Operation method of medium-deep layer buried pipe heat exchanger

Abstract

The invention relates to an operation method of a middle-deep layer buried pipe heat exchanger, which is characterized in that an inner pipe with a switchable flow channel is arranged in the middle-deep layer buried pipe heat exchanger, and a first opening and a second opening are formed in different depth positions, so that the middle-deep layer buried pipe heat exchanger at least has two operation modes of heat taking and cold taking; the limitation that an existing middle-deep layer buried pipe can only execute one-way heat supply operation is broken through, heat supply and cold supply two-way operation is achieved, the application range of the system is expanded, and the long-term operation stability of the system is improved.

Description

Technical Field

[0001] This invention relates to an operation method for a medium-deep buried pipe heat exchanger. By setting a first inner pipe and a second inner pipe in the medium-deep buried pipe heat exchanger, the heat exchanger can have at least two operating modes. This breaks through the limitation of existing medium-deep buried pipes that can only perform unidirectional heating operation, realizing bidirectional operation of heating and cooling, expanding the application range of the system, and improving the long-term operational stability of the system. It belongs to the technical field of buried pipe heat exchangers. Background Technology

[0002] For various electrically driven heat pump systems, the low-temperature heat source is a key factor affecting the operation of the heat pump unit. However, for conventional air-source heat pumps, shallow ground-source heat pumps, and seawater-source heat pumps, the stability of their low-temperature heat sources is subject to certain interference factors. In contrast, medium-deep geothermal heat pumps use medium-deep buried pipe heat exchangers as the low-temperature heat source, utilizing the medium-deep geothermal energy with rock temperatures of around 70-100℃. This provides a relatively high-temperature "low-temperature heat source" for the heat pump without damaging the underground environment, and is largely unaffected by climate conditions, ensuring long-term, stable, and efficient operation of the heat pump unit.

[0003] The structure and principle of the medium-deep underground buried pipe heat exchanger are as follows: a hole 2000-3500m deep is drilled underground, and two coaxial pipes are installed in the hole to form an ultra-long underground coaxial heat exchange pipe, with the bottom sealed. The outer pipe is a stainless steel oil casing with strong pressure resistance, which exchanges heat with the surrounding soil and rock strata. The inner pipe is generally an engineering plastic pipe with good thermal insulation performance. The heat exchange medium (fluid medium, usually water) flows downward between the inner and outer pipes, exchanges heat with the surrounding high-temperature rock strata, and gradually rises in temperature. It then enters the inner pipe from the bottom of the heat exchange hole and flows back to the heat pump unit from bottom to top, serving as the "low-temperature heat source" of the heat pump unit. After heat exchange and cooling in the evaporator of the heat pump unit, it recirculates back into the ultra-long underground coaxial heat exchange pipe, and so on. The heat pump unit extracts heat from the "low-temperature heat source," raises the temperature, and then provides heating. Reference: Actual Analysis of Energy Consumption and Energy Efficiency of Medium-Deep Geothermal Source Heat Pump Heating System, Heating Ventilation & Air Conditioning, No. 8, 2017, pp. 150-154.

[0004] The disadvantages of medium-deep buried pipe heat exchangers are: Unlike shallow buried pipe heat exchangers, existing medium-deep buried pipe heat exchangers can only operate for heating, not cooling. Due to long-term operation for heating, cold deposits gradually form in the soil and rock strata (or rock mass) surrounding the buried pipes. The impact of these cold deposits increases year by year and is difficult to fully recover, leading to a gradual decline in the overall heat exchange capacity of the buried pipe heat exchanger. Current technologies can only limit the total heat extraction, thus failing to fully realize its heat exchange potential. References: "Thermal Influence of Heat Transfer Process of Medium-Deep Buried Pipe Heat Exchanger on Surrounding Rock and Soil," *Heating Ventilation & Air Conditioning*, 2021, Vol. 51, No. 1, pp. 101-107; "Study on the Variation Law of Heat Exchange per Meter of Coaxial Shell Deep Buried Pipe Heat Exchanger," *Industrial Heating*, 2019, Vol. 8, No. 2, pp. 5-9.

[0005] Due to the influence of various factors such as geological structure, formation pressure, radioactive decay, and thermal conductivity, the actual formation temperature below 2000 meters can recover rapidly. Assuming heat is extracted solely from deep layers, the linear heat extraction power can be very high, fully utilizing its potential. However, mid-to-deep buried pipe heat exchangers penetrate soil and rock layers from shallow to deep, requiring consideration of the balanced heat exchange at different depths and the tiered utilization of different geothermal conditions. Therefore, existing technologies struggle to fully realize the heat exchange potential.

[0006] Therefore, whether the structure and function of medium-deep buried pipe heat exchangers can be improved so that they can be used not only for heating in winter but also for cooling in summer is a challenging and far-reaching problem that urgently needs to be solved.

[0007] Public content This invention relates to an operation method for a medium-deep buried pipe heat exchanger. By setting a first inner pipe and a second inner pipe in the medium-deep buried pipe heat exchanger, the medium-deep buried pipe heat exchanger has at least two operating modes, breaking through the limitation of existing medium-deep buried pipes that can only perform unidirectional heating operation, and realizing bidirectional operation of heating and cooling.

[0008] The technical solution of the present invention is: a medium-deep buried pipe heat exchanger, comprising an outer pipe and an inner pipe; the inner pipe is fitted inside the outer pipe; the inner pipe is an inner pipe capable of flow channel switching, used to form several heat exchange cycle modes; The inner tube has a first opening and a second opening. The first opening is located at the bottom of the medium-deep buried pipe heat exchanger, and the second opening is located in the middle part of the medium-deep buried pipe heat exchanger. By activating the first opening, and / or the second opening, and correspondingly activating different inner tube flow channels, several heat exchange cycle modes are formed. The different inner tube flow channels are respectively connected to the first opening, and / or the second opening.

[0009] As a preferred embodiment of the present invention, the area above the second opening between the outer tube and the inner tube is a shallow flow channel of the outer tube, and the area below the second opening between the outer tube and the inner tube is a deep flow channel of the outer tube. The heat exchange cycle mode includes: The inner pipe section above the second opening depth and the second opening are connected to the deep flow channel of the outer pipe, so that only the heat exchange medium in the outer pipe section below the second opening depth is in a circulating flow state and exchanges heat with the surrounding soil and rock layers; or, the inner pipe section above the second opening depth and the second opening are connected to the shallow flow channel of the outer pipe, so that only the heat exchange medium in the outer pipe section above the second opening depth is in a circulating flow state and exchanges heat with the surrounding soil and rock layers; or, the heat exchange medium in both the shallow flow channel and the deep flow channel of the outer pipe is in a circulating flow state and exchanges heat with the surrounding soil and rock layers.

[0010] For example, the heat exchange cycle mode includes heat extraction mode and cold extraction mode; In the heat extraction operation, a heat exchange medium circulation is formed through the first opening and / or the second opening, and the entire or part of the pipe section of the medium-deep buried pipe heat exchanger is used to exchange heat with the surrounding soil and rock layers. In the cooling operation, a heat exchange medium is circulated through the second opening, and the shallow pipe section of the medium-deep buried pipe heat exchanger located above the second opening exchanges heat with the surrounding soil and rock layers.

[0011] As a preferred embodiment of the present invention, the medium-deep buried heat exchanger is connected to a circulation drive system for driving the heat exchange medium to circulate; the circulation drive system can be used to perform operations such as enabling or disabling the first opening, enabling or disabling the second opening, and enabling different inner pipe channels.

[0012] The circulation drive system includes, but is not limited to, drive equipment, circulation pipelines, and loop switching devices. The selection of the specific outer pipe flow channel, and / or inner pipe flow channel, and / or heat exchange medium circulation direction in the medium-deep buried pipe heat exchanger is mainly controlled by the circulation drive system.

[0013] It should be noted that the circulation drive system is typically located outside the medium-deep buried heat exchanger. When the medium-deep buried heat exchanger is operating, a drive device (e.g., a circulation pump) is required to drive the heat exchange medium to circulate. Furthermore, to achieve different circulation loops, corresponding loop switching devices (e.g., connecting water jackets, connecting pipelines, reversing valves, flow distribution valves, one or more outlet ports, one or more return ports, etc.) need to be configured outside the buried heat exchanger. The switching of the heat exchange circulation mode, involving operations such as enabling or disabling the first opening, enabling or disabling the second opening, and enabling different inner pipe flow channels, is mainly controlled by the circulation drive system. The medium-deep buried heat exchanger of this invention is a necessary foundation for achieving the above functions.

