Buried coaxial sleeve efficient phase change energy storage device

Abstract

The utility model discloses a buried coaxial sleeve efficient phase change energy storage device which comprises a solar heat collector, a heat exchanger, a user side, an energy storage well and a buried energy storage device. The buried energy storage device comprises an outer pipe and a heat preservation inner pipe which are installed in the energy storage well and coaxially arranged in a sleeved mode, and an annular space formed between the outer pipe and the energy storage well is filled with heat insulation backfill materials. The bottom end of the outer pipe is welded and sealed by a carbon steel plate; the top of the inner heat-preservation pipe is open, the bottom end of the inner heat-preservation pipe is closed and makes contact with the inner bottom face of the outer pipe, and two symmetrically-distributed notches are formed in the side wall of the bottom of the inner heat-preservation pipe. An energy storage rod array composed of a plurality of energy storage rods is installed in the heat preservation inner pipe, and all the energy storage rods make contact with the bottom face of the heat preservation inner pipe. The upper end opening of the outer pipe is covered with an outer pipe heat preservation cover plate, and the upper end opening of the heat preservation inner pipe is covered with an inner pipe heat preservation cover plate. The utility model not only overcomes the problem of occupied area of the traditional heat storage device, but also improves the heat preservation effect of the device after being placed underground.

Description

Technical Field

[0001] This utility model relates to the development of solar energy and industrial waste heat utilization, specifically to a buried coaxial sleeve high-efficiency phase change energy storage device. Background Technology

[0002] To address the intermittency of solar energy, short-term or inter-seasonal energy storage devices are often used to achieve long-term heating. Phase change thermal energy storage technology stores solar energy and other high-temperature waste heat in a storage medium. During rain or snowfall, the heat is released for heating through a phase change in the storage medium. For users with large energy demands, a large space is often required to accommodate the thermal storage device. Even when placed outdoors, it still requires a certain amount of land, thus affecting the widespread application of solar energy technology to some extent. Utility Model Content

[0003] In view of the shortcomings of existing solar energy and thermal storage electric boiler energy supply technologies, this utility model provides a buried coaxial sleeve high-efficiency phase change energy storage device. This device not only overcomes the problem of traditional thermal storage devices occupying space, but also improves the heat preservation effect of the device after being placed underground.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A buried coaxial sleeve high-efficiency phase change energy storage device includes a solar collector, a heat exchanger, a user-side unit, an energy storage well, and a buried energy storage device.

[0006] The buried energy storage device includes an outer pipe and an insulated inner pipe installed coaxially inside an energy storage well. The annular space formed between the outer pipe and the energy storage well is filled with insulating backfill material. The bottom end of the outer pipe is sealed by welding carbon steel plate, and the top is open. The top of the insulated inner pipe is open, the bottom end is closed and the bottom end contacts the bottom surface of the outer pipe. Two symmetrically distributed slots are provided on the bottom side wall of the insulated inner pipe. An energy storage rod array consisting of multiple energy storage rods is installed inside the insulated inner pipe, and all energy storage rods are in contact with the bottom surface of the insulated inner pipe. An outer pipe insulation cover plate is provided at the upper opening of the outer pipe, and an inner pipe insulation cover plate is provided at the upper opening of the insulated inner pipe. The outer pipe insulation cover plate and the inner pipe insulation cover plate are respectively provided with the outer pipe inlet / outlet and the inner pipe inlet / outlet, and the inner pipe inlet / outlet coaxially extends out of the outer pipe inlet / outlet.

[0007] The inner pipe inlet and outlet are connected to the solar collector via the primary side outlet pipe of the solar collector, and also to the heat exchanger via the primary side outlet pipe of the heat exchanger; the outer pipe inlet / outlet is connected to the solar collector via the primary side inlet pipe of the solar collector, and also to the heat exchanger via the primary side inlet pipe of the heat exchanger; the user side is connected to the heat exchanger via the secondary side outlet pipe and the secondary side inlet pipe of the heat exchanger, and also to the solar collector via the secondary side outlet pipe and the secondary side inlet pipe of the solar collector.

