A medium-deep buried tube heat exchanger

Abstract

The present invention discloses a novel medium-deep buried tube heat exchanger, which includes a heat exchanger body. According to the temperature distribution in the drilling depth direction, the temperature of the rock and soil mass is successively divided into a variable temperature layer, an isothermal layer, and a temperature increasing layer from top to bottom. The heat exchanger body is successively connected with a straight pipe section, a single spiral section, and a double spiral section from top to bottom. Water inlet pipes and water outlet pipes are arranged in the straight pipe section, the single spiral section, and the double spiral section. The water inlet pipe of the straight pipe section, the water inlet pipe of the single spiral section, and the water inlet pipe of the double spiral section are successively connected, and the water outlet pipe of the straight pipe section, the water outlet pipe of the single spiral section, and the water outlet pipe of the double spiral section are successively connected. The bottom of the water inlet pipe of the double spiral section is connected to the bottom of the water outlet pipe of the double spiral section. A hollow triangular support, a support rod, and a hollow guide installation head are used to naturally form an integral heat exchange structure for the straight pipe section, the single spiral section, and the double spiral section. The present invention has outstanding advantages such as high heat exchange efficiency, strong pressure-bearing capacity, less heat loss, and high construction quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of buried tube heat exchangers, and particularly relates to a medium-deep buried tube heat exchanger. Background Art

[0002] At present, vertical buried tube heat pump systems can be divided into shallow buried tube heat pump systems with a drilling depth generally between 50 and 200 meters and medium-deep buried tube heat pump systems with a drilling depth generally between 1000 and 3000 meters. However, for both shallow and medium-deep buried tube heat pump systems, the buried tube heat exchanger is a key component, and the level of its heat exchange efficiency directly determines the initial investment and system efficiency of the system. To improve the efficiency of the buried tube heat exchanger, many researchers have proposed and studied different structural forms of buried tube heat exchangers. Common structural forms of shallow buried tube heat exchangers include single U-shaped, double U-shaped, and W-shaped, as well as the newly proposed spiral-shaped. The research on these structural forms has greatly promoted the development and application of shallow buried tube heat pump systems. Although the development of shallow buried tube heat exchange technology started relatively early and the technology is relatively mature, medium-deep buried tube heat pump systems have unique advantages such as less land occupation, more stable heat output, being unaffected by outdoor climate, and no cold and heat imbalance phenomenon in shallow buried tubes. Therefore, medium-deep buried tube heat exchange systems have received special attention in recent years, and the structure and thermal performance of their buried tube heat exchangers have become a research hotspot.

[0003] Medium-deep buried tube heat exchangers belong to a technology. Currently, the structure is relatively single, mainly the casing heat exchanger. Initially, both the inner / outer tubes of the casing heat exchanger were made of steel pipes, but there was a serious phenomenon of heat short circuit in the supply and return water. Therefore, currently, the outer tube of the medium-deep casing heat exchanger is generally made of a steel pipe, and the inner tube is generally made of a plastic pipe, which slows down the heat short circuit phenomenon to a certain extent, but there are still obvious deficiencies: ① Only the outer tube wall of the casing type buried tube heat exchanger is in full contact with the rock and soil mass for heat exchange. Moreover, the pipe diameter is large, the pipe wall is thick, and the entire outlet pipe not only cannot exchange heat with the rock and soil mass, but also transfers heat to the inlet pipe, and the heat short circuit is still obvious; ② Compared with the current shallow buried tube heat exchanger, the outer diameter of the casing heat exchanger is generally larger. Although it can increase the heat exchange between the inlet pipe and the rock and soil mass, in the initial pipe well section of the medium-deep borehole, its heat dissipation to the rock and soil mass also increases, that is, the heat loss also increases accordingly. Although the utility model patent (CN 212299509 U) has improved the casing type medium-deep buried tube heat exchanger, increasing the flow velocity of the inlet water in the annular flow channel and the anti-bending deformation ability of the outer tube, while increasing the flow velocity to strengthen the heat exchange with the rock and soil mass, it also increases the heat exchange with the inner tube, that is, the heat short circuit is also enhanced; furthermore, the existing shallow buried tube heat exchanger structure cannot be well applied to the medium-deep layer.

[0004] Whether it is a single U-shaped, double U-shaped, W-shaped, or spiral-shaped (CN111536810B) shallow buried tube heat exchanger, or a casing-type medium-deep buried tube heat exchanger, their structural forms are axisymmetric structures. Their inherent defect is that while increasing the heat transfer area to enhance heat transfer, heat short-circuiting and heat loss also increase. Moreover, for medium-deep buried tube heat exchangers, the defects of this inherent structure are more prominent.

[0005] Therefore, it is necessary to innovate the design of the structure of the medium-deep buried tube heat exchanger. Only in this way can the heat transfer efficiency of the buried tube heat exchanger be maximally improved, the energy output of the borehole pipe well be enhanced, the number of drillings be reduced, and thus the initial investment and floor area be reduced. A medium-deep buried tube heat exchanger is proposed.

