A high-efficiency underground heat exchanger for medium-deep geothermal wells

Abstract

The present invention relates to the technical field of geothermal systems, and specifically discloses a buried high-efficiency heat exchanger in a medium-deep geothermal well, comprising: an outer sleeve, an inner sleeve coaxially embedded in the outer sleeve, and a heat storage slow-flow unit located at the lower end of the inner sleeve; the heat storage slow-flow unit effectively separates a heat exchange flow channel and a return flow channel through a flow partition to prevent direct mixing of cold and hot fluids and avoid thermal short circuits; the spiral diverter and the slow-flow unit are used for dynamic adjustment to extend the fluid's underground residence time, enhance turbulence intensity, and improve heat exchange efficiency; the kinetic energy of the fluid is used to drive turbine blades and a rotating shaft to drive the diverter and reciprocating parts to move, and dynamic adjustment of the fluid path can be achieved without external energy; the slow-flow structure and the flexible capsule reduce the impact of the fluid on the formation and reduce reservoir disturbance; the closed-loop design avoids the extraction of groundwater and prevents pollution, and the inner sleeve insulation cavity blocks radial heat transfer and reduces heat loss in the return flow channel.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal systems, and more specifically, to a buried high-efficiency heat exchanger in a mid-deep geothermal well. Background Art

[0002] As a clean and renewable energy source, geothermal energy mostly adopts closed-loop heat exchange systems in the development of medium and deep geothermal energy, and realizes heat exchange between the heat-carrying fluid and the formation through downhole heat exchangers; however, in traditional shell-and-tube heat exchangers, there is a lack of effective fluid isolation structure between the inner and outer tubes, and the cold and hot fluids are easily mixed directly through the connection, resulting in thermal short circuit; at the same time, due to the lack of a dynamic adjustment mechanism, the fluid residence time in the well is short, the heat exchange is insufficient, and the heat extraction efficiency of a single well is lower than the theoretical value; in addition, the high-speed flow of the heat-carrying fluid has a continuous impact on the reservoir, which can easily cause formation stress imbalance, resulting in casing deformation or decreased formation permeability, and the traditional rigid slow-flow structure cannot dynamically adapt to fluid pressure fluctuations. Summary of the invention

[0003] In order to overcome the above technical problems, the present invention proposes a high-efficiency underground heat exchanger for medium-deep geothermal wells.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A high-efficiency underground heat exchanger for medium-deep geothermal wells, comprising:

[0006] An outer casing, which is buried in the underground formation and is used to conduct geothermal energy;

[0007] An inner sleeve is coaxially embedded in the outer sleeve, a heat exchange channel is formed between the inner sleeve and the outer sleeve, and a return channel for conveying a heat-carrying fluid is provided in the inner sleeve;

[0008] The heat storage slow flow unit is located at the opening of the lower end of the inner sleeve, and includes a flow partition arranged between the heat exchange flow channel and the return flow channel. The flow partition is provided with a fluid driving component on one side of the heat exchange flow channel, and the flow partition is provided with a diverter connected to the fluid driving component on one side of the return flow channel. The lower end of the outer sleeve is also provided with a slow flow component, and the flow partition is provided with a reciprocating component adapted to the slow flow component.

[0009] As a further solution of the present invention: the flow isolation member includes an isolation frame fixed on the inner wall of the outer sleeve, the isolation frame is located at the connection between the heat exchange flow channel and the return flow channel, and a plurality of through grooves are opened circumferentially on the isolation frame, and filters are arranged in the through grooves.

[0010] As a further solution of the present invention: the fluid driving member includes a driving ring rotatably arranged on the flow partition member, and a plurality of turbine blades are circumferentially arranged on the side of the driving ring facing the heat exchange flow channel; and a flow divider is connected to the side of the driving ring facing the return flow channel.

[0011] As a further solution of the present invention: the flow dividing member includes a rotating shaft fixed coaxially with the fluid driving member, the rotating shaft is fixedly connected to the driving ring via a connecting frame, and a spiral flow dividing sheet extending into the return channel is provided on the rotating shaft.

