Super-long gravity heat pipe and double heat pump coupled heat supply system and control method

Abstract

The invention provides an ultra-long gravity heat pipe and double heat pump coupled heat supply system and a control method. The ultra-long gravity heat pipe and double heat pump coupled heat supply system comprises an ultra-long gravity heat pipe system, an air source heat pump system, a user side heat supply system and a control unit. The super-long gravity heat pipe system and the air source heat pump system are both communicated with the user side heating system, and the control unit controls the working state of the super-long gravity heat pipe system and the working state of the air source heat pump system. The ultra-long gravity heat pipe and double heat pump coupled heat supply system realizes efficient utilization of energy through coupling of the ultra-long gravity heat pipe and the double heat pumps, and is suitable for extremely cold environment working conditions; according to the control method of the heat supply system with the ultra-long gravity heat pipe coupled with the double heat pumps, the operation mode is controlled and changed based on different working conditions, and the problem that the heat pumps and the heat pipes are difficult to dynamically match supply and demand is solved.

Description

Technical Field

[0001] The present invention relates to the technical field related to geothermal heating, and more precisely to a heating system and a control method for coupling an ultra-long gravity heat pipe with a dual heat pump. Background Art

[0002] The air source heat pump system is a heating system that uses high-level energy to make heat flow from low-level heat source air to high-level heat source. The heat medium of the existing air source heat pump system comes from the outside air. Since most of the air source heat pump systems on the market today are designed to operate at a normal temperature of 0-40°C, in the south where the ambient temperature is higher, air source heat pumps can maintain high energy efficiency. However, in heating applications in northern cities where the temperature is only -10°C in winter, the evaporator side is severely frosted and the compressor pressure ratio increases, causing the heating coefficient (COP) to drop sharply below 1.5, and even triggering shutdown protection. Although some technologies have attempted to improve low-temperature adaptability through electric auxiliary heating, the energy consumption cost has increased by 50% to 80%, and the carbon emission problem has not been fundamentally solved.

[0003] The ultra-long gravity heat pipe heating system uses mid-deep geothermal energy to achieve heat transfer through the phase change cycle of the working fluid. It has the characteristics of passive operation, no mechanical power consumption, and high long-distance heat transfer efficiency. However, the system needs to use an indirect heat pump (the intermediate heat exchanger transfers the heat to the heat pump evaporator), which produces calorific value loss due to secondary heat exchange. In addition, when the system is in a long-term high-load operation state, the soil temperature will gradually decrease due to insufficient thermal compensation for the underground constant temperature layer, thereby reducing the system's heating capacity. In terms of heating control, the existing system consumes high-temperature heat from the heat pipe inefficiently when the load is low at the beginning of heating; when the load is high during cold waves, it is difficult for the heat pump and heat pipe to dynamically match supply and demand, which is prone to insufficient heating or energy waste.

[0004] To solve the above problems, the Chinese patent with publication number CN116951522A discloses a medium-deep geothermal source heat pump heating system using an ultra-long gravity heat pipe, combining the heat pipe condenser and the heat pump evaporator into a condenser evaporator to improve the heat exchange efficiency. However, the application only describes the condenser evaporator from the perspective of its function in the heating system, without describing the specific structure and working principle of the condenser evaporator in detail. The Chinese patent with publication number CN115435415B discloses a geothermal energy and air energy combined heating and cooling system, which can ensure the normal startup of the air source heat pump system in a low temperature environment by using part of the geothermal energy to heat the gas medium in the air source heat pump system. However, the system uses shallow geothermal energy, and the outlet water temperature is low, which cannot meet the high-efficiency operation under extremely low temperature conditions, and the heat exchange process consumes pump power and has low thermal efficiency.

[0005] In summary, there is a need in the art for a coupled heating system that can integrate the advantages of efficient heat transfer of ultra-long gravity heat pipes and flexible efficiency improvement of heat pumps, and can adapt to all climates and all compliance scenarios. The system needs to break through the limitations of a single heat source, improve energy utilization efficiency, and adapt to extremely low-temperature working environments, so as to improve the applicability of clean heating technology and reduce costs, and promote the large-scale application of clean heating technology. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a heating system coupled with an ultra-long gravity heat pipe and a dual heat pump, which realizes efficient energy utilization through the coupling of the ultra-long gravity heat pipe and the dual heat pump, and is applicable to extremely cold environmental conditions.

[0007] Another purpose of the present invention is to provide a control method for a heating system coupled with an ultra-long gravity heat pipe and a dual heat pump, which controls and changes the operation mode based on different working conditions, and solves the problem that it is difficult for the heat pump and the heat pipe to dynamically match the supply and demand.

