High-efficiency heat exchanger for medium-depth geothermal energy

Abstract

The application discloses a kind of high-efficiency heat exchangers for middle-deep geothermal energy, belong to geothermal technical field, to solve the problem of high cost of heat exchanger development and utilization, heat loss is big in heat exchange link, system stability is poor, and low continuous heat extraction capacity.Problem.The heat exchanger includes outer tube, center tube, flow control distributor, and the flow control distributor is arranged on the center tube.The center tube is coaxially arranged in the outer tube, and the outer tube is divided into three sections from top to bottom, namely heat preservation tube, conversion tube and heat exchange tube.The volume of the conversion tube is in the shape of a circular truncated cone.The application splits the outer tube structure into three sections based on the original straight-up and straight-down inner and outer tube structure, changes the operating flow pattern of the heat exchange medium, and improves the heat extraction capacity of a single well.The upper heat preservation tube is heat-insulated on the outside and heat-insulated on the inside, and the downward fluid flows at a high speed, which prevents heat exchange between the heat exchange medium and the rock-soil body outside the tube and reduces heat loss.In the conversion tube section and the heat exchange tube section, the heat exchange medium flow pattern characteristics are changed and the heat exchange area is increased to achieve maximum heat exchange with geothermal energy in the formation temperature-increasing section.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geothermal energy, and particularly relates to a high-efficiency heat exchanger for medium-deep geothermal energy. BACKGROUND

[0002] As a kind of clean energy, geothermal energy is a renewable clean energy existing in the form of heat in rocks, which is derived from the molten magma and the decay of radioactive substances in the earth's interior. With its advantages of clean and environmentally friendly, large reserves and renewable, it is more and more favored by people. At present, the medium-deep geothermal energy heating technology applied in clean heating is relatively mature, but there are still problems such as high development and utilization cost, large heat loss in heat exchange link, poor system stability and low continuous heat extraction capacity, which limit the development and utilization of medium-deep geothermal energy.

[0003] The reason is concentrated on the heat exchanger. The existing coaxial sleeve heat exchanger structure is of fixed same diameter form, which can extract heat but the heat extraction effect is not ideal. The main reasons are that the heat loss of the downlink heat exchange medium in the heat exchanger is large; the flow state of the uplink and downlink heat exchange medium is unchanged throughout the process, and the heat exchange rate does not match the heat extraction rate; there is no heat storage capacity, and the continuous heat extraction capacity is poor; and the above reasons lead to low heat extraction capacity, poor economy and low cost performance of single-hole medium-deep geothermal energy.

[0004] Based on the reasons in the above background technology, the research and development personnel proposes a high-efficiency heat exchanger for medium-deep geothermal energy. SUMMARY

[0005] The purpose of the present application is to provide a high-efficiency heat exchanger for medium-deep geothermal energy, to solve the problems of high development and utilization cost of heat exchanger, large heat loss in heat exchange link, poor system stability and low continuous heat extraction capacity.

[0006] In order to solve the above problems, the technical scheme of the present application is as follows:

[0007] A high-efficiency heat exchanger for medium-deep geothermal energy, comprising an outer pipe, a center pipe and a flow control distributor, the flow control distributor being arranged on the center pipe; the center pipe is coaxially arranged in the outer pipe, the outer pipe is divided into upper, middle and lower three sections, and is sequentially a heat preservation pipe, a conversion pipe and a heat exchange pipe from top to bottom, the volume of the conversion pipe is in the shape of a circular truncated cone.

[0008] The pipe diameter ratio between the heat preservation pipe and the heat exchange pipe is 0.4-0.9.

[0009] The pipe length ratio between the heat preservation pipe and the heat exchange pipe is 0.04-0.4.

[0010] The buried depth of the heat preservation pipe from the ground is a≥100 meters.

[0011] The inner wall of the heat preservation pipe is provided with a heat insulation layer, which is used to isolate the heat conduction between the heat exchange medium and the heat preservation pipe when the heat exchange medium goes down, and reduce the system heat loss.

[0012] The side of the conversion pipe facing the central pipe is provided with fins. The flow state of the heat exchange medium is changed locally, the heat exchange pipe is transitioned, and the heat exchange is enhanced.

[0013] The outer part of the heat preservation pipe and the conversion pipe is provided with a heat preservation layer. The heat is prevented from being lost to the rock-soil body outside the heat preservation pipe.

[0014] The heat preservation pipe is connected with an inlet, and the central pipe is connected with an outlet.

[0015] The outer pipe, the central pipe and the flow control distributor are arranged in a pit below the ground, and the pit is 2500cm-3000cm away from the ground. This is beneficial to the installation of the heat exchanger and the connection of the pipeline, and does not affect the use function of the ground.

