Vertical deeply-buried casing pipe for extracting terrestrial heat

Abstract

The utility model discloses a vertical deeply-buried casing pipe for extracting terrestrial heat. The casing pipe adopts a heat preservation steel pipe as an upper inner pipe and a PE pipe as a lower inner pipe. The metal wire rope is combined with the positioning cross rod to fix the upper inner pipe, and the inner threads of the upper inner pipe and the outer threads of the lower inner pipe are in threaded connection, so that different inner pipe materials are effectively connected. By means of the design, performance superiority of the system in the efficient heat exchange process is guaranteed, cost is effectively controlled, and excellent stability and sealing performance are achieved. The system is suitable for various geothermal energy utilization scenes, the combination of the heat preservation steel pipe and the PE pipe is adopted, energy loss can be reduced, the energy utilization efficiency is improved, and therefore the system has remarkable advantages in the aspects of energy conservation and environmental protection and has wide application prospects.

Description

Technical Field

[0001] This utility model belongs to the field of geothermal energy utilization technology, specifically relating to a vertically buried sleeve for extracting geothermal energy. Background Technology

[0002] With the increasing global energy consumption and the resulting climate change, the utilization of renewable energy has become crucial for the transformation of the global energy structure. Geothermal energy, as an important non-carbon-based energy source, is one of the key energy categories attracting attention from the new energy industry and scholars. Traditional ground source heat pump systems typically utilize energy within 300 meters underground, using soil and rock layers as heat storage to achieve building heating or cooling. As requirements for geothermal utilization conditions, such as land area and heat quality, have increased, increasing the depth of heat exchangers and extracting high-grade medium-deep geothermal energy has become a development focus in recent years.

[0003] Closed-loop heat extraction using deeply buried pipes is an important form of utilizing medium-deep geothermal energy, with advantages including cleanliness, environmental friendliness, and no disturbance to groundwater aquifers. Common forms of deep-buried pipe utilization include deep-buried sleeve pipes and deep-buried U-shaped pipes. In deep-buried sleeve pipes, the inner pipe, or central pipe, plays a guiding role in the entire heat exchange process. The heat transfer performance of the inner pipe affects the overall heat exchange characteristics of the buried pipe. If the heat transfer of the inner pipe is too high, it will lead to a decrease in the outlet water temperature, i.e., a decrease in heat exchange efficiency. However, if a lower heat transfer capacity is required for the inner pipe, its material cost will inevitably increase. This is an important issue that current research has not yet fully considered.

[0004] In practical engineering, the inner pipes of deeply buried pipe sleeves mainly fall into two categories: insulated steel pipes and PE pipes. Numerical studies have shown that when using insulated steel pipes with better insulation performance as the inner pipe, the heat transfer intensity of the buried pipe under different inlet water temperatures is approximately 16% higher than that of PE pipes. This demonstrates the significant role of insulated steel pipes in improving the heat transfer performance of deeply buried pipe sleeves. However, in terms of price, insulated steel pipes are approximately 4 to 5 times more expensive than PE pipes, which cost around 20 yuan per meter, while insulated steel pipes cost as much as 80 to 100 yuan per meter. Therefore, controlling costs while ensuring heat transfer efficiency is a pressing issue that needs to be addressed. Utility Model Content

[0005] This invention is based on the inventor's discovery and understanding of the following facts and problems: the use of PE pipes for the inner pipe of existing deep-buried casings leads to a reduction in heat exchange efficiency, while the use of insulated steel pipes leads to high costs.

[0006] This utility model aims to at least partially solve one of the technical problems in related technologies. To this end, this utility model proposes a vertically buried sleeve for geothermal extraction. By adjusting the inner pipe structure and optimizing the selection of the inner pipe material and connection method, it solves the problem of low heat exchange efficiency in existing buried pipe technologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This utility model proposes a vertically buried casing for geothermal extraction, comprising an outer pipe and an inner pipe. The bottom end of the outer pipe is closed, and the inner pipe is radially coaxial with the outer pipe, with the bottom end of the inner pipe being separate from the bottom end of the outer pipe, forming a circulating water channel at the bottom of the casing. The inner pipe comprises an upper inner pipe and a lower inner pipe, which are connected by threads or by snap-fit. The upper inner pipe is an insulated pipe.

