Middle-shallow combined variable-flow buried pipe type underground heat exchanger and control method

Abstract

The invention discloses a medium-shallow combined variable flow buried pipe type underground heat exchanger and a control method, and relates to the technical field of ground source heat pumps. The heat exchanger comprises a ground switching unit, a heat collection unit and a heat exchange unit buried underground. The heat exchange unit comprises a U-shaped buried pipe assembly with the two ends connected to the ground switching unit and a communicating pipe used for communicating the preset depth positions of the two ends of the U-shaped buried pipe assembly. The heat exchange unit further comprises a first one-way valve and a second one-way valve which are installed on the communicating pipe and the U-shaped buried pipe assembly respectively. The first one-way valve and the second one-way valve are reversely mounted to be matched with a four-way reversing valve of the ground switching unit to switch a fluid conduction path; the input end and the output end of the heat collection unit are connected to the two ends of the U-shaped buried pipe assembly respectively, and when the heat collection unit operates, the first one-way valve is closed, and the second one-way valve is connected. The system can adapt to the formation temperature requirements of different working conditions, and the overall energy efficiency ratio of the heat exchanger is improved through the heat collection unit and real-time monitoring of the ground temperature.

Description

Technical Field

[0001] This invention belongs to the field of ground source heat pump technology, specifically relating to a shallow-to-medium depth combined with variable flow buried pipe downhole heat exchanger and its control method. Background Technology

[0002] Clean energy heating is a core direction for energy conservation and carbon reduction in the building sector. Therefore, promoting clean and low-carbon heating methods such as heat pumps, gas, biomass energy, and geothermal energy according to local conditions is the current development goal of the construction industry. In terms of market size, the heating season in the cold and frigid northern regions lasts 120-180 days, with concentrated building heat loads, making the demand for clean heating urgent and the market space vast.

[0003] Gas-fired heating has high operating costs and a heavy burden on users: rural areas in cold regions face severe pollution or high heating costs. Current technologies face challenges such as high initial investment and long payback periods for medium-deep geothermal wells; for example, the payback period for medium-deep geothermal wells at depths of 2000-3000 meters is as long as 13-25 years, and they can only provide heating, not cooling in summer. Shallow ground source heat pumps are limited by land use and have insufficient heating capacity: For example, shallow buried pipes at depths of 0-200 meters occupy a large amount of land; in urban areas where land is scarce, land use restrictions result in low coverage of shallow geothermal heating; moreover, the heat extraction from shallow layers is limited, making it difficult to meet the heating needs of high-density buildings in urban areas. Air source heat pumps suffer severe performance degradation at low temperatures: in extreme low-temperature environments below -15℃ in northern winters, the heating efficiency of air source heat pumps drops by more than 50% compared to normal temperature conditions, making it impossible to stably meet heating demands. Summary of the Invention

[0004] The purpose of this invention is to provide a medium-shallow combined variable flow underground pipe heat exchanger and control method. Through the heat exchange unit structure, the heat extraction position of the U-shaped underground pipe assembly is switched by a four-way reversing valve to adapt to the formation temperature requirements under different working conditions in winter and summer, thereby improving the overall energy efficiency ratio of the heat exchanger.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution.

[0006] In a first aspect, the present invention provides a ground-mounted pipe-type downhole heat exchanger with a combination of shallow and medium-depth variable flow, comprising a heat collection unit, a ground switching unit, and a heat exchange unit buried underground.

[0007] The heat exchange unit includes a U-shaped underground pipe assembly with both ends connected to the ground switching unit and a connecting pipe for connecting the two ends of the U-shaped underground pipe assembly at a preset depth.

[0008] The heat exchange unit also includes a first check valve installed on the connecting pipe and a second check valve installed at the bottom of the lower end of the U-shaped buried pipe assembly; the first check valve and the second check valve are installed in opposite directions to cooperate with the four-way reversing valve of the ground switching unit to switch the fluid conduction path.

[0009] The input and output ends of the heat collection unit are respectively connected to the two ends of the U-shaped buried pipe assembly, and the first one-way valve is closed and the second one-way valve is open when the heat collection unit is running.

[0010] Optionally, the solar collector unit includes a solar collector and a hot water storage tank; the input end of the solar collector is connected to the first output end of the hot water storage tank, the output end of the solar collector is connected to the first input end of the hot water storage tank, and the second input end and the second output end of the hot water storage tank are respectively connected to both ends of the U-shaped buried pipe assembly.

[0011] A first water pump is connected between the input end of the solar collector and the first output end of the hot water storage tank; a second water pump is connected between the second output end of the hot water storage tank and the U-shaped buried pipe assembly.