[0014] In a preferred embodiment of the present invention, there are several second openings distributed at different depths of the medium-deep buried pipe heat exchanger. At any given time, only one of the second openings at a certain depth is set to the active state for communication with the outer pipe. The other openings are set to the hidden state, that is, these openings are in a state that does not affect the current flow of the heat exchange medium.

[0015] It should be noted that the switching operation of enabling or hiding the second opening at different depth positions can be performed by physical switching using an internal mechanical structure, or by logical switching using a cyclic drive system externally.

[0016] As a preferred embodiment of the present invention, the depth of the second opening is greater than or equal to 300m and less than or equal to 2000m.

[0017] It should be noted that setting several second openings at different depths serves to create more flexible flow channel combinations, enabling different operating effects and flexible adjustment of the system's operating state. Therefore, the depth of the second openings needs to vary within a wide range depending on the corresponding operating effect, and different depths of the second openings should be activated under different conditions, while openings at other locations should be set to a hidden state.

[0018] As a preferred technical solution of the present invention, the inner tube can combine the following structures.

[0019] In some embodiments, the inner tube includes a first inner tube and a second inner tube arranged in parallel; the first inner tube extends to the bottom of the medium-deep buried pipe heat exchanger and is provided with a first opening, and the second inner tube extends to the middle part of the medium-deep buried pipe heat exchanger and is provided with a second opening.

[0020] In some embodiments, the inner tube includes a first inner tube and a second inner tube arranged coaxially; the diameter of the first inner tube is smaller than the diameter of the second inner tube, and a portion of the first inner tube is located within the second inner tube. The first inner tube extends to the bottom of the medium-deep buried pipe heat exchanger and has a first opening, while the second inner tube extends to the middle part of the medium-deep buried pipe heat exchanger and has a second opening.

[0021] In some embodiments, the inner tube includes at least one pipe with one or more intermediate openings, and a loop switching interface is provided at the location of one or more of the intermediate openings; the loop switching interface is used to connect the upper pipe and the lower pipe, and the intermediate opening is disposed in the loop switching interface; The loop switching interface includes two states that can be switched between each other: through state and cut-off state; When the circuit switching interface is in a through state, the middle opening in the circuit switching interface is closed, and the upper pipe and the lower pipe connected to the circuit switching interface are in a connected state. When the circuit switching interface is in the off state, the middle opening in the circuit switching interface is open, the inner pipe runs directly from the upper pipe to the middle opening, and the lower pipe connected to the circuit switching interface is in the closed state.

[0022] As a preferred embodiment of the present invention, the circuit switching interface includes a switching mechanism, a baffle, and a central opening; the switching mechanism drives the baffle to rotate or rotate and move. When the circuit switching interface is in a straight-through state, the baffle moves to the position of the middle opening and closes the middle opening, while simultaneously making the upper pipe and the lower pipe connected to the circuit switching interface in a connected state. When the circuit switching interface is in the off state, the baffle moves to the position of the lower pipe connected to the circuit switching interface and closes the lower pipe, while opening the middle opening.

[0023] As a preferred embodiment of the present invention, the actuator of the circuit switching interface is one of an electric actuator, a pneumatic actuator, or a hydraulic actuator, or any combination of electric actuators, pneumatic actuators, and hydraulic actuators; the control module of the actuator is located outside the buried pipe heat exchanger, and is connected to the actuator through a cable inserted into the buried pipe, or / and a pipeline, and drives the actuator through the control module.

[0024] As a preferred embodiment of the present invention, an airbag assembly is provided in the outer tube near the second opening, the airbag assembly including an opening and closing airbag.

[0025] Correspondingly, the operating method of a medium-deep buried pipe heat exchanger according to the present invention is as follows: The medium-deep buried pipe heat exchanger is defined as including an outer pipe and an inner pipe with switchable flow channels; the inner pipe is provided with a first opening and a second opening, the first opening being located at the bottom of the medium-deep buried pipe heat exchanger and the second opening being located in the middle part of the medium-deep buried pipe heat exchanger; the inner pipe is used to form several heat exchange cycle modes. The heat exchange cycle mode is selected as needed to handle cooling, heating, and / or heat storage conditions; the heat exchange cycle modes include: The inner pipe section above the second opening depth position and the outer pipe section below the second opening depth position are connected, so that the heat exchange medium in the outer pipe section below the second opening depth position is in a circulating flow state and exchanges heat with the surrounding soil and rock layers; it is applied to heat extraction conditions and / or heat storage conditions. Alternatively, the inner pipe section above the second opening depth and the second opening are connected to the outer pipe section above the second opening depth, so that the heat exchange medium in the outer pipe section above the second opening depth is in a circulating state and exchanges heat with the surrounding soil and rock layers; applicable to cooling or heating conditions. Alternatively, the heat exchange medium in all external pipe sections can be in a state of circulation and exchange heat with the surrounding soil and rock layers; this can be applied to heat extraction conditions.

[0026] As a preferred technical solution of the present invention, in some embodiments, the operation method of the medium-deep buried pipe heat exchanger includes a cooling mode, a full-process heating mode, and / or a heating diversion mode, and / or a shallow circulation heating mode, and / or a deep circulation heating mode, and / or a complete heat storage mode.

[0027] It should be noted that cooling mode is executed in cooling operation; heating mode and heat storage mode can be considered general concepts; heating mode can be reflected in full-process heating mode, heating diversion mode, shallow circulation heating mode, deep circulation heating mode, etc.; heat storage mode can be reflected in heating diversion mode, deep circulation heating mode, complete heat storage mode, etc. Therefore, a specific operating mode may have multiple attributes simultaneously, possibly possessing both heating and heat storage attributes.

[0028] Using the location of the second opening as a boundary, the medium-deep buried pipe heat exchanger is defined as including the following flow channels: a first shallow flow channel in the inner pipe, a second shallow flow channel in the inner pipe, a deep flow channel in the inner pipe, a shallow flow channel in the outer pipe, and a deep flow channel in the outer pipe. The return port for the heat exchange medium input and the outlet port for the heat exchange medium output are also defined. Then, the user-side system is connected. The user-side system includes a circulation drive system, which drives the heat exchange medium to circulate according to a specified heat exchange circulation pattern.

[0029] When the full-process heat extraction mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, shallow flow channel of outer pipe, deep flow channel of outer pipe, first opening, deep flow channel of inner pipe, first shallow flow channel of inner pipe, and outlet.

[0030] When the cooling mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, inner pipe second shallow flow channel, second opening, outer pipe shallow flow channel, and outlet. Alternatively: return port, shallow flow channel of outer tube, second opening, second shallow flow channel of inner tube, outlet.

[0031] When the heat exchange medium is in the heat extraction and diversion mode, it is diverted at the liquid outlet. A portion of the heat exchange medium is transported externally, and after heat exchange, it flows back through the liquid return port. The other portion of the heat exchange medium flows directly back into the medium-deep buried pipe heat exchanger. The flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: Part of the heat exchange medium: first return port, outer tube shallow flow channel, outer tube deep flow channel, first opening, inner tube deep flow channel, inner tube first shallow flow channel, and outlet; The other part of the heat exchange medium includes: the second return port, the second shallow flow channel of the inner tube, the second opening, the deep flow channel of the outer tube, the first opening, the deep flow channel of the inner tube, the first shallow flow channel of the inner tube, and the outlet.

[0032] When the shallow circulation heat extraction mode is executed, the flow direction of the heat exchange medium in the medium-deep buried pipe heat exchanger is as follows: return port, shallow flow channel of outer pipe, second opening, second shallow flow channel of inner pipe, and outlet. This mode has cold accumulation properties, releasing coolness to the surrounding shallow soil and rock layers during the circulation process.

[0033] When the deep circulation heat extraction mode is executed, the flow direction of the heat exchange medium in the medium-deep buried pipe heat exchanger is as follows: return port, inner pipe second shallow flow channel, second opening, outer pipe deep flow channel, first opening, inner pipe deep flow channel, inner pipe first shallow flow channel, and outlet. This mode has some heat storage properties, and also releases some heat to the surrounding deep soil and rock layers during the circulation heat extraction process.

