Shallow geothermal energy exchange method adopting U-shaped pipe type permeable pipe pile

Abstract

The invention provides a shallow geothermal energy exchange method adopting U-shaped pipe type permeable pipe piles. The shallow geothermal energy exchange method comprises the following steps that S1, the U-shaped pipe type permeable pipe piles are prefabricated; s2, U-shaped pipe type permeable pipe piles are installed; s3, underground water enters a pipe cavity through a water permeable hole and makes contact with a U-shaped pipe; s4, the circulating medium flows through the U-shaped pipe, and in the whole flowing process, the circulating medium continuously exchanges heat with the water body in the pile through the pipe wall; and S5, through the water permeable holes, the underground water in the pipe pile is influenced by seepage of the underground water outside the pipe pile, and therefore the underground convective heat exchange function is achieved. The provided shallow geothermal energy exchange method can break through the barrier of solid heat conduction, and the heat exchange capacity is remarkably enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat exchange, in particular to a shallow geothermal energy exchange method using a U-shaped tube type water permeable pipe pile. BACKGROUND

[0002] With the continuous development of building energy saving and renewable energy utilization technology, ground source heat pump systems are widely used due to their high efficiency, stability and environmental protection. The system exchanges heat with rock-soil through the heat exchanger buried in the ground to achieve building heating and cooling. The traditional ground source heat pump system mainly uses vertical U-shaped buried pipe, that is, U-shaped high-density polyethylene pipe is buried in the borehole, and after backfilling, a ground buried pipe heat exchanger is formed. However, this technology has the disadvantages of high initial investment, large land occupation of drilling construction, and possible impact on underground hydrogeological environment.

[0003] In order to overcome the above-mentioned shortcomings, a technology combining ground buried pipe heat exchanger with building foundation structure, energy pile, has emerged as the times require. The energy pile is a heat exchange pipe pre-buried in the traditional concrete pile foundation which bears the load of the upper structure, so that the pile foundation plays the functions of structure bearing and geothermal exchange. This method significantly reduces the additional drilling cost and land occupation of the ground source heat pump system, realizes the integrated and efficient use of underground space, and is considered as an important innovation in the field of geothermal energy development.

[0004] The conventional U-shaped tube energy pile used in the prior art. Through the flow of circulating fluid in the pipeline, heat exchange between the pile concrete and the surrounding rock-soil is realized. Although the traditional energy pile technology has achieved successful application, its heat exchange efficiency still has bottlenecks, mainly limited by the following two inherent defects: (1) Heat exchange completely depends on solid heat transfer, and its efficiency is limited: the heat transfer path of the traditional energy pile is "circulating fluid → pipe wall → concrete pile body → pile-soil contact surface → surrounding soil". The whole process mainly relies on the heat conduction of solid, and the thermal conductivity of rock-soil is generally low, resulting in large thermal resistance and difficult to further improve the heat exchange efficiency. (2) "Pile-soil contact thermal resistance" problem: there may be gaps or non-dense contact between the pile body and the surrounding soil, which will form additional contact thermal resistance, further hinder the heat transfer, and affect the overall energy efficiency of the system.

[0005] In summary, although the existing U-shaped tube energy pile technology solves the problem of drilling cost, the core contradiction of relying on pure solid heat conduction and limited heat exchange efficiency has not been effectively solved. Therefore, there is an urgent need for a new type of energy pile technology that can break through the barrier of solid heat conduction and significantly enhance the heat exchange capacity.

[0006] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies of the prior art. SUMMARY

[0007] The application aims to provide a shallow geothermal energy exchange method using U-shaped tubular water-permeable pipe piles, which can break through the barrier of solid heat conduction and significantly enhance the heat exchange capacity.