[0008] To achieve the above purpose, the present invention provides a heating system coupled with an ultra-long gravity heat pipe and a dual heat pump, including an ultra-long gravity heat pipe system, an air source heat pump system, a user-side heating system, and a control unit; the ultra-long gravity heat pipe system includes an ultra-long gravity heat pipe, and the ultra-long gravity heat pipe is connected to an ammonia-heat pump working medium direct heat exchange unit and a heat exchanger through pipelines, and the ammonia-heat pump working medium direct heat exchange unit and the heat exchanger are respectively connected to the user-side heating system through pipelines; the air source heat pump system includes an air inlet pipe, a fan, an air preheater, and an air source heat pump unit connected in sequence through pipelines, an air outlet pipe is connected to the air source heat pump unit, and the air source heat pump unit is connected to the user-side heating system through a pipeline; a switching valve group is installed on the pipeline connecting the ultra-long gravity heat pipe to the ammonia-heat pump working medium direct heat exchange unit and the heat exchanger, and an electric valve group, a flowmeter group, and a temperature sensor group are installed on the pipelines connecting the ammonia-heat pump working medium direct heat exchange unit and the heat exchanger to the user-side heating system; an air electric valve group, a fifth temperature sensor, and a third flowmeter are installed on the pipeline connecting the air source heat pump unit to the user-side heating system; the air preheater is connected to the switching valve group through a pipeline, and a shunt regulating valve is installed on the pipeline.

[0009] Preferably, the user-side heating system includes a water supply main pipe, a water return main pipe, a circulation water pump, a sixth temperature sensor, a seventh temperature sensor, and a fourth flowmeter. The water supply main pipe is connected to the ammonia-heat pump working medium direct heat exchange unit, the heat exchanger, and the air source heat pump unit through pipelines respectively. The water return main pipe is connected to the ammonia-heat pump working medium direct heat exchange unit, the heat exchanger, and the air source heat pump unit through pipelines respectively. The sixth temperature sensor and the fourth flowmeter are installed on the water supply main pipe, and the circulation water pump and the seventh temperature sensor are installed on the water return main pipe.

[0010] Preferably, the control unit controls the on-off states of the switching valve group, the electric valve group, the shunt regulating valve, and the air electric valve group according to the data collected by the flowmeter group, the temperature sensor group, the fifth temperature sensor, and the third flowmeter.

[0011] Preferably, the ultra-long gravity heat pipe has an evaporation section and an adiabatic section, and the top of the ultra-long gravity heat pipe has a working medium outlet and a working medium inlet, and the working medium outlet and the working medium inlet are respectively connected to the ammonia-heat pump working medium direct heat exchange unit through pipelines; a second temperature sensor is arranged outside the ultra-long gravity heat pipe.

[0012] Preferably, a first switching valve, a third switching valve, and a first temperature sensor are installed on the pipeline connecting the working medium outlet to the ammonia-heat pump working medium direct heat exchange unit, and a second switching valve and a fourth switching valve are installed on the pipeline connecting the working medium inlet to the ammonia-heat pump working medium direct heat exchange unit; the first switching valve and the second switching valve are respectively connected to the air preheater through pipelines, and the third switching valve and the fourth switching valve are respectively connected to the heat exchanger through pipelines.

[0013] Preferably, the ammonia-heat pump working medium direct heat exchange unit is connected to the water supply main pipe and the water return main pipe through two pipelines respectively. A first electric valve, a first flowmeter, and a third temperature sensor are installed on one pipeline, and a second electric valve is installed on the other pipeline; the heat exchanger is connected to the water supply main pipe and the water return main pipe through two pipelines respectively. A third electric valve, a second flowmeter, and a fourth temperature sensor are installed on one pipeline, and a fourth electric valve is installed on the other pipeline.

[0014] Preferably, the ammonia-heat pump working medium direct heat exchange unit includes a first evaporator, a first compressor, a first condenser, and a first throttle valve connected in series end to end through pipelines. The first evaporator is connected to the ultra-long gravity heat pipe through a pipeline, and the first condenser is connected to the user-side heating system through a pipeline; the first evaporator is a double-sided phase change evaporator.

[0015] Preferably, the opening degree of the flow dividing regulating valve 205 is negatively correlated with the outdoor temperature T2, and satisfies: opening degree ratio = 20% + 2% × (-T2 - 10), and (T2 ≤ -10°C).