[0034] When the full heat storage mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, first shallow flow channel of inner pipe, deep flow channel of inner pipe, first opening, deep flow channel of outer pipe, second opening, second shallow flow channel of inner pipe, and outlet; and the outlet and return port are connected to form a circulation. Alternatively: return port, second shallow flow channel of inner tube, second opening, deep flow channel of outer tube, first opening, deep flow channel of inner tube, first shallow flow channel of inner tube, and outlet; and connect the outlet and return port to form a circulation.

[0035] In a preferred embodiment of the present invention, there are several second openings distributed at different depths of the medium-deep buried pipe heat exchanger. At any given time, only one of the second openings at a certain depth is set to the active state for communication with the outer pipe. The other openings are set to the hidden state, that is, these openings are in a state that does not affect the current flow of the heat exchange medium.

[0036] As a preferred embodiment of the present invention, the depth of the second opening is greater than or equal to 300m and less than or equal to 2000m.

[0037] It should be noted that when dividing the flow channels based on the position of the second opening, if the second opening consists of several openings at different depths, the position of the opening currently in use should be used as the basis for division.

[0038] As a preferred embodiment of the present invention, before the heat storage condition is executed, heat exchange medium is drawn out to the outside through the inner pipe, and gas is injected into the inside through the outer pipe. The process stops when the shallow flow channel of the outer pipe is filled with gas, which is used to block the heat exchange between the shallow flow channel of the outer pipe and the surrounding soil and rock layers (when the heat storage condition is executed, the liquid level of the heat exchange medium should be slightly higher than the position of the second opening, and a certain gas pressure should be maintained to avoid gas loss). After the heat storage condition is executed, heat exchange medium is injected into the inside through the inner pipe, and gas is drawn out to the outside through the outer pipe. The process stops when the gas in the shallow flow channel of the outer pipe is emptied.

[0039] The beneficial effects of this invention are: 1. In the prior art, the areas where medium-deep buried pipe heat exchanger systems are used are usually high-latitude regions. These regions are characterized by winter heat loads that are much higher than summer cooling loads, but there are still cooling loads to be addressed in summer. This invention achieves a significant improvement in system utilization by flexibly switching the internal flow channels of the medium-deep buried pipe heat exchanger, enabling the entire pipe section to extract heat from the soil and rock layers during winter heating and the use of a portion of shallower pipe sections to release heat and extract coolness during summer cooling. 2. By flexibly switching the internal flow channels of the medium-deep buried pipe heat exchanger, when dealing with the problem of user-side load fluctuations during winter heating, a heat extraction and diversion mode is adopted when the user-side load is in a low-load state. This mode can utilize the shallow pipe section for heat extraction and the deep pipe section for heat storage, and can be used to cope with peak loads on the user side. 3. By flexibly switching the internal flow channels of the medium-deep buried pipe heat exchanger, and taking advantage of the transition season before winter, the full heat storage mode is implemented to make full use of the more active geothermal heat flow in the deep area, offset the cold accumulation around the middle and deep pipe sections, and further enhance the heat extraction capacity of the medium-deep buried pipe heat exchanger in winter. 4. Existing research indicates that when medium-deep buried pipe heat exchangers are used solely for heating, the influence radius of cold accumulation varies significantly at different depths. Consequently, the spacing of buried pipes in heat exchangers must be designed based on the maximum influence radius during project design (e.g., hole spacing set at 80-100 meters). By employing the flexible switching of internal flow channels in this invention and comprehensively applying multiple heat exchange circulation modes, the influence radius of cold accumulation across the entire depth direction can be made more uniform and smaller, making denser arrangement schemes possible (e.g., hole spacing set at approximately 30-50 meters), thereby reducing the difficulty of design and construction. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the first type of medium-deep buried pipe heat exchanger provided in the embodiments of this disclosure; Figure 2 This is a schematic diagram of a second type of medium-deep buried pipe heat exchanger provided in an embodiment of the present disclosure; Figure 3 A schematic diagram of a third type of medium-deep buried pipe heat exchanger provided in this disclosure (including a partially enlarged view of two loop switching interfaces). Figure 4 This is a schematic diagram of a fourth type of medium-deep buried pipe heat exchanger provided in an embodiment of the present disclosure; Figure 5 To and Figure 2 A diagram showing the corresponding inward inflation state; Figure 6 To and Figure 2 The corresponding diagram showing the outward exhaust state; Figure 7 To and Figure 2 Corresponding airbag application effect diagram (I); Figure 8 To and Figure 2 Corresponding airbag application effect diagram (II); Figure 9 This is an exploded view of the flow channel of the medium-deep buried pipe heat exchanger disclosed herein; Figure 10 This is a flowchart of the full-process heat extraction mode operation. Figure 11 Flowchart for cooling mode operation (I); Figure 12 Flowchart for cooling mode operation (II); Figure 13 Flowchart of the heat extraction and diversion mode operation; Figure 14 This is a flowchart of the shallow circulation heat extraction mode operation. Figure 15 This is a flowchart of the deep circulation heat extraction mode operation. Figure 16 Flowchart for full thermal storage mode operation (I); Figure 17 Flowchart for full thermal storage mode operation (II); In the diagram: 1. Outer pipe; 101. Shallow flow channel of outer pipe; 102. Deep flow channel of outer pipe; 2. Inner pipe; 21. First inner pipe; 22. Second inner pipe; 201. First shallow flow channel of inner pipe; 202. Second shallow flow channel of inner pipe; 203. Deep flow channel of inner pipe; 211. Upper pipe; 212. Lower pipe; 301. First opening; 302. Second opening; 302a. First intermediate opening; 302b. Second intermediate opening; 4. Outlet; 5. Return port; 5a. First return port; 5a. Second return port; 6. User-side system; 7. Flow distributor; 8. Loop switching interface; 8a. First loop switching interface; 8b. Second loop switching interface; 801. Shell frame structure; 802. Rotating shaft; 803. Connecting rod; 804. Baffle; 9. Soil and rock strata; 10. Inflation management module; 11. Gas; 12a. Shallow opening and closing airbag of outer tube; 12b. Deep opening and closing airbag of outer tube. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0042] It should be noted that, unless the context explicitly requires it, the words "comprising," "including," and similar terms in the entire specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0043] Furthermore, it should be understood in the description of this disclosure that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Additionally, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more, and "several" means one or more.

[0044] Furthermore, it should be understood in the description of this disclosure that the terms "shallow layer", "intermediate layer", "deep layer", "bottom", "middle", "middle part", etc. are used only for the purpose of describing relative positional relationships and do not correspond to specific depth values. The depth positions may not be exactly the same in different embodiments or may be flexibly set, and cannot be generalized.

[0045] This disclosure provides a medium-deep buried pipe heat exchanger, including an outer pipe 1 and an inner pipe 2, wherein the inner pipe 2 is fitted inside the outer pipe 1; the inner pipe 2 is an inner pipe 2 capable of flow channel switching, used to form several heat exchange cycle modes; the inner pipe 2 has a first opening 301 and a second opening 302 (for communication with the outer pipe 1), the first opening 301 is located at the bottom of the medium-deep buried pipe heat exchanger, and the second opening 302 is located in the middle part of the medium-deep buried pipe heat exchanger; by activating the first opening 301, or / and activating the second opening 302, and correspondingly activating different inner pipe flow channels, several heat exchange cycle modes are formed.

[0046] The medium-deep buried heat exchanger is connected to a circulation drive system to drive the heat exchange medium to circulate; the circulation drive system can be used to enable or disable the first opening 301, enable or disable the second opening 302, and enable different inner pipe flow channels.

[0047] The circulation drive system includes, but is not limited to, drive equipment, circulation pipelines, and loop switching devices. The selection of the specific outer pipe flow channel, and / or inner pipe flow channel, and / or heat exchange medium circulation direction in the medium-deep buried pipe heat exchanger is mainly controlled by the circulation drive system.

[0048] It should be noted that when the buried pipe heat exchanger is working, a driving device (such as a circulating pump) is required to drive the heat exchange medium to circulate; and in order to realize different circulation loops, corresponding loop switching devices (such as connecting water jackets, connecting pipelines, reversing valves, flow distribution valves, one or more liquid outlets, one or more liquid return ports, etc.) need to be configured outside the buried pipe heat exchanger; the above are all combinations of conventional technologies in the field, and will not be described in detail in the present invention.