[0012] The heat collection unit enables resource storage during the transition season, ensuring heat supply in winter and improving the overall energy efficiency ratio of the heat exchanger. The heat collection unit, in conjunction with the first and second one-way valves, ensures that heat is supplied only to the middle formation during the transition season.

[0013] Optionally, the U-shaped underground pipe assembly includes an ascending pipe and a descending pipe; a second one-way valve is connected between the ascending pipe and the descending pipe;

[0014] The two ends of the connecting pipe are respectively connected to the preset depth positions of the downcomer and the upcomer.

[0015] By assembling a U-shaped underground pipe assembly with riser and downcomer pipes, and installing connecting pipes at preset depths at both ends of the U-shaped underground pipe assembly, a highly efficient combination of shallow and medium-depth geothermal energy is achieved, reducing construction difficulty and simplifying the switching process between medium-depth and shallow geothermal energy.

[0016] Optionally, the burial depth of the heat exchange unit is determined comprehensively based on the formation thermal properties, heat load requirements, and burial costs.

[0017] Optionally, the burial depth of the U-shaped underground pipe assembly is set to 500 meters based on the geological thermal properties, heat load requirements, and burial costs.

[0018] By comprehensively considering the formation thermal properties, heat load requirements, and burial costs, the burial depth of the U-shaped underground pipe assembly is set to 500 meters, which significantly reduces drilling costs. At the same time, cross-seasonal energy storage improves the overall economic efficiency of the system.

[0019] Optionally, the preset burial depth of the connecting pipe is set to 120 meters based on the geological thermal properties, heat load requirements, and the burial depth of the U-shaped underground pipe assembly.

[0020] By setting up connecting pipes to form a shallow independent heat exchange loop, the first heat extraction mode can be used to extract the heat stored in the shallow strata to achieve a reasonable drop in shallow ground temperature and control of stratum thermal balance during winter heating. Then, the mode is switched to the middle layer geothermal heat extraction mode, relying on the stable high-temperature heat source in the middle layer to ensure heating efficiency and effect. At the same time, the heat exchange design combining shallow and medium layers greatly optimizes the burial depth of the U-shaped buried pipe, which significantly saves drilling costs compared to traditional medium and deep geothermal drilling.

[0021] Optionally, during summer cooling, the fluid flows from the four-way reversing valve through the downcomer into the connecting pipe, and then through the first check valve, the riser, and the four-way reversing valve in sequence to cool the building.

[0022] By combining the first one-way valve with the four-way reversing valve, heat exchange can be carried out using only the shallow layer during summer cooling, thus achieving shallow storage of summer heat.

[0023] Optionally, during winter heating, there are two modes: a first winter heating mode and a second winter heating mode. When heating is needed in winter, the first winter heating mode is used until the shallow ground temperature at a preset depth to the ground surface recovers to a preset ground temperature threshold, after which the second winter heating mode is switched.

[0024] In the first winter heating mode, the fluid enters the connecting pipe from the four-way reversing valve through the downcomer, and then flows through the first check valve through the riser and the four-way reversing valve to heat the building.

[0025] In the second winter heating mode, the fluid enters the riser pipe from the four-way reversing valve, and after passing through the second one-way valve, it flows through the downcomer pipe and the four-way reversing valve in sequence to heat the building.

[0026] During winter heating, the heat stored in the shallow layer during summer is extracted first. Then, the fluid flow direction is changed by a four-way reversing valve. The shallow and middle layers are switched by using the reverse installation of the first and second one-way valves. An independent heat exchange loop is formed in the shallow layer through the set connecting pipe. In winter heating, the heat stored in the shallow layer can be extracted first through the first heat extraction mode to achieve a reasonable drop in shallow ground temperature and control of ground heat balance. Then, the system switches to the middle layer geothermal heat extraction mode. The heating efficiency and effect are guaranteed by relying on the stable high-temperature heat source in the middle layer. At the same time, the heat exchange design combining shallow and middle layers greatly optimizes the burial depth of the U-shaped buried pipe.

[0027] Optionally, during the transitional season for heat collection, the fluid enters the riser pipe from the input end of the heat collection unit, passes through the second one-way valve, and then flows out through the downcomer pipe back to the input end of the heat collection unit.

[0028] By utilizing the solar collector unit and the second one-way valve, the system compensates for the drop in ground temperature caused by winter heating in the middle layer during the spring and autumn transition periods, thereby improving overall energy efficiency.

[0029] In a second aspect, the present invention provides a control method for a shallow-medium combined variable flow buried tubular downhole heat exchanger as described in the first aspect above, comprising:

[0030] The heat exchanger's operating mode is determined based on the acquired seasonal parameter information;

[0031] Based on the heat exchanger's operating mode, the fluid conduction path of the heat exchange unit is controlled by the ground switching unit;

[0032] Based on the acquired ground temperature data, adjust the water pump control parameters in the ground switching unit or the heat collection unit until the ground temperature is within the preset error range.