[0008] The primary side outlet pipe and the primary side inlet pipe of the solar collector are respectively equipped with a primary side outlet control valve and a primary side inlet control valve; the primary side outlet pipe and the primary side inlet pipe of the heat exchanger are respectively equipped with a primary side outlet control valve and a primary side inlet control valve; the secondary side outlet pipe and the secondary side inlet pipe of the heat exchanger are respectively equipped with a user side inlet control valve and a user side outlet control valve; the secondary side outlet pipe and the secondary side inlet pipe of the solar collector are respectively equipped with a secondary side outlet control valve and a secondary side inlet control valve.

[0009] A collector-side variable frequency circulating pump is installed on the primary side water inlet pipe of the solar collector, a source-side variable frequency circulating pump is installed on the primary side water inlet pipe of the heat exchanger, and a user-side variable frequency circulating pump is installed on the secondary side water inlet pipe of the heat exchanger.

[0010] Furthermore, the slot is rectangular in shape, with a height of 1 / 10 of the height of the inner insulation tube and a side length of 1 / 4 of the inner diameter circumference of the inner insulation tube.

[0011] Furthermore, the top and bottom ends of the heat-insulating inner tube are respectively fixedly connected to the upper and lower ends of the energy storage rod array by a fixing device.

[0012] Furthermore, the fixture is a frame made of stainless steel, which consists of at least 10 rods. One end of each rod is fixed to the center of the same circle, and the other ends are evenly distributed around the circumference of the circle. Each rod has multiple fixing rings equidistantly arranged along its length, and a fixing ring is also arranged at the center of the circle. The fixing rings at corresponding positions on all rods form a ring. The inner diameter of the fixing ring matches the outer diameter of the energy storage rod. The fixing rings at the top and bottom of the fixture are in a one-to-one correspondence.

[0013] Furthermore, the surface of the inner insulated tube is coated with an aerogel heat-insulating coating, and the inner and outer walls have anti-corrosion layers.

[0014] Furthermore, the energy storage rod is a tube with raised longitudinal metal fins of rectangular cross-section on its outer wall. The upper and lower ports are sealed, and both the inner and outer walls have anti-corrosion layers. The interior is filled with phase change material.

[0015] Furthermore, the energy storage rod has multiple rings of highly thermally conductive longitudinal rectangular metal ribs equidistantly arranged along the axial direction on the middle sidewall, each ring including multiple highly thermally conductive longitudinal rectangular metal ribs evenly distributed along the circumference.

[0016] Furthermore, the number of highly thermally conductive longitudinal rectangular metal fins distributed in each ring is 10 to 12.

[0017] Furthermore, the height of the high thermal conductivity longitudinal rectangular metal rib is 2~4mm, and the thickness of the rib should preferably be 1 / 4 of the height.

[0018] Furthermore, the outer surface of the outer tube insulation cover is wrapped with a polyurethane insulation material layer, and the outer surface of the inner tube insulation cover is sprayed with an aerogel heat insulation coating layer.

[0019] The beneficial effects of this utility model are as follows: Compared with the conventional phase change thermal storage devices currently used, this utility model not only overcomes the problem of the traditional hot water storage tank occupying space, but also avoids heat loss caused by natural convection with air by burying it underground. It also further reduces the increase in construction costs caused by the insulation of the thermal storage device. In addition, under the same volume, the thermal storage device with the coaxial sleeve heat exchange structure has a larger heat exchange area than the cubic thermal storage device, which is conducive to the phase change material in the energy storage rod absorbing or releasing heat more easily. Moreover, the high thermal conductivity longitudinal rectangular metal fins arranged on the outer wall of the energy storage rod can further enhance the convective heat exchange with the fluid, thereby improving the overall energy storage efficiency of the phase change energy storage device. Attached Figure Description

[0020] To more clearly illustrate the embodiments of this utility model patent, the accompanying drawings will be briefly described below.

[0021] Figure 1 This is a structural cross-section of the underground coaxial sleeve high-efficiency phase change energy storage device of this utility model and a schematic diagram of its system connection.

[0022] Figure 2 This is a structural diagram of the underground coaxial sleeve high-efficiency phase change energy storage device of this utility model.

[0023] Figure 3 This is a structural diagram of the thermal insulation inner tube.

[0024] Figure 4 This is a top view of the insulated inner tube.