[0016] The present invention provides a control method for a heating system coupling an ultra-long gravity heat pipe and a dual heat pump, which is characterized in that it is used to control the heating system coupling the ultra-long gravity heat pipe and the dual heat pump, and includes the steps:

[0017] (S1) Real-time monitor the gaseous ammonia temperature T1, the outdoor temperature T2 and the heating load Q;

[0018] (S2) Mode determination:

[0019] If T1 ≥ 50°C and Q ≤ Q1, enter Mode 1, where the low load threshold Q1 is 30% - 50% of the designed maximum load;

[0020] If T1 < 50°C or Q > Q1, enter Mode 2;

[0021] If T2 ≤ -10°C and Q ≥ Q2, enter Mode 3, where the high load threshold Q2 is 80% - 100% of the designed maximum load;

[0022] (S3) Mode execution:

[0023] Mode 1: The gaseous ammonia directly heats the heating water through the heat exchanger, and at the same time starts the air source heat pump unit 206 to supplement the heating;

[0024] Mode 2: The gaseous ammonia enters the ammonia working medium heat pump unit for efficiency improvement, outputs high-temperature hot water, and operates in coordination with the air source heat pump unit;

[0025] Mode 3: Shunt the gaseous ammonia to preheat the air in proportion, and the remaining gaseous ammonia is improved in efficiency through the ammonia working medium heat pump unit, and the air source heat pump unit operates based on the preheated air;

[0026] (S4) Regulation:

[0027] Dynamically adjust the output water temperatures of the ammonia working medium heat pump unit and the air source heat pump unit, and mix them to the target temperature.

[0028] Preferably, in the step (S4),

[0029] (1) Read the real-time data (T3, T4, T6, current flow rates q1, q2);

[0030] (2) Calculate the theoretical mixing ratio q1 / q 2；

[0031] (3) Adjust the opening degrees of the first electric valve and the fifth electric valve through the PID control algorithm to make the actual mixing temperature T approach T6;

[0032] (4) If T continuously deviates from the target value by more than ±2°C for more than 30 seconds, the following compensation mechanism is triggered:

[0033] If T < T6, the opening of the first electric valve is preferentially increased;

[0034] If T > T6, the opening of the fifth electric valve is preferentially increased.

[0035] Compared with the prior art, the advantages of a heating system and a control method coupling an ultra-long gravity heat pipe and a dual heat pump disclosed by the present invention are as follows:

[0036] 1. The heating system coupling the ultra-long gravity heat pipe and the dual heat pump can achieve efficient energy utilization, switch working modes according to different load conditions, and can cover the working condition requirements at different temperatures;

[0037] 2. The heating system coupling the ultra-long gravity heat pipe and the dual heat pump preheats air by shunting the ammonia gas of the ultra-long gravity heat pipe, solves the problems that a traditional air source heat pump cannot start at extremely low temperatures and has too low COP, realizes zero additional energy consumption for air preheating, and saves more than 60% of energy compared with the electric auxiliary heating scheme; after the shunted ammonia gas is condensed, it returns to the heat pipe cycle without external working medium supplement;

[0038] 3. The heating system coupling the ultra-long gravity heat pipe and the dual heat pump directly exchanges heat by introducing the heat pipe cycle working medium into the heat pump evaporator, has good thermodynamic performance, a smaller floor area and lower system costs; the designed double-sided phase change evaporator has a capillary structure outside the heat exchange tubes to promote ammonia condensation, and the longitudinal partition inclination design meets the requirement of rapid liquid ammonia flow;

[0039] 4. The heating system coupling the ultra-long gravity heat pipe and the dual heat pump combined with an air source heat pump can reduce the extraction amount of medium-deep geothermal energy and avoid the influence of the ultra-long gravity heat pipe system on the soil temperature field due to long-term full-load operation;

[0040] 5. The control method of the heating system coupling the ultra-long gravity heat pipe and the dual heat pump proposes an operation strategy based on different working conditions, solves the problem that it is difficult for the heat pump and the heat pipe to dynamically match supply and demand; by adjusting the output ratio of the ammonia working medium heat pump and the air source heat pump, the load demand of 30% - 100% can be covered, the air source heat pump operates based on the ambient temperature (COP = 2.5 - 3.0), and the comprehensive COP is increased to 3.8 - 4.2 after the dual heat pumps cooperate. Description of the Drawings

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] As Figure 1 shown in the figure is the structural schematic diagram of a heating system coupling an ultra-long gravity heat pipe and a dual heat pump according to the present application.

[0043] As Figure 2 shown in the figure is the structural schematic diagram of the first evaporator of a heating system coupling an ultra-long gravity heat pipe and a dual heat pump according to the present application. Specific embodiments

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] As Figure 1 shown, a heating system coupling an ultra-long gravity heat pipe and a dual heat pump according to the present application includes an ultra-long gravity heat pipe system 1, an air source heat pump system 2, a user-side heating system 3, and a control unit. Both the ultra-long gravity heat pipe system and the air source heat pump system 2 are connected to the user-side heating system 3. The ultra-long gravity heat pipe system 1 includes an ultra-long gravity heat pipe, a switching valve group, an ammonia-heat pump working medium direct heat exchange unit 109, a heat exchanger 110, an electric valve group, a flowmeter group, and a temperature sensor group. The ultra-long gravity heat pipe is connected to the ammonia-heat pump working medium direct heat exchange unit 109 and the heat exchanger 110 through pipelines. The ammonia-heat pump working medium direct heat exchange unit 109 and the heat exchanger 110 are respectively connected to the user-side heating system 3 through pipelines.

