Energy efficiency improving system for shallow ground heat exchanger

Abstract

The invention discloses an energy efficiency improving system for a shallow buried pipe heat exchanger. A closed or semi-closed heat storage area unit is arranged in a surrounding mode through area heat insulation plates. The heat storage area unit comprises a plurality of heat storage wells, a plurality of shallow water lifting wells, a plurality of deep water lifting wells, a plurality of solar water heaters, a heat storage water tank, a plurality of U-shaped vertical buried pipes and a ground source heat pump machine room; the buried depth of the regional heat insulation plate is arranged in soil of an earth crust constant temperature zone and penetrates through an earth crust daily variable temperature zone and an earth crust annual variable temperature zone from top to bottom, the buried depth H of the regional heat insulation plate is larger than or equal to H2 + 0.5-1 m, and H2 is the depth of the annual variable temperature zone; the heat storage well is of an inner and outer sleeve type hollow structure provided with a plurality of horizontal branch pipes shaped like a cross or a Chinese character'jing ', and the horizontal branch pipes are arranged in soil of a crustal annual variable temperature zone and a constant temperature zone. The buried depth H of the upper horizontal branch pipe is greater than or equal to H1 + 0.5-1m, and the buried depth H of the lower horizontal branch pipe is greater than or equal to H2 + 0.5-1m; h1 is the daily variable temperature zone depth, and H2 is the annual variable temperature zone depth.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable clean energy utilization, and particularly relates to an energy efficiency improvement system for a shallow buried pipe heat exchanger. Background Art

[0002] Geothermal energy, as a renewable clean energy, has been widely promoted and applied. However, due to factors such as region, climate environment, shallow crust geothermal field, and underground aquifer, the popularization and application of shallow U-shaped vertical buried pipe ground source heat pump heating technology have certain limitations.

[0003] Due to the zonal phenomenon of the shallow crust geothermal field, which is divided into the variable temperature zone, constant temperature zone, and increasing temperature zone from top to bottom. In the northern region of China, the depth of the daily variable temperature zone is only 1m - 2m, the depth of the annual variable temperature zone can reach 15m - 20m, the depth of the constant temperature zone is mostly 20 - 30m underground, and the depth of the increasing temperature zone is mostly above 30m.

[0004] An underground aquifer refers to the rock or soil layer in the crust that can store and flow groundwater. It is usually located several meters to dozens of meters below the surface, has a certain thickness, permeability, and fluidity. The position of the aquifer mostly shows a layered structure and can be divided into three types: impermeable layer, semi-permeable layer, and permeable layer according to its physical properties and geological conditions.

[0005] During the heating operation in winter, the water in the U-shaped vertical buried pipe absorbs the heat in the soil of the increasing temperature zone, the temperature of the water increases, and when it flows through the daily variable temperature zone and annual variable temperature zone of the shallow crust, it releases heat and the water temperature gradually decreases, resulting in a decrease in the water temperature entering the ground source heat pump unit and a decrease in the heating COP value of the unit by about 5 - 10%. Especially in cold and severely cold regions, the above problems are particularly prominent. The inlet water temperature of the unit is greatly affected by the soil in the variable temperature zone. Since the heat extraction in winter is greater than the heat extraction in summer, and there is a long-term heat energy interaction between the buried pipe system and the underground soil. After the ground source heat pump system is used for a period of time, the temperature of the soil changes greatly, and the soil cannot provide enough heat and temperature for heat transfer with the buried pipe system, resulting in a local "cold accumulation" phenomenon, making the heat exchange effect of the subsequent ground source heat pump system poor, the heating effect in winter of the project is poor, and even it cannot operate normally, and other heat sources need to be used to ensure the reliable and stable operation of the system. Therefore, the local "geothermal imbalance" problem is the main technical obstacle affecting the application and popularization of ground source heat pump technology.