[0033] Based on the water pump control parameters when the ground temperature is within the preset error range, heat exchange is carried out through the heat exchange unit;

[0034] The heat exchanger operates in three modes: a summer cooling mode, a winter heating mode, and a transitional season heat collection mode. The winter heating mode includes a first winter heating mode and a second winter heating mode.

[0035] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0036] This invention achieves combined heat exchange between the middle and shallow layers by using a U-shaped buried pipe assembly of the heat exchange unit and a connecting pipe installed at a preset depth in the U-shaped buried pipe assembly. By installing a second one-way valve and a first one-way valve in the middle section of the U-shaped buried pipe assembly and the connecting pipe, and by cooperating with a four-way reversing valve, it achieves heat exchange through the shallow layer in summer and heat exchange through the middle layer in winter, thus ensuring the heating effect.

[0037] This invention achieves shallow geothermal heating in summer through a second one-way valve and a four-way reversing valve. The shorter fluid path optimizes pump power consumption and improves cooling efficiency. This invention integrates efficient cooling, stable heating, and seasonal energy scheduling functions into a single device, improving equipment utilization. Furthermore, by collecting heat during the transitional season and extracting cooling energy in summer to supplement heat to the middle and shallow layers, it achieves long-term balance of the geothermal field. This invention achieves efficient and stable heating and cooling functions by coupling shallow and medium-depth geothermal energy with solar energy and other energy sources.

[0038] This invention achieves shallow cooling in summer through a second one-way valve and a four-way reversing valve, resulting in a shorter fluid path, optimized power consumption of the water pump, and effectively improved cooling energy efficiency ratio. In winter, it prioritizes the extraction of heat accumulated in the shallow strata during summer, pushing the shallow ground temperature back to its initial state and preventing excessively high shallow ground temperatures from affecting cooling efficiency in the following summer. Once the shallow ground temperature reaches the standard, it switches to mid-layer heat extraction, relying on the stable high-temperature heat source in the mid-layer to ensure high energy efficiency and stability of winter heating. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the system principle and the structure of the buried pipe downhole heat exchanger of the present invention;

[0040] Figure 2 This is a flowchart illustrating the overall operation strategy of the system of the present invention;

[0041] In the attached diagram: U-shaped underground pipe assembly 100, downcomer 1001, riser 1002, connecting pipe 101, first check valve 102, second check valve 103, four-way reversing valve 104, solar collector 107, first switching valve 105, second switching valve 106, third switching valve 108, and fourth switching valve 109. Detailed Implementation

[0042] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0043] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0044] Example 1

[0045] This embodiment introduces a shallow-to-medium depth combined with variable flow buried pipe downhole heat exchanger, such as... Figure 1 As shown, it includes: a ground switching unit, a heat collection unit, and a heat exchange unit buried underground;

[0046] The ground switching unit includes a four-way reversing valve for switching between intermediate and shallow heat exchange and for controlling the pump head and flow rate.

[0047] The heat exchange unit includes a U-shaped underground pipe assembly with both ends connected to the ground switching unit and a connecting pipe for connecting the two ends of the U-shaped underground pipe assembly at a preset depth.

[0048] The U-shaped underground pipe assembly is buried in the middle layer at a depth of 200-600 meters. The two ends of the connecting pipe are respectively connected to the two ends of the U-shaped underground pipe assembly and buried in the shallow layer at a depth of 0-200 meters.

[0049] The heat exchange unit also includes a first check valve installed on the connecting pipe and a second check valve installed at the bottom of the lower end of the U-shaped underground pipe assembly; the first and second check valves are installed in opposite directions to cooperate with the four-way reversing valve of the ground switching unit to switch the fluid conduction path. The first and second check valves enable the on / off control of the connecting pipe and the U-shaped underground pipe assembly.

[0050] The first and second one-way valves are installed in opposite directions to cooperate with the four-way reversing valve of the ground switching unit to switch the fluid conduction path. By installing the first one-way valve in the middle section of the connecting pipe and the second one-way valve in the bottom middle section of the U-shaped buried pipe assembly in the opposite direction to the first one-way valve, this installation method ensures that the connecting pipe and the U-shaped buried pipe assembly will not be conducting simultaneously, and allows selection between the connecting pipe and the U-shaped buried pipe assembly by controlling the fluid inflow direction. The four-way reversing valve enables switching between mid-level heat exchange and shallow heat exchange.

[0051] The input and output ends of the heat collection unit are respectively connected to the two ends of the U-shaped buried pipe assembly. When the heat collection unit is running, the first one-way valve is closed and the second one-way valve is open. The heat collection unit is used to supplement heat to the middle layer when the heat exchanger stops working, thereby increasing the temperature of the middle layer. By closing the first one-way valve and opening the second one-way valve, heat is not supplemented to the shallow layer, thus preventing the shallow layer temperature from becoming too high during summer when heat exchange occurs through the shallow layer.