[0049] For ease of explanation, such as Figure 9As shown, with the position of the second opening 302 as the boundary, the multiple flow channels in the medium-deep buried pipe heat exchanger are set as follows: inner pipe first shallow flow channel 201, inner pipe second shallow flow channel 202, inner pipe deep flow channel 203, outer pipe shallow flow channel 101, and outer pipe deep flow channel 102.

[0050] The inner tube 2 with switchable flow channels specifically includes the following structural forms, which can be used individually or in combination, all of which can constitute a structure such as Figure 9 The flow channel architecture shown.

[0051] The first type is the "parallel double inner tube" structure, such as Figure 1 As shown, two inner tubes 2 of different depths are inserted side-by-side into the outer tube 1; that is, the inner tube 2 includes a first inner tube 21 and a second inner tube 22 arranged side-by-side; the first inner tube 21 extends to the bottom of the medium-deep buried pipe heat exchanger and is provided with a first opening 301 (opening depth D1), and the second inner tube 22 extends to the middle part of the medium-deep buried pipe heat exchanger and is provided with a second opening 302 (opening depth D2). At this time, the first inner tube 21 forms the first shallow flow channel 201 and the deep flow channel 203 of the inner tube, and the second inner tube 22 forms the second shallow flow channel 202 of the inner tube; the outer tube shallow flow channel 101 and the outer tube deep flow channel 102 are sequentially formed between the two inner tubes and the outer tube 1 at position D2.

[0052] The second type is the "coaxial double inner tube" structure, such as Figure 2 As shown, the inner tube 2 includes a first inner tube 21 and a second inner tube 22 arranged coaxially. The diameter of the first inner tube 21 is smaller than that of the second inner tube 22, and a portion of the first inner tube 21 is located within the second inner tube 22. The first inner tube 21 extends to the bottom of the medium-deep buried pipe heat exchanger and has a first opening 301 (opening depth D1). The second inner tube 22 extends to the middle part of the medium-deep buried pipe heat exchanger and has a second opening 302 (opening depth D2). At this time, the first inner tube 21 forms the first shallow flow channel 201 and the deep flow channel 203 of the inner tube, and the flow channel between the second inner tube 22 and the first inner tube 21 forms the second shallow flow channel 202 of the inner tube. The outer tube shallow flow channel 101 and the outer tube deep flow channel 102 are sequentially formed between the outer tube and the outer tube 1 at position D2.

[0053] The third type is the "multi-opening inner tube" structure, such as... Figure 3As shown, the inner pipe 2 includes at least one pipe with one or more intermediate openings (and also includes a bottom opening), and a loop switching interface is provided at the location of one or more of the intermediate openings; the loop switching interface is used to connect the upper pipe 211 and the lower pipe 212, and the intermediate opening is located in the loop switching interface; The loop switching interface includes two switchable states: a through state and a closed state. When the loop switching interface is in the through state, the middle opening of the loop switching interface is closed, and the upper pipe 211 and the lower pipe 212 connected to the loop switching interface are in a connected state. When the loop switching interface is in the closed state, the middle opening of the loop switching interface is open, the inner pipe 2 runs directly from the upper pipe 211 to the middle opening, and the lower pipe 212 connected to the loop switching interface is in a closed state.

[0054] It should be noted that, in Figure 3 In the inner tube 2, intermediate openings (i.e., first intermediate opening 302a and second intermediate opening 302b, serving as second openings at different depths) and a bottom opening are respectively provided at two depth positions. The bottom opening is the first opening 301 (opening depth is D1). In practical applications, at least one intermediate opening should be provided. When multiple intermediate openings exist, i.e., several second openings distributed at different depths of the medium-deep buried pipe heat exchanger, at any given time, only openings at no more than one depth position are set to the active state for communication with the outer tube, while the other openings are set to the hidden state, which is equivalent to these openings being in a state that does not affect the flow of the heat exchange medium in the current mode. Of course, all intermediate openings can be set to the hidden state, for example, when executing the full-process heat extraction mode.

[0055] by Figure 3 For example, the intermediate openings set at the two depth positions correspond to the first loop switching interface 8a and the second loop switching interface 8b, respectively. At this time, the first loop switching interface 8a is in a straight-through state, and the first intermediate opening 302a (opening depth D2) is in a closed and hidden state; the second loop switching interface 8b is in a cut-off state, and the second intermediate opening 302b (opening depth D3) is in an open state; under this condition, the inner tube 2 is divided into a shallow inner tube flow channel and a deep inner tube flow channel 203 at the D3 position, and the outer tube 2 is divided into a shallow outer tube flow channel 101 and a deep outer tube flow channel 102 at the D3 position between the outer tube 1 and the inner tube 2.

[0056] by Figure 3Based on this, if the states of the first loop switching interface 8a and the second loop switching interface 8b are swapped, that is: if the first loop switching interface 8a is adjusted to the cut-off state, then the first intermediate opening 302a (opening depth D2) is in the open state; if the second loop switching interface 8b is in the through state, then the second intermediate opening 302b (opening depth D3) is in the closed hidden state; in this case, the inner tube 2 is divided into the inner tube shallow flow channel and the inner tube deep flow channel 203 by the D2 position, and the outer tube shallow flow channel 101 and the outer tube deep flow channel 102 are divided into the outer tube shallow flow channel 101 and the outer tube deep flow channel 102 by the D2 position between the outer tube 2 and the outer tube 1.

[0057] As a preferred technical solution of the present invention, such as Figure 3 As shown, the circuit switching interface includes a switching mechanism, a baffle 804, and a central opening; the switching mechanism drives the baffle 804 to rotate or rotate and move. When the circuit switching interface is in a straight-through state, the baffle 804 moves to the position of the middle opening and closes the middle opening, while making the upper pipe 211 and the lower pipe 212 connected to the circuit switching interface 8 in a connected state. When the circuit switching interface is in the off state, the baffle 804 moves to the position of the lower pipe 212 connected to the circuit switching interface 8 and closes the lower pipe 212, while opening the middle opening.

[0058] like Figure 3 As shown, the circuit switching interface includes a housing frame structure 801, a rotating shaft 802, a connecting rod 803, and a baffle 804. The housing frame structure 801 is an internally continuous cylinder with the same or similar diameter as the inner tube 2. The upper and lower ends of the housing frame structure 801 are fixedly connected to the upper pipe 211 (i.e., the upper inner tube) and the lower pipe 212 (i.e., the lower inner tube), respectively. The housing frame structure 801 has a central opening on its side. The rotating shaft 802 is located inside the housing frame structure 801. The rotating shaft 802 is rotatably connected to the connecting rod 803. The outer side of the connecting rod 803 is fixedly connected to the baffle 804. The baffle 804 can be made of an elastic material, such as rubber.

[0059] The upper pipe 211 is an inner pipe located above the loop switching interface 8 and is fixedly connected to the upper part of the loop switching interface 8; the lower pipe 212 is an inner pipe located below the loop switching interface and is fixedly connected to the lower part of the loop switching interface. The specific method of fixed connection can be threaded connection, bonding, welding, etc.

[0060] like Figure 3The first loop switching interface 8a is shown in the form (straight-through state). The connecting rods 803 on both sides are driven by the switching mechanism to rotate to the horizontal position, so that the baffle 804 fits against the middle opening (first middle opening 302a) on both sides and closes it, while the inner tube flow channel in the vertical direction is in the open state; the direction of the dashed arrow is the flow path of the medium. like Figure 3 The second loop switching interface 8b is shown in the form (closed state). The connecting rods 803 on both sides are driven by the switching mechanism to rotate downward by a certain angle, so that the baffles 804 on both sides are connected to each other at the lower pipe 212 and close the lower pipe 212. At the same time, the middle openings (second middle openings 302b) on both sides are in the open state; the direction of the dashed arrow is the flow path of the medium. In this case, the first intermediate opening 302a is hidden, and the second intermediate opening 302b is used as the second opening 302. Of course, the first circuit switching interface 8a can also be switched to the closed state, in which case the first intermediate opening 302a is used as the second opening 302.

