CN214581876U

CN214581876U - Underground enhanced heat exchange system

Info

Publication number: CN214581876U
Application number: CN202120134410.0U
Authority: CN
Inventors: 刘强; 徐雅静; 张磊
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2021-01-19
Filing date: 2021-01-19
Publication date: 2021-11-02
Anticipated expiration: 2031-01-19

Abstract

The utility model discloses a heat transfer system is reinforceed in pit, it relates to the energy utilization field, and heat transfer system is reinforceed in pit includes: a first wellbore lowered into the geothermal reservoir and a second wellbore positioned above and in communication with the first wellbore; a convection through hole is formed in the side wall of the first shaft; the fixed table is arranged at the bottom of the second shaft; the heat exchanger sleeve is arranged in the second shaft, and a drain hole is formed in the side wall of the heat exchanger sleeve; a tubular body disposed in the first wellbore; the pump body is connected to the fixed table, an inlet of the pump body is communicated with the pipe body, and an outlet of the pump body is communicated with the heat exchanger sleeve; the heat pump system comprises a spiral heat exchanger arranged in a heat exchanger sleeve, a working medium descending pipe, a working medium ascending pipe, a compressor, a condenser, a throttle valve and working medium filled in the heat pump system. This application can realize "getting heat and not getting water" to the geothermol power deep well, realizes high-efficient heat transfer and geothermal energy's sustainable use's purpose.

Description

Underground enhanced heat exchange system

Technical Field

The utility model relates to an energy utilization field, in particular to heat transfer system is reinforceed in pit.

Background

The geothermal energy is recyclable natural heat energy extracted from the earth crust, has the characteristics of large reserves, wide distribution, cleanness, environmental protection, high utilization coefficient and the like, and has good heat source stability and no influence of seasonal weather compared with solar energy and wind energy. The geothermal resources in China are rich, the geothermal storage capacity which can be exploited is equivalent to 2560 hundred million tons of standard coal, and more than 70 percent of the geothermal resources are medium-low temperature geothermal resources below 150 ℃. The regions with rich geothermal resources in China are highly overlapped with the heating regions, so that the development of geothermal energy heating is to reduce the coal consumption and CO in China₂An important measure of emissions.

The traditional hydrothermal geothermal energy development technology mainly extracts underground water directly, and the underground water level in northern areas is low, so that the power consumption of a water pump is high, and the operation cost is high. In order to protect underground water resources, the underground water resources must be recharged in the same layer, and a recharging well needs to be arranged, so that the drilling cost is high. The recharge quantity of geothermal water depends on the stratum structure, the recharge rate in northern areas is generally low, the underground water level is reduced, and even the ground sinks when the groundwater level is serious; on the other hand, the underground water contains gases such as hydrogen sulfide and the like, which can cause chemical pollution on the surface of the ground and can also cause thermal pollution when the underground water is unfavorable for recharging; at present, geothermal projects which do not carry out recharging operation are called to stop in China. In addition, the scaling of geothermal water in the pipes and the heat exchanger can bring certain influence on the operation. Therefore, there is a need to develop a new geothermal energy development technology that can take heat but not water, so as to realize the environmental protection, low cost and sustainable development of geothermal energy.

SUMMERY OF THE UTILITY MODEL

In order to overcome the above-mentioned defect of prior art, the embodiment of the utility model provides a technical problem that will solve provides a heat transfer system is reinforceed in the pit, and it can realize "getting hot not getting water" to the geothermol power deep well, realizes the sustainable use of high-efficient heat transfer and geothermal energy.

The embodiment of the utility model provides a concrete technical scheme is:

a downhole enhanced heat exchange system, comprising:

a first wellbore lowered into a geothermal reservoir and a second wellbore positioned above and in communication with the first wellbore, the first wellbore having a diameter smaller than a diameter of the second wellbore; a convection through hole is formed in the side wall of the first shaft so that convection can be formed between the inside of the first shaft and underground water in the geothermal reservoir;

a fixed table disposed at the bottom of the second wellbore; the heat exchanger sleeve is arranged in the second shaft and extends along the vertical direction, and a drain hole is formed in the side wall of the heat exchanger sleeve; a vertically extending tubular body disposed in the first wellbore; the pump body is connected to the fixed table, an inlet of the pump body is communicated with the upper end of the pipe body, and an outlet of the pump body is communicated with the lower end of the heat exchanger sleeve;

the heat pump system comprises a spiral heat exchanger arranged in a heat exchanger sleeve, a working medium descending pipe connected with a working medium inlet at the upper end of the heat exchanger, a working medium ascending pipe connected with a working medium outlet at the lower end of the heat exchanger, a compressor, a condenser, a throttle valve and working medium filled in the heat pump system, wherein the compressor, the condenser and the throttle valve are sequentially connected between the working medium ascending pipe and the working medium descending pipe, and the working medium can be heated into gas by underground water in the heat exchanger sleeve.