[0052] In summary, this implementation achieves efficient utilization of the equipment by burying the connecting pipes and U-shaped buried pipe assemblies of the heat exchange unit in the shallow and middle layers. The first and second check valves located in the middle sections of the connecting pipes and U-shaped buried pipe assemblies ensure that the flow path can be selected by changing the fluid flow direction. The four-way reversing valve changes the fluid flow direction, enabling the heat exchanger to switch between the middle and shallow layers. Combining the middle and shallow layers, heat exchange is achieved in summer through the shallow layer and in winter through the middle layer, ensuring effective heating.

[0053] Example 2

[0054] Based on the same technical concept as Embodiment 1, this embodiment provides a shallow-to-medium depth buried pipe downhole heat exchanger with variable flow, such as... Figure 1 As shown, it specifically includes:

[0055] The heat exchange unit includes a U-shaped underground pipe assembly connected to a ground switching unit at both ends and a connecting pipe for connecting the two ends of the U-shaped underground pipe assembly at preset depths. The heat exchange unit also includes a first check valve installed on the connecting pipe and a second check valve installed at the bottom of the lower end of the U-shaped underground pipe assembly. The first and second check valves are installed in opposite directions to cooperate with the four-way reversing valve of the ground switching unit to switch the fluid conduction path. The U-shaped underground pipe assembly includes an ascending pipe and a descending pipe; a second check valve connects the ascending pipe and the descending pipe; the two ends of the connecting pipe are respectively connected to the preset depths of the descending pipe and the ascending pipe.

[0056] The U-shaped underground pipe assembly includes an ascending pipe and a descending pipe; a second check valve is connected between the ascending pipe and the descending pipe.

[0057] The connecting pipe is connected at predetermined depths to the downcomer and riser pipes, respectively. By forming a U-shaped buried pipe assembly with the riser and downcomer pipes and the connecting pipe, a highly efficient combination of shallow and medium-depth geothermal energy is achieved, reducing construction difficulty and simplifying the switching process between medium-depth and shallow geothermal energy. The fluid flow during heat exchanger operation includes:

[0058] When cooling is needed in summer, the fluid enters the connecting pipe from the four-way reversing valve through the downcomer 1001, and then flows through the first check valve in sequence through the riser 1002 and the four-way reversing valve to cool the building.

[0059] By combining the first one-way valve with the four-way reversing valve, heat exchange can be carried out using only the shallow layer during summer cooling, thus achieving shallow storage of summer heat.

[0060] When heating in winter, there are two modes: a first winter heating mode and a second winter heating mode. When heating in winter, the first winter heating mode is used until the shallow ground temperature at a preset depth to the ground surface recovers to a preset ground temperature threshold, and then the second winter heating mode is switched.

[0061] In the first winter heating mode, the fluid enters the connecting pipe from the four-way reversing valve through the downcomer, and then flows through the first one-way valve, the riser pipe, and the four-way reversing valve in sequence to heat the building.

[0062] In the second winter heating mode, the fluid enters the riser pipe from the four-way reversing valve, and after passing through the second one-way valve, it flows through the downcomer pipe and the four-way reversing valve in sequence to heat the building.

[0063] During winter heating, the system prioritizes extracting the summer heat stored in the shallow layer. Then, a four-way reversing valve changes the fluid flow direction. The reverse installation of the first and second one-way valves enables switching between shallow and mid-layer geothermal modes. An independent heat exchange loop is formed in the shallow layer through the connecting pipe. In winter heating, the system first extracts the heat stored in the shallow strata through the first heating mode to achieve a reasonable drop in shallow ground temperature and control of the strata's thermal balance. Subsequently, it switches to the mid-layer geothermal heating mode, relying on the stable high-temperature heat source in the mid-layer to ensure heating efficiency and effect. At the same time, the combined shallow and mid-layer heat exchange design significantly optimizes the burial depth of the U-shaped buried pipe, greatly saving drilling costs compared to traditional mid-deep geothermal drilling.

[0064] During the transitional season, the fluid enters the riser pipe 1002 from the input end of the heat collection unit, passes through the second one-way valve, and flows out through the downcomer pipe 1001 back to the input end of the heat collection unit.

[0065] By utilizing the solar collector unit and the second one-way valve, the system compensates for the drop in ground temperature caused by winter heating in the middle layer during the spring and autumn transition periods, thereby improving overall energy efficiency.

