Ground heat exchanger
By incorporating curved pipes and expansion steel strips into the heat exchanger, the problem of poor contact between the heat exchange tubes and the soil was solved, thereby improving heat exchange efficiency and saving construction costs.
Patent Information
- Application Number
- CN202511354277.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-22
- Publication Date
- 2025-12-16
AI Technical Summary
Existing heat exchangers suffer from poor heat exchange performance due to the distance between the heat exchange tubes and the surrounding soil and rock, and they also occupy a large area of the ground, increasing demolition and coordination costs.
By using curved pipes and expansion steel strips to ensure full contact between the heat exchange tubes and the soil, and by setting multiple expansion steel strips evenly distributed along the inner side of the heat exchange tubes, the contact area between the heat exchange tubes and the surrounding soil and rock layers is increased, forming an S-shaped loop structure and improving heat exchange efficiency.
It enhances the heat exchange efficiency between the heat exchange fluid and the surrounding soil and rock layers, reduces the footprint of the buried pipe heat exchanger, and lowers construction costs.
Smart Images
Figure CN121140221A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of ground heat exchanger, in particular to a ground heat exchanger. BACKGROUND
[0002] Geothermal energy is a renewable resource, and the ground source heat pump technology using geothermal energy is composed of a heat pump unit and a heat exchanger buried in the ground, and heat exchange between the system and the ground is achieved through circulating fluid. In winter, the heat pump unit can absorb heat from the ground for building heating; in summer, the heat in the building can be absorbed and transferred to the ground for release, achieving refrigeration.
[0003] The heat exchanger in the prior art forms a circulation loop with the heat pump unit through the parallel arrangement of the heat exchange pipes, but there is a certain distance between the heat exchange pipes in the ground borehole and the surrounding rock-soil body, and the heat in the heat exchange pipes cannot be fully exchanged with the surrounding rock-soil body, resulting in poor heat exchange effect. The quantitative heat exchange requirement occupies a larger surface area, causing an increase in the cost of demolition and coordination. SUMMARY
[0004] The present application is made to solve the above technical problems, and the purpose is to provide a ground heat exchanger, which is arranged in a ground borehole and comprises: an inlet pipe; an outlet pipe; at least three heat exchange pipes, both ends of which are connected to the inlet pipe and the outlet pipe; and an expanded steel belt arranged as an open ring and abutting the inner side of the heat exchange pipe. The heat exchange pipe can form a straight section arranged in parallel along the axial direction of the ground borehole and a curved section connected to the adjacent two straight sections in the ground borehole.
[0005] To achieve the above purpose, the present application provides a ground heat exchanger arranged in a ground borehole, which comprises: an inlet pipe; an outlet pipe; at least three heat exchange pipes, both ends of which are connected to the inlet pipe and the outlet pipe; and an expanded steel belt arranged as an open ring and abutting the inner side of the heat exchange pipe. The heat exchange pipe can form a straight section arranged in parallel along the axial direction of the ground borehole and a curved section connected to the adjacent two straight sections in the ground borehole.
[0006] Preferably, a plurality of heat exchange pipes are arranged in a cylindrical body around the same axis, and the heat exchange pipes abut the side wall of the ground borehole.
[0007] Preferably, the expanded steel belt is provided with a plurality of strips arranged uniformly on the inner side of the heat exchange pipe along the axial direction of the ground borehole.
[0008] Preferably, the diameter of the cylindrical body is greater than or equal to 500 mm.
[0009] Preferably, the heat exchange pipe comprises a PE pipe, a heat exchange interlayer and a carbon fiber protective layer, the heat exchange interlayer is arranged between the PE pipe and the carbon fiber protective layer, and the PE pipe abuts the expanded steel belt.
[0010] Preferably, the liquid outlet pipe comprises a bending section and a vertical section, the bending section is connected to the heat exchange pipe, and the bending section is arranged along the inner wall of the ground borehole in a direction away from the liquid inlet pipe.
[0011] Preferably, the distance between the bending section and the liquid inlet pipe is greater than the radius of the ground borehole.
[0012] Preferably, a metal sleeve is further arranged on the vertical section.