[0009] The outer pipe serves as a channel for circulating water to flow in. The low-temperature circulating water is heated by exchanging heat with the surrounding high-temperature rock and soil, thereby achieving the purpose of geothermal extraction.

[0010] The upper inner pipe is made of insulated pipe, preferably insulated steel pipe. Its function is to work together with the lower inner pipe to guide the high-temperature circulating water obtained from the heat exchange of the outer pipe to the ground heating system.

[0011] The lower inner pipe is a PE pipe, which works together with the upper inner pipe to guide the high-temperature circulating water obtained from the heat exchange of the outer pipe to the ground heating system. The PE pipe can be supported by the buoyancy of the water, so there is no need to provide additional support for the inner pipe.

[0012] The vertically buried casing is placed inside a vertical deep well and fixed in the soil and rock by cementing. The burial depth of the bottom end of the outer casing is set at 1500~3500m. Cementing is used to fix the outer casing, ensuring that the outer casing will not undergo large deformation and displacement, while ensuring that groundwater in the soil and rock will not cross layers.

[0013] A traction rope is installed at the top of the deep well. One end of the traction rope is connected to the top of the upper inner tube, and the other end is connected to any fixed device outside the upper inner tube.

[0014] A positioning crossbar is provided between the wall of the upper inner tube and the wall of the outer tube, and the positioning crossbar is located in the diametrical direction of the upper inner tube and the outer tube. The upper inner tube and the outer tube abut against each other through the positioning crossbar to maintain the stability of the position between the inner tube and the outer tube.

[0015] There are multiple ways to connect the upper inner tube and the lower inner tube, such as threaded connection or snap-fit ​​connection, to ensure the overall stability and sealing of the system;

[0016] Preferably, a threaded connection is used to ensure good sealing and durability of the connection between the upper and lower inner tubes.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The vertical deep-buried sleeve disclosed in this utility model effectively reduces the heat dissipation of shallow near-surface layers and improves the overall heat exchange efficiency by setting an insulated pipe as the upper inner pipe in the near-surface section. Compared with using an insulated pipe throughout the entire section, only the near-surface section uses an insulated pipe, which reduces the production cost of the sleeve while still minimizing the loss of heat exchange efficiency, thus achieving high-efficiency heat exchange of the buried pipe.

[0019] The vertical deep-buried sleeve disclosed in this utility model has high stability and sealing performance. The upper inner tube is fixed by metal wire rope and positioning crossbar. The upper inner tube and the lower inner tube are connected by internal and external threads to ensure that the system has good stability and sealing performance during operation and avoid leakage and displacement problems. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the vertical deeply buried sleeve of this utility model;

[0021] Figure 2 This is a schematic diagram of the cross-section of the vertically buried sleeve of this utility model;

[0022] Figure 3 This utility model Figure 1 A magnified view of a portion of the upper inner tube A;

[0023] Figure 4 This utility model Figure 1 A magnified view of a portion of the connection point B between the upper and lower inner tubes;

[0024] Figure 5 This is a schematic diagram showing the connection between the upper inner tube and the lower inner tube of this utility model via a snap fastener.

[0025] The components include an outer pipe 1, an inner pipe 2, an upper inner pipe 21, a lower inner pipe 22, cementing cement 4, soil and rock 5, a metal wire rope 6, a positioning crossbar 7, an inner thread of the upper inner pipe 8, an outer thread of the lower inner pipe 9, an inner concave annular groove 211 of the upper inner pipe, and an outer convex ring 221 of the lower inner pipe. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. The description is for explanation and not limitation of the present invention.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings:

[0028] like Figure 1 and Figure 2 As shown, the vertical deep-buried casing for geothermal extraction includes an outer pipe 1 and an inner pipe 2. The bottom end of the outer pipe 1 is closed, and the inner pipe 2 is coaxial with the outer pipe 1 in the length direction. The bottom end of the inner pipe 2 is separate from the bottom end of the outer pipe 1, connecting the inner cavity of the outer pipe and the inner cavity of the inner pipe, forming a circulating water channel at the bottom of the casing.