[0008] In order to achieve the above-mentioned purpose, the application provides the following technical scheme: The shallow geothermal energy exchange method using U-shaped tubular water-permeable pipe piles is improved in that the method comprises the following steps: Step S1, prefabricating a U-shaped tubular water-permeable pipe pile; the U-shaped tubular water-permeable pipe pile comprises: a pipe pile, which comprises a hollow cylindrical pipe pile, a hollow part forms a pipe cavity, a through hole is uniformly arranged on the side wall of the pipe pile in a radial direction as a water-permeable hole, and the water-permeable hole is uniformly added in an axial direction of the pipe pile; a U-shaped pipe, which comprises a hollow pipe bent into a U shape and arranged in the pipe cavity; a closed end of the U-shaped pipe extends into the bottom of the pipe pile; a first branch pipe and a second branch pipe of the U-shaped pipe are arranged in parallel and connected to the top end of the pipe pile; Step S2, installing the U-shaped tubular water-permeable pipe pile; the U-shaped tubular water-permeable pipe pile is extruded into a soil body containing groundwater seepage; Step S3, groundwater enters the pipe cavity through the water-permeable hole and contacts the U-shaped pipe; Step S4, circulating medium with a first temperature t1 flows into the first branch pipe of the U-shaped pipe, flows through the lower part of the pipe pile, and then enters the second branch pipe after passing through the U-shaped elbow; in the whole flow process, the circulating medium continuously exchanges heat with the water in the pile through the pipe wall, and when the circulating medium flows to the outlet of the second branch pipe, the temperature changes to a second temperature t2, and then the circulating medium enters a plate heat exchanger and exchanges heat with refrigerant of a building heat pump circulation system; Step S5, the groundwater in the pipe pile is affected by the seepage of the groundwater outside the pipe pile through the water-permeable hole, so as to realize the function of underground convection heat exchange.

[0009] Preferably, the step S1 further comprises: fixing a hole position module on a pile body mold when prefabricating the pipe pile, so as to uniformly arrange the through hole; and the through hole is additionally provided with a filter screen.

[0010] Preferably, the U-shaped pipe is fixed in the pipe cavity through a support frame; the first branch pipe and the second branch pipe can extend out of the top of the pile and have sufficient reserved length.

[0011] Preferably, when the U-shaped tube needs to absorb the heat energy of the underground water body, the step S4 comprises: the low-temperature t1 circulating medium enters the first branch pipe of the U-shaped tube, and then enters the geothermal circulation system through the second branch pipe of the U-shaped tube; in the flowing process, the circulating medium continuously absorbs the heat of the underground water in the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature is increased to the second temperature t2, and then enters the plate heat exchanger to exchange heat with the refrigerant of the building heat pump circulation system. The step S5 comprises: due to the influence of the underground water seepage, the underground water in the pipe pile continuously exchanges heat with the underground water outside the pipe pile, and continuously provides heat for the U-shaped tube.

[0012] Preferably, when the U-shaped tube needs to release the heat energy to the underground water body, the step S4 comprises: The high-temperature t1 circulating medium enters the first branch pipe of the U-shaped tube, and then enters the geothermal circulation system through the second branch pipe of the U-shaped tube; in the flowing process, the circulating medium continuously releases the heat of the underground water in the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature is decreased to the second temperature t2, and then enters the plate heat exchanger to absorb the surface waste heat; The step S5 comprises: the underground water in the pipe pile continuously absorbs the heat energy in the U-shaped tube, and then dissipates the heat to the outside of the pipe pile through the water-permeable hole; the underground water outside the pipe pile continuously absorbs the heat in the pipe pile.

[0013] Preferably, the method further comprises the step S6: the first branch pipe of the U-shaped tube is connected with the first temperature sensor, so as to measure the first temperature t1; the first branch pipe of the U-shaped tube is connected with the second temperature sensor, so as to measure the second temperature t2; the control system 203 monitors the temperature difference of the circulating medium in real time ; when ΔT < threshold value, the control system 203 controls the water pump 201 to stop working; when the control system 203 monitors ΔT ≥ threshold value, the water pump 201 is started to work again.

[0014] Compared with the closest prior art, the technical scheme of the embodiment of the present application has the following beneficial effects: 1. Introducing the convection of underground water, improving the traditional heat transfer mode: the heat of the traditional energy pile can only be slowly conducted to the surrounding rock-soil body through the pile body, and the heat transfer path is long and the thermal resistance is large. The water-permeable pipe pile provides a flow channel for the underground water, and the convection heat transfer of the fluid is considered. After the circulating liquid in the U-shaped tube of the pile exchanges heat with the pile body, it heats or cools the surrounding water-permeable pipe pile. Then, the underground water around the pile continuously flows through the heated / cooled water-permeable pipe pile under the action of the hydraulic gradient. The flowing underground water acts as an efficient "heat carrier", actively convecting and transporting heat from the pile body to the far rock-soil body (or extracting heat from the far rock-soil body to the pile body). The efficiency of this "convection heat transfer" relying on fluid flow is higher than that of pure solid heat transfer.