[0006] Therefore, for those skilled in the art, designing a set of energy efficiency improvement system or method for shallow U-shaped vertical buried pipes, enabling it to improve the heat exchange efficiency of the U-shaped vertical buried pipes in the variable temperature zone soil of the shallow crust and the inlet water temperature of the ground source heat pump unit to solve the local "geothermal imbalance or cold accumulation" problem is an urgent technical problem to be solved by those skilled in the art. Summary of the Invention

[0007] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a shallow buried pipe U-type heat exchanger energy efficiency improvement system, by setting a heat storage well and an insulation layer in the shallow crust temperature variable zone to increase the temperature of the soil and water in the aquifer in the shallow temperature variable zone; using a passive pressurization method to increase the water runoff or seepage velocity in the aquifer to strengthen the heat exchange between the U-shaped vertical buried pipe and the surrounding soil and water, eliminate the local "geothermal imbalance or cold accumulation" phenomenon, and improve the heat exchange efficiency of the U-shaped vertical buried pipe.

[0008] In order to achieve the above technical objectives, the present invention adopts the following scheme: A shallow buried pipe heat exchanger energy efficiency improvement system, which uses a regional heat insulation board to enclose a closed or semi-closed heat storage area unit, so that the soil or heat storage layer in the crust temperature change zone can passively store heat to improve the heat exchange efficiency of the U-shaped vertical buried pipe in the crust daily temperature change zone and annual temperature change zone; The heat storage area unit includes several heat storage wells, several shallow water extraction wells or recharging wells, several deep water extraction wells or recharging wells, several solar water heaters, hot water storage tanks, several U-shaped vertical buried pipes, water extraction pumps, circulation pumps, water extraction pipelines, recharging pipelines, water delivery pipelines and ground source heat pump room; The regional heat insulation board is arranged at the periphery of the U-shaped vertical buried pipe heat exchange area and is a ring-shaped or square connection structure, which is used to prevent the heat exchange or transfer between the U-shaped vertical buried pipe and the external soil; The buried depth of the regional thermal insulation board is set in the soil of the constant temperature zone of the earth's crust, and passes through the daily temperature zone and the annual temperature zone of the earth's crust from top to bottom. The buried depth H≥H2+0.5~1m (H2 is the depth of the annual temperature zone); The heat storage well is an inner and outer sleeve type hollow structure with a plurality of horizontal branch pipes in a "cross" or "well" shape, and the horizontal branch pipes are arranged in the soil of the annual temperature zone and the constant temperature zone of the earth's crust; the upper horizontal branch pipe is buried at a depth of H≥H1+0.5~1m, and the lower horizontal branch pipe is buried at a depth of H≥H2+0.5~1m; (H1 is the depth of the daily temperature zone, and H2 is the depth of the annual temperature zone); A heat storage cylinder is arranged in the horizontal branch pipe of the heat storage well, and a phase change heat storage material is arranged in the heat storage cylinder; The water extraction and recharging depths of the plurality of water extraction wells and recharging wells are arranged in a multi-level stepped layered manner, and are divided into shallow water extraction wells or shallow recharging wells, deep water extraction wells or deep recharging wells; the shallow water extraction wells have the same depth as the shallow recharging wells, and the deep water extraction wells have the same depth as the deep recharging wells. The purpose of such a structural arrangement is to ensure water extraction and recharging in the same layer, so as to avoid cross-contamination of water quality and soil in different underground water layers; The solar water heater is a light tube, flat plate, or groove type solar water heater collector; The heat storage tank is provided with a phase change heat storage material; The described heat storage water tank is provided with interfaces connected to the cold water pipe and the hot water pipe of the solar water heater, and completes the transfer and storage of heat through a circulation pump, a cold water pipe, and a hot water pipe; The described heat storage water tank is provided with interfaces connected to the heat storage outlet and return water pipes of the heat storage well, and completes the transfer and storage of heat from the heat storage well through a lift pump, a heat storage return water pipe, and a heat storage outlet pipe; Among the described several U-shaped vertical buried pipes, there are a U-shaped return water riser and a U-shaped outlet water riser, which are respectively connected to the inside of the ground source heat pump machine room through a horizontal return water pipe, a horizontal inlet water pipe, and a main pipeline; Preferably, the water intake and recharge positions of the shallow water extraction well and the recharge well are set in the variable temperature zone or the constant temperature zone water-bearing soil layer within 15 - 30 m from the ground surface; Preferably, the water intake and recharge positions of the deep water extraction well and the recharge well are set in the increasing temperature zone water-bearing soil layer more than 30 - 100 m below the ground surface; Preferably, the water intake and recharge positions of the water extraction well and the recharge well are set in multiple levels in different underground water-bearing soil layers in a stepped manner, and the gradient height is determined according to the thickness of the confined layer or the impervious layer, and the gradient height is greater than 15 - 20 m.