[0046] An ultra-long gravity heat pipe is installed with a switching valve group on the pipeline connecting it to the ammonia-heat pump working medium direct heat exchange unit 109 and the heat exchanger through a pipeline. Electric valve groups, flowmeter groups, and temperature sensor groups are installed on the pipelines where the ammonia-heat pump working medium direct heat exchange unit 109 and the heat exchanger 110 are connected to the user-side heating system 3. The air source heat pump system 2 includes an air inlet pipe 201, a fan 202, an air preheater 203, an air outlet pipe 204, a flow control valve 205, an air source heat pump unit 206, an air electric valve group, a fifth temperature sensor 209, and a third flowmeter 210. The air inlet pipe 201, the fan 202, the air preheater 203, and the air source heat pump unit 206 are connected in sequence through pipelines. The air outlet pipe 204 is connected to the air source heat pump unit 206. The air source heat pump unit 206 is connected to the user-side heating system 3 through a pipeline. An air electric valve group, a fifth temperature sensor 209, and a third flowmeter 210 are installed on the pipeline where the air source heat pump unit 206 is connected to the user-side heating system 3. The air preheater 203 is connected to the switching valve group through a pipeline, and a flow control valve 205 is installed on the pipeline.

[0047] The user-side heating system 3 includes a water supply main pipe 301, a return water main pipe 302, a circulation water pump 304, a sixth temperature sensor 303, a seventh temperature sensor 305, and a fourth flowmeter 306. The water supply main pipe 301 is connected to the ammonia-heat pump working medium direct heat exchange unit 109, the heat exchanger 110, and the air source heat pump unit 206 through pipelines respectively. The return water main pipe 302 is connected to the ammonia-heat pump working medium direct heat exchange unit 109, the heat exchanger 110, and the air source heat pump unit 206 through pipelines respectively. The sixth temperature sensor 303 and the fourth flowmeter 306 are installed on the water supply main pipe 301. The circulation water pump 304 and the seventh temperature sensor 305 are installed on the return water main pipe 302.

[0048] The control unit controls the on-off states of the switching valve group, the electric valve group, the flow control valve 205, and the air electric valve group based on the data collected by the flowmeter groups, the temperature sensor groups, the fifth temperature sensor 209, and the third flowmeter 210, and changes the working state of the heating system coupled by the ultra-long gravity heat pipe and the dual heat pump.

[0049] The heating system coupling the ultra-long gravity heat pipe and the dual heat pump can, through the switching function, directly utilize the high-temperature heat of the heat pipe at low loads (COP approaches infinity); at medium and high loads, the ammonia refrigerant heat pump is used to improve efficiency (COP reaches 4.0 - 4.5); in extremely cold environments, the air is shunted and preheated, so that the COP of the air source heat pump is restored from 1.3 to above 2.8, covering the full operating conditions from -30°C to 50°C. The ammonia in the ultra-long gravity heat pipe can be shunted to the air preheater to preheat the air, which can solve the problems that the traditional air source heat pump cannot start at extremely low temperatures and has too low COP, realize air preheating with zero additional energy consumption, and save more than 60% of energy compared with the electric auxiliary heating scheme; after the shunted ammonia is condensed, it returns to the heat pipe cycle without external refrigerant supplementation. The combined air source heat pump can reduce the extraction amount of medium and deep geothermal energy, and avoid the influence of the ultra-long gravity heat pipe system on the soil temperature field due to long-term full-load operation.