Preferably, a filter screen for removing sand is arranged at the lower end of the pipe body.

Preferably, the drain hole is located above the heat exchanger.

Preferably, the working medium ascending pipe is externally coated with a heat insulating material, and the working medium descending pipe is externally coated with a heat insulating material; the outer wall surface of the heat exchanger sleeve is coated with a heat insulating material; the outer wall surface of the pipe body is coated with a heat insulating material.

Preferably, the pump body is located below the liquid level and near the static liquid level, and the heat exchanger is located above the static liquid level.

Preferably, the heat exchanger includes a first coil and a second coil, a radial dimension of an overall shape of the second coil is smaller than a radial dimension of an overall shape of the first coil, and the second coil is located at a middle portion of the first coil.

Preferably, the height of the heat exchanger in the vertical direction is greater than the width in the horizontal direction.

Preferably, the inner wall surface of the heat exchange tube of the heat exchanger is provided with a groove extending in a spiral shape.

Preferably, water in the heat exchanger sleeve flows from bottom to top under the driving of the pump body, and the working medium in the heat exchanger flows from top to bottom.

The technical scheme of the utility model following beneficial effect that is showing has:

the underground enhanced heat exchange system sucks geothermal water in a first shaft of a geothermal reservoir through a pump body, the geothermal water flows into a heat exchanger sleeve upwards after being sucked, and exchanges heat with a spiral heat exchanger arranged in the heat exchanger sleeve, so that a working medium in the heat exchanger absorbs heat and is vaporized; the geothermal water cooled by the heat exchanger is discharged to an annular space between the second shaft and the heat exchanger sleeve from the side wall of the heat exchanger sleeve through a water discharge hole, falls into the first shaft under the action of gravity, and circulates in the manner. Working medium in the heat exchanger is vaporized and then rises through the working medium ascending pipe to be discharged to the outside of the well, the working medium is compressed into high-pressure gas through the compressor and is greatly heated, and the working medium flows through the condenser to release heat so as to supply the heat to a heat user. And then the working medium is decompressed and cooled by a throttle valve to become a gas-phase working medium and a liquid-phase working medium, the two-phase working medium flows to the heat exchanger in the first shaft through a working medium descending pipe to exchange heat and heat, then flows out through a working medium ascending pipe, and the cycle is repeated. In the whole process, geothermal water in the geothermal reservoir only circularly flows in the pipe body, the heat exchanger sleeve, the second shaft and the first shaft, underground water is not extracted and output to the outside of a well, the purposes of 'taking heat but not taking water' of a geothermal deep well are realized, the purposes of efficient heat exchange and sustainable utilization of geothermal energy are also realized, and underground water resources are effectively protected. In addition, geothermal water flows in a circulating manner in the well all the time in the whole operation process, recharging operation is not needed, pollution to the geothermal water is avoided, and chemical pollution to the ground surface is also avoided. Therefore, the underground enhanced heat exchange system has the advantages of environmental protection, low cost and sustainable development.

Specific embodiments of the present invention are disclosed in detail with reference to the following description and the accompanying drawings, which specify the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the present invention are not so limited in scope. The embodiments of the invention include many variations, modifications and equivalents within the spirit and scope of the appended claims. Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for helping the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. The skilled person in the art can, under the teaching of the present invention, choose various possible shapes and proportional dimensions to implement the invention according to the specific situation.

FIG. 1 is a schematic structural diagram of a downhole portion of a downhole enhanced heat exchange system according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an uphole part of the downhole heat transfer enhancement system in the embodiment of the present invention.

