminals and completely solving the problem of indoor temperature drop during defrosting, thus improving heating comfort. All heat exchange coils in this invention are sealed and isolated from the water storage space within the pressurized outer shell, preventing contact between the working fluid and water and avoiding contamination and corrosion. The pressurized energy storage water exchange tank of this invention can achieve natural stratified heat storage. After long-term operation, the upper layer of the tank maintains a consistently high temperature, providing a stable heat source for the secondary water-source heat pump and avoiding the heating capacity reduction problem caused by excessively low heat source temperature when directly drawing heat from the air. Simultaneously, the tank itself can store excess heat, balancing system load fluctuations and improving overall operational stability.

[0021] Preferably, the first heat exchange coil 6 is located below the second heat exchange coil 7, the first water inlet 12 is located at the lower part of the pressure-bearing shell 5, and the first water outlet 13 is located at the upper part of the pressure-bearing shell 5. The lower part of the pressure-bearing housing 5 is provided with a second water outlet 16, and the upper part of the pressure-bearing housing 5 is provided with a second water inlet 17. The second water outlet 16 and the second water inlet 17 are connected by a water pump 18.

[0022] This invention, by adding a water pump, creates forced water circulation within the water tank, accelerating the internal water circulation and thus reducing the heat exchange temperature difference. Forced water circulation also speeds up the defrosting process. Because the water path inside the tank is short and has low water resistance, it can accommodate high-flow, low-head water pumps, allowing for the selection of pumps with lower rated power, thereby reducing auxiliary power consumption and improving overall system energy efficiency.

[0023] Preferably, the heat exchange coil is a spiral corrugated heat exchange coil, and the outer wall of the heat exchange coil is provided with continuous corrugated protrusions; the outer side of the pressure-bearing shell is provided with a heat insulation layer.

[0024] The heat exchange coil of this invention can be a spiral corrugated structure, wound into equidistant concentric circles, an Archimedean spiral, or a stacked mosquito coil shape, with continuous corrugated protrusions, effectively increasing the heat exchange area. Simultaneously, it can disturb the water flow inside the tank, reduce the thermal resistance of the heat exchange boundary layer, enhance the heat exchange effect between the water in the tank and the heat exchange medium inside the heat exchange coil, and improve heat exchange efficiency. Multiple heat exchange coils can be evenly distributed in different temperature zones, ensuring both low-temperature heat release during primary condensation and medium-temperature heat extraction during secondary evaporation, without interference. The pressurized energy storage water exchange tank of this invention, combined with an external insulation layer, not only reduces heat loss from the tank but also improves the overall anti-freezing capability of the equipment, making it better suited for low-temperature operation in uninsulated buildings and solving the problem of equipment freezing damage in winter in extremely cold regions. This invention integrates the pressurized energy storage water tank design, achieving space saving, cost reduction, and reduced heat loss.

[0025] See Figure 2 and Figure 3 It also includes a third heat exchange coil 19 disposed inside the pressure-bearing outer shell 5. The third heat exchange coil 19 is located below the first heat exchange coil 6. The third heat exchange coil 19 includes a third inlet 20 and a third outlet 21. The third inlet 20 is connected to the outlet of the second air source heat pump circuit 22 or the outlet of the solar collector 23, and the third outlet 21 is connected to the inlet of the second air source heat pump circuit 22 or the inlet of the solar collector 23.

[0026] This invention also reserves an interface for a multi-energy recovery heat exchange circuit. The multi-energy source can be solar energy or industrial waste heat. The industrial waste heat is selected from one of the following: high-temperature flue gas waste heat, cooling medium waste heat, wastewater and waste gas waste heat, chemical reaction waste heat, waste heat from high-temperature products and slag, and waste heat from combustible waste gas, waste liquid, and waste materials. The multi-energy recovery circuit can connect a solar collector to a third heat exchange coil, or it can directly exchange heat with a pressurized energy storage hot water tank without the need for additional heat exchange coils. Furthermore, for industrial waste heat recovery, when the waste heat source is a pressurized device, the water from the waste heat source can be directly connected to the pressurized energy storage hot water tank to complete the heat exchange, eliminating the need for additional heat exchange coils and greatly improving heat exchange efficiency. This invention can efficiently integrate multiple low-grade heat sources such as solar energy, industrial wastewater, and cooling return water, storing excess solar heat in a water tank, reducing the operating time of the air source heat pump, further reducing heating operating costs, improving the system's energy efficiency and environmental adaptability, and better meeting the current development needs of low-carbon and energy-saving heating.