[0050] Specifically, the ultra-long gravity heat pipe has an evaporation section 101 and an adiabatic section 102, and the top of the ultra-long gravity heat pipe has a refrigerant outlet 103 and a refrigerant inlet 104. The refrigerant outlet 103 and the refrigerant inlet 104 are respectively connected to the ammonia-heat pump refrigerant direct heat exchange unit 109 through pipelines. A second temperature sensor 116 is arranged outside the ultra-long gravity heat pipe. A first switching valve 105, a third switching valve 107 and a first temperature sensor 115 are installed on the pipeline connecting the refrigerant outlet 103 and the ammonia-heat pump refrigerant direct heat exchange unit 109, and a second switching valve 106 and a fourth switching valve 108 are installed on the pipeline connecting the refrigerant inlet 104 and the ammonia-heat pump refrigerant direct heat exchange unit 109. The first switching valve 105 and the second switching valve 106 are respectively connected to the air preheater 203 through pipelines, and the third switching valve 107 and the fourth switching valve 108 are respectively connected to the heat exchanger 110 through pipelines. The liquid ammonia absorbs the medium and deep geothermal energy in the evaporation section 101 to form saturated steam, and the gaseous ammonia is transported from the refrigerant outlet after passing through the adiabatic section 102. The temperature of the gaseous ammonia is negatively correlated with the heat extraction amount. The gaseous ammonia passes through the first switching valve 105 and the third switching valve 107 and enters the heat exchanger 110 to condense and release heat. The condensed liquid ammonia passes through the fourth switching valve 108 and the second switching valve 106 and returns to the bottom of the ultra-long gravity heat pipe from the refrigerant inlet 104 to complete one cycle. The water supply pipeline of the heat exchanger 110 is connected to the water supply main pipe 301 through a third electric valve 113 and a second flow meter 118; the return water pipeline of the heat exchanger 110 is connected to the return water main pipe 302 through a fourth electric valve 114.

[0051] The ammonia-heat pump working medium direct heat exchange unit 109 is connected to the water supply main pipe 301 and the return water main pipe 302 respectively through two pipes. A first electric valve 111, a first flow meter 117, and a third temperature sensor 119 are installed on one of the pipes, and a second electric valve 112 is installed on the other pipe. The heat exchanger 110 is connected to the water supply main pipe 301 and the return water main pipe 302 respectively through two pipes. A third electric valve 113, a second flow meter 118, and a fourth temperature sensor 120 are installed on one of the pipes, and a fourth electric valve 114 is installed on the other pipe.

[0052] The ammonia-heat pump working medium direct heat exchange unit 109 includes a first evaporator 1091, a first compressor 1092, a first condenser 1093, and a first throttle valve 1094 connected in series end to end through pipes. The first evaporator 1091 is connected to the ultra-long gravity heat pipe through a pipe, and the first condenser 1093 is connected to the user-side heating system 3 through a pipe. The first evaporator 1091 is a double-sided phase change evaporator, which is used to condense gaseous ammonia into liquid ammonia and drive the refrigerant to evaporate and improve efficiency. The liquid ammonia absorbs medium-deep geothermal energy in the evaporation section 101 of the ultra-long gravity heat pipe to form saturated vapor, and is transported as gaseous ammonia through the adiabatic section 102 by the working medium outlet 103. After passing through the first switching valve 105 and the third switching valve 107, it enters the first evaporator 1091 of the ammonia working medium heat pump unit 109 to condense and release heat. The condensed liquid ammonia passes through the fourth switching valve 108 and the second switching valve 106 and returns to the bottom of the ultra-long gravity heat pipe through the working medium inlet 104 to complete one cycle. The water supply pipeline of the first condenser 1093 of the ammonia working medium heat pump unit 109 is connected to the water supply main pipe 301 through the first electric valve 111 and the first flow meter 117; the return water pipeline of the condenser 1093 of the ammonia working medium heat pump unit 109 is connected to the return water main pipe 302 through the second electric valve 112.

[0053] See Figure 2 , the first evaporator 1091 is a shell-and-tube heat exchanger. The refrigerant is inside the tube and ammonia is outside the tube. Inside the tube, there are tube sheets 10911 at both ends, a longitudinal partition plate 10915 connecting the two tube sheets 10911, heat exchange tubes 10916, several baffle plates 10914 installed on the longitudinal partition plate 10915, and a shell-side inlet 10912 and a shell-side outlet 10913 located on both sides of the longitudinal partition plate 10915 respectively. High-temperature ammonia gas enters the first evaporator 1091 from the shell-side inlet 10912, passes through multiple baffle plates 10914 and the openings of the longitudinal partition plate 10915, and becomes liquid ammonia and flows out from the shell-side outlet 10913.

[0054] Preferably, the outer wall surface of the heat exchange tube 10916 adopts a capillary structure to accelerate the dripping of liquid ammonia, so as to avoid the reduction of the condensation efficiency due to an overly thick liquid film. The longitudinal partition 10915 is inclined 5° towards the opening, which is beneficial to the reflux of the condensed liquid ammonia. Preferably, the tube wall of the heat exchange tube 10916 is made of a highly thermally conductive and corrosion-resistant metal (such as titanium alloy or nickel-based alloy), with a thickness of 0.5 - 2 mm.

[0055] The air source heat pump unit 206 includes a second evaporator 2061, a second compressor 2062, a second condenser 2063, and a second throttle valve 2064 connected in series head to tail through pipes. The second evaporator 2061 is connected to the air preheater 203 through a pipe, and the second condenser 2063 is connected to the user-side heating system 3 through a pipe.