[0015] 2. Eliminate pile-soil contact thermal resistance: the traditional solid concrete energy pile and soil exist micro gap and not dense contact, form additional contact thermal resistance, hinder heat transfer. While the present application adopts the permeable pipe pile, groundwater fills and flows in the pores of the permeable pipe pile and the surrounding soil, realizing seamless and full wet surface contact. Water as a good heat conducting medium, perfectly fills all the contact gaps, making the thermal connection between the pile body and the water body extremely close, and the contact thermal resistance of the soil can be completely eliminated.

[0016] 3. The effective heat exchange area of the traditional energy pile is limited to the outer geometric surface area of the pile, while the effective heat exchange area of the present application is the huge internal pore surface area of the entire permeable pile. Groundwater flows through these winding pores and exchanges heat with concrete, greatly increasing the heat exchange area. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute improper limitations on the present application. Among them: Figure 1 It is a schematic diagram of the pipe pile structure cross section involved in the present application; Figure 2 It is a schematic diagram of the pipe pile structure and a schematic diagram of its control system involved in the present application; Among them: 101, pipe pile; 102, water in the pile; 103, U-shaped pipe; 104, permeable hole; 201, water pump; 202, evaporator; 203, control system; 204, throttle valve; 205, condenser; 206, compressor. DETAILED DESCRIPTION

[0018] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. Each example is provided by way of explanation of the present application rather than limiting the present application. In fact, those skilled in the art will appreciate that modifications and variations can be made in the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. Therefore, it is intended that the present application include such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0019] In the following description, the terms "first / second / third" are merely to distinguish similar objects, and do not represent a specific order of the objects. Understandably, "first / second / third" can be interchanged in a specific order or sequence as allowed, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description herein is for describing the embodiments of the present disclosure only and is not intended to be limiting of the present disclosure.

[0021] In the description of the present application, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom" and the like is based on the orientation or positional relationship shown in the drawings and is only for the convenience of describing the present application and does not require the present application to be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. The terms "connected", "connected", "provided" used in the present application should be understood broadly, for example, can be fixedly connected, can also be detachably connected; can be directly connected, can also be indirectly connected through an intermediate component; can be wired electrical connection, wireless electrical connection, or wireless communication signal connection, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0022] The present application relates to a shallow geothermal energy exchange method using a U-shaped tubular water permeable pipe pile, which is improved in that the method comprises the following steps: Step S1, prefabricating a U-shaped tubular water permeable pipe pile; the U-shaped tubular water permeable pipe pile comprises: Pipe pile 101, the pipe pile comprises a hollow cylindrical pipe pile, and a hollow part forms a pipe cavity; a through hole is uniformly provided on the pipe wall along the radial direction of the pipe pile as a water permeable hole; the water permeable hole is uniformly added along the axial direction of the pipe pile. Specifically, the pipe pile used in the present application is cast with high-strength concrete, and the pile body forms a prefabricated hollow pipe pile. A closed circular bottom plate is arranged at the bottom of the pile body, and the diameter of the circular bottom plate matches the diameter of the pile body; the circular bottom plate cooperates with the pile body, and the hollow part forms a pipe cavity. A through hole is uniformly provided along the circumference of the pipe wall of the pipe pile (i.e. the radial direction of the pipe pile), and the number of through holes is not limited, subject to engineering construction, such as Figure 1 As shown in the figure, four through holes are provided in the radial direction of the pipe pile. At the same time, the through holes are uniformly added along the axial direction of the pipe pile. Preferably, the pipe pile used in the present application is a water permeable concrete pipe pile. When the pipe pile is cast, the hole position module is fixed on the pile body mold in priority, and the water permeable hole 104 is uniformly provided. At the same time, the water permeable hole is provided with a filter screen to prevent soil particles from flowing into the pile cavity and to ensure water permeability.

[0023] U-shaped tube 103, comprising a hollow tube bent into a U-shaped tube, arranged in the pipe cavity; the closed end of the U-shaped tube extends into the bottom of the pipe pile; the first branch pipe and the second branch pipe of the U-shaped tube are arranged in parallel and are connected to the top end of the pipe pile.

[0024] Specifically, the material of the U-shaped pipe is not limited, and a material with good corrosion resistance and heat conduction performance is preferably selected. Preferably, the U-shaped pipe 103 of the present application adopts a high-density polyethylene (HDPE) pipe, which is pre-bent and formed in the factory and fixed in the hollow layer by a support frame, i.e., located in the central region of the hollow pile. It is ensured that the inlet branch pipe (first branch pipe) and the outlet branch pipe (second branch pipe) can protrude out of the top of the pile, and the reserved length is sufficient.

