Variable-diameter inner tube coaxial casing heat exchanger for medium-deep geothermal heat exchange

Abstract

The utility model belongs to new energy development and utilization technical field especially relates to a kind of coaxial casing heat exchanger for variable diameter inner tube of middle-deep geothermal heat exchange, it includes outer tube and inner tube, inner tube is arranged in outer tube inside, and inner tube bottom and outer tube bottom are not contacted between, and inner tube is made of multiple different diameter pipe sections, the utility model passes through the inner tube structure of diameter change and strengthens flow field disturbance, effectively destroys thermal boundary layer, improves heat exchange efficiency, and enough according to stratum geothermal parameter flexible inner tube structure diameter change, adapt to different geological conditions, and need not adjust outer tube structure, facilitate engineering implementation.

Description

Technical Field

[0001] This utility model belongs to the field of new energy development and utilization technology, and in particular relates to a variable diameter inner tube coaxial sleeve heat exchanger for medium-deep geothermal heat exchange. Background Technology

[0002] In the field of medium-deep geothermal development, coaxial tube heat exchangers are widely used due to their relatively simple structure and convenient installation. Existing coaxial tube heat exchangers typically consist of an outer tube of fixed diameter and an inner tube of fixed diameter, forming an annular channel between them. Fluid flows within this annular channel and the inner tube, achieving heat exchange with the formation. However, this traditional coaxial tube heat exchanger has significant limitations. Because the inner and outer tube diameters are fixed, the flow field is stable inside the tubes, resulting in insufficient heat exchange between the fluid, the tube wall, and the ground, leading to low heat exchange efficiency. This is especially true in areas with uneven geothermal resource distribution or groundwater flow, where geothermal parameters (such as temperature and thermal conductivity) can change significantly. The fixed-diameter inner tube cannot adjust the flow field to accommodate these changes, further exacerbating the poor heat exchange performance in these regions. For example, in a certain medium-deep geothermal development project, the traditional fixed-diameter coaxial tube heat exchanger, used in areas with groundwater flow, exhibits a heat exchange efficiency approximately 20% lower than in areas without groundwater flow, severely impacting the development and utilization benefits of geothermal resources. Furthermore, to achieve the required heat exchange, it is necessary to increase the heat exchanger's operating time or fluid flow rate, which not only increases energy consumption but also raises the equipment wear rate.

[0003] This invention designs a variable-diameter inner tube coaxial sleeve heat exchanger for medium-deep geothermal heat exchange to solve the above problems. Utility Model Content

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A variable-diameter inner tube coaxial sleeve heat exchanger for medium-deep geothermal heat exchange includes an outer tube and an inner tube. The inner tube is disposed inside the outer tube, and the bottom of the inner tube does not contact the bottom of the outer tube. The inner tube is composed of multiple tube segments of different diameters.

[0005] As a preferred option, the inner pipe diameter changes in a stepped manner, that is, the pipe section diameter changes in a stepped manner along the axial direction.

[0006] As a preferred option, the inner pipe diameter changes gradually, that is, the pipe section diameter changes continuously and smoothly along the axial direction.

[0007] As a preferred option, the inner pipe diameter changes periodically, that is, the pipe section diameter changes periodically along the axial direction.

[0008] As a preferred option, the outer tube is a cylindrical tubular structure made of corrosion-resistant material.

[0009] As a preferred option, the inner tube is made of a metal material with good thermal conductivity and corrosion resistance.

[0010] Compared with existing technologies, the advantages of this utility model are: 1. This utility model enhances flow field disturbance through an inner tube structure with varying diameter, effectively disrupts the thermal boundary layer, improves heat exchange efficiency, and allows for flexible diameter changes of the inner tube structure according to geothermal parameters of the strata, adapting to different geological conditions without requiring adjustments to the outer tube structure, thus facilitating engineering implementation.

[0011] 2. This utility model reduces drilling depth or flow rate for the same heat demand by improving heat exchange efficiency, thereby reducing energy consumption and costs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram showing the stepped change of the inner tube of this utility model.

[0013] Figure 2 This is a schematic diagram showing the gradual change of the inner tube of this utility model.

[0014] Figure 3 This is a schematic diagram showing the stepped and periodic combination of the inner tube of this utility model.

[0015] The labels in the diagram are: 1. Outer pipe; 2. Inner pipe; 3. Working fluid; 4. Formation. Detailed Implementation

[0016] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following embodiments or drawings are used to illustrate this utility model, but are not intended to limit the scope of this utility model.

