Multi-scale perturbation enhanced coaxial type middle-deep geothermal heat exchanger

Abstract

The application provides a multi-scale perturbation enhanced coaxial type middle-deep geothermal heat exchanger, which comprises an outer sleeve pipe, an inner return pipe and a perturbation module, the inner return pipe is arranged in the outer sleeve pipe, a gap exists between the outer wall of the inner return pipe and the inner wall of the outer sleeve pipe, the gap is an annular gap flow channel, the perturbation module comprises a plurality of main guide vanes, a V-shaped guide vane array and a micro convex point array, the V-shaped guide vane array comprises a plurality of V-shaped guide vanes, the V-shaped guide vane array is located downstream of the main guide vanes, the micro convex point array comprises a plurality of convex points, and the micro convex point array is arranged in the leeward area of the main guide vanes and the V-shaped guide vane array.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and more specifically, to a coaxial medium-deep geothermal heat exchanger enhanced by multi-scale perturbation. Background Technology

[0002] With the development of my country's energy industry, the energy structure is gradually shifting from being dominated by fossil fuels to a more diversified and cleaner energy source. Medium-deep geothermal resources, due to their large reserves, high stability, and long sustainable utilization period, have become one of the important directions for clean energy development and utilization, and are gradually being promoted and applied in northern my country. Coaxial tube heat exchangers are key equipment in medium-deep geothermal development systems. Their outer tubes, as the core heat transfer carrier between the "rock and soil heat" and the "working fluid inside the tube," directly determine the overall energy efficiency level of the geothermal utilization system.

[0003] However, the existing structural design of coaxial jackets for medium-deep geothermal systems still faces many technical challenges. Firstly, traditional coaxial jackets often employ a smooth outer tube structure, which easily leads to the formation of a thick laminar boundary layer within the tube, resulting in a low convective heat transfer coefficient, a significant heat transfer bottleneck in the high-temperature section, low geothermal resource utilization, and substantial energy waste. Secondly, currently common heat transfer enhancement schemes often improve heat transfer performance by adding external structures such as welded fins or flow dividers to the tube wall. Chinese patent CN112923592A discloses a scheme for enhancing heat exchange in a casing heat exchanger for medium-deep geothermal wells using inner and outer fins. Although this structure can improve the heat exchange performance of the outer tube and the final outlet water temperature, stress concentration and fracture are prone to occur at the root of the welded fins and the diverter plate under the high temperature and pressure environment of medium-deep geothermal wells. In addition, geothermal working fluids generally contain corrosive impurities such as chloride ions, calcium and magnesium ions, which can easily cause corrosion failure of the fins. At the same time, the welding process not only increases the processing cost by about 40%–50%, but also may cause the working fluid to leak due to micro-gaps, which may cause potential pollution to groundwater resources.

[0004] Furthermore, Chinese patent CN218781451U proposes a coaxial sleeve heat exchanger structure that enhances heat exchange through a split tube and spiral fins. While this scheme can improve the uniformity of outlet water temperature and heat exchange performance, the fins and split structure significantly increase the friction resistance, requiring a more powerful circulating pump to operate the system, thus leading to a decrease in the overall energy efficiency ratio. Moreover, existing external fins often adopt a full-tube arrangement, resulting in "over-enhancement" in non-high-temperature heat exchange sections. This not only fails to bring significant heat exchange benefits but also increases friction resistance and reduces the overall system economy.

[0005] In summary, existing technologies cannot achieve efficient, low-resistance, and long-term stable enhanced heat exchange of coaxial geothermal jackets while ensuring structural reliability and system economy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a coaxial medium-deep geothermal heat exchanger with multi-scale perturbation enhancement.

[0007] According to one aspect of the present invention, a coaxial medium-deep geothermal heat exchanger with multi-scale perturbation enhancement includes an outer tube, an inner return tube, and a perturbation module. The inner return tube is disposed inside the outer tube, and there is a gap between the outer wall of the inner return tube and the inner wall of the outer tube. The gap is an annular flow channel. The perturbation module is disposed on the inner wall of the outer tube.