[0012] As a further solution of the present invention: the reciprocating part includes a sleeve and a sliding rod, the sleeve is fixed in the outer sleeve by a mounting frame, the sliding rod is axially slidably arranged in the sleeve, and a plurality of limit strips extending along the axial direction are arranged on the sliding rod; the end of the sliding rod away from the rotating shaft is connected to the flow-reducing part, the end of the sliding rod facing the rotating shaft is fixed with a telescopic cylinder, and a rotating cylinder adapted to the telescopic cylinder is fixed to the lower end of the rotating shaft; a plurality of first protrusions are circumferentially arranged on the telescopic cylinder, and a plurality of second protrusions adapted to the first protrusions are circumferentially arranged on the rotating cylinder; a spring is arranged between the sleeve and the telescopic cylinder, and the spring is movably sleeved on the sliding rod.

[0013] As a further solution of the present invention: the flow-delaying member comprises a flexible capsule, and the flexible capsule is arranged at the bottom of the outer sleeve. A connecting disk adapted to the reciprocating member is arranged in the center of the flexible capsule.

[0014] As a further solution of the present invention: a cavity connected to the flexible capsule is formed at the lower end of the outer sleeve, and a through hole is formed at the bottom of the cavity.

[0015] As a further solution of the present invention: the heat storage slow flow unit also includes a vibrating piece, which includes a plurality of mounting rods circumferentially distributed on the telescopic cylinder, and a vibrating ball adapted to the filter is arranged at one end of the mounting rod away from the telescopic cylinder.

[0016] As a further solution of the present invention: the outer casing is installed in the stratum through a bracket, and a liquid inlet pipe connected to the heat exchange channel is provided on the outer casing, a confluence bin connected to the return channel is provided at the upper end of the outer casing, a liquid outlet pipe is provided on the confluence bin, and the end of the liquid outlet pipe away from the confluence bin is connected to a thermal collector box.

[0017] As a further solution of the present invention: a heat-insulating cavity is provided in the inner sleeve.

[0018] Beneficial effects of the present invention:

[0019] The heat exchange flow channel and the return flow channel are effectively separated by the flow partition to prevent the direct mixing of cold and hot fluids and avoid thermal short circuits; the spiral diverter and the slow flow component are used for dynamic adjustment to extend the fluid residence time downhole, enhance the turbulence intensity, and improve the heat exchange efficiency; the kinetic energy of the fluid is used to drive the turbine blades and the shaft, drive the diverter and the reciprocating parts to move, and realize the dynamic adjustment of the fluid path without external energy. The synergistic effect of the flexible capsule and the vibrating part can adaptively slow down the flow rate and prevent the filter from being blocked, ensuring the long-term stable operation of the system; the slow flow structure and the flexible capsule reduce the impact of the fluid on the formation and reduce reservoir disturbance; the closed-loop design avoids the extraction of groundwater and prevents pollution, and the inner casing insulation cavity blocks radial heat transfer and reduces heat loss in the return flow channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 It is a three-dimensional schematic diagram of the present invention;

[0022] Figure 2 A three-dimensional schematic diagram of another viewing angle of the present invention;

[0023] Figure 3 is a cross-sectional view of the outer sleeve in the present invention;

[0024] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0025] Figure 5 It is a schematic diagram of the structure of the heat storage slow flow unit in the present invention;

[0026] Figure 6 It is a structural schematic diagram of the heat storage slow flow unit in the present invention from another perspective;

[0027] Figure 7 It is a three-dimensional schematic diagram of the heat storage slow flow unit in the present invention;

[0028] Figure 8 It is a cross-sectional view of the heat storage slow flow unit in the present invention;

[0029] Fig. 9 for Figure 8 Enlarged view of point B in the middle.