Reference numerals of the above figures:

1. a well cover; 2. a working medium downcomer; 3. a heat exchanger; 31. a first spiral pipe; 32. a second spiral pipe; 4. a working medium riser; 5. a heat exchanger sleeve; 6. a pump body; 7. a pipe body; 8. a filter screen; 9. a convection passage; 10. a fixed table; 11. a second wellbore; 12. cementing cement; 13. a header; 14. a drain hole; 15. a thermally insulating material; 16. a compressor; 17. a condenser; 18. a throttle valve; 100. a static liquid level; 200. a geothermal reservoir.

Detailed Description

The details of the present invention can be more clearly understood with reference to the accompanying drawings and the description of the embodiments of the present invention. However, the specific embodiments of the present invention described herein are for the purpose of explanation only, and should not be construed as limiting the invention in any way. Given the teachings of the present invention, the skilled person can conceive of any possible variants based on the invention, which should all be considered as belonging to the scope of the invention. It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "mounted," "connected," and "connected" are to be construed broadly and may include, for example, mechanical or electrical connections, communications between two elements, direct connections, indirect connections through intermediaries, and the like. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In order to realize "not getting hot water" to geothermol power deep well, realize the sustainable use's of high-efficient heat transfer and geothermal energy purpose, provided a heat transfer system is reinforceed in the pit in this application, fig. 1 is the embodiment of the utility model provides an in the pit reinforce the structural schematic diagram of heat transfer system underground part, fig. 2 is the embodiment of the utility model provides an in the pit reinforce the structural schematic diagram of heat transfer system underground part, as shown in fig. 1 and fig. 2, reinforce heat transfer system in the pit and can include: a first wellbore lowered into the geothermal reservoir 200 and a second wellbore 11 positioned above and in communication with the first wellbore, the first wellbore having a diameter smaller than a diameter of the second wellbore 11; a convection through hole is formed in the side wall of the first shaft so that convection is formed between the inside of the first shaft and the underground water in the geothermal reservoir 200; a fixed table 10 arranged at the bottom of the second shaft 11; the heat exchanger sleeve 5 is arranged in the second shaft 11 and extends along the vertical direction, and a drain hole 14 is formed in the side wall of the heat exchanger sleeve 5; a vertically extending pipe body 7 disposed in the first wellbore; the pump body 6 is connected to the fixed table 10, an inlet of the pump body 6 is communicated with the upper end of the pipe body 7, and an outlet of the pump body 6 is communicated with the lower end of the heat exchanger sleeve 5; the heat pump system comprises a spiral heat exchanger 3 arranged in a heat exchanger sleeve 5, a working medium descending pipe 2 connected with a working medium inlet at the upper end of the heat exchanger 3, a working medium ascending pipe 4 connected with a working medium outlet at the lower end of the heat exchanger 3, a compressor 16, a condenser 17 and a throttle valve 18 which are sequentially connected between the working medium ascending pipe 4 and the working medium descending pipe 2, and a working medium filled in the heat pump system, wherein the working medium can be heated into gas by underground water in the heat exchanger sleeve 5 in the heat exchanger 3.

The underground enhanced heat exchange system sucks geothermal water in a first shaft of a geothermal reservoir 200 upwards through a pipe body 7 through a pump body 6, the geothermal water flows upwards into a heat exchanger sleeve 5 after being sucked, and exchanges heat with a spiral heat exchanger 3 arranged in the heat exchanger sleeve 5, so that the heat absorption temperature of a working medium in the heat exchanger 3 is increased and vaporized; the geothermal water cooled by the heat exchanger 3 is discharged to an annular space between the second shaft 11 and the heat exchanger sleeve 5 from the side wall of the heat exchanger sleeve 5 through a water discharge hole 14, falls into the first shaft under the action of gravity, and circulates in the manner. The working medium in the heat exchanger 3 is vaporized, ascends through the working medium ascending pipe 4 and is discharged to the outside of the well, the working medium is compressed into high-pressure gas through the compressor 16 and is greatly heated, and the working medium flows through the condenser 17 to release heat so as to supply the heat to a heat user. And then the working medium is decompressed and cooled by a throttle valve 18 to become a gas-phase working medium and a liquid-phase working medium, the two-phase working medium flows to a heat exchanger 3 in the first shaft through a working medium descending pipe 2 to exchange heat and heat, then flows out through a working medium ascending pipe 4, and the cycle is repeated. In the whole process, geothermal water in the geothermal reservoir 200 only circularly flows in the pipe body 7, the heat exchanger sleeve 5, the second shaft 11 and the first shaft, underground water is not extracted and output to the outside of the well, so that the purposes of 'taking heat and not taking water' from a geothermal deep well are realized, underground water resources are effectively protected, and efficient heat exchange and sustainable utilization of geothermal energy are realized. In addition, geothermal water flows in a circulating manner in the well all the time in the whole operation process, recharging operation is not needed, pollution to the geothermal water is avoided, and chemical pollution to the ground surface is also avoided. Therefore, the underground enhanced heat exchange system has the advantages of environmental protection, low cost and sustainable development.