[0061] As a preferred embodiment of the present invention, the actuator of the circuit switching interface is one of an electric actuator, a pneumatic actuator, or a hydraulic actuator, or any combination of electric actuators, pneumatic actuators, and hydraulic actuators; the control module of the actuator is located outside the buried pipe heat exchanger, and is connected to the actuator through a cable inserted into the buried pipe, or / and a pipeline, and drives the actuator through the control module.

[0062] The fourth type is the "coaxial multi-opening double inner tube" structure, such as... Figure 4 As shown, this is actually a structure combining a "coaxial double inner tube" structure and a "multi-opening inner tube" structure. Specifically, based on the "coaxial double inner tube" structure, a loop switching interface 8 is provided in the middle of the second inner tube 22. The structure and working principle of the loop switching interface 8 are similar to... Figure 3 Similar; and Figure 3 In contrast to the structure, such as Figure 4 As shown, a loop switching interface 8 is provided in the middle of the second inner tube 22 to form a first intermediate opening 302a, and the opening at the bottom of the second inner tube 22 naturally forms a second intermediate opening 302b. By controlling the loop switching interface 8, the first intermediate opening 302a or the second intermediate opening 302b can be flexibly enabled, that is, the second opening at different depths can be set to the enabled state.

[0063] It should be noted that, due to the relatively long length of the buried pipe, for ease of explanation, Figure 1-4The underground pipe was cut off, omitting a portion of the conventional pipe section.

[0064] In summary, apart from switching the second opening at different depths, the switching of various heat exchange cycle modes is not actively completed internally by the buried pipe heat exchanger of the present invention; the structure of the buried pipe heat exchanger of the present invention constitutes the necessary basic hardware conditions for realizing the flow channel switching function, and various heat exchange cycle modes can be realized by combining it with the external circulation drive system.

[0065] The above mainly describes the various structures of the buried pipe heat exchanger of the present invention; the following focuses on describing the operation process of the buried pipe heat exchanger of the present invention in conjunction with specific application scenarios.

[0066] An operating method for a medium-deep buried pipe heat exchanger according to the present invention is as follows: The medium-deep buried pipe heat exchanger comprises an outer pipe 1 and an inner pipe 2 with switchable flow channels; the inner pipe 2 is provided with a first opening 301 and a second opening 302, the first opening 301 being located at the bottom of the medium-deep buried pipe heat exchanger and the second opening 302 being located in the middle part of the medium-deep buried pipe heat exchanger; the inner pipe 2 is used to form several heat exchange cycle modes. Select the appropriate heat exchange cycle mode as needed to handle cooling, heating, or heat storage conditions; the heat exchange cycle modes include: The inner pipe section above the depth position of the second opening 302 and the outer pipe section below the depth position of the second opening 302 are connected, so that the heat exchange medium in the outer pipe section below the depth position of the second opening 302 is in a circulating flow state and exchanges heat with the surrounding soil and rock layers 9; it is applied to heat extraction conditions and / or heat storage conditions. Alternatively, the inner pipe section above the depth position of the second opening 302 and the outer pipe section above the depth position of the second opening 302 are connected, so that the heat exchange medium in the outer pipe section above the depth position of the second opening 302 is in a circulating flow state and exchanges heat with the surrounding soil and rock layers 9; applicable to cooling or heating conditions. Alternatively, the heat exchange medium in all external pipe sections can be in a state of circulation and exchange heat with the surrounding soil and rock layers 9; this can be applied to heat extraction conditions.

[0067] In some embodiments, the operation method of the medium-deep buried pipe heat exchanger includes full-process heat extraction mode, and / or heat extraction diversion mode, and / or shallow circulation heat extraction mode, and / or deep circulation heat extraction mode, and / or complete heat storage mode.

[0068] For ease of explanation, such as Figure 9As shown, taking the position of the second opening 302 as the boundary, the medium-deep buried pipe heat exchanger is defined as including the following flow channels: inner pipe first shallow flow channel 201, inner pipe second shallow flow channel 202, inner pipe deep flow channel 203, outer pipe shallow flow channel 101, and outer pipe deep flow channel 102; then, the return port 5 for the heat exchange medium input and the outlet port 4 for the heat exchange medium output of the medium-deep buried pipe heat exchanger are determined and connected to the user-side system 6.

[0069] When the full-process heat extraction mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 10 As shown): return port 5, outer pipe shallow flow channel 101, outer pipe deep flow channel 102, first opening 301, inner pipe deep flow channel 203, inner pipe first shallow flow channel 201, and outlet 4; at this time, outlet 4 is connected to user-side system 6, circulating and transporting heat exchange medium for heat exchange, and then connected to return port 5 by user-side system 6; the temperature of heat exchange medium at outlet 4 is higher than that of heat exchange medium at return port 5.

[0070] When the cooling mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 11 (As shown): return port 5, inner tube second shallow flow channel 202, second opening 302, outer tube shallow flow channel 101, outlet 4; Or (e.g.) Figure 12 (As shown): return port 5, outer tube shallow flow channel 101, second opening 302, inner tube second shallow flow channel 202, outlet 4; At this time, the liquid outlet 4 is connected to the user-side system 6, where the heat exchange medium is circulated and transported for heat exchange, and then connected to the return liquid outlet 5 by the user-side system 6; the temperature of the heat exchange medium at the liquid outlet 4 is lower than that at the return liquid outlet 5.

[0071] When the heat exchange medium is in the heat extraction and diversion mode, diversion occurs at outlet 4. A portion of the heat exchange medium is transported externally, and after heat exchange, it returns through return outlet 5. The other portion of the heat exchange medium directly returns to the medium-deep buried pipe heat exchanger. The flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 13 (as shown) A portion of the heat exchange medium consists of: first return port 5a, outer tube shallow flow channel 101, outer tube deep flow channel 102, first opening 301, inner tube deep flow channel 203, inner tube first shallow flow channel 201, and outlet 4. At this time, outlet 4, after being diverted by flow distributor 7, delivers a portion of the heat exchange medium to user-side system 6 for heat exchange, and then user-side system 6 connects to first return port 5a. The temperature of the heat exchange medium at outlet 4 is higher than that at first return port 5a. The other part of the heat exchange medium consists of: the second return port 5b, the second shallow flow channel 202 of the inner tube, the second opening 302, the deep flow channel 102 of the outer tube, the first opening 301, the deep flow channel 203 of the inner tube, the first shallow flow channel 201 of the inner tube, and the outlet 4. At this time, the outlet 4, after being diverted by the flow distributor 7, directly delivers the other part of the heat exchange medium to the second return port 5b to form a circulation. It should be noted that in order to achieve the diversion of the heat exchange medium, the return port needs to be divided into two, namely the first return port 5a and the second return port 5b. The characteristic of this mode is that it can keep the temperature of the heat exchange medium in the shallow flow channel 101 of the outer pipe at a relatively low level, which is conducive to the formation of "cold accumulation" in the soil and rock layers 9 in the shallow underground area.

[0072] When the shallow circulation heat extraction mode is executed, the flow direction of the heat exchange medium in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 14 (As shown): return port 5, outer pipe shallow flow channel 101, second opening 302, inner pipe second shallow flow channel 202, and outlet 4. This mode has cold accumulation properties, releasing cold to the surrounding shallow soil and rock layers 9 during circulation; at this time, outlet 4 is connected to the user-side system 6, circulating and transporting heat exchange medium for heat exchange, and then connected to return port 5 by user-side system 6; the temperature of the heat exchange medium at outlet 4 is higher than that at return port 5; The characteristic of this mode is that it can rapidly reduce the temperature of the heat exchange medium in the shallow flow channel 101 of the outer tube, and it is mainly used in low load conditions or short cycle operation.

[0073] When the deep circulation heat extraction mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 15 (As shown): return port 5, inner tube second shallow flow channel 202, second opening 302, outer tube deep flow channel 102, first opening 301, inner tube deep flow channel 203, inner tube first shallow flow channel 201, and outlet 4. At this time, outlet 4 is connected to user-side system 6, circulating and transporting heat exchange medium for heat exchange, and then connected to return port 5 by user-side system 6; the temperature of the heat exchange medium at outlet 4 is higher than that at return port 5; This mode has some heat storage properties. During the heat extraction process, it gradually increases the temperature of the heat exchange medium in the buried pipe and may also release some heat to the soil and rock strata 9 in the middle area. The characteristic of this mode is that it can continuously output a heat exchange medium with a high temperature.