[0025] Legend:

[0026] 1. Solar collector; 2. Secondary side outlet pipe of solar collector; 3. Secondary side inlet pipe of solar collector; 4. Secondary side inlet control valve of solar collector; 5. Secondary side outlet control valve of solar collector; 6. User-side variable frequency circulating pump; 7. User-side outlet control valve; 8. User side; 9. User-side inlet control valve; 10. Secondary side outlet pipe of heat exchanger; 11. Secondary side inlet pipe of heat exchanger; 12. Heat exchanger; 13. Primary side inlet control valve of heat exchanger; 14. Primary side outlet control valve of heat exchanger; 15. Primary side inlet pipe of solar collector; 16. 17. Solar collector primary side water inlet control valve; 18. Solar collector primary side water outlet control valve; 19. Solar collector primary side water outlet pipe; 20. Heat exchanger primary side water inlet pipe; 21. Heat exchanger primary side water outlet pipe; 22. Inner pipe inlet; 23. Outer pipe outlet; 24. Soil; 25. Insulating backfill material; 26. Outer pipe; 27. Insulated inner pipe; 28. High thermal conductivity longitudinal rectangular metal ribs; 29. ​​Energy storage rod; 30. Fixing device; 31. Energy storage well; 32. Outer pipe insulation cover plate; 33. Inner pipe insulation cover plate; 34. Source side variable frequency circulation pump; 35. Collector side variable frequency circulation pump. Detailed Implementation

[0027] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments.

[0028] like Figure 1 As shown, this utility model provides a buried coaxial sleeve high-efficiency phase change energy storage device, including a solar collector 1, a heat exchanger 12, a user side 8, an energy storage well 30, and a buried energy storage device.

[0029] Preferably, the energy storage well 30 adopts a large-diameter borehole with a diameter of 1.20~1.60m and a depth of 5~10m.

[0030] The buried energy storage device includes an outer pipe 25 and an insulated inner pipe 26 installed coaxially within an energy storage well 30. The annular space formed between the outer pipe 25 and the energy storage well 30 is filled with insulating backfill material 24. The bottom end of the outer pipe 25 is sealed by welding with carbon steel plate, and the top is open. The top of the insulated inner pipe 26 is open, the bottom end is closed and the bottom end contacts the inner bottom surface of the outer pipe 25. Two symmetrically distributed slots are provided on the bottom side wall of the insulated inner pipe 26. Preferably, the slots are rectangular in shape, with a height of 1 / 10 of the height of the insulated inner pipe 26 and a side length of 1 / 4 of the inner diameter circumference of the insulated inner pipe 26. The design of the slots here is to ensure that the fluid flows out through the bottom of the inner insulated tube 26 and then enters the annular space formed by the outer tube 25 and the inner insulated tube 26 through the two slots and then flows out. The inner insulated tube 26 is equipped with an array of energy storage rods consisting of multiple energy storage rods 28, and all energy storage rods 28 are in contact with the bottom surface of the inner insulated tube 26. The upper opening of the outer tube 25 is covered with an outer tube insulation cover plate 31, and the upper opening of the inner insulated tube 26 is covered with an inner tube insulation cover plate 32. It is preferred to install them by welding. The outer tube insulation cover plate 31 and the inner tube insulation cover plate 32 are respectively provided with an outer tube inlet / outlet 22 and an inner tube inlet / outlet 21, and the inner tube inlet / outlet 21 coaxially passes through the outer tube inlet / outlet 22.

[0031] The inner pipe inlet / outlet 21 is connected to the solar collector 1 via the primary side outlet pipe 18 of the solar collector, and is also connected to the heat exchanger 12 via the primary side outlet pipe 20 of the heat exchanger; the outer pipe inlet / outlet 22 is connected to the solar collector 1 via the primary side inlet pipe 15 of the solar collector, and is also connected to the heat exchanger 12 via the primary side inlet pipe 19 of the heat exchanger; the user side 8 is connected to the heat exchanger 12 via the secondary side outlet pipe 10 and the secondary side inlet pipe 11 of the heat exchanger, and is connected to the solar collector 1 via the secondary side outlet pipe 2 and the secondary side inlet pipe 3 of the solar collector;

[0032] A primary-side water outlet pipe 18 and a primary-side water inlet pipe 15 of the solar collector are respectively equipped with a primary-side water outlet control valve 17 and a primary-side water inlet control valve 16; a primary-side water outlet pipe 20 and a primary-side water inlet pipe 19 of the heat exchanger are respectively equipped with a primary-side water outlet control valve 14 and a primary-side water inlet control valve 13; a secondary-side water outlet pipe 10 and a secondary-side water inlet pipe 11 of the heat exchanger are respectively equipped with a user-side water inlet control valve 9 and a user-side water outlet control valve 7; a secondary-side water outlet pipe 2 and a secondary-side water inlet pipe 3 of the solar collector are respectively equipped with a secondary-side water outlet control valve 5 and a secondary-side water inlet control valve 4.