[0008] The disturbance module includes multiple main flow vanes, a V-shaped flow vane array, and a micro-protrusion array. The V-shaped flow vane array includes multiple V-shaped flow vanes and is located downstream of the main flow vanes. The micro-protrusion array includes multiple protrusions and is located in the leeward area of ​​the main flow vanes and the V-shaped flow vane array.

[0009] Preferably, multiple disturbance modules are arranged along the axial direction at preset intervals, and any pair of adjacent disturbance modules along the axial direction are staggered in the circumferential direction.

[0010] Preferably, the V-shaped drainage wing array includes at least three V-shaped drainage wings, each V-shaped drainage wing having an angle of 20° to 40° relative to the axial direction, and the deployment angle of the V-shaped drainage wing being 10° to 30°.

[0011] Preferably, the height of the main flow vane protruding from its mounting surface does not exceed 15% of the equivalent hydraulic diameter of the annular gap, the height of the V-shaped flow guide vane protruding from its mounting surface does not exceed 10% of the equivalent hydraulic diameter of the annular gap, and the height of the micro-protrusion array protruding from its mounting surface does not exceed 5% of the equivalent hydraulic diameter of the annular gap.

[0012] Preferably, the main flow vanes are arranged in a spiral pattern extending circumferentially along the inner wall of the outer sleeve.

[0013] Preferably, the main flow airfoil is inclined relative to the outer tube axis, and its cross-sectional profile has a first confluence and a second confluence. The first confluence is located in a low region near the incoming flow side, and the second confluence is located in a high region far from the incoming flow side, thereby forming an airfoil flow guide structure with lift effect.

[0014] Preferably, the protrusions are one or more of the following structures: hemispherical, truncated conical, and elliptical cylindrical, and are arranged in a matrix or staggered manner in the leeward area of ​​the main flow vane and the V-shaped guide vane array.

[0015] Preferably, the cross-sectional profile of the main flow vane is formed by two arcs, and the two arcs form an acute angle at the first confluence and are connected by a circular arc transition at the second confluence.

[0016] Preferably, the cross-sectional profile of the dominant airfoil includes a rounded wedge or a rounded trapezoid.

[0017] Preferably, it also includes a mounting plate, which is attached to the inner wall of the outer sleeve, and the mounting plate is equipped with a main flow vane, a V-shaped flow vane array, and a micro-protrusion array.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention forms a multi-scale perturbation system from macroscopic to microscopic levels through the nested combination of a main flow vane, a V-shaped guide vane array, and a micro-convex point array. The main flow vane induces helical centrifugal motion in the mainstream, the V-shaped guide vane array precisely guides the fluid near the wall, and the micro-convex point array triggers turbulence locally. This multi-scale synergistic effect significantly improves the convective heat transfer coefficient under conditions of relatively small pressure drop increments.

[0019] The disturbance modules are arranged at intervals along the axial direction, and adjacent modules are staggered in the circumferential direction. This staggered design disrupts the full development of the fluid boundary layer, forces the fluid to continuously redistribute within the flow channel, avoids the thickening of the laminar sublayer, and achieves a long-term stable and enhanced heat transfer effect throughout the entire flow channel.

[0020] By setting a micro-protrusion array in the leeward area of ​​the main flow vane and V-shaped guide vane array, this invention specifically solves the problem of "stagnant dead zones" easily generated on the leeward side of traditional disturbance components. The local disturbances induced by the micro-protrusion array not only enhance the heat transfer in this area, but also prevent the precipitation and scaling of minerals in geothermal water through high-frequency pulsating flow, significantly improving the long-term operational reliability and maintenance-free cycle of the system.

[0021] The V-shaped guide vanes, with their specific dual tilt angles (20°–40° relative to the axial direction and 10°–30° tilt angle), and the strictly controlled protrusion heights of each component (based on a 15%, 10%, and 5% gradient limit of the equivalent hydraulic diameter of the annular gap), enable the heat exchanger to precisely adapt to the temperature differences and heat flow patterns of medium-deep geothermal environments. Under the same load, this can reduce the circulation flow rate by approximately 5%–12% or increase the return water temperature by approximately 2–6 °C, significantly reducing the power consumption of the circulation pump.