[0025] Step S2, installing the U-shaped pipe type water permeable pipe pile; the U-shaped pipe type water permeable pipe pile is extruded into the soil containing underground water seepage. Specifically, the site is measured and positioned. The precast U-shaped pipe type water permeable pipe pile is sunk to the design elevation by using a static pressure method or a vibration method, and is fixed in the soil below the aquifer. This step replaces the complex processes of site drilling, reinforcing cage lowering, concrete pouring, and curing of the traditional energy pile, greatly shortening the construction period. Preferably, the U-shaped pipe type water permeable pipe pile can also be fixed in a reinforcing cage matching its size to improve the fixing effect.

[0026] Step S3, the underground water enters the pipe cavity through the water permeable hole and contacts the U-shaped pipe.

[0027] Step S4, the circulating medium with the first temperature t1 flows into the first branch pipe of the U-shaped pipe, flows through the lower part of the pipe pile, and then enters the second branch pipe after passing through the U-shaped elbow. In the whole flow process, the circulating medium continuously exchanges heat with the water in the pile through the pipe wall, and when the circulating medium flows to the outlet of the second branch pipe, the temperature changes to the second temperature t2, and then enters the plate heat exchanger to exchange heat with the refrigerant of the building heat pump circulation system. Step S5, through the water permeable hole, the underground water in the pipe pile is affected by the seepage of the underground water outside the pipe pile, thereby realizing the function of underground convection heat exchange.

[0028] The water permeable concrete pipe pile provides a flow channel for underground water. After the circulating liquid in the U-shaped pipe in the pile exchanges heat with the pile body, the water in the pile is heated or cooled, and then the underground water around the pile continuously flows through the heated or cooled water permeable concrete pipe pile under the action of the hydraulic gradient.

[0029] Preferably, when the U-shaped pipe needs to absorb the heat energy of the water body, step S4 includes: the low-temperature t1 circulating medium enters the first branch pipe of the U-shaped pipe, and then enters the geothermal circulation system through the second branch pipe of the U-shaped pipe; during the flow process, the circulating medium continuously absorbs the heat of the underground water in the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature increases to the second temperature t2, and then enters the plate heat exchanger to exchange heat with the refrigerant of the building heat pump circulation system. Step S5 includes: due to the influence of the seepage of the underground water, the underground water in the pipe pile continuously exchanges heat with the underground water outside the pipe pile, and continuously provides heat for the U-shaped pipe.

[0030] Specifically, when a U-shaped pipe needs to absorb heat energy from the water, such as Figure 2 As shown, a low-temperature circulating medium (cold water) with a first temperature t1 is pressurized by a water pump 201 and injected into the first branch pipe (inlet branch pipe) of the U-shaped pipe 103. During the flow of the cold water through the U-shaped pipe, the heat of the water around the pile seeps into the water body inside the pile (102) through the permeable holes, forming groundwater convection heat exchange. At the same time, the heat of the water around the pile is also conducted to the water body inside the pile (102) through the pipe pile (101). The water body inside the pile (102) continuously provides heat energy to the cold water in the U-shaped pipe, causing the low-temperature cold water with the first temperature t1 to continuously absorb heat and rise to the second temperature t2 during the flow of the U-shaped pipe. Then, it enters the plate heat exchanger through the second branch pipe (outlet branch pipe) of the U-shaped pipe, realizing the forced convection heat exchange process between the water body inside the pile and the circulating medium in the U-shaped pipe. At the same time, in step S5, the groundwater outside the pipe pile can continuously provide heat energy and enter the inside of the pipe pile, thereby enabling the U-shaped pipe to continuously absorb heat energy.

[0031] The geothermal circulation system includes, in sequence, an evaporator 202, a throttling valve 204, a condenser 205, and a compressor 206. The outlet end of the evaporator 202 is connected to the first branch pipe (inlet branch pipe) of the U-shaped tube; the inlet end of the evaporator 202 is connected to the second branch pipe (outlet branch pipe) of the U-shaped tube.

[0032] Preferably, the water pump 201, used for the inlet water volume of the circulating medium in the U-tube, is located between the outlet end of the evaporator 202 and the first branch pipe (inlet branch pipe) of the U-tube.