[0056] The first temperature sensor 115 is used to measure the outlet ammonia temperature (T1), the second temperature sensor 116 is used to measure the outdoor temperature (T2), the third temperature sensor 119 is used to measure the outlet water temperature (T3) of the ammonia refrigerant heat pump unit 109, the fourth temperature sensor 120 is used to measure the outlet water temperature (T4) of the heat exchanger 110, the fifth temperature sensor 209 is used to measure the outlet water temperature (T5) of the air source heat pump unit 206, the sixth temperature sensor 303 is used to measure the temperature (T6) of the main water supply pipe 301, and the seventh temperature sensor 305 is used to measure the temperature (T7) of the main return water pipe 302;

[0057] The first flowmeter 117 is used to measure the outlet water flow rate (q1) of the ammonia refrigerant heat pump unit 109, the second flowmeter 118 is used to measure the outlet water flow rate (q2) of the heat exchanger 110, the third flowmeter 210 is used to measure the outlet water flow rate (q3) of the air source heat pump unit 206, and the fourth flowmeter is used to measure the outlet water flow rate (q4) of the main water supply pipe 301;

[0058] The first electric valve 111, the second electric valve 112, the third electric valve 113, the fourth electric valve 114, the fifth electric valve 207, the sixth electric valve 208, the first switching valve 105, the second switching valve 106, the third switching valve 107, the fourth switching valve 108, the shunt regulating valve 205, and the fan 202 are all connected to the control unit. The opening degree of the shunt regulating valve 205 is negatively correlated with the outdoor temperature T2 and satisfies: opening degree ratio = 20% + 2% × (-T2 - 10), and (T2 ≤ -10°C).

[0059] This application also discloses a control method for a heating system coupled with an ultra-long gravity heat pipe and a dual heat pump, including the steps:

[0060] S1: Real-time monitor the gaseous ammonia temperature T1, the outdoor temperature T2, and the heating load Q;

[0061] S2: Mode determination:

[0062] · If T1 ≥ 50°C and Q ≤ Q1, enter Mode 1, where the low-load threshold Q1 is 30% - 50% of the designed maximum load;

[0063] · If T1 < 50°C or Q > Q1, enter Mode 2;

[0064] · If T2 ≤ -10°C and Q ≥ Q2, enter Mode 3, where the high-load threshold Q2 is 80% - 100% of the designed maximum load;

[0065] S3: Mode execution:

[0066] Mode 1: Gaseous ammonia directly heats the heating water through the heat exchanger 110, and at the same time starts the air source heat pump unit 206 to supplement the heating;

[0067] Mode 2: Gaseous ammonia enters the ammonia working fluid heat pump unit 109 for efficiency improvement, outputs high-temperature hot water, and operates in coordination with the air source heat pump unit 206;

[0068] Mode 3: Gaseous ammonia is proportionally shunted to preheat the air, and the remaining gaseous ammonia is improved in efficiency through the ammonia working fluid heat pump unit 109, and the air source heat pump unit 206 operates based on the preheated air;

[0069] S4: Regulation:

[0070] Dynamically regulate the output water temperatures of the ammonia working fluid heat pump unit 109 and the air source heat pump unit 206 and mix them to the target temperature.

[0071] Among them, the three modes in step S3 are specifically as follows:

[0072] Mode 1:

[0073] If T1 ≥ 50°C and Q ≤ Q1, through the control unit, open port a and port c of the first switching valve 105, port a and port b of the third switching valve 107, port a and port c of the second switching valve 106, port a and port b of the fourth switching valve 108, the third electric valve 113, the fourth electric valve 114, the fifth electric valve 207, the sixth electric valve 208, and other valves are normally closed. The ultra-long gravity heat pipe supplies heat in coordination with the air source heat pump unit 206 through the heat exchanger 110.

[0074] Applicable to the initial stage of heating or scenarios with large day-night temperature differences, saving 15% - 20% of the annual operating cost

[0075] The ultra-long gravity heat pipe directly releases heat by the direct condensation of gaseous ammonia in the heat exchanger, without power consumption, and the system energy efficiency ratio (COP) approaches infinity, reducing the operating cost; at low loads, the air source heat pump usually operates with a relatively high COP, and the output water temperature can be maintained at 45 - 50°C (when the ambient temperature is relatively high).

[0076] Mode 2:

[0077] If T1 < 50°C or Q > Q1, through the control unit, open ports a and c of the first switching valve 105, ports a and c of the third switching valve 107, ports a and c of the second switching valve 106, ports a and c of the fourth switching valve 108, the first electric valve 111, the second electric valve 112, the fifth electric valve 207, and the sixth electric valve 208, and keep other valves closed. The ultra-long gravity heat pipe supplies heat in cooperation with the ammonia refrigerant heat pump unit 109 and the air source heat pump unit 206.