[0030] In the figure:

[0031] 100, outer sleeve; 110, confluence chamber; 120, liquid inlet pipe; 130, bracket; 140, heat collecting box; 150, liquid outlet pipe; 160, inner sleeve; 161, heat insulation cavity; 170, heat exchange flow channel; 180, return channel;

[0032] 200, heat storage slow flow unit; 210, flow partition; 211, isolation frame; 212, through groove; 220, fluid driving member; 221, driving ring; 222, turbine blade; 230, flow divider; 231, rotating shaft; 232, connecting frame; 233, spiral flow divider; 240, reciprocating member; 241, sleeve; 242, mounting frame; 243, sliding rod; 244, telescopic cylinder; 245, rotating cylinder; 246, first protrusion; 247, second protrusion; 248, limiting strip; 249, spring; 250, flow slow flow member; 251, flexible capsule; 252, connecting plate; 253, cavity; 254, through hole; 260, vibrating member; 261, mounting rod; 262, vibrating ball. DETAILED DESCRIPTION

[0033] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and the functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the contents of this specification. Each example may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples.

[0034] See also Figure 1 , Figure 2 and Figure 3 The present invention discloses a medium-deep geothermal underground high-efficiency heat exchanger, comprising an outer casing 100, an inner casing 160 and a heat storage slow flow unit 200, wherein the outer casing 100 is buried in the underground formation for conducting geothermal energy; the inner casing 160 is coaxially embedded in the outer casing 100, a heat exchange channel 170 is formed between the inner casing 160 and the outer casing 100, and a return channel 180 for conveying a heat-carrying fluid is arranged in the inner casing 160;

[0035] See also Figure 5 and Figure 6 The heat storage slow flow unit 200 is located at the opening of the lower end of the inner sleeve 160, and includes a flow partition 210 disposed between the heat exchange flow channel 170 and the return flow channel 180. The flow partition 210 is located on one side of the heat exchange flow channel 170 and is provided with a fluid driving member 220. The flow partition 210 is located on one side of the return flow channel 180 and is provided with a flow divider 230 connected to the fluid driving member 220. The lower end of the outer sleeve 100 is also provided with a slow flow member 250, and the flow partition 210 is provided with a reciprocating member 240 adapted to the slow flow member 250;

[0036] Specifically, the heat exchange channel 170 is located between the outer casing 100 and the inner casing 160. The heat-carrying fluid (such as cold water) enters the well from the ground through the heat exchange channel 170 to absorb the heat of the formation; the return channel 180 is arranged inside the inner casing 160, and is used to transport the heat-carrying fluid (hot water) after absorbing the heat back to the ground; the flow partition 210 in the heat storage slow flow unit 200 is located between the heat exchange channel 170 and the return channel 180, and plays a role in separating the fluids, preventing the fluids from directly mixing between the two channels, and avoiding thermal short circuits; the fluid driving component 220 is installed on the side of the flow partition 210 facing the heat exchange channel 170, and is used to The power of fluid flow drives the fluid driving member 220 to move; the flow dividing member 230 is connected to the fluid driving member 220, and is located on the side of the flow dividing member 210 facing the return channel 180, and the flow dividing member 230 is driven by the fluid driving member 220 to divert the fluid in the return channel 180; the reciprocating member 240 is installed on the flow dividing member 210, and is adapted to the flow slowing member 250, and reciprocating motion is achieved through the power of the fluid driving member 220; the flow slowing member 250 is installed at the lower end of the outer casing 100, and is driven by the reciprocating member 240 to achieve reciprocating motion, which is used to slow down the flow rate of the fluid, prolong the residence time of the fluid in the well, and improve the heat exchange efficiency;

[0037] The heat-carrying fluid (such as cold water) enters the well from the ground through the pipeline and reaches the heat exchange flow channel 170. The outer casing 100 absorbs heat through the contact with the formation. The fluid after absorbing heat returns to the ground through the return channel 180 in the inner casing 160. The heat storage slow flow unit 200 dynamically adjusts the flow path and speed of the fluid through the power of the fluid driving member 220 to optimize the heat exchange effect. The slow flow member 250 and the reciprocating member 240 slow down the flow rate of the fluid to avoid direct impact of the fluid on the reservoir and reduce disturbance to the reservoir. The flow isolation member 21 The design of 0 and the diverter 230 effectively prevents the fluid from directly mixing between the heat exchange channel 170 and the return channel 180, avoids short-circuit transfer of heat, and improves the heat exchange efficiency; through the power of the fluid driving component 220, the heat storage slow flow unit 200 can be dynamically adjusted according to the flow state of the fluid, ensuring that the fluid stays in the well for a longer time and the heat exchange with the formation is more sufficient; the heat storage slow flow unit 200 is driven by the kinetic energy of the fluid, does not require an external power source, and can automatically adjust according to the flow and pressure changes of the fluid to adapt to different operating conditions.