[0022] The dominant airfoil is constructed using rounded wedges, rounded trapezoids, or streamlined arcs, with rounded transitions connecting them. This airfoil-like design ensures disturbance strength while minimizing energy loss from localized drag and flow separation, thus guaranteeing the system's high energy efficiency.

[0023] By integrating and attaching the various disturbance components to the inner wall of the outer casing using mounting plates, modular prefabrication and on-site installation of the enhanced heat exchange structure are achieved. This structure not only improves production efficiency but also enhances the adaptability of the heat exchanger to outer casings with different well diameters and geological conditions. Attached Figure Description

[0024] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of the multi-scale disturbance-enhanced coaxial medium-deep geothermal heat exchanger of the present invention. Figure 2 This is a schematic diagram of the disturbance module; Figure 3 A schematic diagram of the main airflow vane; Figure 4 A schematic diagram of a V-shaped airflow deflector; Figure 5 The disturbance module of this invention is periodically arranged along the well depth and enhances the turbulence of the downstream annular fluid by 5–10 m. In the figure, 1 is the outer tube; 2 is the disturbance module; 3 is the main flow vane; 4 is the V-shaped flow guide vane; 5 is the micro-protrusion array; 6 is the annular flow channel; and 7 is the inner return tube. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0026] Example 1: A multi-scale perturbation-enhanced coaxial medium-deep geothermal heat exchanger, such as Figure 1 As shown, the system includes an outer casing, an inner return pipe 7, and an annular flow channel 6 formed between them. Several disturbance modules 2 are periodically arranged along the axial direction on the inner wall of the outer casing. Each disturbance module 2 includes: a main flow vane 3 for applying a tangential velocity component to the annular fluid to establish a swirling background; a V-shaped guide vane array disposed downstream of the main flow vane 3 for inducing longitudinal vortex pairs and forming multi-scale vortex chains; and a micro-protrusion array 5 disposed in the leeward area of ​​the main flow vane 3 and the V-shaped guide vane array for suppressing stagnation dead zones and reducing scaling deposits.

[0027] In this embodiment, as Figure 2 As shown, the disturbance modules 2 are arranged periodically along the axial direction, and the axial spacing between adjacent disturbance modules 2 is 5–20 m. The adjacent disturbance modules 2 are also staggered and rotated in the circumferential direction to avoid the formation of fixed low-temperature or high-temperature strips in the annular gap, thereby improving the heat transfer uniformity.

[0028] In this embodiment, as Figure 4As shown, the V-shaped guide vane array 4 includes no less than 3 V-shaped guide vanes, each V-shaped guide vane having an angle of 20°–40° relative to the axial direction and an inclination angle of 10°–30°, in order to form stable longitudinal vortex pairs and enhance fluid shearing under the background of swirling flow; the protrusion height of the airfoil-shaped main flow structure does not exceed 15% of the equivalent hydraulic diameter of the annular gap, the protrusion height of the wall-mounted composite V-shaped guide vane structure does not exceed 10% of the equivalent hydraulic diameter of the annular gap, and the protrusion height of the micro-protrusion array 5 does not exceed 5% of the equivalent hydraulic diameter of the annular gap, thereby controlling the increase of resistance while ensuring the enhanced heat transfer effect.

[0029] In this embodiment, as Figure 3 As shown, the main flow vane 3 is arranged in a continuous or discontinuous spiral direction along the inner wall of the outer sleeve 1, and its cross-sectional shape is a rounded wedge, a rounded trapezoid, or an airfoil, in order to reduce flow separation and improve swirling stability.

[0030] In this embodiment, the micro-bump array 5 includes several hemispherical, truncated conical or elliptical cylindrical bumps, which are arranged in a matrix or staggered manner in the leeward area of ​​the main flow vane 3 and the V-shaped flow guide vane array to form micro-scale vortices locally to clean dead areas and suppress scale deposition.