[0078] The heat pump couples and improves the efficiency of the heat of ammonia gas and the heat of air, and outputs high-temperature hot water (such as 50 - 65°C) for end-use; reduces the extraction amount of medium-deep geothermal energy, and avoids the influence of the ultra-long gravity heat pipe system on the soil temperature field due to long-term full-load operation; by adjusting the output ratio of the ammonia refrigerant heat pump and the air source heat pump, it can cover 30% - 100% of the load demand; the air source heat pump operates based on the ambient temperature (COP = 2.5 - 3.0), and the comprehensive COP is increased to 3.8 - 4.2 after the cooperation of the two heat pumps.

[0079] Mode 3:

[0080] If T2 ≤ -10°C and Q ≥ Q2, through the control unit, open ports a, b, and c of the first switching valve 105, ports a and c of the third switching valve 107, ports a, b, and c of the second switching valve 106, ports a and c of the fourth switching valve 108, the first electric valve 111, the second electric valve 112, the fifth electric valve 207, the sixth electric valve 208, and the flow dividing regulating valve 205, and keep other valves closed. Preheat the air by proportionally dividing the gaseous ammonia, and the remaining gaseous ammonia supplies heat in cooperation with the ammonia refrigerant heat pump unit 109 and the air source heat pump unit 206.

[0081] It can continuously supply heat in extremely low-temperature environments without the risk of shutdown; realize air preheating with zero additional energy consumption through heat pipe working medium flow division, saving more than 60% of energy compared with the electric auxiliary heating scheme; the condensed divided ammonia gas returns to the heat pipe cycle without external working medium supplementation.

[0082] It should be noted that in the above step S4, setting the target water supply temperature T6 according to the heating end demand includes the steps:

[0083] (1) Read real-time data (T3, T4, T6, current flow rates q1, q2);

[0084] (2) Calculate the theoretical mixing ratio q1 / q 2；

[0085] (3) Adjust the opening degrees of the first electric valve 111 and the fifth electric valve 207 through the PID control algorithm to make the actual mixing temperature T approach T6;

[0086] (4) If T continuously deviates from the target value by more than ±2°C for more than 30 seconds, the following compensation mechanism is triggered:

[0087] · If T < T6, the opening degree of the first electric valve 111 is preferentially increased (increasing the proportion of high-temperature water);

[0088] · If T > T6, the opening degree of the fifth electric valve 207 is preferentially increased (increasing the proportion of low-temperature water).

[0089] The theoretical mixing ratio q1 / q2 is calculated by the following formula:

[0090] q1 / q2 = (T4 - T) / (T3 - T)

[0091] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heating system of an ultra-long gravity heat pipe coupled with a dual heat pump, characterized in that: It includes an extra-long gravity heat pipe system, an air source heat pump system, a user-side heating system and a control unit; the extra-long gravity heat pipe system includes an extra-long gravity heat pipe, which is connected to an ammonia-heat pump working fluid direct heat exchange unit and a heat exchanger through a pipeline, and the ammonia-heat pump working fluid direct heat exchange unit and the heat exchanger are respectively connected to the user-side heating system through pipelines; the air source heat pump system includes an air inlet pipe, a fan, an air preheater, and an air source heat pump unit connected in sequence through pipelines, the air source heat pump unit is connected to an air outlet pipe, and the air source heat pump The unit is connected to the user-side heating system through a pipeline; a switching valve group is installed on the pipeline connecting the super-long gravity heat pipe with the ammonia-heat pump working fluid direct heat exchange unit and the heat exchanger, and an electric valve group, a flow meter group and a temperature sensor group are installed on the pipeline connecting the ammonia-heat pump working fluid direct heat exchange unit and the heat exchanger with the user-side heating system; an air electric valve group, a fifth temperature sensor and a third flow meter are installed on the pipeline connecting the air source heat pump unit with the user-side heating system; the air preheater is connected to the switching valve group through a pipeline, and a diversion regulating valve is installed on the pipeline.

2. The heating system of the ultra-long gravity heat pipe coupled with the dual heat pumps according to claim 1, characterized in that: The user-side heating system includes a water supply main, a return water main, a circulating water pump, a sixth temperature sensor, a seventh temperature sensor and a fourth flow meter. The water supply main is connected to the ammonia-heat pump working fluid direct heat exchange unit, the heat exchanger and the air source heat pump unit through pipelines, respectively. The return water main is connected to the ammonia-heat pump working fluid direct heat exchange unit, the heat exchanger and the air source heat pump unit through pipelines, respectively. The sixth temperature sensor and the fourth flow meter are installed on the water supply main, and the circulating water pump and the seventh temperature sensor are installed on the return water main.

