Quincunx ground heat exchanger and construction method

Abstract

The quincunx ground heat exchanger comprises an inner pipe, outer pipes and a bottom sealing section, the multiple outer pipes are arranged on the outer wall of the inner pipe at intervals, every two adjacent outer pipes are not in contact, the contact area of the outer pipes and the stratum is effectively increased, and the heat exchange amount and the heat exchange efficiency of the outer pipes are remarkably improved; the outer wall surface of the inner pipe is tangent to the contour line of the outer wall surface of the outer pipe, and the contact area is obviously reduced through point contact between the outer pipe and the inner pipe, so that heat loss caused by heat exchange of high-temperature fluid in the inner pipe to the outer pipe is reduced; in the construction process, the backfill material with low heat conductivity coefficient is filled between the outer part of the inner pipe and the adjacent outer pipe, so that the outward heat loss of the thermal fluid in the inner pipe is further reduced, the single well heat extraction efficiency of the buried pipe is greatly improved, and the construction cost of utilizing the geothermal energy in the middle-deep layer is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of underground pipe heat exchanger structures, and in particular relates to a plum blossom-shaped underground pipe heat exchanger and a construction method. Background Art

[0002] A ground heat exchanger, also known as an underground heat exchanger or ground source heat pump, is a device that uses underground heat energy for air conditioning and heating. It uses pipes buried underground and the stable temperature of underground soil or water sources to achieve heat exchange with the fluid in the pipe. The shell-and-tube underground heat exchanger is a type of underground heat exchanger. It uses a shell-and-tube structure to achieve heat exchange between the underground and the fluid in the pipe. It is composed of coaxial shells of different diameters connected by U-shaped elbows. In order to reduce the number of drillings and thus save initial investment, the casing-in-ground heat exchanger is a type of heat exchanger commonly used for geothermal extraction. However, due to its limited heat exchange area, research on improving the heat exchange efficiency based on this type of heat exchanger has gradually reached a bottleneck. Summary of the invention

[0003] The object of the present invention is to provide a plum blossom-shaped underground pipe heat exchanger and a construction method thereof, so as to overcome the technical problem of low heat exchange efficiency of the existing casing-type underground pipe heat exchanger.

[0004] In order to solve the above problems, the present invention adopts the following technical solutions: A plum blossom-shaped underground heat exchanger comprises an inner tube, a plurality of outer tubes are installed at intervals outside the inner tube, and the same end of the inner tube and the plurality of outer tubes are connected to a bottom closed section; The inner tube and the outer tube are in point contact; The thermal conductivity of the inner tube is lower than that of the outer tube.

[0005] Furthermore, the inner tube and the outer tube are both cylindrical tubes.

[0006] Furthermore, the diameter of the inner tube is larger than the diameter of the outer tube.

[0007] Furthermore, the inner tube is a PE tube.

[0008] Furthermore, the outer tube is made of a stainless steel tube.

[0009] Furthermore, the bottom closed section is a hollow cylindrical structure.

[0010] Furthermore, a through hole is formed on an end surface of one side where the bottom closed section is connected to the inner tube and the outer tube.

[0011] Furthermore, multiple outer tubes are evenly spaced outside the inner tube.

[0012] Furthermore, the inner tube and the plurality of outer tubes all have smooth inner wall structures.