[0006] In summary, the structural design of the existing buried tube heat exchanger cannot well adapt to the borehole temperature distribution, the effective utilization rate of the drilling depth is not high, and there are obvious heat short-circuiting and heat loss phenomena in the medium-deep buried tube heat exchanger. Aiming at the deficiencies of the existing buried tube heat exchangers, based on the analysis of the vertical temperature distribution and heat transfer process of the drillings and the principle of heat transfer enhancement, a medium-deep buried tube heat exchanger is creatively given. This heat exchanger has outstanding advantages such as high heat transfer efficiency, less heat loss, strong pressure-bearing capacity, and high construction quality. Summary of the Invention

[0007] The present invention provides a medium-deep buried tube heat exchanger, which adopts different heat exchanger structures in different depth sections of the drilling. Along the drilling depth direction, the heat exchange structure is successively composed of a straight pipe section, a single spiral section, and a double spiral section. In the straight pipe section, there are 3 inlet straight pipes and 3 outlet straight pipes. On the same horizontal plane, the 3 outlet pipes are located at the 3 vertices of an equilateral triangle, that is, evenly distributed on the circumcircle of the equilateral triangle, and the 3 inlet pipes are located at the midpoints of the 3 sides of the equilateral triangle, that is, evenly distributed on the inscribed circle of the equilateral triangle; in the single spiral section, the outlet pipe is a straight pipe, while the inlet pipe is a spiral pipe, and the outlet pipe is located outside the spiral pipe; in the double spiral section, both the inlet and outlet pipes are spiral pipes, the inlet pipe is an inner spiral, and the outlet pipe is a coaxial outer spiral; and the pipe centers of the inlet and outlet pipes are located on concentric circles with different radii; the inlet and outlet pipes are connected by a U-shaped elbow at the bottom of the double spiral section. The outlet pipe located at the vertex of the equilateral triangle is connected to the inlet pipe at the midpoint of the opposite side, and a hollow guiding installation head is provided at the U-shaped bend; to ensure the installation quality of the heat exchanger, a hollow triangular fixed pipe pitch is adopted, a hollow triangle and a support rod are used to fix the pitch, and a hollow guiding installation head is used to protect the U-shaped elbow and reduce the installation resistance.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A medium-deep buried tube heat exchanger, comprising a heat exchanger body, and the heat exchanger body is successively communicated with a straight pipe section, a single spiral section and a double spiral section from top to bottom. The water inlet pipe is successively a straight pipe, a spiral pipe and a spiral pipe from top to bottom along the pipe well, and the water inlet straight pipe, the middle inlet spiral pipe and the lower inlet spiral pipe are successively communicated; the water outlet pipe is successively a water outlet spiral pipe, a water outlet straight pipe and a water outlet straight pipe from bottom to top along the pipe well, and the water outlet spiral pipe, the middle water outlet straight pipe and the upper water outlet straight pipe are successively communicated; the water inlet pipe and the water outlet pipe are communicated through a U-shaped elbow at the bottom of the double spiral section, and the water outlet pipe corresponding to the vertex of the triangle is communicated with the water inlet pipe corresponding to the center position of the opposite side of the vertex.

[0010] For the above medium-deep buried tube heat exchanger, three water inlet pipes and three water outlet pipes are provided in the straight pipe section, the single spiral section and the double spiral section. The three water outlet pipes in the straight pipe section, the single spiral section and the double spiral section are respectively arranged on the circumcircle where the three vertices A, B, and C of the triangle are located, and the three water inlet pipes are respectively arranged on the incircle where the midpoints D, E, and F of the three sides of the triangle are located; for the convenience of description, let the D point be the midpoint of the corresponding side of the vertex A, that is, D is the midpoint of the connection line between the vertices B and C; E is the midpoint of the corresponding side of the vertex B, that is, E is the midpoint of the connection line between the vertices A and C; F is the midpoint of the corresponding side of the vertex C, that is, F is the midpoint of the connection line between the vertices A and B. Each water inlet pipe located at the midpoint of the corresponding side of the triangle vertex flows through the straight pipe section, the single spiral section and the double spiral section and then flows into the bottom of the pipe well, flows into the water outlet pipe at the corresponding vertex through the U-shaped elbow, and then successively flows out through the outer spiral pipe in the double spiral section, the water outlet straight pipe in the single spiral section and the water outlet straight pipe on the outer ring in the straight pipe section.

[0011] In the double spiral section, the horizontal projection of the water outlet outer spiral pipe is located on the circular ring where the vertices A, B, and C are located; the pipe centers of the water outlet straight pipes in the single spiral section and the straight pipe section are located at the positions of the vertices A, B, and C of the equilateral triangle. The pipe centers of the water inlet pipes in the straight pipe section are located at the positions of the midpoints D, E, and F of the three sides in the equilateral triangle; in the single spiral section, the water inlet pipe is a spiral pipe, and the horizontal projection of the pipe center of the water inlet spiral pipe in this section is located on the incircle of the equilateral triangle ABC where the water outlet straight pipe in this section is located; in the double spiral section, the water inlet pipe is an inner spiral pipe, and the horizontal projection of the pipe center of the water inlet spiral pipe in this section is still located on the incircle of the equilateral triangle ABC. The water inlet pipes, the water outlet pipes, and between the water inlet and outlet pipes do not directly contact each other, and the horizontal distance from the pipe center of the water outlet pipe to the axis of the pipe well is twice the horizontal distance from the pipe center of the water inlet pipe to the axis of the pipe well.