[0009] Preferably, the phase change temperature of the phase change heat storage material in the heat storage well is 30 - 40 °C; Preferably, the phase change temperature of the phase change heat storage material in the heat storage water tank is 70 - 80 °C.

[0010] The beneficial effects of the present invention are as follows: By arranging vertical heat insulation plates and heat storage wells in the crustal diurnal variable temperature zone soil and annual variable temperature zone soil, the present invention not only effectively increases the temperature of the shallow soil and aquifer in the crustal variable temperature zone, but also effectively improves the heat exchange efficiency of the U-shaped vertical buried pipes in the variable temperature zone, reduces or eliminates the phenomenon of "geothermal imbalance or cold accumulation", thereby improving the heating COP value of the ground source heat pump unit and the operation stability of the system, meeting the requirements of energy conservation, high efficiency, low carbon, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the system structure and the shallow crust soil structure section of the embodiment of the present invention; Figure 2 It is a schematic elevation structure diagram of the heat storage well of the present invention; Figure 3 It is a schematic plan layout diagram of the heat storage well, the lifting and recharge well, and the U-shaped vertical buried pipes of the present invention; In the drawings: 1. Area heat insulation board, 2. Shallow water extraction well, 3. Recharge pipeline, 4. Heat storage well, 5. Heat storage outlet pipe, 6. Solar water heater, 7. Cold water pipe, 8. Hot water pipe, 9. Heat storage return pipe, 10. Circulation pump, 11. Deep water extraction well, 12. Heat storage water tank, 13. Heat coupling return pipe, 14. Heat coupling supply pipe, 15. Ground source heat pump machine room, 16. User side supply pipe, 17. User side return pipe, 18. Daily variable temperature zone soil, 19. Annual variable temperature zone soil, 20. Constant temperature zone soil, 21. Water extraction pump, 22. U-shaped vertical buried pipe, 23. Control valve, 24. Heat storage cylinder, 25. Phase change heat storage material, 41. Horizontal branch pipe, 42. Heat storage well riser pipe, 43. Flow equalizing orifice plate, 44. Upper cover of casing, 45. Upper cover of inner pipe, 46. Lower sealing plate of inner pipe, 47. Lower sealing plate of casing, 48. Perforated holes, 411. Outer sleeve of branch pipe, 412. Inner sleeve of branch pipe, 413. Outer sealing plate, 421. Outer sleeve riser pipe, 422. Inner riser pipe, 423. Inner sealing plate of branch pipe. Detailed implementation mode

[0012] The present invention will be described in detail below through specific embodiments. Those who understand this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification; it should be noted, however, that the following specific implementation modes do not impose technical limitations on the technical solution. Under the guidance of the following technical solution, those skilled in the art can make further technical extensions. The protection scope of this patent application shall be subject to the claims.

[0013] Embodiment 1: An energy efficiency improvement system for a shallow buried tube heat exchanger. Its basic theory is: by setting up an adiabatic and heat insulation structure to prevent heat exchange between the soil inside and outside the "thermal island"; using a heat storage well system to store heat and forcing the heat storage layer of the soil inside the "thermal island" to passively exchange heat; adopting a multi-stage step-by-step shallow and deep water extraction or recharge well forced heat exchange technology to passively and forcibly increase the head difference of the runoff water in the upstream and downstream soils of the heat exchange area of the "thermal island", and increase the groundwater runoff velocity V = KI (V is the flow velocity, K is the permeability coefficient, and I is the hydraulic gradient), so that the groundwater in the variable temperature zone or constant temperature zone of the soil seeps from the upstream through the U-shaped vertical buried pipe 22 to the downstream, thereby increasing the heat exchange performance of the U-shaped vertical buried pipe 22, and thus improving the COP value of the ground source heat pump unit.