[0038] In one embodiment, see Figure 7 and Figure 8 The flow partition 210 includes an isolation frame 211 fixed on the inner wall of the outer sleeve 100, the isolation frame 211 is located at the connection between the heat exchange flow channel 170 and the return flow channel 180, and a plurality of through grooves 212 are opened on the circumference of the isolation frame 211, and a filter screen is arranged in the through groove 212;

[0039] Specifically, the isolation frame 211 is located at the connection between the heat exchange channel 170 and the return channel 180, and serves to separate the two fluid channels, preventing the cold water in the heat exchange channel 170 from directly mixing with the hot water in the return channel 180, thereby avoiding heat short circuit; the isolation frame 211 is fixed on the inner wall of the outer casing 100, providing structural support for the entire flow isolation member 210, ensuring its stability in the underground high-pressure environment; the design of the through groove 212 allows the fluid to flow in a unidirectional and orderly manner between the heat exchange channel 170 and the return channel 180, which not only ensures the dynamic exchange of the fluid, but also ensures the stability of the fluid. The circumferential distribution of the through grooves 212 makes the flow of the fluid more uniform, reduces the accumulation or turbulence of the fluid in the local area, and thus optimizes the flow path of the fluid; the filter is arranged in the through grooves 212 to filter impurities (such as silt, particles, etc.) in the fluid, which can prevent the impurities from entering the return channel 180, avoid clogging the pipeline or damaging the equipment, and by filtering the impurities, the filter can protect other components of the heat exchanger (such as the fluid driving component 220, the diverter 230, etc.) from wear and tear, thereby extending the service life of the equipment;

[0040] The design of the isolation frame 211 and the through groove 212 effectively prevents the cold water in the heat exchange channel 170 from directly mixing with the hot water in the return channel 180, avoiding short-circuit transfer of heat, thereby significantly improving the heat exchange efficiency; the circumferential distribution of the through groove 212 makes the fluid flow more uniform, reduces the turbulence and local accumulation of the fluid, and further optimizes the heat exchange effect; the filter can effectively filter impurities in the fluid, prevent impurities from entering the return channel 180 and other equipment components, and reduce equipment wear; the design of the isolation frame 211 and the through groove 212 can slow down the flow rate of the fluid, avoid direct impact of the fluid on the reservoir, thereby reducing disturbance to the reservoir, and reducing reservoir disturbance helps to protect the formation structure, extend the service life of the heat exchanger, and at the same time improve the stability and reliability of the system.

[0041] For further information, see Figure 7 and Figure 8 The fluid driving member 220 includes a driving ring 221 rotatably disposed on the flow partition 210, and a plurality of turbine blades 222 are circumferentially disposed on a side of the driving ring 221 facing the heat exchange flow channel 170; a flow divider 230 is connected to a side of the driving ring 221 facing the return flow channel 180;

[0042] Specifically, when the heat-carrying fluid (such as cold water) enters the return channel 180 from the heat exchange channel 170 through the flow partition 210, the fluid impacts the turbine blades 222, converting its kinetic energy into the rotational mechanical energy of the drive ring 221, thereby providing power for the entire heat storage slow flow unit 200 without the need for an external power source; the drive ring 221 converts the kinetic energy captured by the turbine blades 222 into rotational motion, and transmits the power to the diverter 230 through its connection with the diverter 230;

[0043] The design of the driving ring 221 can ensure the stability of the rotational motion and avoid unstable power transmission caused by fluid pulsation or uneven flow; the design of the turbine blades 222 can effectively capture the kinetic energy of the fluid, reduce the direct impact of the fluid on the reservoir, and further reduce reservoir disturbance; the diverter 230 is connected to the other side of the driving ring 221, and its movement is driven by the rotation of the driving ring 221 to achieve dynamic diversion of the fluid in the return channel 180, thereby optimizing the flow path of the fluid in the return channel 180 and further improving the heat exchange efficiency.