[0066] refer to Figure 1 As shown, the specific heat exchanger operation steps include:

[0067] Summer High-Efficiency Cooling Mode: Switch the four-way reversing valve to allow the circulating fluid to flow through the section above 120 meters. Because the shallow ground temperature is relatively low in summer, and the circulation path is short with low resistance, heat can be efficiently absorbed from the building and released into the shallow soil and rock, achieving efficient cooling. In this mode, the first one-way valve 102 is open, the second one-way valve 103 is closed, the first switching valve 105 is closed, the second switching valve 106 is closed, and the third switching valve 108 and the fourth switching valve 109 are open.

[0068] Winter heating mode: This mode is divided into a first winter heating mode and a second winter heating mode. When heating is needed in winter, the first winter heating mode is activated first until the shallow ground temperature at a preset depth to the surface recovers to a preset ground temperature threshold. Then, the second winter heating mode is switched on. Fluid flows through a shallow loop at a depth of over 120 meters to extract shallow heat stored during the summer, preventing the shallow soil temperature from rising and affecting cooling in the following year. Once the shallow soil temperature returns to its initial value, the second winter heating mode is switched on, and the fluid flows through the entire 500-meter U-shaped loop. The tube utilizes the stable temperature of deep strata, which is higher than that of shallow strata, to stably extract deep heat to meet heating needs. In the first winter heating mode, the first one-way valve 102 is open, the second one-way valve 103 is closed, the first switch valve 105 and the second switch valve 106 are closed, and the third switch valve 108 and the fourth switch valve 109 are open. In the second winter heating mode, the second one-way valve 103 is open, the first one-way valve 102 is closed, the first switch valve 105 and the second switch valve 106 are closed, and the third switch valve 108 and the fourth switch valve 109 are open.

[0069] During the transitional season for heat collection: In spring and autumn, the heat collected by the solar collectors is injected into the ground at a depth of 500 meters through solar thermal collection pipelines, inter-seasonal energy storage pipelines, and related valve controls. This heat is then stored to compensate for the drop in ground temperature caused by heat extraction in winter, realizing the inter-seasonal energy storage concept of "summer heat for winter use." In this mode, the first one-way valve 102 is closed, the second one-way valve 103 is open, the first switching valve 105 and the second switching valve 106 are open, and the third switching valve 108 and the fourth switching valve 109 are closed.

[0070] The input and output ends of the heat collection unit are connected to the two ends of the U-shaped buried pipe assembly, respectively. When the heat collection unit is running, the first one-way valve is closed and the second one-way valve is open. The heat collection unit enables resource storage during the summer-winter transition season, ensuring heat supply in winter and improving the overall energy efficiency ratio of the heat exchanger.

[0071] The solar collector unit includes a solar collector and a hot water storage tank; the input end of the solar collector is connected to the first output end of the hot water storage tank, and the output end of the solar collector is connected to the first input end of the hot water storage tank; the second input end and the second output end of the hot water storage tank are respectively connected to both ends of the U-shaped buried pipe assembly; a first water pump is connected between the input end of the solar collector and the first output end of the hot water storage tank; a second water pump is connected between the second output end of the hot water storage tank and the U-shaped buried pipe assembly. Figure 1 The heat collection unit shown also includes a first switching valve 105 and a second switching valve 106. The first switching valve 105 and the second switching valve 106 can ensure that the heat collection unit is not affected when cooling is taken in summer and heating is taken in winter.

[0072] The heat exchanger also includes a heat collection unit, the input end and the output end of which are respectively connected to the two ends of the U-shaped buried pipe assembly. When the heat collection unit is running, the first one-way valve is closed and the second one-way valve is open.

[0073] The solar collector unit includes a solar collector and a hot water storage tank; the input end of the solar collector is connected to the first output end of the hot water storage tank, the output end of the solar collector is connected to the first input end of the hot water storage tank, and the second input end and the second output end of the hot water storage tank are respectively connected to the two ends of the U-shaped buried pipe assembly.

[0074] A first water pump is connected between the input end of the solar collector and the first output end of the hot water storage tank; a second water pump is connected between the second output end of the hot water storage tank and the U-shaped buried pipe assembly.

[0075] The heat collection unit enables resource storage during the transition season, ensuring heat supply in winter and improving the overall energy efficiency ratio of the heat exchanger. The heat collection unit, in conjunction with the first and second one-way valves, ensures that heat is supplied only to the middle formation during the transition season.

[0076] The burial depth of the heat exchange unit is determined by a combination of factors, including the thermal properties of the strata, the building's heat load requirements, and the installation cost.

[0077] The burial depth of the U-shaped underground pipe assembly is set at 500 meters based on the thermal properties of the strata, the building's heat load requirements, and the burial cost.

[0078] By comprehensively considering the geological thermal properties, building heat load requirements, and burial costs, the burial depth of the U-shaped underground pipe assembly is set to 500 meters, which significantly reduces drilling costs. At the same time, cross-seasonal energy storage improves the overall economic efficiency of the system.