[0013] Preferably, a thermal insulation layer pipe is further arranged between the metal sleeve and the liquid outlet pipe.
[0014] Preferably, the length of the metal sleeve is greater than the length of the thermal insulation layer pipe and less than the length of the liquid outlet pipe, and the length of the thermal insulation layer is greater than or equal to 100 m.
[0015] According to the above description and practice, the ground heat exchanger is arranged in the ground borehole, and comprises a liquid inlet pipe, a liquid outlet pipe, a heat exchange pipe and an expanded steel belt. The heat exchange pipe is arranged in at least three, and the two ends are connected to the liquid inlet pipe and the liquid outlet pipe, respectively. The heat exchange liquid enters from the liquid inlet pipe, flows through the heat exchange pipe, exchanges heat with the rock-soil layer near the ground heat exchanger, and then flows out from the liquid outlet pipe. The expanded steel belt is arranged as an open ring and abuts to the inner side of the heat exchange pipe. When the expanded steel belt is needed to make the heat exchange pipe abut to the surrounding rock-soil layer, the open of the expanded steel belt can be expanded by external force, so that the expanded steel belt expands outward, abuts and pushes the heat exchange pipe to be close to the surrounding rock-soil layer, thereby reducing the distance between the heat exchange liquid in the heat exchange pipe and the surrounding rock-soil layer and increasing the heat exchange efficiency between the heat exchange liquid and the surrounding rock-soil layer. The heat exchange pipe can be arranged in the ground borehole in a straight section along the axis of the ground borehole and a bending section connected to the adjacent two straight sections, so that the heat exchange pipe can be arranged and bent in the ground borehole according to actual needs. At this time, the heat exchange pipe is arranged in an S-shaped loop, thereby increasing the flow path of the heat exchange liquid in the heat exchange pipe, ensuring the contact area between the heat exchange liquid and the surrounding rock-soil layer, and improving the heat exchange efficiency of the ground heat exchanger. BRIEF DESCRIPTION OF DRAWINGS
[0016] Fig. 1 It is a structural schematic diagram of the ground heat exchanger involved in an embodiment of the present application.
[0017] Fig. 2 It is a sectional view of the ground heat exchanger involved in an embodiment of the present application.
[0018] Fig. 3 It is a sectional view of the heat exchange pipe of the ground heat exchanger involved in an embodiment of the present application.
[0019] Fig. 4 It is a sectional view of the liquid outlet pipe of the ground heat exchanger involved in an embodiment of the present application.
[0020] The reference numerals in the drawings are: 1, inlet pipe; 2, outlet pipe; 21, bending section; 22, vertical section; 3, heat exchange pipe; 31, straight section; 32, bending section; 33, PE pipe; 34, heat exchange interlayer; 35, carbon fiber protective layer; 4, expanded steel belt; 5, metal sleeve; 6, heat preservation layer pipe. DETAILED DESCRIPTION
[0021] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the description.
[0022] In addition, the drawings are to be considered in all respects as illustrative and not restrictive; identical reference numerals have been used, where possible, to denote identical elements throughout the figures; and the repetition of description, if any, can be omitted by referring to the previous description of the same elements. It is to be noted that the terms "comprises", "comprising", "includes", "including", "has", "having" and the like are to be construed in an open-ended way, meaning that they are used to introduce one or more elements, but not to exclude additional elements. The terms "first", "second", and the like, do not denote any order, quantity, combination or important / primary / secondary / tertiary distinction, but are used to distinguish one element from another. The terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like merely indicate the orientation in the drawings and are used for convenience only in describing the present application and its attachments; they do not actually limit the position and / or orientation of the devices or elements being referred to, which can be otherwise positioned and / or oriented. The terms "coupled" and "connected", along with derivatives thereof, can be used. It should be understood that these terms are not intended as synonyms for each other. Rather, particular intent is to be attributed to the connection based on the context in which the term is used. For example, depending on the circumstances, "connected" can be utilized as synonym for "coupled" and, in the same context, utilized as synonym for "mechanically connected" or "electrically connected". For example, it will be said that the device A is "coupled" to the device B when it is directly connected to the device B either mechanically or electrically. It will also be said that the device A is "coupled" to the device B when there are other intervening devices or components between device A and device B, either mechanically or electrically. The term "comprising" is not used as a limitation in the sense that it does not also mean "consisting only of" or "consisting of".