[0044] For further information, see Figure 7 and Figure 8 The flow dividing member 230 includes a rotating shaft 231 fixed coaxially with the fluid driving member 220, the rotating shaft 231 is fixedly connected to the driving ring 221 through a connecting frame 232, and a spiral flow dividing piece 233 extending into the return channel 180 is provided on the rotating shaft 231;

[0045] Specifically, the rotating shaft 231 is fixedly connected to the driving ring 221 through the connecting frame 232, and the power of the fluid driving member 220 is transmitted to the spiral diverter 233 to ensure the realization of the diversion action; the design of the rotating shaft 231 ensures the stability of the rotational motion and avoids the uneven power transmission caused by fluid pulsation or uneven flow; the spiral diverter 233 extends into the return channel 180, and diverts the fluid through its spiral structure, optimizing the flow path of the fluid in the return channel 180. The spiral diverter 233 can increase the turbulence intensity of the fluid and improve the heat exchange efficiency between the fluid and the pipe wall. The spiral diverter 233 uses its spiral shape to evenly distribute the fluid in the return channel 180, reduce local turbulence or dead zones, and thereby reduce local heat accumulation, effectively alleviating the thermal short circuit phenomenon.

[0046] Also, see Figure 7 , Figure 8 and Fig. 9 The reciprocating member 240 includes a sleeve 241 and a slide bar 243. The sleeve 241 is fixed in the outer sleeve 100 through a mounting frame 242. The slide bar 243 is axially slidably arranged in the sleeve 241. The slide bar 243 is provided with a plurality of limit strips 248 extending in the axial direction. The end of the slide bar 243 away from the rotating shaft 231 is connected to the slow flow member 250. A telescopic cylinder 244 is fixed to the end of the slide bar 243 facing the rotating shaft 231. A rotating cylinder 245 adapted to the telescopic cylinder 244 is fixed to the lower end of the rotating shaft 231. A plurality of first protrusions 246 are circumferentially arranged on the telescopic cylinder 244, and a plurality of second protrusions 247 adapted to the first protrusions 246 are circumferentially arranged on the rotating cylinder 245. A spring 249 is arranged between the sleeve 241 and the telescopic cylinder 244, and the spring 249 is movably sleeved on the slide bar 243.

[0047] Specifically, when the fluid driving member 220 drives the rotating shaft 231 to rotate circumferentially, the rotating shaft 231 drives the rotating cylinder 245 to rotate synchronously. Since the second protrusion 247 on the rotating cylinder 245 cooperates with the first protrusion 246 on the telescopic cylinder 244, when the second protrusion 247 on the rotating cylinder 245 contacts the corresponding first protrusion 246 on the telescopic cylinder 244, the telescopic cylinder 244 can be pushed away from the rotating cylinder 245, so that the spring 249 is compressed; and when the second protrusion 247 on the rotating cylinder 245 and the corresponding first protrusion 246 on the telescopic cylinder 244 are staggered from each other, the telescopic cylinder 244 axially approaches the rotating cylinder 245 under the elastic force of the spring 249; and so on and so forth, with the continuous rotation of the rotating cylinder 245, the telescopic cylinder 244 can be driven to perform periodic axial reciprocating telescopic motion, thereby driving the sliding rod 243 to perform reciprocating telescopic motion relative to the sleeve 241;

[0048] It should be noted that the reciprocating member 240 can convert the rotational motion into the axial telescopic motion. The reciprocating member 240 drives the slow flow member 250 to realize the reciprocating motion through the periodic telescopic motion of the slide rod 243. This motion can further optimize the flow state of the fluid in the well, slow down the flow rate of the fluid, and prolong its residence time in the well, thereby significantly improving the heat exchange efficiency, reducing the direct impact of the fluid on the reservoir, and reducing the disturbance of the reservoir.