[0031] In this embodiment, the disturbance module 2 is an integral ring structure that can be fixed to the inner wall of the outer casing 1 by welding, brazing, mechanical connection or additive manufacturing, and can be modularly combined according to well depth and working conditions.

[0032] In this embodiment, the heat exchanger is suitable for medium-deep geothermal wells, underground energy storage wells, oil and gas wells, or other coaxial casing underground heat exchange systems.

[0033] In this embodiment, the swirling shear layer and longitudinal vortex chain formed by the disturbance module 2 in the annular gap remain stable within a 5–10 m axial distance downstream, thereby increasing the average convective heat transfer coefficient within this distance by at least 15% compared to the smooth annular gap.

[0034] Example 2: like Figure 1 As shown, the multi-scale disturbance-enhanced coaxial medium-deep geothermal heat exchanger proposed in this invention includes a periodically arranged disturbance module 2 in an outer casing 1, forming an annular flow channel 6 between the module and the inner return pipe 7. This structure is suitable for medium-deep geothermal wells, underground energy storage wells, and geothermal heat pump heat exchange wells with depths of 800–3000 m, and is a highly efficient enhanced heat exchange core component developed for medium-deep geothermal heating projects in northern my country.

[0035] Traditional coaxial geothermal heat exchangers typically employ a smooth outer tube structure. Although the fluid within the annulus is in a turbulent state under high Reynolds number conditions, a stable thermal boundary layer with a thickness reaching 8%–15% of the hydraulic diameter still forms near the tube wall. In this region, radial mixing of the fluid is weak, and heat transfer is limited, resulting in near-wall heat transfer resistance accounting for over 55% of the total thermal resistance. This becomes the main bottleneck restricting the heat transfer efficiency of medium-deep geothermal systems. While traditional enhancement methods such as continuous fins and spiral fins can improve the local heat transfer coefficient to some extent, they significantly increase frictional resistance, requiring a more powerful circulating pump and ultimately reducing the overall system efficiency ratio.

[0036] To address the aforementioned issues, this embodiment proposes a multi-scale perturbation enhancement approach of "short-segment perturbation – long-range turbulent extension." By discretely arranging perturbation modules 2 on the inner wall of the outer casing 1, and utilizing swirling induction and longitudinal vortex chain extension mechanisms, a large-scale enhanced heat transfer effect is achieved with limited drag. Each perturbation module 2 occupies only 150–300 mm of axial length, but the swirling shear layer and longitudinal vortex chain it induces can persist for 5–10 m axial distance downstream, maintaining a high turbulent kinetic energy level in the annular fluid within this section and significantly enhancing radial mixing capacity, thereby forming a non-local enhanced heat transfer section.

[0037] The disturbance module 2 includes at least a main flow vane 3, a V-shaped guide vane 4, and a micro-bump array 5. The main flow vane 3 is arranged spirally or obliquely along the inner wall of the outer sleeve 1, mainly used to apply a tangential velocity component to the fluid and establish a stable swirling background flow field in the annular gap; the V-shaped guide vane 4 is set in the downstream region of the main flow vane 3, inducing continuous longitudinal vortices in the swirling shear layer, so that the fluid continues to undergo radial mixing; the micro-bump array 5 is arranged at the position where low-velocity stagnation zone is easily formed, used to create wake channels and suppress scaling and deposition.

[0038] refer to Figure 5 Based on the well depth and formation temperature difference distribution characteristics, the well depth section is divided into a low-temperature section (0–800m), a medium-temperature section (800–1500m), and a high-temperature section (1500–2500m). In the low-temperature section, the formation heat flux density is low. To avoid the increase of ineffective resistance, the perturbation module 2 is arranged at a low density, with 5–8 sets per 100m. In the medium-temperature section, the arrangement density is moderately increased, with 12–18 sets per 100m. In the high-temperature section, the formation heat flux density is the highest. To make full use of high-grade geothermal resources, 20–30 sets of perturbation module 2 are arranged per 100m, so that the enhanced heat transfer area is concentrated in the high heat flux density section, thereby achieving the optimal match between the enhancement effect and the system economy.