[0013] In a second aspect, a construction method of a plum blossom-shaped buried pipe heat exchanger is provided, comprising the following steps: Adhere multiple outer tubes to the outer wall of the inner tube at intervals; Connect the ends of the inner tube and the outer tube to the bottom closed section; The assembled ground heat exchanger is inserted into the underground borehole and backfill material is injected into the hole.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a plum blossom-shaped underground pipe heat exchanger, comprising an inner pipe with one end fixed on a bottom closed section and a plurality of outer pipes spaced apart on the outer wall of the inner pipe. The thermal conductivity of the inner pipe is designed to be lower than that of the outer pipe. While maintaining a size of underground space occupied by a general sleeve-type underground pipe heat exchanger, the heat exchange area between the outer pipe and the surrounding soil is effectively increased, so that the heat exchange amount and heat exchange efficiency of the outer pipe are significantly improved; the outer wall surface of the inner pipe is tangent to the contour line of the outer wall surface of the outer pipe, and point contact is established between the outer pipe and the inner pipe, so that the contact area is significantly reduced, thereby reducing the heat loss caused by the heat exchange from the high-temperature fluid in the inner pipe to the outer pipe; the present invention can improve the heat extraction efficiency of the heat exchanger by placing an optimized structure of the underground pipe heat exchanger without changing the cost of drilling a geothermal well, thereby reducing the energy utilization cost and improving the utilization efficiency of geothermal energy.

[0015] Preferably, the diameter of the inner tube is designed to be larger than the diameter of the outer tube, thereby ensuring that a plurality of outer tubes and one inner tube form a heat exchange system.

[0016] Preferably, multiple outer tubes outside the inner tube are evenly spaced and arranged on the outer wall of the inner tube, and the outer tubes are distributed circumferentially along the inner tube and laid evenly, so that the heat exchanger is arranged tightly as a whole, minimizing the required drilling aperture.

[0017] The present invention provides a construction method for a plum blossom-shaped buried pipe heat exchanger. During the construction process, a drilling rig is first used to drill a hole underground, and then the assembled new buried pipe heat exchanger is placed underground. Finally, backfill material is injected into the borehole for cementing. By filling the backfill material with low thermal conductivity coefficient outside the inner pipe and between adjacent outer pipes, the outer pipe fluid and the outer wall of the inner pipe are separated by the outer pipe wall and the borehole backfill material, and the inner and outer pipe fluids are further blocked, further reducing the heat loss of the inner pipe hot fluid to the outside. The heat exchange capacity and heat exchange efficiency of the buried pipe heat exchanger are significantly improved, and the heat extraction efficiency of the buried pipe single well is greatly improved, thereby saving the construction cost of utilizing medium and deep geothermal energy and promoting the wide application of geothermal energy heating technology in the field of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a structural diagram of a plum blossom-shaped underground pipe heat exchanger in an embodiment of the present invention; Figure 2 This is a top structural diagram of a plum blossom-shaped underground heat exchanger in an embodiment of the present invention; Figure 3 This is a structural diagram of the bottom end of a plum blossom-shaped underground heat exchanger in an embodiment of the present invention; Figure 4 The present invention is a flowchart of a construction method of a plum blossom-shaped buried pipe heat exchanger in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] A plum blossom-shaped underground heat exchanger, such as Figure 1As shown, it includes an inner tube, an outer tube and a bottom closed section, wherein a plurality of outer tubes are arranged on the outer wall of the inner tube at intervals, and adjacent outer tubes are not in contact with each other, which effectively increases the contact area between the outer tube and the formation, and the heat exchange between the outer tube and the outside is better, thereby improving the heat exchange effect; In order to improve the heat exchange efficiency, the plum blossom-shaped underground heat exchanger of the present invention is designed to have a lower thermal conductivity coefficient of the inner tube than that of the outer tube in the selection of the inner and outer tubes, that is, the inner tube is made of a material with low thermal conductivity efficiency, thereby avoiding the heat loss of the hot fluid in the inner tube to the outside; the outer tube is made of a material with high thermal conductivity, which can fully exchange heat with the surrounding soil; like Figure 2 As shown, the outer tube and the inner tube of the structure of the present invention are in point contact, and the outer wall of the inner tube is tangent to the contour line of the outer wall of the outer tube, so that the contact area between the inner tube and the outer tube is significantly reduced, thereby reducing the heat loss caused by heat exchange from the high-temperature fluid in the inner tube to the outer tube.

[0025] In an optional implementation manner, the inner tube is a PE tube, the outer tube is a stainless steel tube, the ends of the multiple outer tubes are water inlets, and the ends of the inner tubes are water outlets, so the diameter of the inner tube is designed to be larger than the diameter of the outer tube; The plurality of outer tubes are bonded to the inner tube by adhesive, and the outer tubes are evenly spaced.