[0049] The synchronous movement of the flow slowdown member 250 and the flow diverter member 230 can synergistically optimize the flow path of the fluid. The flow slowdown member 250 prolongs the residence time of the fluid in the well by slowing down the flow rate of the fluid, while the flow diverter member 230 further improves the heat exchange efficiency by optimizing the fluid distribution. This synergistic effect can significantly reduce the thermal short circuit phenomenon and ensure that the heat is fully transferred to the heat-carrying fluid. The synchronous movement of the flow slowdown member 250 and the flow diverter member 230 can also reduce the direct impact of the fluid on the reservoir and reduce reservoir disturbance. By optimizing the fluid flow state, the formation structure can be protected and the service life of the heat exchanger can be extended.

[0050] Accordingly, see Figure 7 and Figure 8 The slow-flow member 250 includes a flexible capsule 251, which is disposed at the bottom of the outer sleeve 100, and a connecting plate 252 adapted to the reciprocating member 240 is disposed in the center of the flexible capsule 251;

[0051] Specifically, the flexible capsule 251, under the push of the reciprocating member 240, can receive and wrap the heat-carrying fluid entering the return channel 180. When the flexible capsule 251 is recessed downward, the fluid is received in the capsule, thereby slowing down the flow rate of the fluid. The stretching and contraction movement of the flexible capsule 251 can evenly distribute the fluid in the return channel 180, reduce local turbulence or dead zones, and further optimize the flow path of the fluid.

[0052] The flexible material property of the flexible capsule 251 enables it to absorb the impact energy of the fluid, reduce the direct impact of the fluid on the internal structure of the heat exchanger, and reduce equipment wear. The elastic property of the flexible capsule 251 can reduce the vibration generated during the movement of the reciprocating member 240 and enhance the stability of the system.

[0053] By accommodating and pushing out the fluid by the flexible bladder 251, the residence time of the fluid underground is prolonged, thereby increasing the heat exchange time between the fluid and the formation and improving the heat exchange efficiency; the dynamic adjustment function of the flexible bladder 251 can further reduce the thermal short-circuit phenomenon between the heat exchange channel 170 and the return channel 180, ensuring that the heat is fully transferred to the heat-carrying fluid; the flexible bladder 251 slows down the fluid flow rate, avoids the direct impact of the fluid on the reservoir, reduces reservoir disturbance, and protects the formation structure.

[0054] For the flexible capsule 251, polyurethane (PU) or polyethylene (PE) can be used as the main material. Both materials have good flexibility, corrosion resistance and elasticity, and can meet the operation requirements of the flexible capsule 251 in the underground environment. The high elasticity of polyurethane makes it more suitable for frequent stretching and contraction movements, while polyethylene performs well in durability and cost-effectiveness.

[0055] Also, see Figure 8 , considering that the flexible capsule 251 will cause the air pressure at the bottom of the outer sleeve 100 to change when it is stretched and contracted, a cavity 253 connected to the flexible capsule 251 is opened at the lower end of the outer sleeve 100, and a through hole 254 is opened at the bottom of the cavity 253; in this way, when the flexible capsule 251 is stretched and contracted, the air in the cavity 253 can adaptively enter and exit the through hole 254, so as to always maintain the balance of the air pressure inside the cavity 253 to ensure that the flexible capsule 251 can be smoothly contracted or extended; through the design of the cavity 253 and the through hole 254, the flexible capsule 251 will not be hindered by the change of air pressure during the stretching and contraction process, so as to ensure that it can smoothly complete the dynamic adjustment function; in addition, the air pressure balance function reduces the mechanical stress caused by the change of air pressure, reduces the wear of the flexible capsule 251 and related components, and extends the service life of the equipment.