[0033] A collector-side variable frequency circulating pump 34 is installed on the primary side water inlet pipe 15 of the solar collector, an active-side variable frequency circulating pump 33 is installed on the primary side water inlet pipe 19 of the heat exchanger, and a user-side variable frequency circulating pump 6 is installed on the secondary side water inlet pipe 11 of the heat exchanger.

[0034] Preferably, the top and bottom ends of the heat-insulating inner tube 26 are fixedly connected to the upper and lower ends of the energy storage rod array by a fixture 29.

[0035] Preferably, the thermal insulation backfill material 24 is composed of inexpensive materials with low thermal conductivity such as bentonite, loess, and clay.

[0036] Preferably, the inner insulated pipe 26 is made of carbon steel pipe or polyethylene pipe as the base material, the pipe surface is sprayed with aerogel heat insulation coating, and the inner and outer walls are treated with anti-corrosion.

[0037] Preferably, the energy storage rod 28 is a tube integrally formed from a high thermal conductivity metal material such as carbon steel or alloy steel. The outer wall of the energy storage rod 28 is covered with raised longitudinal metal fins with a rectangular cross-section. The upper and lower ends are sealed, and the inner and outer walls are treated with anti-corrosion coating. The interior is filled with a phase change material, which can be an inorganic phase change material, an organic phase change material, or a mixture thereof. Preferably, there are 28 energy storage rods 28.

[0038] Preferably, multiple rings of highly thermally conductive longitudinal rectangular metal fins 27 are equidistantly arranged along the axial direction on the middle sidewall of the energy storage rod 28. Each ring includes 10-12 highly thermally conductive longitudinal rectangular metal fins 27 evenly distributed circumferentially. The fin height is 2-4 mm, and the fin thickness is preferably 1 / 4 of the height. This design can enhance the convective heat transfer intensity between the circulating fluid and the outer wall of the energy storage rod 28, promote the heat absorption / release rate of the phase change material inside the energy storage rod 28, and improve the overall heat exchange efficiency of the device of this invention.

[0039] Preferably, the fixture 29 is a frame integrally formed from stainless steel. This frame consists of at least 10 rods, with one end of each rod fixed to the center of a circle and the other ends evenly distributed around the circumference of that circle. Each rod has multiple (preferably 4) fixing rings equidistantly spaced along its length, and a fixing ring is also located at the center of the circle. All the fixing rings at corresponding positions on the rods form a ring. The inner diameter of the fixing ring matches the outer diameter of the energy storage rod 28. The fixing ring is used to insert one end of the energy storage rod, thereby defining the position of the energy storage rod 28 within the insulation inner tube 26. Two fixtures 29 are respectively fixed by welding to the top of the insulation inner tube 26 and at a height of 1 / 10 from the bottom of the insulation inner tube 26, ensuring that the fixing rings of the top and bottom fixtures 29 correspond one-to-one.

[0040] Preferably, both the outer tube insulation cover plate 31 and the inner tube insulation cover plate 32 are integrally formed from stainless steel. The outer tube insulation cover plate 31 is wrapped with a polyurethane insulation material layer, and the outer tube insulation cover plate 32 is sprayed with an aerogel heat insulation coating layer.

[0041] The implementation steps of this utility model are as follows: The energy storage well 30 is constructed using manual excavation or mechanical drilling, with a well diameter of 1.20-1.60m and a well depth of 5-10m. Then, an outer pipe 25 is lowered into the energy storage well 30, and the annular space formed by the energy storage well 30 and the outer pipe 25 is filled with insulating backfill material 24. The inner insulated pipe 26 is installed centrally inside the outer pipe 25, and the energy storage rods 28 are installed sequentially according to the pre-set fixing rings of the fixing device 29, ensuring that each energy storage rod 28 extends to the bottom of the phase change energy storage device. After all the energy storage rods 28 are installed in their preset positions, the inner pipe insulation cover plate 32 and the outer pipe insulation cover plate 31 are installed sequentially by welding. Finally, the inner pipe inlet 21 and the outer pipe outlet 22 are connected to the heating pipeline.