[0017] A variable-diameter inner tube coaxial sleeve heat exchanger for medium-deep geothermal heat exchange, such as Figure 1 As shown, it includes an outer pipe 1 and an inner pipe 2. The inner pipe 2 is located inside the outer pipe 1. The bottom of the inner pipe 2 does not contact the bottom of the outer pipe 1. The inner pipe 2 is composed of multiple pipe sections of different diameters.

[0018] The outer tube 1 is a cylindrical tubular structure made of corrosion-resistant material, while the inner tube 2 is made of a metal material with good thermal conductivity and corrosion resistance.

[0019] The outer pipe 1 is placed inside the formation, and the working fluid 3 flows in the annulus between the inner pipe 2 and the outer pipe 1, and turbulence and eddies are induced by the pipe section structure of the inner pipe 2 with different diameters.

[0020] The diameter and distribution of different pipe segments of the inner pipe 2 are designed according to the geothermal parameters of the target stratum. The geothermal parameters include at least one of thermal conductivity, groundwater flow velocity, temperature gradient, and stratum lithology. For example, in areas with active geothermal activity or strong groundwater flow, the inner pipe 2 is designed with a structure that has more pipe segments of different diameters; in areas with high thermal conductivity, the length of a single pipe segment is extended; in areas with low thermal conductivity or groundwater seepage, the length of a single pipe segment is shortened to enhance the heat exchange effect.

[0021] The thermal conductivity of stratum 4 affects the number and location of pipe segments; the groundwater flow velocity affects the number of pipe segments; the geothermal gradient affects the length and spacing of pipe segments; and the lithology of stratum 4 affects the structural form of pipe segments.

[0022] like Figure 1 As shown, the diameter of the inner tube 2 changes in a stepped manner, that is, the pipe section has a structure in which the diameter changes in a stepped manner along the axial direction.

[0023] like Figure 2 As shown, the diameter of the inner tube 2 changes gradually, that is, the pipe section has a structure in which the diameter changes continuously and smoothly along the axial direction.

[0024] like Figure 3 As shown, the diameter of the inner tube 2 changes periodically, meaning that the pipe section has a structure in which the diameter changes periodically along the axial direction.

[0025] The diameter of the inner tube 2 can be varied in one or more of the three forms mentioned above. Figure 3 This is a schematic diagram showing the step-like and periodic combination of changes in the inner tube.

[0026] The arrows in the accompanying drawings are used to indicate the flow trajectory of the working fluid 3. The working fluid 3 enters from the space inside the outer tube 1 and outside the inner tube 2 from top to bottom. After reaching the bottom of the outer tube 1, it is discharged from the space inside the inner tube 2 from bottom to top.

[0027] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A variable-diameter inner tube coaxial sleeve heat exchanger for medium-deep geothermal heat exchange, characterized in that: It includes an outer tube (1) and an inner tube (2). The inner tube (2) is located inside the outer tube (1). The bottom of the inner tube (2) does not contact the bottom of the outer tube (1). The inner tube (2) is composed of multiple tube segments of different diameters.

2. A coaxial sleeve heat exchanger with a variable diameter inner tube (2) for medium-deep geothermal heat exchange according to claim 1, characterized in that: The diameter of the inner tube (2) changes in a stepped manner, that is, the diameter of the tube section changes in a stepped manner along the axial direction.

3. A coaxial sleeve heat exchanger with a variable diameter inner tube (2) for medium-deep geothermal heat exchange according to claim 1, characterized in that: The diameter of the inner tube (2) changes gradually, that is, the diameter of the tube section changes continuously and smoothly along the axial direction.

4. A coaxial sleeve heat exchanger with a variable diameter inner tube (2) for medium-deep geothermal heat exchange according to any one of claims 1-3, characterized in that: The diameter of the inner tube (2) changes periodically, that is, the diameter of the tube section changes periodically along the axial direction.

5. A coaxial sleeve heat exchanger with a variable diameter inner tube (2) for medium-deep geothermal heat exchange according to claim 1, characterized in that: The outer tube (1) is a cylindrical tubular structure, and the material of the outer tube (1) is a corrosion-resistant material.

6. A coaxial sleeve heat exchanger with a variable diameter inner tube (2) for medium-deep geothermal heat exchange according to claim 5, characterized in that: The inner tube (2) is made of a metal material with good thermal conductivity and corrosion resistance.

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