[0012] The heat medium flows in from the water inlet pipe corresponding to the midpoint of the opposite side facing the vertex, successively passes through the water inlet straight pipe of the straight pipe section, the water inlet spiral pipe of the single spiral section, and the water inlet spiral pipe of the double spiral section, then flows into the water outlet pipe after passing through the U-shaped bend pipe, successively passes through the water outlet spiral pipe of the double spiral section and the water outlet straight pipe of the single spiral section, and finally is discharged from the water outlet straight pipe in the straight pipe section. That is, the heat medium flows in from the water inlet pipe corresponding to the D position, passes through the straight pipe section, the single spiral section, and the double spiral section, then turns back after passing through the U-shaped bend pipe, and then successively flows through the double spiral section, the single spiral section, and the straight pipe section and flows out from the water outlet pipe corresponding to the A position; the heat medium passes through the straight pipe section, the single spiral section, and the double spiral section from the water inlet pipe corresponding to the E position, turns back after passing through the U-shaped bend pipe, then successively flows through the double spiral section, the single spiral section, and the straight pipe section, and finally flows out from the water outlet pipe corresponding to the B position; the water inlet pipe corresponding to the F position passes through the double spiral section, the single spiral section, and the straight pipe section, turns back after passing through the U-shaped bend pipe, then successively flows through the double spiral section, the single spiral section, and the straight pipe section, and finally flows out from the water outlet pipe corresponding to the C position.

[0013] For the above-mentioned medium-deep buried tube heat exchanger, the water outlet pipe of the single spiral section is a straight pipe, the water outlet pipe is on the circumcircle of the triangle, the water inlet pipe is a spiral pipe, and the centers of the spiral pipes are all on the incircle of the triangle.

[0014] For the above-mentioned medium-deep buried tube heat exchanger, the water inlet pipe and the water outlet pipe of the double spiral section are both spiral pipes, and the spiral pipe of the water inlet pipe is on the incircle of the triangle, while the spiral pipe of the water outlet pipe is on the circumcircle of the triangle.

[0015] For the above-mentioned medium-deep buried tube heat exchanger, it further includes a hollow triangular support. Through holes are provided at the positions of the vertices A, B, C of the triangular support and the midpoints D, E, F of the three sides. The three water outlet pipes of the straight pipe section, the single spiral section, and the double spiral section are respectively sleeved in the through holes corresponding to the three vertices A, B, C of the triangular support, and the three water inlet pipes are respectively sleeved in the through holes corresponding to the midpoints D, E, F of the three sides of the triangle.

[0016] For the above-mentioned medium-deep buried tube heat exchanger, it further includes support rods. For metal pipes, no support rods are provided between the two hollow triangular supports in the straight pipe section; in the single spiral section, three support rods are provided between the two hollow triangular supports; in the double spiral section, three support rods are provided between the two hollow triangular supports, and the support rods are arranged outside the inlet and outlet pipes. For plastic pipes, no support rods are provided between the two hollow triangular supports in the straight pipe section either; in the single spiral section, three support rods are provided between the two hollow triangular supports, and the support rods are located outside the water inlet spiral pipe and inside the water outlet straight pipe; in the double spiral section, six support rods are provided between the two hollow triangular supports, three are arranged outside the outer spiral pipe, and three are arranged outside the inner side of the outer spiral and the outer side of the inner spiral.

[0017] In the above-mentioned medium and deep buried tube heat exchanger, a support rod is used to connect the upper and lower triangular brackets corresponding to the spiral tube, so as to ensure that when the inlet and outlet pipes are made of metal pipes (such as ordinary steel pipes, galvanized steel pipes, stainless steel pipes, etc.), the pitch is not damaged during installation; when the inlet and outlet pipes are made of non-metal pipes (such as plastic pipes PB, PE, etc.), several spiral tube fixing pipe clamps need to be transversely arranged on the support rod, and the spiral tube is clamped by the spiral tube fixing pipe clamps to fix the plastic pipe, fix its spiral, and ensure that the pitch is not damaged during installation. This structural form is also applicable to shallow buried tube heat exchangers.

[0018] In the above-mentioned medium and deep buried tube heat exchanger, a hollowed-out guiding installation head is arranged at the bottom of the double spiral tube. At the bottom of the double spiral section, the U-shaped connecting pipes connecting the inlet pipe and the outlet pipe are all arranged inside the hollowed-out guiding installation head. The upper part of the hollowed-out guiding installation head is hemispherical, the lower part is conical, and "droplet"-shaped hollows are evenly distributed on the guiding installation head.