[0027] The third heat exchange coil of this invention can also be connected to a domestic hot water extraction circuit. Tap water flows through the third heat exchange coil under the pressure of the municipal water supply network, and after exchanging heat with the hot water in the pressurized energy storage tank, it can be used directly. This invention achieves a domestic hot water supply with zero water pump power consumption, which is both energy-saving and ensures the cleanliness of the hot water.

[0028] See Figure 1 and Figure 2 The first air source heat pump circuit 1 and the second air source heat pump circuit 22 have the same structure. The first air source heat pump circuit 1 includes a first-stage evaporator 24. The outlet of the first-stage evaporator 24 is connected to the first inlet of the first-stage four-way valve 25. The first outlet of the first-stage four-way valve 25 is connected to the first-stage compressor 26. The first outlet of the first-stage compressor 26 is connected to the second inlet of the first-stage four-way valve 25 through a gas-liquid separator 27. The second outlet of the first-stage compressor 26 is connected to the inlet of the first-stage evaporator 24 through an expansion valve 28, thus forming the first air source heat pump circuit. The second outlet of the first-stage four-way valve 25 is connected to the first inlet 8 of the first heat exchange coil 6, and the first outlet 9 of the first heat exchange coil 6 is connected to the second outlet of the first-stage compressor 26 through the liquid receiver 29. The water source heat pump circuit 2 includes a condenser 30. The first outlet of the condenser 30 is connected to the second inlet 10 of the second heat exchange coil 7 through a liquid receiver 29 and an expansion valve 28. The second outlet 11 of the second heat exchange coil 7 is connected to the inlet of the second-stage compressor 31 through a gas-liquid separator 27. The outlet of the second-stage compressor 31 is connected to the first inlet of the condenser 30, thus forming a water source heat pump circuit. The second outlet of the condenser 30 is connected to the inlet of the terminal heating circuit 3 via the third pipeline 32, the first pipeline 14 is connected to the third pipeline 32, the second inlet of the condenser 30 is connected to the outlet of the terminal heating circuit 3 via the fourth pipeline 33, and the second pipeline 15 is connected to the fourth pipeline 33.

[0029] Furthermore, it also includes a fourth heat exchange coil disposed within the pressure-bearing housing; The inlet of the fourth heat exchange coil is connected to the outlet pipe of the tap water, and the outlet of the fourth heat exchange coil is connected to the outlet pipe of the domestic hot water. The fourth heat exchange coil is located below or above the second heat exchange coil.

[0030] This invention provides a low-energy supply of clean, warm domestic water. When users require clean, warm domestic water, tap water is directly introduced into the fourth heat exchange coil within the pressurized energy storage water exchange tank. The tap water is heated by exchanging heat with the stored water in the tank. The entire process requires no additional water pump; the tap water flows under municipal pressure, thus obtaining clean, warm domestic water without consuming any additional electricity. The fourth heat exchange coil is located in the high-temperature zone of the pressurized energy storage water exchange tank, preferably adjacent to the second heat exchange coil, either below or above it. This ensures that the outlet temperature of the warm domestic water remains stable and meets usage requirements.

[0031] Preferably, the first pipeline 14 is provided with a one-way check valve 34, the second pipeline 15 is provided with a first valve 35, the third pipeline 32 is provided with a second valve 36 and a third valve 37, the first pipeline 14 is connected to the third pipeline 32 between the second valve 36 and the third valve 37, the fourth pipeline 33 is provided with a fourth valve 38 and a fifth valve 39, and the second pipeline 15 is connected to the fourth pipeline 33 between the fourth valve 38 and the fifth valve 39.