[0016] The beneficial effects of the present application are as follows:

[0017] (1) The outer pipe structure is divided into three sections on the basis of the original straight up and down inner and outer pipe structure, the flow state of the heat exchange medium is changed in sections, and the heat extraction amount of a single well is improved. Specifically, the length of the upper heat preservation pipe is more than 100 meters underground, the outer part is heat-preserved and the inner part is heat-insulated, the downward fluid passes through the relatively narrow annular pipe at a relatively high flow rate, the heat exchange between the heat exchange medium in the heat preservation pipe and the rock-soil body outside the pipe is prevented, and the heat loss is minimized; the conversion pipe arranged obliquely enters the large-diameter annular heat exchange space, the flow rate is reduced, and the heat exchange time of the heat exchange medium in the downward process is prolonged as much as possible, so that the heat exchange with the high-temperature rock outside the pipe is fully performed; at the same time, the increase in the diameter increases the heat exchange area and improves the heat exchange capacity; that is, the heat exchange medium realizes the maximum heat exchange with the geothermal energy in the stratum temperature-increasing section in the conversion pipe section and the heat exchange pipe section with a low flow rate and a large heat exchange area, and moves to the bottom of the central pipe for upward movement.

[0018] That is, the heat exchange medium quickly passes through the upper heat preservation pipe section, and the heat loss is reduced; in the heat exchange pipe section where the heat exchange mainly occurs, the flow rate of the heat exchange medium is greatly reduced, the heat exchange time is prolonged, and the heat exchange amount is increased; the heat exchange area is increased, and the heat exchange capacity is improved; the heat preservation pipe section is provided with a heat preservation layer outside and a heat insulation layer inside, so that the heat preservation pipe does not exchange heat with the outside; even if the upward and downward fluids exchange heat, the heat exchange only occurs inside the heat preservation pipe, and there is no heat loss; the volume capacity of the heat exchange medium in the lower heat exchange pipe section is much larger than that in the upper heat preservation pipe section, the heat storage capacity of the lower heat exchange pipe section is greatly enhanced, and the continuous heat extraction capacity of the system is enhanced; the most efficient utilization of geothermal energy is realized in these aspects.

[0019] (2) The flow control liquid separator of the present invention has a simple structure, flexibly controls the inlet and outlet flow rates, and the inlet and outlet flow rate matching is more reasonable; according to the different heat output, the pipe diameter ratio and length ratio between the heat insulation pipe and the heat exchange pipe are adjusted to make the heat output and heat exchange more balanced and stable; the heat insulation pipe is equipped with an insulation layer inside and an insulation layer outside, which reduces heat loss; the overall heat exchange effect of the heat exchanger is enhanced, heat loss is reduced, and heat exchange efficiency is improved; the heat output is more continuous and stable, the heat output efficiency is high, the unit development and utilization cost of geothermal energy is reduced, and the economic effect is significant. Attached Figure Description

[0020] Fig. 1 This is a schematic diagram of a high-efficiency heat exchanger for medium-deep geothermal energy.

[0021] Fig. 2 This is a schematic diagram of the working state of a high-efficiency heat exchanger for medium-deep geothermal energy.

[0022] Fig. 3 This is a schematic diagram of the flow control distributor in a high-efficiency heat exchanger for medium-deep geothermal energy.

[0023] The attached diagram is labeled as follows: 1-Heat exchange tube; 11-Inlet; 2-Central tube; 21-Outlet; 3-Flow control distributor; 4-Insulation tube; 5-Conversion tube; 51-Fin; 6-Insulation layer; 61-Heat insulation layer; 7-Pit. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Therefore, the following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. Example

[0026] like Figs. 1-3 As shown, a high-efficiency heat exchanger for medium-deep geothermal energy is installed entirely below the ground. An inspection hole 7 is provided at the top, which is 2500cm to 3000cm above the ground. This facilitates the installation of the heat exchanger and the connection of pipes, without affecting the functionality of the surface-level equipment.

[0027] The high-efficiency heat exchanger comprises an outer pipe, a center pipe 2, and a flow control distributor 3, the center pipe 2 is coaxially arranged in the outer pipe, the flow control distributor 3 is arranged above the center pipe 2, and the flow control distributor 3 is in communication with the center pipe 2 and a heat preservation pipe 4; the outer pipe is divided into three sections from top to bottom, and the three sections are the heat preservation pipe 4, a conversion pipe 5, and a heat exchange pipe 1 in sequence from top to bottom.