[0026] In this embodiment, a plum blossom-shaped underground heat exchanger is provided, comprising a cylindrical inner tube made of a low thermal conductivity material, a plurality of outer tubes made of a high thermal conductivity material, and a cylindrical closed section at the bottom to connect the inner and outer tubes. The inner and outer tubes are laid closely; Among them, the inner tube is made of materials with low thermal conductivity, mainly various PE pipes, which effectively avoids the heat loss of the hot fluid in the inner tube to the outside. The outer tube is made of materials with high thermal conductivity to fully exchange heat with the surrounding soil, mostly stainless steel pipes. The outer tube is distributed along the circumference of the inner tube and laid evenly, and the inner and outer tubes form a "plum blossom" heat exchanger as a whole. In addition, the outer wall of the inner tube is tangent to the contour line of the outer wall of the outer tube, and the overall arrangement of the heat exchanger is tight, which minimizes the required drilling aperture.

[0027] Optional, such as Figure 3 As shown, the bottom closed section is a cylindrical hollow structure, and the inner and outer tubes are connected to the bottom closed section in an inserted manner.

[0028] In this embodiment, a plum blossom-shaped buried pipe heat exchanger is provided, including an inner pipe and multiple outer pipes in point contact with the inner pipe. Adjacent outer pipes do not contact each other, which effectively increases the contact area between the outer pipe and the formation, and the inner and outer pipes are closely laid.

[0029] The same end of the inner tube and multiple outer tubes are connected to the bottom closed section in an inserted form. The bottom closed section is a cylindrical hollow structure. During operation, low-temperature water flows in from the top through the outer tube, absorbs heat from the external high-temperature soil during the falling process, and after entering the bottom closed section, it flows out from the middle inner tube under pressure and enters the heat-using equipment through the ground system pipeline connected to the structure of the present invention, thereby realizing heating for the building.

[0030] The inner pipe diameter can be 10cm to 30cm, with a wall thickness of about 5mm, and the outer pipe diameter is 6.2cm-18.6cm, ensuring that the outer pipes do not touch each other. The length can be adjusted according to actual needs (usually 50m to 3000m). One end of the pipeline is a bottom closed section, and the other end is a top outlet, which is connected to the pipeline in the ground building system. The inner and outer pipes are bonded with adhesives, and the outer pipes do not touch each other; In still another embodiment of the present invention, the inner walls of the inner and outer tubes are smooth walls.

[0031] The present invention provides a plum blossom-shaped underground heat exchanger. On the one hand, while maintaining the same cross-sectional area of ​​the outer tube as that of a general shell-and-tube underground heat exchanger, the heat exchange area between the outer tube and the surrounding soil is effectively increased, so that the heat exchange amount and heat exchange efficiency of the outer tube are significantly improved; on the other hand, the outer tube and the inner tube of the new underground heat exchanger are in point contact, so the contact area is significantly reduced, thereby reducing the heat loss caused by the heat exchange of the high-temperature fluid in the inner tube to the outer tube; Moreover, the outer tube fluid in the traditional shell-and-tube ground pipe heat exchanger is in direct contact with the outer wall of the inner tube, that is, the heat transfer process between the inner tube fluid and the outer tube fluid is: convection heat exchange between the inner tube fluid and the outer wall of the inner tube, heat conduction through the inner tube wall, and convection heat exchange between the outer tube fluid and the outer wall of the inner tube. The new "plum blossom-shaped" ground pipe heat exchanger proposed in the present invention separates the outer tube fluid from the outer wall of the inner tube by the outer tube wall and the backfill material of the borehole, and the inner and outer tube fluids are further blocked. At this time, the heat transfer process of the inner and outer tube fluids becomes: convection heat exchange between the inner tube fluid and the outer wall of the inner tube, heat conduction through the inner tube wall, heat conduction through the backfill layer, heat conduction through the outer tube wall, and convection heat exchange between the outer tube fluid and the inner wall of the outer tube. The thermal resistance is significantly improved, which further reduces the heat loss of the inner tube hot fluid to the outside. The heat exchange capacity and heat exchange efficiency of the ground pipe heat exchanger are significantly improved.