[0019] In the above-mentioned medium and deep buried tube heat exchanger, the inlet pipe corresponding to the D position in the double spiral section is communicated with the outlet pipe corresponding to the A position through a U-shaped elbow; the inlet pipe corresponding to the E position is communicated with the outlet pipe corresponding to the B position through a U-shaped elbow; the inlet pipe corresponding to the F position is communicated with the outlet pipe corresponding to the C position through a U-shaped elbow.

[0020] In the above-mentioned medium and deep buried tube heat exchanger, a heat insulation layer is sleeved outside the outlet pipe of the straight pipe section.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] On the basis of fully considering the vertical temperature distribution and horizontal heat transfer process of the rock and soil layers in the drilling depth direction, as the depth increases longitudinally, the temperature rises, increasing the effective heat transfer area of the heat absorption section of the rock and soil in the lower drilling, and reducing the heat transfer area of the upper drilling section. This can not only reduce heat loss, but also improve the heat transfer efficiency of the buried tube heat exchanger, and at the same time improve the effective utilization rate of the drilling; horizontally, the inlet pipe is in the inner ring, the outlet pipe is in the outer ring, and the inlet and outlet pipes and the horizontal heat transfer process are in countercurrent heat exchange macroscopically, increasing the heat transfer temperature difference, which can improve the heat transfer efficiency of the high-temperature section of the rock and soil in the lower part of the drilling and reduce the heat dissipation loss to the rock and soil in the upper part of the drilling; compared with the existing medium and deep casing buried tube heat exchanger, under the same drilling conditions, the medium and deep buried tube heat exchanger has a small heat transfer thermal resistance and a fast heat transfer rate; the inlet and outlet pipes have a small diameter and a strong pressure-bearing capacity. In summary, the medium and deep buried tube heat exchanger has outstanding advantages such as high heat transfer efficiency, strong pressure-bearing capacity, less heat loss, and high construction quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the buried tube heat exchanger of the present invention.

[0024] Figure 2 It is the top view of the ground heat exchanger structure of the present invention.

[0025] Figure 3 It is the schematic structural view of adding a fixing clamp for the spiral pipe to the present invention.

[0026] Figure 4 It is the schematic structural view of the hollow guiding installation head of the present invention.

[0027] Wherein: 1 is the hollow guiding installation head; 2 is the support rod; 3 is the outlet spiral pipe; 4 is the triangular bracket; 5a is the inlet spiral pipe; 5b is the inlet spiral pipe; 6, 8, 12 are the inlet pipes; 7, 9, 11 are the outlet pipes; 10 is the triangular hollow; 14 is the wellbore wall; 15 is the insulation layer; 16 is the fixing clamp for the spiral pipe; 17 is the hollow of the guiding installation head; L1 is the double spiral section; L2 is the single spiral section; L3 is the double straight pipe section. Specific embodiments

[0028] The following are the detailed implementation steps of the present invention.

[0029] As Figure 1 , Figure 2 and Figure 3 shown, a medium-deep ground heat exchanger includes a heat exchanger body. According to the temperature distribution in the drilling depth direction, the temperature of the rock and soil mass is successively divided into a variable temperature layer, an isothermal layer, and a temperature increasing layer from top to bottom. Most of the heat exchanger body is located in the temperature increasing layer. Specifically: the heat exchanger body is composed of a straight pipe section L3, a single spiral section L2, and a double spiral section L1 that are connected in sequence from top to bottom. The length of the straight pipe section L3 is determined according to the designed inlet temperature of the heat medium and the thermal response experiment of the drilling rock and soil. If the designed inlet temperature of the heat medium is relatively low, the straight pipe section is generally located in the variable temperature layer. If the inlet heat medium temperature is relatively high, the straight pipe section is located in the variable temperature layer and the isothermal layer. The length of the double spiral section L1 is determined according to the outlet temperature of the heat medium and the thermal response experiment of the drilling rock and soil, and is generally located in the lower part of the temperature increasing layer. The length of the single spiral section depends on the total drilling depth and the lengths of the straight pipe section L3 and the double spiral section L2, that is, it is equal to the total drilling length minus the lengths of L2 and L3 respectively.

[0030] In the straight pipe section L3, the single spiral section L2, and the double spiral section L1, inlet pipes and outlet pipes are provided. The inlet pipes of the straight pipe section L3, the single spiral section L2, and the double spiral section L1 are connected in sequence, and the outlet pipes of the straight pipe section L3, the single spiral section L2, and the double spiral section L1 are connected in sequence; at the bottom of the double spiral section L1, the inlet pipe and the outlet pipe are connected through a U-shaped bend pipe, and the outlet pipe located at the vertex of the equilateral triangle is connected to the inlet pipe located at the midpoint of the opposite side of the vertex.

[0031] Based on the heat transfer enhancement mechanism and the analysis of the thermal resistance in the heat transfer process, combined with the temperature distribution of the geotechnical body in the drilling depth direction, different buried pipe heat exchange structures are adopted in different drilling sections of the same well, and along the drilling depth direction, the heat exchanger area increases successively. During the winter heating season, the temperature of the geotechnical body increases with the increase of the drilling depth. By adopting different heat exchange structure forms, both heat loss can be reduced and heat exchange efficiency can be improved. Compared with the double helix structure, it can not only save pipe materials but also reduce heat loss. Increasing the heat exchange area along the drilling depth direction can improve the heat exchange efficiency with the geotechnical body, or reduce the drilling depth under the same heat demand condition.