[0029] like Figure 1 As shown, the inner tube 2 includes an upper inner tube 21 and a lower inner tube 22. The upper inner tube 21 is connected to the lower inner tube 22, and the upper inner tube 21 is configured as an insulation tube.

[0030] like Figure 3 As shown, the inner tube 2 and the outer tube 1 are abutted by a positioning crossbar 7 in the diameter direction to maintain a relatively stable position. The top of the inner tube 2 is equipped with a traction device metal wire rope 6, the other end of which is connected to any fixed device outside the vertically buried sleeve to maintain the height stability of the inner tube 2.

[0031] When using vertically buried casings, the burial depth is 1500~3500m depending on the actual working conditions. They are installed in the soil and rock 5 and fixed by cementing cement 4.

[0032] like Figure 3 As shown, the positioning device A of the upper inner tube 21 includes a metal wire rope 6 and a positioning crossbar 7.

[0033] like Figure 4 As shown, the connecting device B between the upper inner tube 21 and the lower inner tube 22 includes an internal thread 8 in the upper inner tube and an external thread 9 in the lower inner tube.

[0034] The outer pipe 1 is made of petroleum steel, which can fully utilize its excellent thermal conductivity while ensuring strength, and exchange heat with the rock and soil.

[0035] The upper inner tube 21 is fixed by a metal wire rope 6 and a positioning crossbar 7 to prevent it from shifting during operation.

[0036] The upper inner pipe 21 uses a heat-insulating steel pipe with good thermal insulation performance to ensure that the heat dissipation in the shallow near-surface area is low, thereby reducing the heat loss of water in the near-surface area after geothermal heating and improving heat exchange efficiency.

[0037] The lower inner pipe 22 uses a low-cost PE pipe, which is supported by the buoyancy of water and does not require an additional support structure. This effectively reduces the system cost from both the cost of the pipe itself and the fact that no additional support structure is needed.

[0038] The upper inner tube 21 and the lower inner tube 22 are connected by the inner thread 8 of the upper inner tube and the outer thread 9 of the lower inner tube, ensuring the sealing and stability of the connection.

[0039] The geothermal vertical deep-buried sleeve proposed in this utility model has the following heat exchange process:

[0040] (1) Low-temperature circulating water flows into the outer pipe 1. The low-temperature water flows downward along the annular cross section of the outer pipe 1 and exchanges heat with the surrounding rock and soil 5 along the way, continuously exchanging heat and raising the temperature. The temperature at the bottom of the outer pipe 1 reaches the highest.

[0041] (2) The high-temperature circulating water after heat exchange in the outer tube 1 is transferred to the inner tube 2 at the bottom of the outer tube 1. The inner tube 2 plays a guiding role. When the circulating water flows into the lower inner tube 22, the temperature is relatively high. Therefore, the circulating water will exchange heat with the circulating water in the outer tube at the same depth, resulting in heat loss. The closer to the top of the inner tube, the more serious the heat loss.

[0042] (3) Based on the analysis of the buried pipe depth, the shallower the depth, the greater the temperature difference between the circulating water in the inner pipe 2 and the outer pipe 1, and vice versa. Therefore, in the shallow area with a large temperature difference, i.e. the upper inner pipe 21, heat-insulated steel pipes are used to effectively avoid heat exchange loss caused by the large temperature difference. In the deep area with a small temperature difference, i.e. the lower inner pipe 22, PE pipes are used to effectively avoid the high cost when using too high a proportion of heat-insulated steel pipes.

[0043] (4) In practical applications, the lengths of the upper inner pipe 21 and the lower inner pipe 22 can be adjusted according to different geothermal energy utilization needs. For example, for areas with high heat demand, the length of the insulated steel pipe can be increased to further improve heat exchange efficiency.