[0033] The heat exchange with the refrigerant in the building heat pump cycle system includes: the circulating medium at the second temperature t2 (high temperature) flows into the evaporator 202 and exchanges heat with the refrigerant; the refrigerant vapor that absorbs heat and evaporates enters the compressor 206 to be pressurized and heated; the high-temperature and high-pressure vapor supplies heat to the building in the condenser 205 and condenses into a liquid; the high-pressure liquid refrigerant returns to the evaporator 202 after being depressurized and cooled by the throttling valve 204, completing the cycle.

[0034] Specifically, the refrigeration cycle includes evaporation, compression, condensation, and throttling steps in sequence. Evaporation can be understood as heat absorption and vaporization: in the evaporator 202, the low-temperature, low-pressure liquid refrigerant absorbs heat from the object being cooled (the circulating medium at the second temperature t2) and vaporizes into a low-pressure gaseous state. At this time, the temperature of the cooled environment decreases, thus achieving refrigeration.

[0035] Compression can be understood as increasing pressure and temperature: the compressor 206 compresses the low-pressure gaseous working fluid into a high-pressure gaseous state, while the temperature rises (higher than the ambient temperature) to form a high-pressure, high-temperature gaseous working fluid; Condensation, or exothermic liquefaction: In condenser 205, the high-pressure, high-temperature gaseous working fluid releases heat to the external environment and liquefies back into a high-pressure liquid state; Throttling, i.e. pressure reduction and temperature reduction: the high-pressure liquid working medium passes through the throttle valve 204 to reduce the pressure, and the temperature is lowered accordingly, returning to a low-temperature and low-pressure liquid state, re-entering the evaporator, and completing the cycle.

[0036] Preferably, when the U-shaped tube needs to release the heat energy of the water body, the high-temperature t1 circulating medium enters the first branch pipe of the U-shaped tube, and then enters the geothermal circulation system through the second branch pipe of the U-shaped tube; during the flow process, the circulating medium continuously releases the heat of the underground water inside the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature is lowered to the second temperature t2, and then enters the plate heat exchanger to absorb the surface waste heat; step S5 includes: the underground water inside the pipe pile continuously absorbs the heat energy in the U-shaped tube, and then dissipates the heat to the outside of the pipe pile through the water-permeable hole; the water outside the pipe pile continuously absorbs the heat inside the pipe pile.

[0037] The cooled circulating medium enters the above-ground building group through the second branch pipe of the U-shaped tube, absorbs the heat of the building group, and then enters the water through the first branch pipe of the U-shaped tube for cooling. And circulate, achieve the purpose of cooling the above-ground building group.

[0038] Among them, the plate heat exchanger can make two kinds of heat exchange media (the circulating medium of the water-permeable pipe pile and the refrigerant of the building heat pump circulation system) flow into their respective flow channels respectively, form counterflow or parallel flow, and exchange heat through the plates.

[0039] Preferably, the application also includes a step S6 of using a control system, including: setting a first temperature sensor at the outlet end of the evaporator 202 to measure the first temperature t1; and setting a second temperature sensor at the inlet end of the evaporator 202 to measure the second temperature t2. The control system 203 monitors the temperature difference between the inlet and outlet of the circulating medium of the evaporator 202 in real time When ΔT < threshold, it means that there is basically no temperature difference between the circulating medium temperature in the U-shaped tube and the water body temperature in the pipe pile. At this time, the control system 203 controls the water pump 201 to stop working, prohibits the circulating medium from entering the U-shaped tube, and waits for the underground water body heat to recover; the opening of the throttle valve 204 is adjusted dynamically based on the superheat. When the control system 203 monitors ΔT ≥ threshold, the water pump 201 is started again.

[0040] Among them, adjusting the opening of the throttle valve 204 includes: the heat exchange of the evaporator 202 is affected by the water temperature on the geothermal side. If the water temperature on the geothermal side is high (△T is large), the heat absorption capacity of the evaporator is strong, the refrigerant evaporates quickly, and it may cause the superheat to be too low. At this time, the throttle valve should be adjusted smaller. If the water temperature on the geothermal side is low (△T is small), the heat absorption capacity of the evaporator is weak, the refrigerant evaporates slowly, and it may cause the superheat to be too high. At this time, the throttle valve should be opened larger to increase the refrigerant flow and enhance the heat exchange.

[0041] At the same time, the throttle valve 204 is also linked with the temperature difference AT for control. When the control system 203 detects that AT < threshold (the heat exchange capacity of the geothermal side decreases), the water pump 201 is suspended, and the water body heat is recovered. Further, the throttle valve 204 adjusts the opening degree according to the current superheat, so as to avoid the abnormal operation of the compressor due to the water temperature fluctuation.