[0056] See also Figure 8 The heat storage slow flow unit 200 further includes a vibrating member 260, which includes a plurality of mounting rods 261 circumferentially distributed on the telescopic cylinder 244, and a vibrating ball 262 adapted to the filter screen is disposed at one end of the mounting rod 261 away from the telescopic cylinder 244;

[0057] Specifically, the vibrating ball 262 is installed at the end of the mounting rod 261 on the telescopic cylinder 244 and is adapted to the filter screen; when the flexible capsule 251 stretches and contracts, the vibrating ball 262 will vibrate accordingly and hit the filter screen to prevent the filter screen pores from being blocked by impurities. It can effectively prevent the filter screen pores from being blocked by impurities or particles in the fluid, ensure the water permeability of the filter screen, and maintain the normal flow of the fluid; the vibration effect of the vibrating ball 262 can further optimize the flow state of the fluid between the filter screen and the flexible capsule 251, reduce the resistance to fluid flow, and improve the heat exchange efficiency.

[0058] In yet another embodiment, see Figure 1 , Figure 2 and Figure 3 The outer sleeve 100 is installed in the stratum through a bracket 130. The outer sleeve 100 is provided with a liquid inlet pipe 120 connected to the heat exchange channel 170. The upper end of the outer sleeve 100 is provided with a confluence bin 110 connected to the return channel 180. The confluence bin 110 is provided with a liquid outlet pipe 150. The end of the liquid outlet pipe 150 away from the confluence bin 110 is connected to the heat collecting box 140.

[0059] Specifically, the liquid inlet pipe 120 is connected to the heat exchange channel 170, and is used to inject the low-temperature heat-carrying fluid from the ground into the underground heat exchange channel 170 to start the heat exchange process; the confluence chamber 110 is arranged at the upper end of the outer casing 100, and is used to collect the high-temperature heat-carrying fluid returned from the return channel 180, and plays a role in buffering and stabilizing the fluid pressure to ensure the smooth outflow of the fluid; the heat collecting box 140 is used to collect the high-temperature heat-carrying fluid returned from the liquid outlet pipe 150, and further distribute the heat to the heating system or other heat utilization equipment, and plays a role in heat transfer and distribution to ensure the efficient operation of the system;

[0060] Through the reasonable fluid circulation path design (liquid inlet pipe 120, heat exchange channel 170, return channel 180, confluence chamber 110 and liquid outlet pipe 150), it is ensured that the heat-carrying fluid fully exchanges heat with the formation underground, thereby increasing the heat extraction of a single well. The reasonable fluid circulation design reduces the head and power requirements of the circulating water pump and reduces the operating cost of the system. The system adopts a closed cycle and has no direct contact with the underground aquifer, thus avoiding the extraction and pollution of groundwater and meeting the requirements of cleanliness and environmental protection. The design of the heat collecting box 140 ensures the effective collection and distribution of heat and improves the overall energy utilization efficiency of the system.

[0061] For further information, see Figure 3 and Figure 4, a heat-insulating cavity 161 is provided in the inner sleeve 160; the heat-insulating cavity 161 can effectively reduce the heat transferred from the heat exchange channel 170 to the return channel 180 by forming an insulating space inside the inner sleeve 160, thereby reducing the thermal short circuit phenomenon; the heat-insulating cavity 161 can also keep the temperature of the fluid in the inner sleeve 160 stable, avoid temperature fluctuations caused by heat loss, and thus improve the heat exchange efficiency; the design of the heat-insulating cavity 161 can effectively suppress radial and axial heat transfer, so that the outer wall temperature is maintained at a low level, thereby optimizing the performance of the entire heat exchanger; the heat-insulating cavity 161 avoids the potential impact of temperature changes on the reservoir structure, such as melting of permafrost, by reducing heat transfer.

[0062] The specific implementation modes of the present invention are described above, but the present invention is not limited to the above-mentioned specific implementation modes. The above-mentioned specific implementation modes are merely illustrative and not restrictive. Under the guidance of the present invention, those skilled in the art may also make many forms, all of which are within the protection of the present invention.