[0032] The present invention also provides a control method for the single- or double-stage low-temperature heat pump heating system, comprising the following steps: The system detects the ambient temperature. When the ambient temperature is higher than the set value (which can be -12℃, -11℃, or -7℃), the control system enters a single-stage operation mode: the first air source heat pump or / and the first air source heat pump operate, while the water source heat pump remains off. The system opens the one-way check valve, the second valve, the fourth valve, and the sixth valve to start the water pump. The water is heated through the first heat exchange coil. The terminal heating circuit draws water from the pressurized energy storage hot water tank through the first pipeline, and the return water flows back through the second pipeline and then through the first inlet to the pressurized energy storage hot water tank, thus achieving heat extraction and heating. When the ambient temperature is lower than the set value, the control system enters a two-stage operation mode: the first air source heat pump or / and the first air source heat pump operate simultaneously, while the water source heat pump remains off; the one-way check valve and the first valve are closed, and the second, third, fourth, and fifth valves are opened to start the water pump. The heat generated by the air source heat pump is transferred to the water in the tank through the heat exchange coils in the lower layer of the pressurized energy storage water exchange tank. The water source heat pump absorbs heat from the heat exchange coils in the upper layer of the pressurized energy storage water exchange tank to complete the secondary heating, and then delivers it to the terminal heating circuit through the condenser for heating. When the system needs defrosting, the heat stored in the pressurized energy storage hot water tank is transferred back to the primary evaporator of the air source heat pump through a forced water circulation system to complete the defrosting operation. If the heat storage in the pressurized energy storage hot water tank is insufficient, the secondary water source heat pump is activated to replenish the heat, ensuring that the defrosting process is fast and reliable, and that the terminal heating is not interrupted.

[0033] When there is sufficient solar energy during the day, the system controls the solar energy recovery and heat exchange circuit to start, collecting solar heat through the solar collector and then transporting it to the pressurized energy storage and heat exchange tank for storage, reducing the operating energy consumption of the heat pump system and improving the overall energy utilization efficiency of the system; when there is sufficient solar heat and the heating demand is met, the solar heat stored in the pressurized energy storage and heat exchange tank is directly used to heat the terminal heating circuit, and the air source heat pump and water source heat pump are turned off.

[0034] The single-stage operation mode of this invention only activates the first-stage air source heat pump, which directly heats the water through the lower coil of the pressurized energy storage hot water exchange tank. The terminal heating circuit directly extracts heat from the pressurized energy storage hot water exchange tank, and the second-stage water source heat pump does not start, resulting in minimal energy consumption.

[0035] The dual-stage operation mode of this invention involves a primary air-source heat pump and a secondary water-source heat pump operating in series. The primary air-source heat pump extracts heat from the air and releases it in the middle and / or lower heat exchange coils of a pressurized energy storage and heat exchange tank, heating the water to a medium temperature. The secondary water-source heat pump absorbs heat from the upper coils of the pressurized energy storage and heat exchange tank, performs secondary compression to raise the temperature, and then delivers it to the terminal heating system. This two-stage relay solves the problems of low efficiency and insufficient heating capacity of single-stage heat pumps in extremely cold regions.

[0036] The forced water circulation system of this invention operates continuously throughout the defrosting process, meaning the water pump runs constantly. By driving the water circulation within the tank, it accelerates the transfer of heat to the primary heat pump evaporator, shortens defrosting time, and reduces heat loss during defrosting. Furthermore, the terminal heating system does not stop operating during defrosting. It continuously supplies heat to the terminals using the heat stored in the pressurized energy storage hot water exchange tank, achieving seamless defrosting that synchronizes defrosting and heating.