[0032] As Figure 1 , Figure 2 and Figure 3 shown, the straight pipe section L3, single helix section L2 and double helix section L1 are all provided with three water inlet pipes 6, 8, 12 and three water outlet pipes 7, 9, 11. The three water outlet pipes of the straight pipe section L3, single helix section L2 and double helix section L1 are respectively arranged on the circumferences of the circumcircles corresponding to the three vertices A, B, C of an equilateral triangle, and the three water inlet pipes are respectively arranged on the circumferences of the incircles corresponding to the midpoints D, E, F of the three sides of the equilateral triangle.

[0033] The low-temperature heat medium from the heat exchanger is shunted through the outlet horizontal header and flows into the 3 inlet straight pipes located at the midpoints of the three sides of the equilateral triangle in the straight pipe section L3, and then flows into the spiral pipe in the single helix section L2 in sequence, absorbs the heat of the geotechnical body, raises the temperature of the water inlet pipe, and then flows into the inner spiral pipe in the double helix section. In this pipe section, it continues to absorb the heat of the geotechnical body and further raises the temperature of the water inlet pipe. Finally, it flows into the outer spiral pipe of the double helix section L1 through the U-shaped connecting pipe at the bottom of the double helix section L1, continues to absorb the heat of the geotechnical body in the outer spiral pipe, further raises the temperature of the water outlet pipe, and then flows through the 3 outlet straight pipes located at the vertices of the equilateral triangle in the single helix section L2 and the straight pipe section L3, and finally converges at the outlet horizontal header, flows into the heat exchanger through the outlet horizontal header for heat exchange and cooling, then flows into the inlet horizontal header, and then is shunted into the inlet straight pipes of the straight pipe section L3 to complete the heat exchange cycle.

[0034] The projections of the three outlet pipes of the straight pipe section L3 are located at the vertices of an equilateral triangle, that is, on the circumcircle of the equilateral triangle. The three inlet pipes are located at the midpoints of the equilateral triangle, that is, on the incircle of the equilateral triangle. The six pipes can be fixed by the same equilateral triangle, ensuring the uniform distribution of the pipe spacing and the inlet and outlet pipes in the drilling. At the same time, it is easy to distinguish the inlet and outlet pipes, and it is also convenient for the connection of the inlet and outlet pipes in the drilling to the horizontal header. The temperature of the rock and soil mass in the straight pipe section L3 is relatively low. The inlet and outlet pipes mainly play a conveying role, and the heat exchange area of the inlet and outlet pipes in this section is minimized to reduce the heat dissipation of the inlet and outlet pipes to the rock and soil mass. Since the temperature of the outlet pipe is relatively high and the temperature difference between the outlet pipe and the rock and soil mass is large, in order to further reduce the heat dissipation of the outlet pipe, a heat insulation layer 15 is provided for the outlet pipe in the straight pipe section L3. The temperature difference between the inlet pipe and the rock and soil mass is small, and the heat dissipation of the inlet pipe to the rock and soil mass is very small. Through technical and economic analysis, the inlet pipe in the straight pipe section is not heat-insulated. This structural design can reduce the heat loss of the ground heat exchanger while saving investment. In the straight pipe section L1 of the present invention, the inlet pipes are straight pipes 6, 8, and 10, which are respectively located at positions D, E, and F at the midpoints of the three sides of the equilateral triangle. The temperature of the inlet pipe is generally slightly higher than the temperature of the rock and soil mass in the straight pipe section L3, but the temperature difference with the rock and soil mass is not large. The heat loss of the inlet pipe in this section can be ignored, so no heat insulation layer is sleeved outside the inlet straight pipe of this pipe section. When the heat medium flows downstream along the inlet straight pipe, the temperature of the rock and soil mass outside the pipe gradually increases. When the temperature of the rock and soil mass is higher than the temperature of the heat medium in the inlet straight pipe (for example, when the temperature of the rock and soil mass is 3°C higher than the temperature of the heat medium), the inlet straight pipe becomes a spiral pipe, and until the bottom of the drilling, the inlet pipe is always a spiral pipe. During the flow of the spiral pipe from top to bottom, it continuously absorbs the heat of the rock and soil mass and continuously increases the temperature of the inlet pipe. When the heat medium flows to the bottom of the double-spiral section, it enters the outer spiral outlet pipe in the double-spiral section L1 through the bottom U-shaped elbow. The heat medium continues to be heated by the rock and soil mass in the outer spiral outlet pipe. The use of a spiral pipe for the inlet pipe increases the heat exchange area between the inlet pipe and the rock and soil mass, thereby enhancing the heat exchange between the inlet pipe and the rock and soil mass, and further improving the heat exchange efficiency of the drilling.