[0023] Unless otherwise defined, the terms "mounting", "connected", "connecting" are to be construed broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0024] The present application provides a buried pipe heat exchanger, please refer to Figs. 1 to 4The buried pipe heat exchanger is installed inside a borehole in the ground and includes an inlet pipe 1, an outlet pipe 2, heat exchange pipes 3, and an expansion steel strip 4. At least three heat exchange pipes 3 are provided, with their ends connected to the inlet pipe 1 and the outlet pipe 2 respectively. The heat exchange fluid enters from the inlet pipe 1, flows through the heat exchange pipes 3, exchanges heat with the surrounding soil and rock layers, and then flows out from the outlet pipe 2. The expansion steel strip 4 is an open annular shape that abuts against the inner side of the heat exchange pipes 3. When it is necessary to use the expansion steel strip 4 to bring the heat exchange pipes 3 into contact with the surrounding soil and rock layers, the opening of the expansion steel strip 4 can be widened by external force, causing the expansion steel strip 4 to expand outward, abutting and pushing the heat exchange pipes 3 closer to the surrounding soil and rock layers. This reduces the distance between the heat exchange fluid in the heat exchange pipes 3 and the surrounding soil and rock layers, increasing the heat exchange efficiency between the heat exchange fluid and the surrounding soil and rock layers. The heat exchange tubes 3 can be formed in the ground borehole with straight sections 31 arranged parallel to each other along the borehole axis and bent sections 32 connecting adjacent straight sections 31. This allows the heat exchange tubes 3 to be arranged and bent according to actual needs within the borehole, forming an S-shaped loop. This increases the flow path of the heat exchange fluid within the heat exchange tubes 3, ensuring the contact area between the heat exchange fluid and the surrounding soil and rock layers, while improving the heat exchange efficiency of the buried pipe heat exchanger. Furthermore, in practical applications, when a specific area has certain heat exchange efficiency requirements, this buried pipe heat exchanger can be used without affecting heat exchange efficiency, requiring a smaller footprint and thus saving construction costs.
[0025] Understandably, since buried pipe heat exchangers typically exchange heat with the surrounding soil and rock layers at a specific depth after drilling holes in the ground, in some embodiments, multiple straight sections 31 are arranged in a cylindrical shape around the same axis. Specifically, they can be arranged according to the ground borehole into which the buried pipe heat exchanger needs to be inserted, so that the arrangement of the straight sections 31 conforms to the curvature of the ground borehole and abuts against the sidewall of the ground borehole, thereby reducing the distance between the heat exchange pipe 3 and the surrounding soil and rock layers. On the one hand, this ensures that the buried pipe heat exchanger can exchange heat more fully with the surrounding soil and rock layers through the heat exchange fluid; on the other hand, when a certain amount of heat exchange is required, a smaller buried pipe heat exchanger can still achieve the required heat exchange efficiency.
[0026] Furthermore, in order to improve the heat exchange effect of the heat exchange fluid in the heat exchange tube 3 of the buried pipe heat exchanger, the heat exchange tube 3 is usually set to a relatively long length. In order to ensure that the heat exchange tube 3 can always remain close to the surrounding soil and rock layers, in some embodiments, multiple expansion steel strips 4 are provided. Along the length direction of the straight section 31, multiple expansion steel strips 4 are evenly arranged on the inner side of the straight section 31. On the one hand, by abutting against the inner wall of the heat exchange tube 3 in sequence, it brings it close to the surrounding soil and rock layers, ensuring that the distance between the heat exchange tube 3 and the surrounding soil and rock layers tends to be stable from top to bottom, avoiding poor heat exchange efficiency between the heat exchange fluid and the surrounding soil and rock layers due to a single area being too far away from the surrounding soil and rock layers. On the other hand, by providing multiple expansion steel strips 4, it can also avoid excessive force at the contact point between the heat exchange tube 3 and a single expansion steel strip 4 during long-term use of the buried pipe heat exchanger, which would damage the heat exchange tube 3, cause heat exchange fluid leakage, and affect the heat exchange efficiency of the entire buried pipe heat exchanger. Specifically, when the buried pipe heat exchanger is used in a shallower geothermal section (200m-500m deep) in the middle to deep layers, an expansion steel strip 4 can be installed every 3m on the inner side of the heat exchange pipe 3 to ensure that the heat exchange pipe 3 can fit in close contact with the surrounding soil and rock layers and increase its heat exchange efficiency.