In order to better understand the downhole enhanced heat exchange system of the present application, it will be further explained and illustrated below. As shown in fig. 1, the downhole enhanced heat exchange system may include: the device comprises a first shaft, a second shaft 11, a fixed platform 10, a heat exchanger sleeve 5, a pipe body 7, a pump body 6 and a heat pump system.

As shown in fig. 1, a first shaft is lowered into the geothermal reservoir 200, and meanwhile, a convection through hole is formed in a side wall of the first shaft so that convection is formed between the inside of the first shaft and the groundwater in the geothermal reservoir 200. Geothermal water in the geothermal reservoir 200 flows through the convective pass-through into the first wellbore, which is filled with geothermal water. Convection is formed between the inside of the first shaft and the underground water in the geothermal reservoir 200, so that heat exchange between the geothermal water in the first shaft and the geothermal water in the reservoir is enhanced, and heat compensation of the geothermal water in the first shaft is realized. The geothermal reservoir 200 outside the side wall of the first shaft can be provided with a plurality of convection channels 9 outwards along the radial direction in the circumferential direction, and the convection channels 9 are communicated with the convection through holes, so that geothermal water in the geothermal reservoir 200 far away from the first shaft area can form convection with water in a shaft, and the total heat compensation amount of the geothermal water in the first shaft can be improved.

As shown in fig. 1, a second wellbore 11 is located above and in communication with the first wellbore. The upper end of the second shaft 11 is connected with the ground, and the lower end is connected with the upper end of the first shaft. The diameter of the first well bore is smaller than the diameter of the second well bore 11 so that the junction of the first well bore and the second well bore 11 has a step. The fixed table 10 is arranged at the bottom of the second shaft 11, and the fixed table 10 can be supported by the step, so that other components with larger weight, such as the pump body 6, the heat exchanger sleeve 5, the pipe body 7 and the like, can be arranged or connected on the fixed table 10. The fixed table 10 has a communication hole to enable communication between the upper and lower sides, ensuring that geothermal water returns to the first shaft through the fixed table 10. The outer side of the wall of the upper end of the second shaft 11 is cemented by cementing cement 12. Geothermal water in the geothermal reservoir 200 has a hydrostatic level 100 after flowing into the first wellbore and the second wellbore 11, and the hydrostatic level 100 may be higher than the first wellbore and located between the upper end and the lower end of the second wellbore 11. Well lid 1 is installed to the well head department of second pit shaft 11 to the realization is to first pit shaft and 11 sealed of second pit shaft, avoids gas such as hydrogen sulfide that geothermal water contains in first pit shaft and the second pit shaft 11 to volatilize, from causing earth's surface chemical pollution.

As shown in fig. 1, the heat exchanger sleeve 5 extends in a vertical direction, which is arranged in the second borehole 11. The upper end of the heat exchanger sleeve 5 can be connected to the well lid 1 and can also be arranged on the fixing table 10, so that the weight of the heat exchanger sleeve is supported. The body 7 extends along vertical direction, and it sets up in first pit shaft, and the lower extreme of body 7 can stretch into to the bottom of second pit shaft 11, and the upper end of body 7 can be connected on fixed station 10. The pump body 6 is also arranged in connection with the stationary table 10, preferably inside the heat exchanger sleeve 5. The inlet of the pump body 6 is communicated with the upper end of the pipe body 7, and the outlet of the pump body 6 is communicated with the heat exchanger sleeve 5. The pump body 6 needs to be positioned below the static liquid surface 100, preferably near the static liquid surface 100. When the pump body 6 operates, high-temperature geothermal water at the bottom of the first shaft can be pumped upwards through the pipe body 7, so that the geothermal water enters the heat exchanger sleeve 5 and continues to flow upwards until the geothermal water reaches a drain hole 14 formed in the side wall of the heat exchanger sleeve 5, flows out of the heat exchanger sleeve 5 through the drain hole 14 to an annular space between the second shaft 11 and the heat exchanger sleeve 5, flows to the second shaft 11 under the action of gravity and returns to the bottom of the first shaft, and the process is repeated. As feasible, the lower end of the pipe body 7 can be provided with a filter screen 8 for desanding, so that silt impurities and the like in geothermal water can be filtered. Since the temperature of the geothermal water flowing out of the heat exchanger sleeve 5 through the water discharge hole 14 to the second shaft 11 is already reduced, after the geothermal water flows to the static liquid level 100 in the second shaft 11, due to low temperature and high density, the geothermal water in the first shaft has high temperature and low density, so that a geothermal water self-circulation loop is formed by virtue of density difference, the low-temperature geothermal water continuously absorbs heat and heats up in the process of flowing to the bottom of the well, and the geothermal water at the bottom of the well rises in the pipe body 7.