[0039] This heat exchanger structure is particularly suitable for typical geothermal fields with well depths of 1500–3000 m and geothermal gradients of 2.5–3.5℃ / 100m in geothermal-rich areas such as the North China Plain and the Songliao Basin in my country. It can be used in various application scenarios such as urban centralized heating, regional energy station heating, underground energy storage, and geothermal heat pump systems. By rationally arranging the density and axial spacing of the disturbance modules, the heat exchange capacity of a single well can be significantly improved while ensuring controllable system resistance, thereby increasing the outlet water temperature and the heating power per unit well. This provides efficient, economical, and reliable core equipment support for the large-scale promotion of medium-deep geothermal projects.

[0040] To further verify the engineering applicability and system energy efficiency advantages of the multi-scale perturbation enhanced coaxial medium-deep geothermal heat exchanger of the present invention, a typical geothermal area in the North China Plain in northern my country was selected as an engineering example for in-depth numerical simulation and system-level performance comparison analysis.

[0041] The geothermal wells in this area are approximately 2500m deep, with a geothermal gradient of about 3.3℃ / 100m and a bottom-hole geothermal temperature reaching 85–90℃, making it suitable for medium-deep geothermal heating projects. Typical coaxial geothermal casing dimensions are selected as follows: outer casing 1 has an inner diameter of 0.20m, inner return pipe 7 has an outer diameter of 0.098m, forming an equivalent annular hydraulic diameter of approximately 0.102m. The heat exchange medium is selected as clean water, with an inlet temperature set at 20℃ and an average inlet velocity of 10.0m / s. The simulation considers the effects of gravitational acceleration and the linear variation of geothermal temperature along the well depth, with a geothermal gradient of 0.33℃ / 10m (i.e., 3.3℃ / 100m).

[0042] Regarding the structural parameters of disturbance module 2, the tilt angle of the main flow vane 3 is 25°, and its height is 8% of the annular gap hydraulic diameter; the height of the V-shaped guide vane 4 is 6% of the hydraulic diameter, and its opening angle is 60°; the height of the micro-protrusion array 5 is 3% of the hydraulic diameter. The axial length of a single disturbance module 2 is 200mm. Comparative analysis was conducted for three operating conditions with axial spacing of disturbance modules 2 of 6m, 8m, and 10m.

[0043] First, numerical simulations were performed to investigate the nonlocal enhancement effect of a single disturbance module 2. The results show that, under smooth coaxial casing conditions, the average convective heat transfer coefficient within the annulus is approximately 204 W / (m²·K), and the average heat transfer power per unit well is approximately 400 kW. When a single disturbance module 2 is placed on the inner wall of the outer casing, the turbulent kinetic energy of the fluid in a downstream section of approximately 5.4 m increases by about 32%–48%, and the average heat transfer coefficient in this section increases to approximately 365 W / (m²·K), an increase of about 30%. This indicates that a single disturbance module 2 can significantly enhance heat transfer in a relatively long section.

[0044] Under the multi-module synergistic enhancement condition, when the spacing between the disturbance modules 2 is 6m, the vortex chains induced by adjacent disturbance modules 2 superimpose with each other, increasing the overall average heat transfer coefficient of the annulus by about 36%; when the spacing is 8m, the overall average heat transfer coefficient increases by about 31%; when the spacing is 10m, it can still maintain a stable enhancement effect of about 24%, indicating that the enhancement mechanism of the present invention has strong robustness to the module spacing, which facilitates flexible arrangement on the engineering site according to the well depth and heat flow distribution.