[0042] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A shallow geothermal energy exchange method using a U-tube type permeable pipe pile, characterized by, The method comprises the following steps: Step S1, prefabricating a U-shaped pipe type water permeable pipe pile; the U-shaped pipe type water permeable pipe pile comprises: A pipe pile, which comprises a hollow cylindrical pipe pile, a hollow part forming a pipe cavity; a through hole is uniformly arranged on the side wall of the pipe pile in a radial direction, as a water permeable hole; the water permeable hole is uniformly added in an axial direction of the pipe pile; A U-shaped pipe, which comprises a hollow pipe bent into a U shape, is arranged in the pipe cavity; a closed end of the U-shaped pipe extends into a bottom of the pipe pile; a first branch pipe and a second branch pipe of the U-shaped pipe are arranged in parallel and are connected to a top end of the pipe pile; Step S2, installing the U-shaped pipe type water permeable pipe pile; the U-shaped pipe type water permeable pipe pile is extruded into a soil body containing underground water seepage; Step S3, underground water enters the pipe cavity through the water permeable hole and contacts the U-shaped pipe; Step S4, circulating medium with a first temperature t1 flows into the first branch pipe of the U-shaped pipe, flows through a lower part of the pipe pile, and then enters the second branch pipe after passing through a U-shaped elbow; in the whole flow process, the circulating medium continuously exchanges heat with water in the pipe pile through the pipe wall, and when the circulating medium flows to an outlet of the second branch pipe, the temperature becomes a second temperature t2, and then the circulating medium enters a plate heat exchanger and exchanges heat with refrigerant of a building heat pump circulation system; Step S5, underground water in the pipe pile is affected by seepage of underground water outside the pipe pile through the water permeable hole, so that a ground convection heat exchange function is realized.

2. The method of claim 1, wherein the U-shaped pipe type water permeable pipe pile is used. In the step S1, a hole position module is fixed on a pile body mold when the pipe pile is prefabricated, so as to uniformly arrange the through hole; meanwhile, the through hole is additionally provided with a filter screen.

3. The method of claim 1, wherein the U-shaped pipe type water permeable pipe pile is used. The U-shaped pipe is fixed in the pipe cavity through a support frame; the first branch pipe and the second branch pipe can extend out of the pile top and have sufficient reserved length.

4. The method for exchanging shallow geothermal energy using the U-shaped pipe type water permeable pipe pile according to claim 1, wherein When the U-shaped pipe needs to absorb heat energy of underground water, the step S4 comprises: low-temperature t1 circulating medium enters the first branch pipe of the U-shaped pipe, and then enters a geothermal circulation system through the second branch pipe of the U-shaped pipe; in the flow process, the circulating medium continuously absorbs heat of underground water in the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature increases to the second temperature t2, and then the circulating medium enters the plate heat exchanger and exchanges heat with the refrigerant of the building heat pump circulation system; Step S5 comprises: underground water in the pipe pile continuously exchanges heat with underground water outside the pipe pile due to the influence of seepage of the underground water, and continuously provides heat for the U-shaped pipe.

5. The method of claim 1, wherein the U-shaped pipe type water permeable pipe pile is used. When the U-shaped pipe needs to release heat energy to underground water, the step S4 comprises: High-temperature t1 circulating medium enters the first branch pipe of the U-shaped pipe, and then enters the geothermal circulation system through the second branch pipe of the U-shaped pipe; in the flow process, the circulating medium continuously releases heat of underground water in the pipe pile, and when the circulating medium flows to the outlet of the second branch pipe, the temperature decreases to the second temperature t2, and then the circulating medium enters the plate heat exchanger and absorbs surface waste heat; Step S5 comprises: underground water in the pipe pile continuously absorbs heat energy in the U-shaped pipe, and then dissipates the heat to the outside of the pipe pile through the water permeable hole; water outside the pipe pile continuously absorbs heat in the pipe pile.

6. The method for exchanging shallow geothermal energy using the U-shaped pipe type water permeable pipe pile according to claim 1, wherein The method further comprises a step S6 of connecting the first branch of the U-shaped tube with a first temperature sensor for measuring a first temperature t1; connecting the first branch of the U-shaped tube with a second temperature sensor for measuring a second temperature t2; and monitoring by the control system (203) the temperature difference of the circulating medium in real time ; when ΔT < a threshold value, the control system (203) controls the water pump (201) to stop working; and when the control system (203) monitors that ΔT ≥ the threshold value, the water pump (201) is started again.

Images