[0074] When the full heat storage mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows (e.g., Figure 16As shown): return port 5, inner tube first shallow flow channel 201, inner tube deep flow channel 203, first opening 301, outer tube deep flow channel 102, second opening 302, inner tube second shallow flow channel 202, and outlet 4; and the outlet 4 is connected to the return port 5 to form a circulation; Or (e.g.) Figure 17 As shown): return port 5, inner tube second shallow flow channel 202, second opening 302, outer tube deep flow channel 102, first opening 301, inner tube deep flow channel 203, inner tube first shallow flow channel 201, and outlet 4; and the outlet 4 is connected to the return port 5 to form a circulation; The characteristic of this mode is that some of the heat in the bottom region of the medium-deep buried pipe heat exchanger is transferred to the middle region, thereby improving the distribution of the underground temperature field and facilitating long-term operation.

[0075] It should be noted that in certain operating conditions, such as cooling mode and full heat storage mode, two circulation methods are listed: forward circulation and reverse circulation. Reverse circulation should be preferred, even though it requires adding some components and making the structure more complex in the design of the circulation drive system; such flow direction design is essential.

[0076] Taking shallow buried pipe heat exchangers as an example, their typical operation mode is heat extraction in winter and cooling in summer. However, the heat exchange medium circulation direction is the same in both winter and summer, with no reverse circulation design. This is because the depth of shallow buried pipe heat exchangers is only 100-150 meters, and the change in geothermal gradient along the depth direction is very small. However, for medium-deep buried pipe heat exchangers, the depth generally exceeds 2000 meters, and the influence of the geothermal gradient is a non-negligible factor. Therefore, adopting a circulation direction that follows the geothermal gradient is more conducive to heat exchange, that is, maintaining a relatively stable internal and external temperature difference rather than forming a "scissors difference," which is beneficial for the tiered utilization of different geothermal temperatures. Otherwise, it will affect the heat exchange process and disturb the distribution of the underground temperature field.

[0077] It should be noted that the heat extraction and diversion mode can be regarded as a combination of heat extraction and heat storage conditions. This mode has two extreme states: one is that there is no flow in the external loop, which becomes the complete heat storage mode; the other is that there is no flow in the shallow flow channel 101 of the outer pipe, which becomes the deep circulation heat extraction mode. In this case, while extracting heat, a portion of heat will be stored in the deep region to cope with the peak load of the system.

[0078] The following will explain the specific applications in two cases: "setting a second opening at one depth position" and "setting a second opening at two different depth positions".

[0079] In the first embodiment, the second opening 302 is provided only at one depth position, so as to Figure 2 Taking the structure as an example, the corresponding operation process is as follows. As example data, D1 is set to 2500 meters and D2 is set to 800 meters. At this time, the shallow layer is the range of 0-800 meters in depth and the deep layer is the range of 800-2500 meters in depth.

[0080] In summer, the cooling mode is implemented. Only the heat exchange medium in the shallow outer pipe section is in a circulating state and exchanges heat with the shallow soil and rock layer 9, releasing heat to the soil and rock layer 9 and cooling it. The heat exchange medium in the deep pipe section is in a static state, and the heat exchange is negligible. After summer operation, the temperature of the shallow soil and rock layer 9 rises, while the temperature of the deep soil and rock layer 9 changes very little.

[0081] During the transitional season before winter, a full heat storage mode is implemented if necessary. At this time, the shallow flow channel 101 of the outer pipe is idle, so the heat exchange between the outer pipe and the shallow soil and rock layer 9 is very small. At the same time, the heat exchange medium in the deep flow channel 102 of the outer pipe is in a circulating flow state and exchanges heat with the deep soil and rock layer 9. That is, the heat in the soil and rock layer 9 with a higher temperature at the bottom of the buried pipe is taken out and gradually released into the deep soil and rock layer 9, so that the temperature of the entire deep soil and rock layer 9 is increased.

[0082] In winter, the full-process heat extraction mode is mainly implemented. The heat exchange medium in all external pipe sections is in a state of circulation and exchanges heat with the soil and rock layer 9 to extract heat from the soil and rock layer 9. After winter operation, the temperature of the shallow soil and rock layer 9 drops and can meet the conditions for summer cooling operation. The temperature of the deep soil and rock layer 9 also drops. If the drop is large, it is necessary to implement the full heat storage mode appropriately in the transition season before winter.

[0083] As a preferred technical solution of the present invention, in order to cope with the fluctuation of user-side heat load in winter, a heat extraction and diversion mode can be adopted in a timely manner. That is, when the user-side is at a low load, the heat extraction and diversion mode is executed. At this time, the heat exchange medium in the deep flow channel 102 of the outer pipe exchanges heat with the deep soil and rock layer 9, that is, heat is extracted from the soil and rock layer 9 at the bottom of the buried pipe where the temperature is relatively high. Part of the extracted heat is transferred to the external system to meet the user-side low load and returns to the deep area of ​​the outer pipe through the shallow flow channel 101 of the outer pipe. The other part returns directly to the deep area of ​​the outer pipe through the second shallow flow channel 202 of the inner pipe and gradually releases heat into the deep soil and rock layer 9, thereby increasing the temperature of the entire deep soil and rock layer 9 and the temperature of the heat exchange medium. When the user side is under peak load, the full-process heat extraction mode is executed. By utilizing the heat stored in the deep soil and rock layers 9 and the heat stored by the heating of the heat exchange medium, the buried pipe heat exchanger can maintain a higher heat output power than usual for a period of time, thereby meeting the application requirements of peak load.

[0084] It is particularly important to note that in existing applications of medium-deep buried pipe heat exchangers, the conventional technical means to cope with fluctuations in user-side heat load are mainly qualitative or quantitative regulation. When the user-side load is high, the return water temperature at return port 5 is relatively low (e.g., the extreme temperature is around 5º), and when the user-side load is low, the return water temperature at return port 5 is relatively high (e.g., 20-30º). Since the current application only involves unidirectional heat extraction, this approach is reasonable and not problematic. However, after long-term operation, it is possible that the reference temperature of the shallow soil and rock layers will gradually increase, while the reference temperature of the medium-deep soil and rock layers will gradually decrease, and the radius of influence of cold accumulation at different depths will vary significantly. The problem with this operation is: 1. If heat is released into the shallow soil and rock layer in winter, then it will be impossible to extract coolness from the shallow soil and rock layer in summer. Therefore, the traditional operating mode is completely unacceptable for the technical solution of this invention. 2. The inability to effectively utilize shallow soil and rock layers for heat extraction limits the heat extraction power of medium-deep buried pipe heat exchangers. 3. When the user side is at a low load, the total heat output of the buried pipe heat exchanger is also reduced, and the heat output potential of the buried pipe heat exchanger is not utilized.

[0085] Therefore, in this embodiment, both the full-process heat extraction mode and the heat extraction diversion mode require continuous heat extraction from the shallow soil and rock layers. This means the temperature of the heat exchange medium returning in the shallow flow channel 101 of the outer pipe should be maintained at a low level. For example, to simplify the system control logic, the return water temperature at the return port 5 can be fixed at 5-10º. Correspondingly, when the user-side load is low, the heat extraction diversion mode is executed, and the total heat extraction of the buried pipe heat exchanger remains essentially unchanged. Only a portion of the heat is used on the user side, while the remaining extracted heat is stored in the deep region. When the user-side load is high, the full-process heat extraction mode is executed, releasing the heat accumulated in the deep region. In simple terms, the buried pipe heat exchanger operates at a constant flow rate, dynamically adjusting the flow rate of the heat exchange medium output to the user side according to fluctuations in the user-side heat load. Excess flow is directly returned to the buried pipe. The user side operates at a variable flow rate, maintaining a relatively constant return water temperature at the return port 5.

[0086] In this embodiment, the shallow soil and rock layer is defined as a depth range of 0-800 meters. This is because, based on the initial underground temperature field distribution characteristics, the initial temperature of the soil and rock layer at a depth of 800 meters is approximately 40°C, close to the operating limit of the summer cooling cycle. In actual engineering operation, the heating mode should be operated first in winter to lower the temperature of the shallow soil and rock layer, thus enabling the cooling mode to operate in summer and forming a closed loop of "winter heating + summer cooling." Furthermore, since the application scenarios for deep buried pipe heat exchangers are mostly in mid-to-high latitude regions, where summer cooling loads are low and winter heating loads are high, the summer cooling capacity in this invention is clearly lower than the winter heating capacity, perfectly aligning with existing application scenarios. Moreover, when the summer cooling load differs significantly from the winter heating load, if the above measures can fully meet the summer cooling demand, a separate refrigeration system is unnecessary, significantly reducing system complexity and construction investment.