[0032] Working principle: As described above, in the "plum blossom-shaped" underground heat exchanger, low-temperature water flows in through the water inlet of the outer tube, first enters the inner part of the outer tube, and fully exchanges heat with the surrounding soil. During this process, the temperature of the water flowing into the outer tube gradually increases. After the heat exchange with the soil, the water flow in the outer tube continues to flow downward, enters the closed section at the bottom of the underground heat exchanger, and merges into the inner tube. The fluid in the inner tube flows from bottom to top. Due to its material with a low thermal conductivity, it avoids heat loss to the outside as much as possible, and finally flows out of the heat exchanger system from the outlet of the inner tube to complete the heat exchange process.

[0033] The present invention also provides a construction method of a plum blossom-shaped buried pipe heat exchanger, such as Figure 4 As shown, the following steps are included: Adhere multiple outer tubes to the outer wall of the inner tube at intervals; Connect the ends of the inner tube and the outer tube to the bottom closed section; The assembled ground heat exchanger is inserted into the underground borehole and backfill material is injected into the hole.

[0034] During the construction process, a drilling rig is first used to drill underground, then the assembled new buried pipe heat exchanger is placed underground, and finally backfill material is injected into the borehole for cementing.

[0035] The new "plum blossom" shaped heat exchanger can increase the heat exchange capacity of the buried pipe per unit area and cost without increasing the drilling cost and ground floor space.

[0036] The buried pipe heat exchanger separates the outer pipe fluid from the inner pipe outer wall by the outer pipe wall and the borehole backfill material. The borehole backfill material uses a material with a low thermal conductivity, which further blocks the inner and outer pipe fluids and reduces the heat loss of the inner pipe hot fluid to the outside.

[0037] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A plum blossom-shaped underground heat exchanger, characterized in that: It comprises an inner tube, a plurality of outer tubes are installed at intervals outside the inner tube, and the same end of the inner tube and the plurality of outer tubes are connected with a bottom closed section; The inner tube and the outer tube are in point contact; The thermal conductivity of the inner tube is lower than that of the outer tube.

2. The plum blossom-shaped underground heat exchanger according to claim 1, characterized in that: The inner tube and the outer tube are both cylindrical tubes.

3. The plum blossom-shaped underground heat exchanger according to claim 2, characterized in that: The diameter of the inner tube is greater than the diameter of the outer tube.

4. A plum blossom-shaped underground heat exchanger according to claim 1 or 2, characterized in that: The inner tube is a PE tube.

5. A plum blossom-shaped underground heat exchanger according to claim 1 or 2, characterized in that: The outer tube is made of a stainless steel tube.

6. The plum blossom-shaped underground heat exchanger according to claim 1, characterized in that: The bottom closed section is a hollow cylindrical structure.

7. The quincunx-shaped underground heat exchanger according to claim 6, characterized in that: A through hole is formed on an end surface of the bottom closed section at one side where the bottom closed section is connected to the inner tube and the outer tube.

8. The plum blossom-shaped underground heat exchanger according to claim 1, characterized in that: A plurality of outer tubes are evenly spaced outside the inner tube.

9. The quincunx-shaped underground heat exchanger according to claim 8, characterized in that: The inner tube and the plurality of outer tubes all have smooth inner wall structures.

10. A construction method for a plum blossom-shaped underground heat exchanger, characterized in that: Based on the plum blossom-shaped buried pipe heat exchanger according to any one of claims 1 to 9, The following steps are involved: Adhere multiple outer tubes to the outer wall of the inner tube at intervals; Connect the ends of the inner tube and the outer tube to the bottom closed section; The assembled ground heat exchanger is inserted into the underground borehole and backfill material is injected into the hole.

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