[0035] In the double - helix section L1 of the present invention, the water outlet pipe is an outer spiral pipe. The heat medium passes through the U - shaped elbow and flows into the water outlet spiral pipe 3 from the water inlet spiral pipe 5b. As the heat medium flows upward in the water outlet spiral pipe, the temperature of the rock and soil mass gradually decreases, while the temperature of the heat medium gradually increases, and the temperature difference between the rock and soil mass and the heat medium gradually becomes smaller. When the temperature difference decreases to a certain extent (for example, when the temperature of the rock and soil mass is less than 3 - 4 °C different from the temperature of the heat medium), the water outlet spiral pipe becomes a straight pipe. In the double - helix section, the temperature of the rock and soil mass is significantly higher than that of the water outlet pipe. In order to further absorb the heat in the rock and soil mass, it is necessary to increase the heat - exchange area of the water outlet pipe. Therefore, the water outlet pipe is set as a spiral pipe to improve the heat - exchange efficiency of the drilling. In the single - helix section, the temperature difference between the water outlet pipe and the temperature of the rock and soil mass in this pipe section is small. To reduce the circulation resistance and save pipe materials, the water outlet pipe is set as a straight pipe in the single - helix section L2. Because the temperature difference between the water outlet pipe and the rock and soil mass is not large and the heat - exchange area is small, the heat exchange amount between the water outlet pipe and the rock and soil mass is extremely small, and there is no need to lay a heat - insulation layer outside the water outlet pipe in this pipe section. In the straight - pipe section L3, the water outlet straight pipes 9, 11, and 7 are respectively located at the vertices A, B, and C of an equilateral triangle. The temperature of the water outlet pipe is significantly higher than that of the rock and soil mass. Although the water outlet pipe is still a straight - pipe section and the heat - exchange area is small, due to the large temperature difference, the heat loss cannot be ignored. Through technical and economic comparison, it is advisable to lay a heat - insulation layer 15 outside the water outlet pipe, which can significantly reduce the heat loss of the water outlet pipe and ensure the temperature of the water outlet pipe. This structural design can improve the effective utilization rate of the drilling depth while reducing the heat loss.

[0036] In the ground - buried tube heat exchanger of the present invention, the pipe - well section with the water inlet pipe as a spiral pipe 5a and the water outlet pipe as a straight - pipe section is called the single - helix section L2; the pipe - well section with both the water inlet and outlet pipes as spiral pipes is called the double - helix pipe section L1, and the pipe - well section with both the water inlet and outlet pipes as straight pipes is called the straight - pipe section L3. The length of the straight - pipe section L3 depends on the water inlet temperature and the temperature of the rock and soil mass; the length of the double - helix pipe section L1 depends on the temperature of the water outlet pipe and the temperature of the rock and soil mass. The water inlet pipe in the double - helix section L1 is an inner spiral pipe 5b. In the double - helix section, the heat from the rock and soil mass is first transferred to the water outlet spiral pipe 3 in the L1 section, and then to the inner - spiral water inlet pipe 5b. By adopting the way of counter - current heat transfer in the horizontal direction with the rock and soil mass, using an inner and outer double - spiral pipe, with the outer spiral as the water outlet pipe and the inner spiral as the water inlet pipe, the heat exchange with the rock and soil mass can be enhanced, and the temperature of the water outlet pipe can be further increased.

[0037] Both the water inlet pipe 5b and the water outlet pipe 3 in the double - helix section L1 of the present invention are spiral pipes. The water inlet pipe is an inner spiral pipe 5b. The spiral pipe of the water inlet pipe is on the inscribed circle of an equilateral triangle, while the water outlet pipe is an outer spiral pipe. The water outlet spiral pipe is on the circumscribed circle of this triangle, and the inner and outer spiral pipes are concentric spiral pipes, and the outer - spiral radius is twice the inner - spiral radius.

[0038] In the deep buried tube heat exchanger of the present invention, the temperature of the rock and soil mass in the double spiral section at the bottom is higher than the temperatures of the inlet and outlet water pipes. To maximize the utilization of the heat of the rock and soil mass in this well section, both the inlet and outlet water pipes are arranged as spiral pipes, further increasing the heat exchange area to improve the utilization rate of the heat of the rock and soil mass. The inlet spiral pipe is arranged in the inner ring, and the outlet spiral pipe is arranged in the outer ring. The outlet water pipe is located at a relatively higher temperature during the transverse heat transfer process, while the inlet water pipe is located at a relatively lower temperature during the transverse heat transfer process. Generally speaking, the buried tube heat exchanger and the rock and soil mass perform countercurrent heat exchange, so the heat exchange temperature difference can be increased, and the heat exchange efficiency can be further improved.

[0039] In the initial section of the drilling of the present invention, the inlet and outlet water pipes adopt straight pipe sections, aiming to reduce the heat exchange area, so the heat loss can be reduced. The inlet and outlet water pipes of the present invention do not directly contact each other, which can effectively avoid the heat short circuit existing in the shell-and-tube heat exchanger. In addition, the lengths of the straight pipe section L3, the single spiral section L2, and the double spiral section L1 of the present invention need to be determined according to the drilling response experiment, theoretical analysis, and numerical simulation experiment, depending on the characteristics of the rock and soil mass and the local water table height, etc.