[0037] Furthermore, the system monitors the water temperature difference between the upper and lower layers of the pressurized energy storage hot water tank in real time. When the water temperature difference exceeds the set temperature difference value, which can be 3℃, 4℃ or 5℃, the forced water circulation system is activated to balance the internal temperature of the pressurized energy storage hot water tank and improve the overall heat exchange efficiency.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A single- or double-stage low-temperature heat pump heating system, characterized in that: It includes a first air source heat pump circuit, a water source heat pump circuit, a terminal heating circuit, and a pressurized energy storage and hot water exchange tank; The pressurized energy storage and hot water exchange tank includes a pressurized outer shell, and at least two sets of heat exchange coils are provided inside the pressurized outer shell, including a first heat exchange coil and a second heat exchange coil. Each set of heat exchange coils is respectively arranged in different temperature stratification areas inside the pressurized outer shell. The first heat exchange coil includes a first inlet and a first outlet. The first inlet is connected to the outlet of the first air source heat pump circuit, and the first outlet is connected to the inlet of the first air source heat pump circuit. The second heat exchange coil includes a second inlet and a second outlet. The second inlet is connected to the outlet of the water source heat pump circuit, and the second outlet is connected to the inlet of the water source heat pump circuit. The pressure-bearing outer shell is provided with a first water inlet and a first water outlet. The first water outlet is connected to the inlet of the terminal heating circuit through a first pipeline; the first water inlet is connected to the outlet of the terminal heating circuit through a second pipeline.

2. The single- or double-stage low-temperature heat pump heating system according to claim 1, characterized in that, The first heat exchange coil is located below the second heat exchange coil, the first water inlet is located at the lower part of the pressure-bearing shell, and the first water outlet is located at the upper part of the pressure-bearing shell. The lower part of the pressure-bearing shell is provided with a second water outlet, and the upper part of the pressure-bearing shell is provided with a second water inlet. The second water outlet and the second water inlet are connected by a water pump.

3. The single- or double-stage low-temperature heat pump heating system according to claim 1, characterized in that, The heat exchange coil is a spiral corrugated heat exchange coil, and the outer wall of the heat exchange coil is provided with continuous corrugated protrusions; the outer side of the pressure-bearing shell is provided with a heat insulation layer.

4. The single- or double-stage low-temperature heat pump heating system according to any one of claims 1-3, characterized in that, It also includes a third heat exchange coil disposed inside the pressure-bearing shell, the third heat exchange coil being located below the first heat exchange coil, the third heat exchange coil including a third inlet and a third outlet; the third inlet is connected to the outlet of the second air source heat pump circuit, the outlet of the multi-energy recovery heat exchange circuit, or the outlet of the domestic hot water heat extraction circuit, and the third outlet is connected to the inlet of the second air source heat pump circuit, the inlet of the multi-energy recovery heat exchange circuit, or the inlet of the domestic hot water heat extraction circuit.

5. The single- or double-stage low-temperature heat pump heating system according to claim 4, characterized in that, The first air source heat pump circuit and the second air source heat pump circuit have the same structure. The first air source heat pump circuit includes a first-stage evaporator. The outlet of the first-stage evaporator is connected to the first inlet of a first-stage four-way valve. The outlet of the first-stage four-way valve is connected to a first-stage compressor. The first outlet of the first-stage compressor is connected to the second inlet of the first-stage four-way valve through a gas-liquid separator. The second outlet of the first-stage compressor is connected to the inlet of the first-stage evaporator through an expansion valve, thus forming the first air source heat pump circuit. The third inlet of the first-stage four-way valve is connected to the first outlet of the first heat exchange coil, and the first inlet of the first heat exchange coil is connected to the second outlet of the first-stage compressor through a liquid receiver. The water source heat pump circuit includes a condenser. The first outlet of the condenser is connected to the second inlet of the second heat exchange coil through a liquid receiver and an expansion valve. The second outlet of the second heat exchange coil is connected to the inlet of the secondary compressor through a gas-liquid separator. The outlet of the secondary compressor is connected to the first inlet of the condenser, thus forming a water source heat pump circuit. The second outlet of the condenser is connected to the inlet of the terminal heating circuit via a third pipeline, and the first pipeline is connected to the third pipeline. The second inlet of the condenser is connected to the outlet of the terminal heating circuit via a fourth pipeline, and the second pipeline is connected to the fourth pipeline.