[0044] Example 1

[0045] The vertical buried casing includes an outer pipe 1 and an inner pipe 2. The bottom end of the outer pipe 1 is closed, and the inner pipe 2 is coaxial with the outer pipe 1 in the length direction. The bottom end of the inner pipe 2 is separate from the bottom end of the outer pipe 1, forming a circulating water channel at the bottom of the casing.

[0046] The inner tube 2 includes an upper inner tube 21 and a lower inner tube 22, which are connected. The upper inner tube 21 is configured as an insulated steel pipe. The connecting device B between the upper inner tube 21 and the lower inner tube 22 includes an internal thread 8 in the upper inner tube and an external thread 9 in the lower inner tube.

[0047] The inner tube 2 and the outer tube 1 are abutted by a positioning crossbar 7 in the diameter direction to maintain a relatively stable position. The top of the inner tube 2 is equipped with a traction device metal wire rope 6, the other end of which is connected to any fixed device outside the vertically buried sleeve to maintain the height stability of the inner tube 2.

[0048] Based on the actual working conditions, the burial depth is 2539m, and it is set in the soil and rock 5 and fixed by cementing cement 4.

[0049] The inner pipe 2 uses a 200m insulated steel pipe as the upper inner pipe 21 and a 2300m PE pipe as the lower inner pipe 22.

[0050] Example 2

[0051] The vertical buried sleeve includes an outer pipe 1 and an inner pipe 2. The bottom end of the outer pipe 1 is closed, and the inner pipe 2 is coaxial with the outer pipe 1 in the length direction. The bottom end of the inner pipe 2 is separate from the bottom end of the outer pipe 1, connecting the interior of the outer pipe 2 and the inner pipe 1 to form a circulating water channel.

[0052] The inner pipe 2 includes an upper inner pipe 21 and a lower inner pipe 22, which are connected. The upper inner pipe 21 is configured as an insulated steel pipe. The connecting device B between the upper inner pipe 21 and the lower inner pipe 22 includes a concave annular groove 211 in the upper inner pipe 21 and a convex annular groove 221 in the lower inner pipe, with a longitudinal section as shown in Figure 22. Figure 5 As shown.

[0053] The inner tube 2 and the outer tube 1 are abutted by a positioning crossbar 7 in the diameter direction to maintain a relatively stable position. The top of the inner tube 2 is equipped with a traction device metal wire rope 6, the other end of which is connected to any fixed device outside the vertically buried sleeve to maintain the height stability of the inner tube 2.

[0054] Based on the actual working conditions, the burial depth is 3439m, and it is set in the soil and rock 5 and fixed by cementing cement 4.

[0055] The inner pipe 2 uses a 350m insulated steel pipe as the upper inner pipe 21 and a 3050m PE pipe as the lower inner pipe 22.

[0056] Comparative Example 1

[0057] The vertical buried casing includes an outer pipe 1 and an inner pipe 2. The bottom end of the outer pipe 1 is closed, and the inner pipe 2 is coaxial with the outer pipe 1 in the length direction. The bottom end of the inner pipe 2 is separate from the bottom end of the outer pipe 1, forming a circulating water channel at the bottom of the casing that connects the outer pipe and the interior of the inner pipe.

[0058] The inner pipe 2 is made of insulated steel pipe. The inner pipe 2 and the outer pipe 1 are supported by a positioning crossbar 7 in the diameter direction to maintain a relatively stable position. The top of the inner pipe 2 is equipped with a traction device metal wire rope 6, the other end of which is connected to any fixed device outside the vertically buried sleeve to maintain the height stability of the inner pipe 2.

[0059] Based on the actual working conditions, the burial depth is 2539m, and it is installed in the soil and rock 5 and fixed by cement 4. The inner pipe 2 is a 2500m long PE pipe.

[0060] Comparative Example 2

[0061] The vertical buried casing includes an outer pipe 1 and an inner pipe 2. The bottom end of the outer pipe 1 is closed, and the inner pipe 2 is coaxial with the outer pipe 1 in the length direction. The bottom end of the inner pipe 2 is separate from the bottom end of the outer pipe 1, forming a circulating water channel at the bottom of the casing that connects the outer pipe and the interior of the inner pipe.