3. The heating system of the ultra-long gravity heat pipe coupled with the dual heat pumps according to claim 2, characterized in that: The control unit controls the on / off states of the switching valve group, the electric valve group, the shunt regulating valve and the air electric valve group through the data collected by the flow meter group, the temperature sensor group, the fifth temperature sensor and the third flow meter.

4. The heating system of the ultra-long gravity heat pipe coupled with the dual heat pumps as claimed in claim 3, characterized in that: The super-long gravity heat pipe has an evaporation section and an insulation section, and the top of the super-long gravity heat pipe has a working fluid outlet and a working fluid inlet, the working fluid outlet and the working fluid inlet are respectively connected to the ammonia-heat pump working fluid direct heat exchange unit through pipelines; a second temperature sensor is arranged outside the super-long gravity heat pipe.

5. The heating system of the ultra-long gravity heat pipe coupled with dual heat pumps as claimed in claim 4, characterized in that: A first switching valve, a third switching valve and a first temperature sensor are installed on the pipeline connecting the working fluid outlet and the ammonia-heat pump working fluid direct heat exchange unit, and a second switching valve and a fourth switching valve are installed on the pipeline connecting the working fluid inlet and the ammonia-heat pump working fluid direct heat exchange unit; the first switching valve and the second switching valve are respectively connected to the air preheater through pipelines, and the third switching valve and the fourth switching valve are respectively connected to the heat exchanger through pipelines.

6. The heating system of the ultra-long gravity heat pipe coupled with the dual heat pumps according to claim 5, characterized in that: The ammonia-heat pump working fluid direct heat exchange unit is connected to the water supply main and the return water main through two pipes, one of which is equipped with a first electric valve, a first flow meter, and a third temperature sensor, and the other is equipped with a second electric valve; the heat exchanger is connected to the water supply main and the return water main through two pipes, one of which is equipped with a third electric valve, a second flow meter, and a fourth temperature sensor, and the other is equipped with a fourth electric valve.

7. The heating system of the super-long gravity heat pipe coupled with the dual heat pumps according to claim 6, characterized in that: The ammonia-heat pump working fluid direct heat exchange unit includes a first evaporator, a first compressor, a first condenser, and a first throttle valve which are connected in series through pipelines. The first evaporator is connected to the extra-long gravity heat pipe through a pipeline, and the first condenser is connected to the user-side heating system through a pipeline; the first evaporator is a double-sided phase change evaporator.

8. The heating system of the ultra-long gravity heat pipe coupled with dual heat pumps according to claim 6, characterized in that: The opening degree of the diversion regulating valve 205 is negatively correlated with the outdoor temperature T2, and satisfies: opening ratio = 20% + 2% × (-T2-10), and (T2 ≤ -10°C).

9. A control method for a heating system coupled with an ultra-long gravity heat pipe and a dual heat pump, characterized in that: A heating system for controlling an ultra-long gravity heat pipe coupled with a dual heat pump according to any one of claims 1 to 8, comprising the steps of: (S1) real-time monitoring of gaseous ammonia temperature T1, outdoor temperature T2 and heating load Q; (S2) Mode determination: If T1 ≥ 50°C and Q ≤ Q1, enter mode 1, where the low load threshold Q1 is 30% to 50% of the designed maximum load; If T1<50℃ or Q>Q1, enter mode 2; T2≤-10℃ and Q≥Q2, enter mode 3, where the high load threshold Q2 is 80% to 100% of the designed maximum load; (S3) Mode execution: Mode 1: Gaseous ammonia directly heats the heating water through the heat exchanger, and the air source heat pump unit 206 is started to supplement the heating; Mode 2: Gaseous ammonia enters the ammonia working fluid heat pump unit to improve efficiency, outputs high-temperature hot water, and operates in coordination with the air source heat pump unit; Mode 3: The gaseous ammonia is diverted in proportion to preheat the air, and the remaining gaseous ammonia is used to improve the efficiency of the ammonia working fluid heat pump unit, and the air source heat pump unit operates based on the preheated air; (S4) Adjustment: Dynamically adjust the output water temperature of the ammonia heat pump unit and the air source heat pump unit and mix them to the target temperature.

10. The control method of the heating system of the super-long gravity heat pipe coupled with the dual heat pumps according to claim 9, characterized in that: In the step (S4), (1) Read real-time data (T3, T4, T6, current flow q1, q2); (2) Calculate the theoretical mixing ratio q1 / q 2； (3) adjusting the opening of the first electric valve and the fifth electric valve through the PID control algorithm so that the actual mixing temperature T approaches T6; (4) If T deviates from the target value by more than ±2°C for more than 30 seconds, the following compensation mechanism is triggered: If T<T6, the opening of the first electric valve is increased first; If T>T6, the opening of the fifth electric valve is increased first.

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