[0079] The pre-set burial depth of the connecting pipe is 120 meters, based on the thermal properties of the strata, the building's heat load requirements, and the burial depth of the U-shaped underground pipe assembly.

[0080] By setting up connecting pipes to form a shallow independent heat exchange loop, the first heat extraction mode can be used to extract the heat stored in the shallow strata to achieve a reasonable drop in shallow ground temperature and control of stratum thermal balance during winter heating. Then, the mode is switched to the middle layer geothermal heat extraction mode, relying on the stable high-temperature heat source in the middle layer to ensure heating efficiency and effect. At the same time, the heat exchange design combining shallow and medium layers greatly optimizes the burial depth of the U-shaped buried pipe, which significantly saves drilling costs compared to traditional medium and deep geothermal drilling.

[0081] In summary, this embodiment achieves shallow heating in summer through a second one-way valve and a four-way reversing valve, resulting in a shorter fluid path, optimized power consumption of the water pump, and improved cooling energy efficiency ratio. This embodiment also achieves efficient and stable heating and cooling functions by coupling shallow geothermal energy with solar energy and other energy sources.

[0082] Example 3

[0083] Based on the same technical concept as Embodiments 1 and 2, this embodiment provides a buried pipe type downhole heat exchanger, such as Figure 1 As shown, the specific structure includes:

[0084] A vertically buried 500-meter-deep U-shaped underground pipe assembly 100, including a downcomer 1001 and an upcomer 1002, is a key component for the system to efficiently extract geothermal energy from the middle layer during winter.

[0085] At a depth of approximately 120 meters in the U-shaped pipe, a connecting pipe 101 is installed to connect the downcomer pipe 1001 and the ascender pipe 1002 of the U-shaped pipe at that depth.

[0086] A first check valve 102 is installed on the connecting pipe at a depth of 120 meters; a second check valve 103 is installed at a depth of 500 meters, with the first check valve 102 and the second check valve 103 installed in opposite directions. By controlling the opening and closing of the two check valves, the circulating fluid path is switched.

[0087] A four-way directional valve 104 is installed in the ground pipeline. Since 102 and 103 are one-way valves and installed in opposite directions, the fluid can flow through a 500-meter U-shaped pipe or only through a shallow loop of more than 120 meters by switching the four-way directional valve 104 on the ground.

[0088] This embodiment addresses the clean heating / cooling needs of a 10,000㎡ high-density building in a northern urban area, and constructs a shallow-to-medium flow combined with a variable flow underground pipe heat exchanger:

[0089] (1) A U-shaped underground pipe is vertically buried at a depth of 500 meters as the main body. The pipe material is high-density polyethylene pipe that is resistant to high temperature and corrosion. A connecting pipe is set at a depth of 120 meters to connect the downpipe and the uppipe of the U-shaped pipe.

[0090] (2) A horizontal connecting pipe is installed at a depth of 120m. It is preferred to use the same material and diameter as the main pipe and connect it to the downcomer and the upcomer through a heat fusion connection.

[0091] (3) Install a four-way reversing valve on the ground pipeline. Its four ports are respectively connected to the inlet of the U-shaped downpipe, the outlet of the U-shaped uppipe, the circulating water pump, and the building heat exchange end. The fluid path control is realized by switching the valve ports.

[0092] (4) In accordance with the project land boundary restrictions, optimize the density of underground pipe installation and set up 10 sets of the above-mentioned U-shaped underground pipe components to meet the building's heat and cold load requirements;

[0093] (5) Install a solar thermal system and collector 107 with a thermal collection area of ​​500㎡. Connect the system to the underground pipe system through pipelines and set up a heat replenishment valve to control the heat replenishment path.

[0094] Based on the heat exchanger built in Example 1, and considering the climate characteristics of this northern city, with a heating season of 150 days, an extreme low temperature of -18℃, and a cooling season of 90 days, the following operations were performed:

[0095] (1) In summer, from June to August, the high-efficiency cooling mode is used: the ground four-way reversing valve is switched so that the circulating fluid flows only through the shallow loop above 120 meters of the U-tube. Taking advantage of the characteristic that the average temperature of the shallow layer within 120m is 20℃, the building is cooled and the cooling EER reaches 4.2.