[0040] As Figure 1 and 3 As shown in and , the deep buried tube heat exchanger further includes a hollow triangular support 10. Through holes are provided at the positions of the vertices A, B, C of the triangular support and the corresponding positions D, E, F of the three sides. The three outlet water pipes of the straight pipe section L3, the single spiral section L2, and the double spiral section L1 are respectively sleeved in the through holes corresponding to the three vertices A, B, C of the triangular support, and the three inlet water pipes are respectively sleeved in the through holes corresponding to the midpoints D, E, F of the three sides of the triangle. Between the upper and lower triangular supports 10 corresponding to the spiral pipes, they are connected by support rods 2. A number of spiral pipe fixing pipe clamps 16 are horizontally arranged on the support rods, and the spiral pipe fixing pipe clamps are clamped on the spiral pipes. The deep buried tube heat exchanger is provided with a horizontal triangular support, which can not only naturally integrate the heat exchange structures of different drilling sections into a whole, but also fix the pipe spacing between the buried tubes, and at the same time facilitate the distinction between the inlet and outlet water pipes, thereby improving the construction quality; between the hollow triangular supports, there are support rods for keeping the pitch of the inlet and outlet spiral pipes unchanged during installation, overcoming the disadvantages that it is not easy to ensure the pipe spacing and pitch during the installation of the shallow buried tube heat exchanger. The guiding installation head of the deep buried tube heat exchanger is hollowed out, the triangular support is hollow, and the spiral is coaxial with the drilling, which can ensure that the existing construction technology is still applicable; at the same time, it is convenient for the flushing of the backfill material, so that the backfill material is in close contact with the pipe wall and the drilling wall 14, reducing the contact thermal resistance, and further improving the buried tube heat exchange efficiency.

[0041] As Figure 1 、 Figure 2 and Figure 3As shown in the figure, for the medium-deep buried tube heat exchanger, the outlet pipe corresponding to position A of the double spiral section L1 is connected to the inlet pipe corresponding to the midpoint D of the opposite side of position A through a U-shaped bend pipe; the outlet pipe corresponding to position B is connected to the inlet pipe corresponding to the midpoint E of the opposite side of position B through a U-shaped bend pipe; the outlet pipe corresponding to position C is connected to the inlet pipe corresponding to the midpoint F of the opposite side of position C through a U-shaped bend pipe. A hollowed-out guiding installation head is arranged at the bottom of the double spiral pipe, and the U-shaped connecting pipes of the inlet and outlet pipes of the double spiral section L1 are all arranged inside the hollowed-out guiding installation head 1.

[0042] The inlet and outlet pipes of the medium-deep buried tube heat exchanger are connected through the bottom U-shaped bend pipes. The outlet pipes located at the vertices of the equilateral triangle are connected to the inlet pipes at the midpoints of the opposite sides, rather than to the nearest outlet pipes. This can increase the bending radius of the U-shaped bend pipes and facilitate the manufacture of the U-shaped bend pipes.

[0043] As Figure 4 shown in the figure, a hollowed-out guiding installation head 1 is provided at the U-shaped bend of the present invention. On the one hand, it can protect the bottom U-shaped bend pipes, and on the other hand, it is convenient for installation and can avoid damage or deformation of the U-shaped bend pipes during installation; the hollowing is provided on the guiding installation head to facilitate the compaction of the backfill material. Therefore, the above measures can effectively ensure the construction quality.

[0044] Compared with the existing casing-type buried tube heat exchanger, in the same drilling well, under the same flow rate and pressure-bearing capacity, the diameters of the inlet and outlet pipes of the medium-deep buried tube heat exchanger are small, the flow velocity is high, and the pipe walls are thin. Therefore, the heat transfer thermal resistance is small, and the efficiency of the buried tube heat exchanger can be further improved.

[0045] On the basis of fully considering the vertical temperature distribution and the lateral heat transfer process of the drilling well, the present invention creatively utilizes the advantages of the 3U-shaped, spiral-shaped, and casing-type buried tube heat exchangers, overcomes their disadvantages, and effectively avoids the occurrence of the heat short-circuit phenomenon. Along the longitudinal direction of the drilling well, as the temperature rises, the heat exchange area increases, that is, the effective heat exchange area of the heat absorption section is increased, and the ineffective heat exchange area of the heat dissipation section is reduced, which can not only reduce the heat loss, but also improve the heat exchange efficiency and the effective utilization rate of the drilling well; in the lateral direction, the inlet pipes are in the inner ring and the outlet pipes are in the outer ring. The inlet and outlet pipes and the lateral heat transfer process are in countercurrent heat exchange macroscopically, which can further improve the heat exchange efficiency; compared with the existing medium-deep casing-type buried tube heat exchanger, under the same drilling well, the medium-deep buried tube heat exchanger has a small heat transfer thermal resistance and a fast heat transfer rate; the diameters of the inlet and outlet pipes are small and the pressure-bearing capacity is strong. To sum up, the medium-deep buried tube heat exchanger has outstanding advantages such as high heat exchange efficiency, strong pressure-bearing capacity, less heat loss, and high construction quality.