[0027] Understandably, since the buried pipe heat exchanger is equipped with at least three heat exchange tubes 3, the cylinder formed by the heat exchange tubes 3 being bent along the same axis inside the ground borehole according to actual needs is the minimum ground borehole diameter of the buried pipe heat exchanger. In order to ensure that the heat exchange tubes 3 are completely inserted to the corresponding depth, in some embodiments, the diameter of the cylinder is greater than or equal to 500mm, specifically, it can be 500mm, 550mm, 600mm, 650mm, 700mm, etc., to ensure that there is at least a 50mm gap between any two straight sections 31 and bent sections 32, so that there is enough space around the heat exchange tubes 3 and they can be tightly wrapped by the heat exchange medium, ensuring a good overall heat exchange effect, and the size of the ground borehole diameter can be adjusted according to the actual number of heat exchange tubes 3.
[0028] To protect the heat exchange tube 3 from damage caused by abrasion or overheating from the surrounding soil and rock layers, in some embodiments, the heat exchange tube 3 includes a PE pipe 33, a heat exchange jacket 34, and a carbon fiber protective layer 35. The heat exchange jacket 34 is disposed between the PE pipe 33 and the carbon fiber protective layer 35, and the carbon fiber protective layer 35 abuts against the expansion steel strip 4. The PE pipe 33 is typically made of polyethylene, which has good compressive and stress resistance, capable of withstanding the pressure of the heat exchange fluid flowing inside the pipe and the stress generated by the thermal expansion and contraction of the heat exchange fluid during heat exchange, ensuring stable flow of the heat exchange fluid within the heat exchange tube 3. Furthermore, the PE pipe 33 has good corrosion resistance and flexibility, allowing it to withstand a certain amount of ground pressure and maintain the required shape, making it easier to adjust the shape of the heat exchange tube 3 before burial. The heat exchange jacket 34 is the main path for heat transfer between the surrounding soil and rock layers and the heat exchange fluid. It has high thermal conductivity and is typically a mixture of bentonite, cement, and water, or a composite material with excellent thermal conductivity such as graphene, to achieve the required thermal conductivity. The heat exchange jacket 34 enhances the thermal conductivity of the heat exchange tube 3 and improves its thermal efficiency. The carbon fiber protective layer 35 further strengthens the overall strength of the heat exchange tube 3. It is usually set independently and fitted outside the heat exchange jacket 34. When there are too many stones and debris in the surrounding soil layer, it can protect the buried pipe heat exchanger from damage when drilling deep into the ground.
[0029] Understandably, since the heat exchange fluid in the heat exchange tube 3 typically has a certain temperature difference with the heat exchange fluid in the inlet pipe 1 when it flows out of the outlet pipe 2, in order to ensure that the heat exchange fluid can flow out of the outlet pipe 2 stably, in some embodiments, the outlet pipe 2 includes a bent section 21 and a vertical section 22. The bent section 21 is connected to the heat exchange tube 3 and is set along the inner wall of the ground borehole in a direction away from the inlet pipe 1, thereby increasing the distance between the inlet pipe 1 and the outlet pipe 2. This avoids the heat exchange fluid from being too close to the outlet pipe 2, which would cause heat exchange and affect the heat exchange effect when the heat exchange fluid in the inlet pipe 1 enters the heat exchange tube 3. In addition, since the bent section 21 is set along the inner wall of the ground borehole, secondary heat exchange can still be carried out through contact with the surrounding rock and soil, further improving the heat exchange effect.