[0045] Further system-level simulations were conducted by deploying the perturbation structure only in the 800m high-temperature section at the bottom of the well. The results show that, while maintaining a constant system heat supply, the perturbation-enhanced coaxial sleeve of this invention reduces the circulating flow rate by approximately 8%–14%, while increasing the system's overall energy efficiency ratio (COPsys) from 3.2–3.5 for traditional smooth coaxial systems to 3.8–4.2. Using a centralized heating system in urban areas of North China as an example, calculations show that under the same heating load conditions, the unit heating power consumption is reduced by approximately 18%–26%, resulting in a significant reduction in annual operating electricity costs, demonstrating excellent economic efficiency.

[0046] In summary, the results show that the multi-scale perturbation enhancement structure proposed in this embodiment can not only significantly improve local and overall heat exchange performance, but also significantly improve the energy consumption and overall energy efficiency ratio of the circulating pump at the system level, achieving synergistic optimization of heat exchange performance and operating economy, and has good engineering promotion value.

[0047] The calculation results from the above embodiments are used to help illustrate the working principle of the multi-scale disturbance-enhanced coaxial medium-deep geothermal heat exchanger mentioned in this invention. For example... Figure 1 As shown, the present invention arranges disturbance modules 2 discretely along the axial direction on the inner wall of the outer sleeve 1, so that the annular fluid, while maintaining the overall flow continuity, periodically undergoes three processes: swirling induction, longitudinal vortex chain enhancement, and microscale disturbance renormalization, thereby constructing a stable multi-scale cooperative disturbance flow field.

[0048] Under smooth coaxial sleeve conditions, although the annular fluid is in a high Reynolds number turbulent state under engineering flow conditions, a stable thermal boundary layer of considerable thickness will still form in the near-wall region. This boundary layer has weak radial mixing ability and its thermal resistance accounts for more than 55% of the total thermal resistance, becoming the main bottleneck restricting the heat transfer capacity of the coaxial geothermal system. Once formed, this type of boundary layer will remain stable along the axial direction, meaning that even if the fluid continues to flow along the pipe, the heat transfer performance cannot be substantially improved.

[0049] The disturbance module 2 arranged in this embodiment serves as a high-efficiency vortex generator. First, the main flow vane 3 applies a tangential velocity component to the fluid, establishing a stable swirling background flow field within the annular gap. This transforms the fluid trajectory from traditional axial parallel flow to a spiral upward three-dimensional flow, thereby significantly extending the fluid's residence time in the near-wall region and providing a rotating basic flow field for subsequent disturbance structures.

[0050] Under this swirling flow background, the V-shaped guide vane 4 induces the formation of stable longitudinal vortex pairs, which further develop into continuous longitudinal vortex chains. The longitudinal vortex pairs can continuously entrain the high-temperature fluid near the wall to the mainstream region, while continuously pressing the low-temperature fluid in the mainstream against the pipe wall, causing the thermal boundary layer to undergo "dynamic stripping" and continuously disrupting the original stable boundary layer structure along the axial direction, thereby significantly reducing the near-wall heat transfer resistance.

[0051] Unlike traditional continuous fin or transverse rib reinforcement methods, this invention employs a discrete disturbance extension reinforcement mechanism, which ensures the stable existence of the vortex structure within a 5–10 m downstream section, resulting in a non-local reinforcement effect characterized by a short disturbance source and a long reinforcement zone. This mechanism effectively decouples the length of the reinforcement zone from the length of the drag generation zone, enabling the system to achieve large-scale enhanced heat transfer at a relatively low drag cost.

[0052] Furthermore, the staggered arrangement of the present invention can prevent the fluid from forming a stable wake channel behind the disturbance module 2. After the fluid bypasses the first disturbance module 2 and separates, it will directly impact the second disturbance module 2 located at the downstream staggered position, thereby forcing the fluid to continuously change its flow direction. This not only significantly enhances the radial mixing degree, but also further increases the secondary flow intensity Se by about 10%–15% compared to the in-line arrangement.

[0053] The micro-bump array 5 induces the formation of microscale vortices in the low-speed stagnation zone, which increases the shear stress in the near-wall region by about 10%–20%, effectively inhibiting the deposition of scale on the wall surface and the formation of stable stagnation zones, thereby improving long-term operational reliability.