Claims

1. A high-efficiency underground heat exchanger for medium-deep geothermal wells, characterized in that: include: An outer casing (100) is buried in the underground stratum and is used to conduct geothermal energy; An inner sleeve (160) coaxially embedded in the outer sleeve (100), a heat exchange flow channel (170) being formed between the inner sleeve (160) and the outer sleeve (100), and a return flow channel (180) for conveying a heat-carrying fluid being provided in the inner sleeve (160); A heat storage slow flow unit (200) is located at the opening of the lower end of the inner sleeve (160), comprising a flow partition (210) arranged between the heat exchange flow channel (170) and the return flow channel (180), wherein the flow partition (210) is provided with a fluid driving component (220) on one side of the heat exchange flow channel (170), and the flow partition (210) is provided with a flow dividing component (230) connected to the fluid driving component (220) on one side of the return flow channel (180), and a slow flow component (250) is further provided at the lower end of the outer sleeve (100), and a reciprocating component (240) adapted to the slow flow component (250) is provided on the flow partition (210).

2. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 1 is characterized in that: The flow partition (210) comprises an isolation frame (211) fixed on the inner wall of the outer sleeve (100), the isolation frame (211) being located at the connection between the heat exchange channel (170) and the return channel (180), a plurality of through grooves (212) being circumferentially formed on the isolation frame (211), and filter screens being arranged in the through grooves (212).

3. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 1 is characterized in that: The fluid driving member (220) comprises a driving ring (221) rotatably arranged on the flow partition member (210), and a plurality of turbine blades (222) are circumferentially arranged on a side of the driving ring (221) facing the heat exchange flow channel (170); and a flow divider (230) is connected to a side of the driving ring (221) facing the return flow channel (180).

4. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 1 is characterized in that: The flow dividing member (230) comprises a rotating shaft (231) fixed coaxially with the fluid driving member (220); the rotating shaft (231) is fixedly connected to the driving ring (221) via a connecting frame (232); and a spiral flow dividing sheet (233) extending into the return channel (180) is provided on the rotating shaft (231).

5. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 4 is characterized in that: The reciprocating member (240) comprises a sleeve (241) and a sliding rod (243); the sleeve (241) is fixed in the outer sleeve (100) via a mounting frame (242); the sliding rod (243) is axially slidably arranged in the sleeve (241); a plurality of limit strips (248) extending in the axial direction are arranged on the sliding rod (243); one end of the sliding rod (243) away from the rotating shaft (231) is connected to the slow flow member (250); and one end of the sliding rod (243) facing the rotating shaft (231) is fixed to the slow flow member (250). A telescopic cylinder (244) is fixedly provided, and a rotating cylinder (245) adapted to the telescopic cylinder (244) is fixedly provided at the lower end of the rotating shaft (231); a plurality of first protrusions (246) are circumferentially arranged on the telescopic cylinder (244), and a plurality of second protrusions (247) adapted to the first protrusions (246) are circumferentially arranged on the rotating cylinder (245); a spring (249) is provided between the sleeve (241) and the telescopic cylinder (244), and the spring (249) is movably sleeved on the sliding rod (243).

6. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 1 is characterized in that: The flow-slowing member (250) comprises a flexible capsule (251), the flexible capsule (251) being arranged at the bottom of the outer sleeve (100), and a connecting plate (252) adapted to the reciprocating member (240) being arranged at the center of the flexible capsule (251).

7. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 6 is characterized in that: The lower end of the outer sleeve (100) is provided with a cavity (253) connected to the flexible capsule (251), and the bottom of the cavity (253) is provided with a through hole (254).

8. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 5 is characterized in that: The heat storage slow flow unit (200) further comprises a vibrating piece (260), the vibrating piece (260) comprising a plurality of mounting rods (261) circumferentially distributed on the telescopic cylinder (244), and a vibrating ball (262) adapted to the filter screen is provided at one end of the mounting rod (261) away from the telescopic cylinder (244).

9. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 1 is characterized in that: The outer casing (100) is installed in the stratum via a bracket (130); a liquid inlet pipe (120) connected to a heat exchange channel (170) is provided on the outer casing (100); a confluence bin (110) connected to a return channel (180) is provided at the upper end of the outer casing (100); a liquid outlet pipe (150) is provided on the confluence bin (110); and one end of the liquid outlet pipe (150) away from the confluence bin (110) is connected to a heat collecting box (140).

10. The underground high-efficiency heat exchanger for medium-deep geothermal wells according to claim 9, characterized in that: A heat-insulating cavity (161) is provided in the inner sleeve (160).

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