[0087] Additionally, it should be noted that in applications involving only heating and cooling modes, the first shallow flow channel 201 and the second shallow flow channel 202 of the inner tube can be merged into a unified shallow flow channel. That is, a similar approach can be adopted. Figure 3 However, a simplified structural form with only one intermediate opening (i.e., the second opening) is used. Based on this, if the depth of the second opening needs to be flexibly set, then a completely different approach can be adopted. Figure 3 The structural form.

[0088] In the second embodiment, second openings are provided at two different depth locations (this can be extrapolated to applications where second openings are provided at even more different depth locations), so as to Figure 4 Taking the structure as an example, the corresponding operation process is as follows. As example data, D1 is set to 2500 meters, D2 is set to 800 meters, and D3 is set to 1500 meters. At this time, the shallow layer is the range of 0-800 meters in depth, the middle layer is the range of 800-1500 meters in depth, and the deep layer is the range of 1500-2500 meters in depth.

[0089] In summer, the cooling mode is implemented, and the first intermediate opening 302a is activated. Only the heat exchange medium in the shallow outer pipe section is in a circulating state and exchanges heat with the shallow soil and rock layer 9, releasing heat to the soil and rock layer 9 and cooling it. The heat exchange medium in the intermediate and deep pipe sections is in a static state, and the heat exchange is negligible. After summer operation, the temperature of the shallow soil and rock layer 9 rises, while the temperature changes of the intermediate and deep soil and rock layers 9 are very small.

[0090] During the transitional season before winter, if necessary, a full heat storage mode is implemented, activating the second intermediate opening 302b. At this time, the shallow and intermediate flow channels of the outer pipe are idle, so the heat exchange between the outer pipe 1 and the shallow and intermediate soil and rock layers 9 is minimal. Simultaneously, the heat exchange medium in the deep flow channel 102 of the outer pipe is in a circulating flow state and exchanges heat with the deep soil and rock layers 9, that is, extracting heat from the higher-temperature soil and rock layers 9 at the bottom of the buried pipe and gradually releasing it into the deeper soil and rock layers 9, thereby raising the temperature of the entire deep soil and rock layers 9. Furthermore, depending on the actual engineering situation, the specific depth of the second intermediate opening 302b can be adjusted, or the second opening can be set at different depths for flexible adjustment to achieve a more ideal operating effect. Compared with the first embodiment, the advantage of the second embodiment is that it can improve the heat storage efficiency. By dynamically changing the depth of the second opening 302, heat can be replenished in a targeted manner to the area with the most severe cold accumulation, so that the influence radius of cold accumulation at different depths tends to be consistent.

[0091] In winter, to cope with fluctuations in user-side heat load, full-process heat extraction mode, heat extraction split mode, shallow-layer circulation heat extraction mode, or deep-layer circulation heat extraction mode can be implemented as appropriate. After winter operation, the temperature of the shallow soil and rock layer 9 has decreased and can meet the conditions for summer cooling operation. The temperature of the middle and deep soil and rock layers 9 has also decreased. If the decrease is significant, it is necessary to appropriately implement the full heat storage mode during the transition season before winter.

[0092] Specifically, winter is divided into the early cold period, the severe cold period, and the late cold period, as shown in the following example: During the initial cold period, either the first intermediate opening 302a or the second intermediate opening 302b is activated, primarily employing a deep-layer circulation heat extraction mode. Its advantages include: minimal impact on the shallow layer; the outlet water temperature at outlet 4 and the return water temperature at outlet 5 can be appropriately increased; and a portion of the heat can be stored in the intermediate layer and / or the deep layer for later use. In certain situations, the outlet water temperature at outlet 4 can reach above 50°C (with relatively low flow rates), potentially serving directly as a heat source for the user without requiring a heat pump to enhance the heat energy quality. Furthermore, during this phase, when the heat load is relatively low, the second intermediate opening 302b can be activated with a relatively small circulation flow rate, resulting in a relatively small heat output, primarily affecting the deep layer. When the heat load is relatively high, the first intermediate opening 302a can be activated with a relatively large circulation flow rate, resulting in a relatively large heat output, primarily affecting the intermediate and deep layers. These measures enable more precise system control.

[0093] During periods of severe cold, the first intermediate opening 302a is activated, and the full-process heat extraction mode and the heat extraction diversion mode are alternated as needed. The specific implementation method is the same as in the first embodiment.

[0094] During the late cold period, either the first intermediate opening 302a or the second intermediate opening 302b is activated to execute a shallow circulation heat extraction mode. Its advantages are: it can form a certain amount of cold accumulation in the shallow layer, facilitating cooling operation in summer; the impact on the deeper layers is minimal; and during this stage, when the heat load is relatively high, the second intermediate opening 302b can be activated with a relatively large circulation flow rate, resulting in a relatively large output heat, primarily affecting the shallow and intermediate layers; when the heat load is relatively low, the first intermediate opening 302a can be activated with a relatively small circulation flow rate, resulting in a relatively small output heat, primarily affecting the shallow layer. These measures allow for more refined system control. It should be noted that in the scheme of this invention, during the late cold period, the focus of system operation is not on extracting heat from the bottom area of ​​the buried pipe heat exchanger, but rather on continuously extracting heat from the soil and rock layers 9 in the shallow layer and forming a "cold accumulation."

[0095] In summary, by flexibly and dynamically changing the depth position of the second opening 302, a more refined system control strategy can be implemented during winter operation, resulting in better operational performance.

[0096] It should be noted that the first and second embodiments described above are merely reference examples. Those skilled in the art can combine and apply various working modes according to actual engineering conditions to meet personalized engineering application needs.

[0097] Due to factors such as the extremely long length of the buried pipe and the geothermal gradient in the underground temperature field, the heat exchange process of medium-deep buried pipe heat exchangers is relatively complex. In order to reduce the mixing of hot and cold and unnecessary heat exchange that affect the operation, the following measures can be taken.

[0098] In some embodiments, before the heat storage condition is executed, heat exchange medium is drawn out to the outside through the inner pipe 2, and gas 11 is injected into the outside through the outer pipe 1. The process stops when the shallow flow channel 101 of the outer pipe is filled with gas 11, which is used to block the heat exchange between the shallow flow channel 101 of the outer pipe and the surrounding soil and rock layer 9. After the heat storage condition is executed, heat exchange medium is injected into the inside through the inner pipe 2, and gas 11 is drawn out to the outside through the outer pipe 1. The process stops when the gas 11 in the shallow flow channel 101 of the outer pipe is emptied.

[0099] like Figure 5As shown, before executing the heat storage mode, gas 11 is injected into the outer pipe 1 through the gas management module 10, causing the liquid level of the heat exchange medium in the outer pipe 1 to decrease until it is close to the position of the second opening 302. At this time, since the shallow flow channel 101 of the outer pipe is filled with gas 11, the thermal resistance of the shallow outer pipe section increases significantly, so that when executing the heat storage mode, the heat exchange between the shallow pipe section and the surrounding soil and rock layer 9 is basically stopped.

[0100] It should be noted that the gas 11 is preferably an inert gas, such as nitrogen; during the inflation process, by analyzing parameters such as water intake, inflation volume, and current gas pressure, it is possible to monitor whether the gas 11 is fully filled. After the inflation process is completed, the gas pressure data can be monitored in real time through the inflation management module 10 to maintain a relatively stable pressure value.

[0101] like Figure 6 As shown, after the heat storage operation is completed, gas 11 is drawn out from the outer pipe 1 through the gas management module 10, so that the liquid level of the heat exchange medium in the outer pipe 1 rises to the normal level.

[0102] In some embodiments, an airbag assembly is provided in the outer tube 1 near the second opening 302, the airbag assembly including an opening and closing airbag.