[0028] Specifically, a pipe diameter ratio between the heat preservation pipe 4 and the heat exchange pipe 1 is 0.4-0.9; the pipe diameter ratio is calculated according to the flow state requirement of the heat exchange medium, the pipe material specification, and the economy of the heat exchanger.

[0029] A pipe length ratio between the heat preservation pipe 4 and the heat exchange pipe 1 is 0.04-0.4; the pipe length ratio is calculated according to the different geothermal temperature increasing rates, the heat exchange and heat storage capacity of the heat exchanger, and the economy of the heat exchanger. The length of the heat exchange pipe 1 is preferably between 1000-2500 meters, and the length of the heat preservation pipe 4 is preferably between 100-400 meters, so the pipe length ratio between the heat preservation pipe 4 and the heat exchange pipe 1 is 0.04-0.4. The specific length is selected according to the geothermal condition in the interval.

[0030] The heat preservation pipe 4 is buried at a depth a of greater than or equal to 100 meters from the ground. According to the principle of the geothermal temperature increasing rate, the ground surface is sequentially a variable temperature layer, a constant temperature layer, and an increasing temperature layer. The average depth of entering the increasing temperature layer is about 60 meters in the mainland of China, and the temperature at a depth of 100 meters is about 20℃. The heat preservation pipe 4 is arranged at a depth of greater than or equal to 100 meters to ensure that the heat of the heat exchange medium is not lost to the external rock-soil body as much as possible when the heat exchange medium descends.

[0031] The inner wall of the heat preservation pipe 4 is provided with a heat insulation layer 61. The heat insulation layer 61 prevents heat conduction between the heat exchange medium and the heat preservation pipe 4 when the heat exchange medium descends, and reduces the heat loss of the heat preservation pipe 4. The outer pipes of the heat preservation pipe 4 and the conversion pipe 5 are both provided with a heat preservation layer 6 to prevent heat loss to the rock-soil body outside the heat preservation pipe 4.

[0032] The heat preservation pipe 4 is connected with an inlet 11, and the center pipe 2 is connected with an outlet 21.

[0033] The side of the conversion pipe 5 facing the center pipe 2 is provided with fins 51. The fins 51 locally change the flow state of the heat exchange medium, transition to the heat exchange pipe 1, and enhance heat exchange.

[0034] During operation:

[0035] The heat exchange medium enters the heat preservation pipe 4 from the inlet 11, descends to the heat exchange pipe 1 through the conversion pipe 5, and exchanges heat in the heat exchange pipe 1. Under the action of the heat insulation layer 61 and the heat preservation layer 6, the heat is not lost. The heat exchange medium continues to exchange and store heat in the heat exchange pipe 1, and finally ascends along the center pipe 2 and enters the heat supply system through the outlet 21.

[0036] During the whole process, the flow control distributor 3 controls the flow in and out according to the requirement.

Claims

1. A high-efficiency heat exchanger for medium-deep geothermal energy, comprising an outer tube, a central tube (2), and a flow-controlling distributor (3), wherein the central tube (2) is coaxially disposed within the outer tube, and the flow-controlling distributor (3) is disposed on the central tube (2); characterized in that: The outer pipe is divided into three sections: upper, middle and lower. From top to bottom, they are insulation pipe (4), conversion pipe (5) and heat exchange pipe (1). The conversion pipe (5) has a frustum-shaped volume. The pipe diameter ratio between the insulation pipe (4) and the heat exchange pipe (1) is 0.4-0.

9. The insulation pipe (4) is buried at a depth a≥100 meters from the ground. The outer pipe, the central pipe (2), and the flow control distributor (3) are all located in a pit (7) below the ground. The pit (7) is 2500cm-3000cm from the ground.

2. The high-efficiency heat exchanger for medium-deep geothermal energy as described in claim 1, characterized in that: The length ratio between the insulation pipe (4) and the heat exchange pipe (1) is 0.04-0.

4.

3. A high-efficiency heat exchanger for medium-deep geothermal energy as described in claim 1 or 2, characterized in that: The inner wall of the insulation pipe (4) is provided with a heat insulation layer (61).

4. A high-efficiency heat exchanger for medium-deep geothermal energy as described in claim 3, characterized in that: The conversion tube (5) has fins (51) on the side facing the central tube (2).

5. A high-efficiency heat exchanger for medium-deep geothermal energy as described in claim 4, characterized in that: The insulation pipe (4) and the conversion pipe (5) are provided with an insulation layer (6) on the outside.

6. A high-efficiency heat exchanger for medium-deep geothermal energy as described in claim 1, characterized in that: The insulation pipe (4) is connected to an inlet (11); the central pipe (2) is connected to an outlet (21).

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