[0096] (2) Winter November to March of the following year, heat extraction mode: In early November, mode A is turned on, the fluid flows through the shallow loop above 120 meters to extract the shallow heat stored in summer. After running for about 20 days, the shallow soil temperature recovers from 25℃ to the initial 20℃, and then mode B is switched. The fluid flows through the entire 500-meter U-shaped pipe, the deep stratum is 500m, the average temperature is 28℃, and it is stable for building heating;

[0097] (3) During the transitional seasons of April-May and September-October, the solar thermal supplementation mode is activated: the solar thermal system is turned on, and the collected heat is injected into the 500-meter deep stratum through the supplementation pipeline. The supplementation power is 80kW, and the cumulative supplementation time is about 1200h. This supplements the deep ground temperature drop of about 3℃ caused by winter heat extraction, so that the deep ground temperature is maintained above 25℃, and the ground temperature field balance is achieved.

[0098] In this embodiment, the heat exchanger system provides year-round cooling / heating for the 10,000㎡ building. The operating cost during the heating season is 60% lower than that of gas heating, the initial investment is 80% lower than that of a medium-deep geothermal system, and the geothermal field shows no significant decay after one year of operation, indicating stable system operation.

[0099] Example 4

[0100] Based on the same inventive concept as Embodiment 1, this embodiment introduces a heat exchanger control method, such as... Figure 2 Specifically, it includes:

[0101] The heat exchanger's operating mode is determined based on the acquired seasonal parameter information;

[0102] Based on the heat exchanger's operating mode, the fluid conduction path of the heat exchange unit is controlled by the ground switching unit;

[0103] Based on the acquired ground temperature data, adjust the water pump control parameters in the ground switching unit or the heat collection unit until the ground temperature is within the preset error range.

[0104] Based on the water pump control parameters when the ground temperature is within the preset error range, heat exchange is carried out through the heat exchange unit;

[0105] The heat exchanger operates in three modes: a summer cooling mode, a winter heating mode, and a transitional season heat collection mode. The winter heating mode includes a first winter heating mode and a second winter heating mode.

[0106] Three working modes:

[0107] Summer cooling mode: Switch the four-way reversing valve to allow the circulating fluid to flow through the section above 120 meters. Because the temperature of the shallow ground layer is relatively low in summer, and the circulation path is short and the resistance is low, it can efficiently absorb heat from the building and release it into the shallow soil and rock, achieving efficient cooling.

[0108] Winter heating mode: When heating is needed in winter, the first winter heating mode is activated until the shallow ground temperature at the preset depth to the surface recovers to the preset ground temperature threshold. Then, the second winter heating mode is switched. The fluid flows through a shallow loop at a depth of over 120 meters to extract the shallow heat stored in summer, preventing the shallow soil temperature from rising and affecting the cooling in the following year. After the shallow soil temperature recovers to its initial value, the second winter heating mode is switched. The fluid flows through the entire 500-meter U-shaped pipe, utilizing the stable and higher temperature of the deep strata to stably extract deep heat to meet heating needs. In the first winter heating mode, the first one-way valve 102 is open, the second one-way valve 103 is closed, the first switch valve 105 and the second switch valve 106 are closed, and the third switch valve 108 and the fourth switch valve 109 are open. In the second winter heating mode, the second one-way valve 103 is open, the first one-way valve 102 is closed, the first switch valve 105 and the second switch valve 106 are closed, and the third switch valve 108 and the fourth switch valve 109 are open. This embodiment prevents the rise in shallow soil temperature from affecting the cooling in the following year. After the shallow soil temperature returns to its initial value, it switches to the second winter heating mode. The fluid flows through the entire 500-meter U-shaped pipe, taking advantage of the stable temperature of the deep soil layer, which is higher than that of the shallow layer, to stably extract deep heat to meet the heating demand.

[0109] In spring and autumn, the heat collected by the solar collectors is injected into the ground at a depth of 500 meters through solar thermal collection pipelines, inter-seasonal energy storage pipelines, and related valves for storage. This replenishes the ground temperature drop caused by winter heat extraction, realizing the inter-seasonal energy storage concept of "summer heat for winter use." In this mode, the first one-way valve 102 is closed, the second one-way valve 103 is open, the first switching valve 105 and the second switching valve 106 are open, and the third switching valve 108 and the fourth switching valve 109 are closed.

[0110] In summary, in this embodiment, the heat exchanger provides year-round cooling / heating for the 10,000㎡ building. The operating cost during the heating season is 60% lower than that of gas heating, the initial investment is 80% lower than that of a medium-deep geothermal system, and the geothermal field shows no significant decay after one year of operation, indicating stable system operation.

[0111] In this embodiment, the design heat exchange capacity of the buried pipe heat exchanger is determined based on the building's heat load requirements; the heat exchange capacity per meter of the U-shaped pipe at a depth of 200-600m is calculated based on the ground thermal properties; the optimal installation depth of the connecting pipe is determined based on the ground temperature distribution in the shallow (0-200m) and middle (200-600m) layers; the collector area of ​​the solar supplementary heating system is calculated based on the ratio of summer cooling load to winter heating load; appropriate pump head and flow rate are selected based on system hydraulic calculations; and the opening pressure of the one-way valve is no greater than 0.01MPa.