As shown in fig. 1, the heat pump system may include a heat exchanger 3, a working fluid down pipe 2, a working fluid up pipe 4, a compressor 16, a condenser 17, and a throttle valve 18. Wherein, heat exchanger 3 sets up in heat exchanger sleeve 5, and the heat exchange tube of heat exchanger 3 is the heliciform, and the heliciform axis extends along vertical direction. The heat exchanger 3 is spiral and can effectively improve the heat exchange area of the heat exchanger 3 in the heat exchanger sleeve 5 with limited space. The working medium descending pipe 2 is connected with a working medium inlet at the upper end of the heat exchanger 3, and the working medium ascending pipe 4 is connected with a working medium outlet at the lower end of the heat exchanger 3. Through the structure, the working medium with low relative temperature flows from top to bottom in the spiral heat exchanger 3, the geothermal water in the heat exchanger sleeve 5 flows from bottom to top under the driving of the pump body 6, and the geothermal water with high relative temperature preferentially washes the working medium with raised temperature in the lower end of the heat exchanger 3. The working medium charged in the heat pump system is a working medium which can be heated into gas by underground water in the geothermal reservoir 200 in the heat exchanger 3, can be understood as a low-boiling-point working medium, and can generally be an environment-friendly working medium with the boiling point lower than 0 ℃. The working medium with low boiling point and geothermal water with higher relative temperature form reverse forced convection, and the working medium is heated, boiled and vaporized in the spiral heat exchanger 3. The vaporized working medium rises through the working medium ascending pipe 4. The working medium descending pipe 2 and the working medium ascending pipe 4 can be fixed in a nesting mode through the well cover 1.

As shown in fig. 2, a compressor 16, a condenser 17 and a throttle valve 18 are connected in sequence between the working medium rising pipe 4 and the working medium descending pipe 2. The working medium in the heat exchanger 3 is vaporized, ascends through the working medium ascending pipe 4 and is discharged to the outside of the well, the working medium is compressed into high-pressure gas through the compressor 16 and is greatly heated, and the working medium flows through the condenser 17 to release heat so as to supply the heat to a heat user. Through the process, the equipment can be simplified, and secondary indirect heat exchange is reduced, so that the utilization efficiency of heat is improved. And then the liquid phase working medium is decompressed and cooled by a throttle valve 18 to become a gas phase working medium and a liquid phase working medium, the two phase working medium flows to a heat exchanger 3 in the first shaft through a working medium descending pipe 2 to exchange heat and heat, then flows out through a working medium ascending pipe 4, and the cycle is repeated. The liquid-phase working medium in the working medium descending pipe 2 has high density, and the gaseous working medium in the working medium ascending pipe 4 has low density, so that power is provided for working medium circulation through density difference, and power consumption is reduced.

Preferably, as shown in fig. 2, the heat exchanger 3 is located above the static liquid level 100, for example, it may be at about 2m, and the pump body 6 may be a submersible pump, which only needs to provide the lift from the static liquid level 100 to the heat exchanger 3, and does not need to deliver the geothermal water to the ground, so as to reduce the electric energy consumed by delivering the geothermal water to the ground.