[0030] Furthermore, in some embodiments, the distance between the bend section 21 and the inlet pipe 1 is greater than the radius of the ground borehole. Preferably, the distance between the bend section 21 and the inlet pipe 1 should be 70%-90% of the diameter of the ground borehole. Most preferably, the bend section 21 and the inlet pipe 1 are respectively located at both ends of the diameter of the ground borehole to avoid heat exchange between the heat exchange fluid in the inlet pipe 1 and the outlet pipe 2, thereby improving the heat exchange efficiency between the heat exchange fluid and the surrounding soil and rock layers.
[0031] To protect the outlet pipe 2 and prevent damage from debris such as gravel from the ground, in some embodiments, the buried pipe heat exchanger also includes a metal sleeve 5. The metal sleeve 5 is fitted onto the vertical section 22. On the one hand, it can reduce the friction between the outlet pipe 2 and the surrounding soil and rocks when it is drilled into the ground; on the other hand, it can also protect the vertical section 22 of the outlet pipe 2 from being scratched or punctured by sharp rocks in the rock layer when the outlet pipe 2 is drilled deep into the ground.
[0032] Understandably, the temperature of the heat exchange fluid in the outlet pipe 2 needs to be transported to an external heat pump unit for further processing or utilization. In order to prevent the heat exchange fluid in the outlet pipe 2 from losing temperature, in some embodiments, the buried pipe heat exchanger also includes an insulation layer pipe 6. The insulation layer pipe 6 is set between the metal sleeve 5 and the outlet pipe 2 to ensure that the temperature of the heat exchange fluid in the outlet pipe 2 will not exchange heat with the outside when it is transported out, thus reducing the heat exchange efficiency.
[0033] In some embodiments, the length of the metal sleeve 5 is greater than the length of the insulation layer pipe 6 but less than the length of the outlet pipe 2. This prevents the insulation layer pipe 6 from being scratched by gravel while ensuring the normal transport of the heat exchange fluid through the outlet pipe 2. The length of the insulation layer is greater than or equal to 100m, specifically 100m, 150m, 200m, 250m, 300m, etc., and can be set according to the operating depth of the buried pipe heat exchanger.
[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. A buried pipe heat exchanger, installed inside a borehole in the ground, characterized in that, include: Inlet pipe; Discharge tube; At least three heat exchange tubes are provided, with their two ends connected to the inlet pipe and the outlet pipe, respectively. An expansion steel strip, configured as an open annular ring, abuts against the inner side of the heat exchange tube; The heat exchange tube may form straight sections arranged side by side along the axial direction of the ground borehole and bent sections connecting two adjacent straight sections within the ground borehole.
2. The buried pipe heat exchanger as described in claim 1, characterized in that, The heat exchange tubes are arranged in a cylindrical shape around the same axis, and the heat exchange tubes abut against the sidewall of the ground borehole.
3. The buried pipe heat exchanger as described in claim 2, characterized in that, Multiple expansion steel strips are provided, and they are evenly distributed on the inner side of the heat exchange tube along the axial direction of the ground hole.
4. The buried pipe heat exchanger as described in claim 2, characterized in that, The diameter of the cylinder is greater than or equal to 500 mm.
5. The buried pipe heat exchanger as described in claim 1, characterized in that, The heat exchange tube includes a PE tube, a heat exchange jacket, and a carbon fiber protective layer. The heat exchange jacket is disposed between the PE tube and the carbon fiber protective layer, and the carbon fiber protective layer abuts against the expansion steel strip.
6. The buried pipe heat exchanger as described in claim 1, characterized in that, The outlet pipe includes a bent section and a vertical section. The bent section is connected to the heat exchange pipe and is arranged along the inner wall of the ground borehole in a direction away from the inlet pipe.
7. The buried pipe heat exchanger as described in claim 6, characterized in that, The distance between the bent section and the inlet pipe is greater than the radius of the ground borehole.
8. The buried pipe heat exchanger as described in claim 6, characterized in that, Also includes: A metal sleeve is fitted onto the vertical section.
9. The buried pipe heat exchanger as described in claim 8, characterized in that, Also includes: The insulation layer tube is disposed between the metal sleeve and the liquid outlet tube.
10. The buried pipe heat exchanger as described in claim 9, characterized in that, The length of the metal sleeve is greater than the length of the insulation layer tube but less than the length of the liquid outlet tube, and the length of the insulation layer is greater than or equal to 100m.