[0062] The inner pipe 2 is a fully insulated steel pipe. The inner pipe 2 and the outer pipe 1 are supported by a positioning crossbar 7 in the diameter direction to maintain a relatively stable position. The top of the inner pipe 2 is equipped with a traction device metal wire rope 6, the other end of which is connected to any fixed device outside the vertically buried sleeve to maintain the height stability of the inner pipe 2.

[0063] Based on the actual working conditions, the burial depth is 2539m, and it is installed in the soil and rock 5 and fixed by cement 4. The inner pipe 2 is a 2500m long insulated steel pipe.

[0064] Example of effect

[0065] When using insulated steel pipes with better thermal insulation performance as inner pipes, the heat transfer intensity of the buried pipes under different inlet water temperatures is about 16% higher than that of PE pipes. In terms of buried pipe prices, PE pipes cost about 20 yuan / meter, while insulated steel pipes cost as much as 80 to 100 yuan / meter, making the price of insulated steel pipes about 4 to 5 times that of PE pipes.

[0066] In a vertical buried casing at a depth of 2539 m, when using 200 m of insulated steel pipe as the upper inner pipe and 2300 m of PE pipe as the lower inner pipe, compared with Comparative Example 1 where the entire section is PE pipe, the proportion of insulated steel pipe increases by 8.00%, and the heat loss rate decreases from 100% to 75.65%, that is, the net reduction in heat loss rate is 24.35%. It can be seen that when using effective insulated pipe material as the inner pipe near the ground in a vertical buried casing, heat exchange loss can be significantly reduced.

[0067] In Comparative Example 2, the heat exchange capacity of the inner pipe using a fully insulated steel pipe was increased by 16% compared to that of the fully PE pipe in Comparative Example 1, but the price increased by 400%. This shows that although the insulated steel pipe significantly improves heat exchange, the price of the corresponding material also increases considerably. When the 200 m insulated steel pipe of Example 1 was used as the upper inner pipe, the heat exchange capacity was increased by 3.9% compared to the fully PE pipe, but the price only increased by 32%. This demonstrates that using effective insulated pipe materials as the inner pipe near the ground in vertical deep-buried sleeves can significantly reduce material costs while improving the efficiency of vertical deep-buried sleeves.

[0068] The above content is only for illustrating the technical concept of this utility model and should not be construed as limiting the scope of protection of this utility model. Any modifications made to the technical solution based on the technical concept proposed in this utility model shall fall within the scope of protection of the claims of this utility model.

Claims

1. A vertically buried casing for geothermal extraction, characterized in that, It includes an outer pipe (1) and an inner pipe (2) fitted inside the outer pipe (1); the bottom end of the outer pipe (1) is closed, and the bottom end of the inner pipe (2) is separate from the bottom end of the outer pipe (1), forming a circulating water channel at the bottom of the outer pipe (1); the inner pipe (2) includes an upper inner pipe (21) and a lower inner pipe (22), and the upper inner pipe (21) and the lower inner pipe (22) are connected by threads or snaps; the upper inner pipe (21) is an insulated pipe.

2. The vertically buried casing for geothermal extraction as described in claim 1, characterized in that, The upper inner tube (21) is provided with a metal wire rope (6) at the top. One end of the metal wire rope (6) is connected to the top of the upper inner tube (21), and the other end is connected to any fixed device outside the upper inner tube (21).

3. The vertically buried casing for geothermal extraction as described in claim 1, characterized in that, A positioning crossbar (7) is provided between the wall of the upper inner tube (21) and the wall of the outer tube (1), and the positioning crossbar (7) is located in the diameter direction of the upper inner tube (21) and the outer tube (1).

4. The vertically buried casing for geothermal extraction as described in claim 1, characterized in that, The lower inner tube (22) is a PE pipe.

5. The vertically buried casing for geothermal extraction as described in claim 1, characterized in that, The upper inner pipe (21) is an insulated steel pipe.

6. The vertically buried casing for geothermal extraction as described in claim 1, characterized in that, When in use, it is fixed in the rock and soil (5) by cementing (4), and the burial depth of the bottom end of the outer pipe (1) is set at 1500 ~ 3500m.

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