[0103] Specifically: A retractable airbag is installed in the outer tube 1 near the second opening 302. The airbag is connected to an external control module via a pipe. The airbag has a contracted state and an expanded state. When the control module empties the gas in the airbag (evacuates the gas), the airbag is in the contracted state and does not affect the flow of the heat exchange medium in the outer tube 1. When the control module fills the airbag with gas (inflates the airbag), the airbag is in the expanded state and blocks the flow of the heat exchange medium in the outer tube 1.

[0104] by Figure 2 The example shown is based on the "coaxial double inner tube" structure, such as... Figure 7 , Figure 8 As shown, the opening and closing airbag is divided into two parts: a shallow opening and closing airbag 12a and a deep opening and closing airbag 12b (of course, it can be simplified to only one opening and closing airbag depending on the situation). The shallow opening and closing airbag 12a is located near the upper part of the second opening 302, and the deep opening and closing airbag 12b is located near the lower part of the second opening 302.

[0105] like Figure 7As shown, the shallow opening and closing airbag 12a of the outer tube is in the deployed state, and the deep opening and closing airbag 12b of the outer tube is in the contracted state; this corresponds to the deep heat extraction mode and the complete heat storage mode, which is equivalent to stopping and closing the shallow flow channel 101 of the outer tube, so as to avoid the mixing of hot and cold in the heat exchange medium in the outer tube 1.

[0106] like Figure 8 As shown, the shallow opening and closing airbag 12a of the outer tube is in a contracted state, and the deep opening and closing airbag 12b of the outer tube is in an deployed state; this corresponds to the cooling mode, which is equivalent to stopping and closing the deep flow channel 102 of the outer tube, so as to avoid the mixing of hot and cold in the heat exchange medium in the outer tube 1.

[0107] It should be noted that the airbag structure can serve both heat insulation and flow guidance purposes; other structures with similar functions can also be used. Even without such structures, the flow direction of the heat exchange medium at the second opening 302 is essentially controllable and will not cause significant adverse effects such as hot-cold mixing. Furthermore, the inner tube structure in this invention, especially the "coaxial double inner tube" structure, effectively increases thermal resistance and reduces hot-cold mixing within the buried pipe heat exchanger.

[0108] It should be noted that, especially when operating in a mode with heat storage properties, the temperature difference between the heat exchange medium in the shallow flow channels of the outer and inner pipes will inevitably be relatively large. Therefore, regardless of whether the heat exchange medium in the shallow flow channels of the outer pipe is in a flowing state, it will increase the heat transfer between the inner and outer pipes, thus exacerbating the mixing of hot and cold substances. The preferred solution to this problem is to enhance the insulation effect of the inner pipe, such as increasing the pipe wall thickness and reducing the thermal conductivity of the pipe. Alternatively, control can be implemented through system operation methods. For example, a shallow circulation heating mode can be executed before a deep circulation heating mode is run for an extended period. The shallow circulation heating mode rapidly reduces the temperature of the heat exchange medium in the shallow flow channel of the outer pipe. Then, during the deep circulation heating mode, the heat exchange medium in the shallow flow channel of the outer pipe is in a static state. Although the temperature of the heat exchange medium in the shallow flow channel of the inner pipe is higher, some of its heat will be transferred to the heat exchange medium in the shallow flow channel of the outer pipe, but it will not diffuse into the shallow soil and rock layers, thus avoiding additional losses. After the deep circulation heating mode has been running for a period of time, the temperature of the heat exchange medium in the shallow flow channel of the outer pipe has returned to normal levels, and then another shallow circulation heating mode is executed. This cycle can then be repeated.

[0109] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0110] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

[0111] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for operating a medium-deep buried pipe heat exchanger, characterized in that, The medium-deep buried pipe heat exchanger is defined as including an outer pipe and an inner pipe with switchable flow channels; the inner pipe is provided with a first opening and a second opening, the first opening being located at the bottom of the medium-deep buried pipe heat exchanger and the second opening being located in the middle part of the medium-deep buried pipe heat exchanger; the inner pipe is used to form several heat exchange cycle modes. The heat exchange cycle mode is selected as needed to handle cooling, heating, and / or heat storage conditions; the heat exchange cycle modes include: The inner pipe section above the second opening depth position and the outer pipe section below the second opening depth position are connected, so that the heat exchange medium in the outer pipe section below the second opening depth position is in a circulating flow state and exchanges heat with the surrounding soil and rock layers. It is applicable to heat extraction and / or heat storage conditions; Alternatively, the inner pipe section above the second opening depth and the second opening are connected to the outer pipe section above the second opening depth, so that the heat exchange medium in the outer pipe section above the second opening depth is in a circulating state and exchanges heat with the surrounding soil and rock layers; applicable to cooling or heating conditions. Alternatively, the heat exchange medium in all external pipe sections can be in a state of circulation and exchange heat with the surrounding soil and rock layers; this can be applied to heat extraction conditions.

2. The operating method of a medium-deep buried pipe heat exchanger according to claim 1, characterized in that, Using the location of the second opening as a boundary, the medium-deep buried pipe heat exchanger is defined as including the following flow channels: inner pipe first shallow flow channel, inner pipe second shallow flow channel, inner pipe deep flow channel, outer pipe shallow flow channel, and outer pipe deep flow channel; the return port for the heat exchange medium input and the outlet port for the heat exchange medium output of the medium-deep buried pipe heat exchanger are defined.

3. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the full-process heat extraction mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, shallow flow channel of outer pipe, deep flow channel of outer pipe, first opening, deep flow channel of inner pipe, first shallow flow channel of inner pipe, and outlet.

4. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the cooling mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, inner pipe second shallow flow channel, second opening, outer pipe shallow flow channel, and outlet. Alternatively: return port, shallow flow channel of outer tube, second opening, second shallow flow channel of inner tube, outlet.

5. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the heat exchange medium is in the heat extraction and diversion mode, it is diverted at the liquid outlet. A portion of the heat exchange medium is transported externally, and after heat exchange, it flows back through the liquid return port. The other portion of the heat exchange medium flows directly back into the medium-deep buried pipe heat exchanger. The flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: Part of the heat exchange medium: first return port, outer tube shallow flow channel, outer tube deep flow channel, first opening, inner tube deep flow channel, inner tube first shallow flow channel, and outlet; The other part of the heat exchange medium includes: the second return port, the second shallow flow channel of the inner tube, the second opening, the deep flow channel of the outer tube, the first opening, the deep flow channel of the inner tube, the first shallow flow channel of the inner tube, and the outlet.

6. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the shallow circulation heat extraction mode is executed, the flow direction of the heat exchange medium in the medium-deep buried pipe heat exchanger is as follows: return port, shallow flow channel of outer pipe, second opening, second shallow flow channel of inner pipe, and outlet.

7. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the deep circulation heat extraction mode is executed, the flow direction of the heat exchange medium in the medium-deep buried pipe heat exchanger is as follows: return port, inner pipe second shallow flow channel, second opening, outer pipe deep flow channel, first opening, inner pipe deep flow channel, inner pipe first shallow flow channel, and outlet.

8. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, When the full heat storage mode is executed, the flow direction of the heat exchange medium circulating in the medium-deep buried pipe heat exchanger is as follows: return port, first shallow flow channel of inner pipe, deep flow channel of inner pipe, first opening, deep flow channel of outer pipe, second opening, second shallow flow channel of inner pipe, and outlet; and the outlet and return port are connected to form a circulation. Alternatively: return port, second shallow flow channel of inner tube, second opening, deep flow channel of outer tube, first opening, deep flow channel of inner tube, first shallow flow channel of inner tube, and outlet; and connect the outlet and return port to form a circulation.

9. A medium-deep buried pipe heat exchanger according to claim 2, characterized in that, The number of the second openings is several, and the several second openings are distributed at different depths of the medium-deep buried pipe heat exchanger. At any given time, only one of the second openings at a depth location is set to the enabled state for communication with the outer pipe.

10. The operating method of a medium-deep buried pipe heat exchanger according to claim 2, characterized in that, Before the heat storage operation is executed, heat exchange medium is drawn out from the outside through the inner pipe, while gas is injected from the outside into the inner pipe. The process stops when the shallow flow channel of the outer pipe is full of gas, which is used to block heat exchange between the shallow flow channel of the outer pipe and the surrounding soil and rock layers. After the heat storage operation is completed, heat exchange medium is injected from the outside into the inner pipe, while gas is drawn out from the outside through the outer pipe. The process stops when the gas in the shallow flow channel of the outer pipe is emptied.

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