6. The single- or double-stage low-temperature heat pump heating system according to claim 5, characterized in that, It also includes a fourth heat exchange coil disposed within the pressure-bearing housing; The inlet of the fourth heat exchange coil is connected to the outlet pipe of tap water, and the outlet of the fourth heat exchange coil is connected to the outlet pipe of hot water. The fourth heat exchange coil is located below or above the second heat exchange coil; The multiple energy sources in the multi-energy recovery heat exchange circuit include solar energy or industrial waste heat.

7. The single- or double-stage low-temperature heat pump heating system according to claim 6, characterized in that, The first pipeline is equipped with a one-way check valve, the second pipeline is equipped with a first valve, the third pipeline is equipped with a second valve and a third valve, the first pipeline is connected to the third pipeline between the second valve and the third valve, the fourth pipeline is equipped with a fourth valve and a fifth valve, and the second pipeline is connected to the fourth pipeline between the fourth valve and the fifth valve. The industrial waste heat is selected from one of the following: high-temperature flue gas waste heat, cooling medium waste heat, wastewater and waste gas waste heat, chemical reaction waste heat, high-temperature products and slag waste heat, and combustible waste gas, waste liquid and waste material waste heat. When the waste heat end is a pressurized device, the water from the waste heat end is directly connected to the pressurized energy storage hot water exchange tank to complete the circulating heat exchange.

8. A control method for a single- or double-stage low-temperature heat pump heating system according to any one of claims 1-7, characterized in that, Includes the following steps: The system detects the ambient temperature. When the ambient temperature is higher than the set value, the control system enters a single-stage operation mode: the first air source heat pump or / and the first air source heat pump operate, while the water source heat pump remains off. The one-way check valve, the second valve, the fourth valve, and the sixth valve are opened to start the water pump. The water is heated through the first heat exchange coil. The terminal heating circuit draws water from the pressurized energy storage hot water tank through the first pipeline, and the return water flows back through the second pipeline and then through the first inlet to the pressurized energy storage hot water tank, thus achieving heat extraction and heating. When the ambient temperature is lower than the set value, the control system enters a two-stage operation mode: the first air source heat pump or / and the first air source heat pump operate simultaneously, while the water source heat pump remains off; the one-way check valve and the first valve are closed, and the second, third, fourth, and fifth valves are opened to start the water pump. The heat generated by the air source heat pump is transferred to the water in the tank through the heat exchange coils in the lower layer of the pressurized energy storage water exchange tank. The water source heat pump absorbs heat from the heat exchange coils in the upper layer of the pressurized energy storage water exchange tank to complete the secondary heating, and then delivers it to the terminal heating circuit through the condenser for heating. When the system needs to defrost, the heat stored in the pressurized energy storage hot water tank is used to transfer the heat back to the first-stage evaporator of the air source heat pump through the forced water circulation system to complete the defrosting operation. When there is sufficient solar energy during the day, the system controls the solar energy recovery and heat exchange circuit to start, collecting solar heat through the solar collector and then transporting it to the pressurized energy storage and heat exchange tank for storage. When there is sufficient solar heat and the heating demand is met, the solar heat stored in the pressurized energy storage and heat exchange tank is used directly to heat the terminal heating circuit, and the air source heat pump and water source heat pump are turned off.

9. The control method according to claim 8, characterized in that, The water temperature difference between the upper and lower layers of the pressurized energy storage hot water tank is monitored in real time. When the water temperature difference exceeds the set temperature difference value, the water pump is started.

10. The control method according to claim 9, characterized in that, The set value is -12℃ to -7℃; the set temperature difference value is 3-5℃.

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