In a preferred embodiment, as shown in fig. 1 and 2, the heat exchanger 3 may include a first coil 31 and a second coil 32, the second coil 32 having an overall shape with a radial dimension smaller than that of the first coil 31, and the second coil 32 being located at a middle portion of the first coil 31. The lower end of the working medium downcomer 2 is connected with the working medium inlets at the upper ends of the first spiral pipe 31 and the second spiral pipe 32 respectively. The lower end of the working medium ascending pipe 4 can be connected with a header 13, and the header 13 is respectively connected with the working medium outlets at the lower ends of the first spiral pipe 31 and the second spiral pipe 32. Working media in the first spiral pipe 31 and the second spiral pipe 32 are evaporated in the pipes to form gas, and the gas is collected in the header 13 and then supplied to a ground device through the working medium ascending pipe 4. By the mode, the space in the heat exchanger sleeve 5 can be utilized to the maximum, the number of spiral pipes of the heat exchanger 3 is greatly increased, and therefore the heat exchange area is increased. Moreover, as for the heat exchanger 3 with the spiral tube, compared with the heat exchanger 3 with a straight tube, the structure of the spiral tube is more compact under the same heat exchange area, and the pressure balance in the shell pass can be ensured; in addition, the turbulent flow of fluid outside the pipe is easier to realize, which is beneficial to strengthening heat exchange and improving the overall heat exchange efficiency. Furthermore, the heat exchanger 3 with the first spiral tube 31 and the second spiral tube 32 is provided with a header 13, and the header 13 can achieve the purposes of collecting and mixing the working medium gas and reducing the thermal deviation. As a more preferred embodiment, the heat exchanger 3 may further include a third coil, which may be smaller than a radial dimension of the overall shape of the second coil 32, and which may be disposed at a middle portion of the second coil 32.

In general, it is preferred that the heat exchanger 3 forms a compact high aspect ratio heat exchanger, i.e. the height of the heat exchanger 3 in the vertical direction is larger than the width in the horizontal direction. This makes it possible to increase the heat exchange area of the heat exchanger 3 in the heat exchanger sleeve 5. The working medium with low boiling point and the geothermal water with high temperature form reverse forced convection, and the working medium can better absorb heat and boil in the spiral heat exchange section, so as to improve the heat exchange efficiency.

In a preferred embodiment, the inner wall surface of the spiral heat exchange tube of the heat exchanger 3 may be provided with a groove extending spirally. The cross section of the groove can be rectangular. Therefore, the working medium can rotate when flowing in the heat exchange tube, and then the flow separation area is generated to form vortexes with different strength and different sizes, so that the turbulence is enhanced, strong disturbance of liquid to the wall surface is formed, the separation of bubbles from the wall surface is accelerated, and the heat exchange coefficient of the working medium in the tube is improved.

In order to reduce the heat losses, the outer wall surface of the working medium riser 4 can be coated with a thermally insulating material 15. The outer wall surface of the working substance downcomer 2 may be coated with a thermally insulating material 15. The outer wall surface of the heat exchanger sleeve 5 is coated with a heat insulating material 15. The outer wall surface of the pipe body 7 is coated with a heat insulating material 15. The heat insulating material 15 may be an inorganic heat insulating material having characteristics of corrosion resistance, nonflammability, and high temperature resistance, and may be a heat insulating material having a low thermal conductivity such as asbestos, glass fiber, and diatomaceous earth.

The application also provides a downhole heat transfer enhancement method, which can comprise the following steps:

the geothermal water in the first wellbore convects with the groundwater within the geothermal reservoir 200 through the convection pass-through.

The pump body 6 drives the geothermal water in the first shaft upwards into the heat exchanger sleeve 5 through the pipe body 7 and flushes the heat exchanger 3, and the high-temperature geothermal water and the low-boiling-point working medium in the heat exchanger 3 form reverse forced convection and carry out heat exchange, so that the working medium in the heat exchanger 3 is vaporized.

Geothermal water after heat exchange with working media in the heat exchanger 3 reflows to the second shaft 11 and the first shaft through the drain hole 14.

The vaporized working medium is compressed and heated by a compressor 16 through a working medium ascending pipe 4, and heat is released when the working medium passes through a condenser 17.