[0112] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0113] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0114] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0115] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0116] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A shallow-to-medium flow combined with variable flow underground pipe-type downhole heat exchanger, characterized in that, It includes a heat collection unit, a ground switching unit, and a heat exchange unit buried underground; The heat exchange unit includes a U-shaped underground pipe assembly with both ends connected to the ground switching unit and a connecting pipe for connecting the two ends of the U-shaped underground pipe assembly at a preset depth. The heat exchange unit also includes a first check valve installed on the connecting pipe and a second check valve installed at the bottom of the lower end of the U-shaped buried pipe assembly; the first check valve and the second check valve are installed in opposite directions to cooperate with the four-way reversing valve of the ground switching unit to switch the fluid conduction path. The input and output ends of the heat collection unit are respectively connected to the two ends of the U-shaped buried pipe assembly, and the first one-way valve is closed and the second one-way valve is open when the heat collection unit is running.

2. The shallow-water combined variable flow buried pipe downhole heat exchanger according to claim 1, characterized in that, The solar collector unit includes a solar collector and a hot water storage tank; the input end of the solar collector is connected to the first output end of the hot water storage tank, the output end of the solar collector is connected to the first input end of the hot water storage tank, and the second input end and the second output end of the hot water storage tank are respectively connected to the two ends of the U-shaped buried pipe assembly. A first water pump is connected between the input end of the solar collector and the first output end of the hot water storage tank; a second water pump is connected between the second output end of the hot water storage tank and the U-shaped buried pipe assembly.

3. The shallow-water combined variable flow buried pipe downhole heat exchanger according to claim 1, characterized in that, The U-shaped underground pipe assembly includes an ascending pipe and a descending pipe; a second one-way valve is connected between the ascending pipe and the descending pipe. The two ends of the connecting pipe are respectively connected to the preset depth positions of the downcomer and the upcomer.

4. The shallow-water combined variable flow buried pipe downhole heat exchanger according to claim 1, characterized in that, The burial depth of the heat exchange unit is determined by a combination of factors, including the thermal properties of the formation, the heat load requirements, and the burial cost.

5. The shallow-medium combined variable flow buried pipe downhole heat exchanger according to claim 4, characterized in that, The burial depth of the U-shaped underground pipe assembly is set at 500 meters based on the geological thermal properties, heat load requirements, and burial costs.

6. The shallow-medium combined variable flow buried pipe downhole heat exchanger according to claim 5, characterized in that, The preset burial depth of the connecting pipe is set to 120 meters based on the thermal properties of the strata, heat load requirements, and the burial depth of the U-shaped underground pipe assembly.

7. The shallow-medium combined variable flow buried pipe downhole heat exchanger according to claim 3, characterized in that, During summer cooling, the fluid flows from the four-way reversing valve through the downcomer into the connecting pipe, and then through the first check valve, the riser, and the four-way reversing valve to cool the building.

8. The shallow-medium combined variable flow buried pipe downhole heat exchanger according to claim 3, characterized in that, When heating in winter, there are two modes: a first winter heating mode and a second winter heating mode. When heating in winter, the first winter heating mode is used until the shallow ground temperature at a preset depth to the ground surface recovers to a preset ground temperature threshold, and then the second winter heating mode is switched. In the first winter heating mode, the fluid enters the connecting pipe from the four-way reversing valve through the downcomer, and then flows through the first check valve through the riser and the four-way reversing valve to heat the building. In the second winter heating mode, the fluid enters the riser pipe from the four-way reversing valve, and after passing through the second one-way valve, it flows through the downcomer pipe and the four-way reversing valve in sequence to heat the building.

9. The shallow-medium combined variable flow buried pipe downhole heat exchanger according to claim 3, characterized in that, During the transitional season, the fluid enters the riser pipe from the input end of the heat collection unit, passes through the second one-way valve, and flows out through the downcomer pipe back to the input end of the heat collection unit.

10. A control method for a shallow-medium combined variable flow buried tubular downhole heat exchanger as described in any one of claims 1 to 9, characterized in that, include: The heat exchanger's operating mode is determined based on the acquired seasonal parameter information; Based on the heat exchanger's operating mode, the fluid conduction path of the heat exchange unit is controlled by the ground switching unit; Based on the acquired ground temperature data, adjust the water pump control parameters in the ground switching unit or the heat collection unit until the ground temperature is within the preset error range. Based on the water pump control parameters when the ground temperature is within the preset error range, heat exchange is carried out through the heat exchange unit; The heat exchanger operates in three modes: a summer cooling mode, a winter heating mode, and a transitional season heat collection mode. The winter heating mode includes a first winter heating mode and a second winter heating mode.

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