[0054] By combining the above-mentioned multi-scale disturbance synergistic effects, this invention constructs a three-level enhanced heat transfer mechanism of "swirling background - longitudinal vortex chain - micro-scale vortex group", which enables the fluid to continuously undergo multi-level disturbance reconstruction process along the flow path, thereby significantly reducing boundary thermal resistance, improving the convective heat transfer coefficient of the outer shell of the coaxial geothermal heat exchanger, and fully releasing the thermal energy potential of medium and deep geothermal resources.

[0055] Therefore, compared with traditional smooth coaxial casing, the multi-scale disturbance enhancement structure proposed in this invention can significantly improve the heat exchange of a single well, significantly increase the outlet water temperature of the inner return pipe 7, and significantly improve the overall energy efficiency ratio of the system. It can also achieve synergistic optimization of heat exchange performance and system economy under the premise of ensuring controllable resistance. It is suitable for various engineering application scenarios such as medium-deep geothermal heating, underground energy storage and geothermal heat pump systems.

[0056] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0057] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A coaxial medium-deep geothermal heat exchanger enhanced by multi-scale perturbation, characterized in that, It includes an outer tube, an inner return tube, and a disturbance module. The inner return tube is disposed inside the outer tube, and there is a gap between the outer wall of the inner return tube and the inner wall of the outer tube. The gap is an annular flow channel. The disturbance module is disposed on the inner wall of the outer tube. The disturbance module includes multiple main flow vanes, a V-shaped flow vane array, and a micro-protrusion array. The V-shaped flow vane array includes multiple V-shaped flow vanes and is located downstream of the main flow vanes. The micro-protrusion array includes multiple protrusions and is located in the leeward area of ​​the main flow vanes and the V-shaped flow vane array.

2. The heat exchanger according to claim 1, characterized in that, The disturbance modules are arranged in multiple ways along the axial direction at a preset interval, and any pair of disturbance modules that are adjacent along the axial direction are staggered in the circumferential direction.

3. The heat exchanger according to claim 1, characterized in that, The V-shaped drainage wing array includes at least three V-shaped drainage wings, each of which has an angle of 20° to 40° relative to the axial direction and an unfolding angle of 10° to 30°.

4. The heat exchanger according to claim 1, characterized in that, The height of the main flow vane protruding from its mounting surface does not exceed 15% of the equivalent hydraulic diameter of the annular gap, the height of the V-shaped flow guide vane protruding from its mounting surface does not exceed 10% of the equivalent hydraulic diameter of the annular gap, and the height of the micro-bump array protruding from its mounting surface does not exceed 5% of the equivalent hydraulic diameter of the annular gap.

5. The heat exchanger according to claim 1, characterized in that, The main flow vanes are arranged in a spiral pattern along the inner wall of the outer sleeve in the circumferential direction.

6. The heat exchanger according to claim 1, characterized in that, The main flow vane is inclined relative to the outer tube axis, and its cross-sectional profile has a first confluence and a second confluence, wherein the first confluence is located in a low region near the incoming flow side, and the second confluence is located in a high region far away from the incoming flow side.

7. The heat exchanger according to claim 1, characterized in that, The protrusions are one or more of the following structures: hemispherical, truncated conical, and elliptical cylindrical, and are arranged in a matrix or staggered manner in the leeward area of ​​the main flow vane and the V-shaped guide vane array.

8. The heat exchanger according to claim 1, characterized in that, The cross-sectional profile of the main flow vane is formed by two arcs, and the two arcs form an acute angle at the first confluence and are connected by a circular arc transition at the second confluence.

9. The heat exchanger according to claim 1, characterized in that, The cross-sectional profile of the dominant airfoil includes a rounded wedge or a rounded trapezoid.

10. The heat exchanger according to claim 1, characterized in that, It also includes a mounting plate, which is attached to the inner wall of the outer sleeve, and the mounting plate is equipped with a main flow vane, a V-shaped flow vane array, and a micro-protrusion array.

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