[0046] The technical means disclosed by the technical solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A medium-deep buried tube heat exchanger, comprising a heat exchanger body, characterized in that: The heat exchanger body is composed of a straight pipe section, a single spiral section, and a double spiral section that are connected in sequence from top to bottom. Water inlet pipes and water outlet pipes are provided in the straight pipe section, the single spiral section, and the double spiral section. The water inlet pipe of the straight pipe section, the water inlet pipe of the single spiral section, and the water inlet pipe of the double spiral section are connected in sequence. The water outlet pipe of the straight pipe section, the water outlet pipe of the single spiral section, and the water outlet pipe of the double spiral section are connected in sequence. The bottom of the water inlet pipe of the double spiral section is connected to the bottom of the water outlet pipe of the double spiral section. In the single spiral section, the water outlet pipe is a straight pipe, while the water inlet pipe is a spiral pipe, and the water outlet pipe is located outside the spiral pipe. In the double spiral section, both the water inlet pipe and the water outlet pipe are spiral pipes. The water inlet pipe is an inner spiral, and the water outlet pipe is a coaxial outer spiral.

2. The deep and medium buried tube heat exchanger according to claim 1, characterized in that: Three water inlet pipes and three water outlet pipes are provided in each of the straight pipe section, the single spiral section, and the double spiral section. The three water outlet pipes of the straight pipe section, the single spiral section, and the double spiral section are respectively arranged at the positions corresponding to the three vertices A, B, and C of a triangle, and the three water inlet pipes are respectively arranged at the positions of the midpoints D, E, and F of the three sides of the triangle. Among them, for each water inlet pipe corresponding to the midpoint of the three sides of the triangle, after passing through the straight pipe section, the single spiral section, and the double spiral section in sequence, it is then discharged through the double spiral section, the single spiral section, and the straight pipe section corresponding to the water outlet pipe at the position of the vertex opposite to this side in sequence.

3. The deep buried tube heat exchanger according to claim 2, wherein: The water outlet pipe of the single spiral section is a straight pipe, the water outlet pipe is on the circumcircle of the triangle, the water inlet pipe is a spiral pipe, and the spiral pipes are all on the incircle of the triangle.

4. The deep buried tube heat exchanger according to claim 2, characterized in that: Both the water inlet pipe and the water outlet pipe of the double spiral section are spiral pipes. The spiral pipe of the water inlet pipe is on the incircle of the triangle, while the spiral pipe of the water outlet pipe is on the circumcircle of the triangle.

5. The deep buried tube heat exchanger according to claim 2, wherein: It further includes a hollow triangular bracket. Through holes are provided at the vertices A, B, and C of the triangular bracket and at the central positions D, E, and F of the corresponding three sides. The three water outlet pipes of the straight pipe section, the single spiral section, and the double spiral section are respectively sleeved in the through holes at the positions corresponding to the three vertices A, B, and C of the triangular bracket, and the three water inlet pipes are respectively sleeved in the through holes at the positions corresponding to the midpoints D, E, and F of the three sides of the triangle.

6. The deep and medium buried tube heat exchanger according to claim 5, wherein: The upper and lower triangular brackets corresponding to the single spiral section and the double spiral section are connected by support rods. A number of spiral pipe fixing pipe clamps are horizontally arranged on the support rods, and the spiral pipe fixing pipe clamps are clamped on the spiral pipes.

7. The deep-buried tube heat exchanger according to claim 6, characterized in that: In the single spiral section, support rods are provided between the upper and lower triangular brackets corresponding to the positions between the spiral pipe and the straight pipe. In the double spiral section, inner support rods are provided between the upper and lower triangular brackets corresponding to the positions between the inner spiral pipe and the outer spiral pipe, and outer support rods are also provided outside the outer spiral pipe. Inner spiral pipe fixing pipe clamps for clamping the inner spiral pipe are provided on the inner support rods, and outer spiral pipe fixing pipe clamps for clamping the outer spiral pipe are provided on the outer support rods.

8. The deep and medium buried tube heat exchanger according to any one of claims 2-7, characterized in that: A hollowed-out guiding installation head is provided at the bottom of the double spiral pipe. The water inlet pipe and the water outlet pipe at the bottom of the double spiral section are connected and are both arranged inside the hollowed-out guiding installation head.

9. The deep-buried ground heat exchanger according to claim 8, wherein: The water outlet pipe corresponding to the A position at the bottom of the double spiral section is connected to the water inlet pipe corresponding to the midpoint D position of the opposite side of the A position through a U-shaped elbow pipe. The water outlet pipe corresponding to the B position is connected to the water inlet pipe corresponding to the midpoint E position of the opposite side of the B position through a U-shaped elbow pipe. The water outlet pipe corresponding to the C position is connected to the water inlet pipe corresponding to the midpoint F position of the opposite side of the C position through a U-shaped elbow pipe.

10. The deep and medium-depth buried tube heat exchanger according to claim 1, characterized in that: A heat-insulating layer is sleeved outside the water outlet pipe of the straight pipe section.

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