In a specific embodiment, the downhole enhanced heat exchange system is adopted, wherein the working medium is R134a, the well depth is about 200m, namely the first shaft is set to about 200 m. The temperature of the geothermal water below the tube 7 is between 60 ℃ and 70 ℃. The pump body 6 pumps underground medium-high temperature geothermal water into the heat exchanger sleeve 5 through the pipe body 7 to wash the heat exchanger 3, the working medium throttled and depressurized by the throttle valve 18 enters the spiral heat exchange section of the heat exchanger 3 through the working medium descending pipe 2 to perform countercurrent heat exchange with the geothermal water, the working medium in the heat exchanger 3 is heated and evaporated to form gas, the gas is supplied to the compressor 16 through the working medium ascending pipe 4 after being collected by the header 13, the gas working medium is compressed to form high-temperature high-pressure working medium and enters the condenser 17 to exchange heat with a user end to discharge heat, and the condensed working medium enters the throttle valve 18 to be depressurized into a vapor-liquid two-phase working medium and then enters the working medium descending pipe 2. The density difference of the working medium in the working medium descending pipe 2 and the working medium ascending pipe 4 enables the working medium to circulate and flow circularly, and the COP of the heat pump can reach more than 5. The implementation mode adopts the geothermal single well heat transfer enhancement method which can take heat but not water, and can effectively achieve the purposes of high performance and high efficiency in heat taking and heating.

The underground enhanced heat exchange system and the method have the following advantages: 1. the heat exchange section in the heat exchanger 3 adopts a compact spiral type, so that the heat exchange area per unit volume can be increased, and the heat resistance of convective heat transfer is reduced. 2. The inner wall surface of the spiral heat exchange tube of the heat exchanger 3 is provided with the groove, so that a flow separation area is generated when fluid flows through, vortexes with different strengths and sizes are formed, the structure of the fluid is changed, the turbulence degree is enhanced, and the heat exchange coefficient is improved. 3. The low boiling point working medium and the high temperature geothermal water form reverse forced convection and carry out heat exchange, and the working medium is heated, evaporated and boiled in the spiral heat exchange tube so as to realize enhanced heat exchange. 4. And the cold geothermal water in the first shaft is subjected to heat and mass transfer with the underground water in the geothermal reservoir 200 through the convection channel 9 under the action of pressure in the descending process of the cold geothermal water, so that forced convection is realized, the heat exchange coefficient between the geothermal water is improved, and the temperature rising speed of the cold geothermal water is further improved.

This application has realized "getting heat and not getting water" to geothermol power deep well, effectively solves the problem that the recharge rate that traditional heat technique exists is low, ground subsides, hot water resource exhaustion, thermal pollution, equipment corrosion scale deposit and single well heat transfer system get the heat and lack, heat transfer area is limited, heat exchange efficiency is low etc. has reached the purpose that improves heat transfer coefficient, realizes high-efficient heat transfer and geothermal energy sustainable utilization.

All articles and references disclosed, including patent applications and publications, are hereby incorporated by reference for all purposes. The term "consisting essentially of …" describing a combination shall include the identified element, ingredient, component or step as well as other elements, ingredients, components or steps that do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional. A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.

Claims

1. A downhole enhanced heat exchange system, comprising:

2. The downhole enhanced heat exchange system of claim 1, wherein a filter screen for removing sand is arranged at the lower end of the pipe body.

3. The downhole enhanced heat exchange system of claim 1, wherein the drain hole is located above the heat exchanger.

4. The downhole enhanced heat exchange system of claim 1, wherein the outer wall surface of the working medium riser is coated with an insulating material, and the outer wall surface of the working medium downcomer is coated with an insulating material; the outer wall surface of the heat exchanger sleeve is coated with a heat insulating material; the outer wall surface of the pipe body is coated with a heat insulating material.

5. The downhole enhanced heat exchange system of claim 1, wherein the pump body is located below the fluid level and near the hydrostatic surface, and the heat exchanger is located above the hydrostatic surface.

6. The system of claim 1, wherein the heat exchanger comprises a first coil and a second coil, the second coil having an overall shape with a radial dimension that is smaller than a radial dimension of the overall shape of the first coil, the second coil being located in a middle portion of the first coil.

7. The downhole enhanced heat exchange system of claim 1, wherein the heat exchanger has a height in a vertical direction that is greater than a width in a horizontal direction.

8. The downhole enhanced heat exchange system of claim 1, wherein the inner wall surface of the heat exchange tube of the heat exchanger has a groove extending spirally.

9. The downhole enhanced heat exchange system of claim 1, wherein the water in the heat exchanger sleeve flows from bottom to top under the driving of the pump body, and the working medium in the heat exchanger flows from top to bottom.