[0042] This utility model's underground coaxial sleeve high-efficiency phase change energy storage device has two working modes: heat storage mode and heat release mode.

[0043] Thermal storage mode: During the thermal storage process, the inner pipe inlet 21 and outer pipe outlet 22 are connected to the solar collector 1 through the primary side outlet pipe 18 and primary side inlet pipe 15 of the solar collector. Control valves 16 and 17 and the collector-side variable frequency circulation pump 34 are opened, while the remaining control valves and circulation pumps are closed. The collector-side variable frequency circulation pump 34 draws cooler water from the buried coaxial sleeve high-efficiency phase change energy storage device and delivers it to the solar collector 1 for heating. After heating, the hot water is delivered to the insulated inner pipe 26, where the phase change material in the energy storage rod 28 absorbs heat from the fluid through convection heat transfer, completing the phase change. This cycle repeats until thermal storage is completed. The cooled fluid is pumped to the ground through the annular space between the insulated inner pipe 26 and the outer pipe 25 and returns to the solar collector 1 for further heating. This cycle repeats to achieve heat storage.

[0044] Heat release mode: During the heat release process, the inner pipe inlet 21 and outer pipe outlet 22 are connected to the heat exchanger 12 via the primary side outlet pipe 20 and primary side inlet pipe 19 of the heat exchanger. Control valves 7, 9, 13, and 14 are opened, as are the source-side variable frequency circulation pump 33 and the user-side variable frequency circulation pump 6. The remaining control valves and circulation pumps are closed. During the heat release process, the low-temperature fluid flows into the annular area formed by the outer pipe 26 and the insulated inner pipe 26, reaches the bottom of the energy storage device, flows out through the insulated inner pipe 26, and returns to the ground. During the outflow process, the low-temperature fluid absorbs heat from the energy storage rod, raising the fluid temperature. Then, it enters the heat exchanger 12 through the heating pipe for heat exchange, providing heat to the user side. This cycle repeats to release heat.

[0045] The above description is only a part of the specific embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model.

[0046] Compared with conventional phase change thermal energy storage devices currently in use, this invention not only overcomes the problem of the traditional hot water storage tank's floor space, but also avoids heat loss due to natural convection with the air by burying it underground. This further reduces the increase in construction costs caused by insulation of the thermal energy storage device. In addition, for the same volume, the thermal energy storage device with a coaxial sleeve heat exchange structure has a larger heat exchange area than the cubic thermal energy storage device, which makes it easier for the phase change material in the energy storage rod to absorb or release heat. Moreover, the high thermal conductivity longitudinal metal fins arranged on the outer wall of the energy storage rod can further enhance the convective heat transfer with the fluid, thereby improving the overall energy storage efficiency of the phase change energy storage device.

Claims

1. A buried coaxial sleeve high-efficiency phase change energy storage device, comprising a solar collector (1), a heat exchanger (12), and a user side (8), characterized in that, It also includes energy storage wells (30) and underground energy storage devices; The buried energy storage device includes an outer pipe (25) and an insulated inner pipe (26) installed coaxially within an energy storage well (30). The annular space formed between the outer pipe (25) and the energy storage well (30) is filled with insulating backfill material (24). The bottom end of the outer pipe (25) is sealed by welding with carbon steel plate, and the top is open. The top of the insulated inner pipe (26) is open, the bottom end is closed and the bottom end contacts the bottom surface of the outer pipe (25). Two symmetrically distributed slots are provided on the bottom side wall of the insulated inner pipe (26). The unit is equipped with an array of energy storage rods (28) and all energy storage rods (28) are in contact with the bottom surface of the inner insulated tube (26); the upper opening of the outer tube (25) is covered with an outer tube insulation cover plate (31) and the upper opening of the inner insulated tube (26) is covered with an inner tube insulation cover plate (32). The outer tube insulation cover plate (31) and the inner tube insulation cover plate (32) are respectively provided with an outer tube inlet / outlet (22) and an inner tube inlet / outlet (21), and the inner tube inlet / outlet (21) coaxially passes through the outer tube inlet / outlet (22); The inner pipe inlet / outlet (21) is connected to the solar collector (1) through the primary side outlet pipe (18) of the solar collector, and is also connected to the heat exchanger (12) through the primary side outlet pipe (20) of the heat exchanger; the outer pipe inlet / outlet (22) is connected to the solar collector (1) through the primary side inlet pipe (15) of the solar collector, and is also connected to the heat exchanger (12) through the primary side inlet pipe (19) of the heat exchanger; the user side (8) is connected to the heat exchanger (12) through the secondary side outlet pipe (10) and the secondary side inlet pipe (11) of the heat exchanger, and is also connected to the solar collector (1) through the secondary side outlet pipe (2) and the secondary side inlet pipe (3) of the solar collector; A primary side outlet water pipe (18) and a primary side inlet water pipe (15) of the solar collector are respectively equipped with a primary side outlet water control valve (17) and a primary side inlet water control valve (16); a primary side outlet water pipe (20) and a primary side inlet water pipe (19) of the heat exchanger are respectively equipped with a primary side outlet water control valve (14) and a primary side inlet water control valve (13); a secondary side outlet water pipe (10) and a secondary side inlet water pipe (11) of the heat exchanger are respectively equipped with a user side inlet water control valve (9) and a user side outlet water control valve (7); a secondary side outlet water pipe (2) and a secondary side inlet water pipe (3) of the solar collector are respectively equipped with a secondary side outlet water control valve (5) and a secondary side inlet water control valve (4); A collector-side variable frequency circulating pump (34) is installed on the primary side water inlet pipe (15) of the solar collector, a source-side variable frequency circulating pump (33) is installed on the primary side water inlet pipe (19) of the heat exchanger, and a user-side variable frequency circulating pump (6) is installed on the secondary side water inlet pipe (11) of the heat exchanger.

2. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The slot is rectangular in shape, with a height of 1 / 10 of the height of the inner insulation tube (26) and a side length of 1 / 4 of the inner diameter circumference of the inner insulation tube (26).

3. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The top and bottom ends of the heat-insulating inner tube (26) are fixedly connected to the upper and lower ends of the energy storage rod array by a fixture (29).

4. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 3, characterized in that, The fixture (29) is a frame made of stainless steel metal material. The frame is composed of at least 10 rods. One end of all the rods is fixed to the center of the same circle, and the other end is evenly distributed on the circumference of the circle. Each rod has multiple fixing rings equidistantly arranged along its length, and a fixing ring is also arranged at the center of the circle. The fixing rings at the corresponding positions of all the rods form a ring. The inner diameter of the fixing ring matches the outer diameter of the energy storage rod (28). The fixing rings at the top and bottom of the fixture (29) are in one-to-one correspondence.

5. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The surface of the inner insulated tube (26) is coated with aerogel heat insulation coating, and the inner and outer walls have anti-corrosion layers.

6. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The energy storage rod (28) is a tube with raised longitudinal metal fins of rectangular cross-section on its outer wall. The upper and lower ports are sealed, and both the inner and outer walls have anti-corrosion layers. The interior is filled with phase change material.

7. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The energy storage rod (28) has multiple rings of high thermal conductivity longitudinal rectangular metal ribs (27) evenly spaced along the axial direction on the middle side wall. Each ring includes multiple high thermal conductivity longitudinal rectangular metal ribs (27) evenly distributed along the circumference.

8. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The number of high thermal conductivity longitudinal rectangular metal fins (27) distributed in each ring is 10~12.

9. The underground coaxial bushing high-efficiency phase change energy storage device as described in claim 7 or 8, characterized in that, The height of the high thermal conductivity longitudinal rectangular metal rib (27) is 2~4mm, and the thickness of the rib should be 1 / 4 of the height.

10. The underground coaxial sleeve high-efficiency phase change energy storage device as described in claim 1, characterized in that, The outer surface of the outer tube insulation cover (31) is covered with a polyurethane insulation material layer, and the outer surface of the inner tube insulation cover (32) is sprayed with an aerogel heat insulation coating layer.

Images