[0014] As Figure 1As shown, it includes several regional insulation panels 1, several shallow water extraction wells or recharging wells 2, several heat storage wells 4, several solar water heaters 6, circulation pumps 10, deep water extraction wells 11, heat storage tanks 12, ground source heat pump room 15, user side water supply pipes 16, user side return pipes 17, daily variable temperate soil 18, annual variable temperate soil 19, water extraction pumps 21, heat storage cylinders 24 and other pipes and valves connected thereto. The regional insulation panels 1 are arranged at the periphery of the heat exchange area of ​​the U-shaped vertical buried pipe 22, and a closed or semi-closed heat storage area unit is enclosed through a ring or square connection structure, so that the soil or heat storage layer in the crustal variable temperate zone passively stores heat to improve the heat exchange efficiency of the U-shaped vertical buried pipe 22 in the crustal daily variable temperate zone and annual variable temperate zone. The solar water heater 6 is a light tube, flat plate, groove type solar water heater.

[0015] A plurality of heat storage wells 4, a plurality of shallow water extraction wells 2, a plurality of deep water extraction wells 11, a plurality of solar water heaters 6, a heat storage tank 12, a plurality of U-shaped vertical buried pipes 22, a water extraction pump 21, a circulation pump 10, a reinjection pipeline 3 and a ground source heat pump room 15 are arranged in the heat storage area unit; because the reinjection pipeline 3 is arranged in the shallow water extraction well 2 and the deep water extraction well 11, the shallow water extraction well 2 and the deep water extraction well 11 are both water extraction wells and reinjection wells.

[0016] Preferably, the water intake and recharging positions of the shallow water extraction well 2 and the shallow recharging well are set in the annual temperate soil 19 or the constant temperature soil 20 within 15 to 30 meters from the ground; Preferably, the water intake and water recharging positions of the deep water extraction well 11 and the deep recharging well are set in the water-bearing soil layer in the warming zone within 30 to 120 m from the ground; Preferably, the water intake and recharging positions of the shallow water extraction well 2 and the deep water extraction well 11 are arranged in multiple steps, and in different underground water-bearing soil layers, the gradient height is determined according to the thickness of the pressure-bearing layer or the impermeable layer, and the gradient height is greater than 15 to 20 meters.

[0017] A regional insulation board 1 is arranged around the shallow diurnal temperate soil 18, annual temperate soil 19 and part of the constant temperature soil 20 where the U-shaped buried heat exchanger 22 is located to form a closed or semi-closed heat storage area unit, so that the diurnal temperate soil 18 and annual temperate soil 19 of the earth's crust form a heat storage layer to passively store heat to improve the heat exchange efficiency of the heat storage area unit where the U-shaped vertical buried pipe 22 is located. This design sets the soil within a certain depth range of the local U-shaped vertical buried pipe 22 into a "thermal island" and prevents heat exchange between the soil inside and outside the "thermal island".

[0018] In this system, the heat storage well system used includes several heat storage wells 4, heat storage outlet pipes 5, solar water heaters 6, circulating pumps 10, heat storage water tanks 12 and valve components and connectors such as cold water pipes 7, hot water pipes 8, and heat storage return pipes 9 of the solar water heaters connected thereto; the heat extracted by the solar water heaters 6 is directed to the heat storage wells 4 through the above components to achieve basic heat supply.

[0019] The present embodiment also includes a plurality of shallow water extraction or recharging wells 2, deep water extraction or recharging wells 11, water extraction pumps 21 and valve components and connectors such as water extraction or recharging pipelines 3 connected thereto; the buried depth of the regional insulation board 1 is set in the constant temperature zone soil 20, penetrating the daily temperature zone 18 and the annual temperature zone 19 of the earth's crust from top to bottom, and its buried depth H≥H2+0.5~1m, and the H2 is the depth of the annual temperature zone soil 19.

[0020] The heat storage well 4 is an inner and outer sleeve type hollow structure with a plurality of horizontal branch pipes 41 in a "cross" or "well" shape. A lifting pump 21 is provided at the bottom of the heat storage well 4. A heat storage cylinder 24 is provided in the horizontal branch pipe 41. A phase change heat storage material 25 is provided in the heat storage cylinder 24. The phase change temperature of the phase change heat storage material 25 in the heat storage well 4 is 30-40°C.

[0021] The heat storage mechanism of the heat storage well is as follows: in summer and autumn, the hot water heated by the solar water heater 6 enters the hot water storage tank 12 through the circulation pump 10 and the corresponding pipeline, part of the heat is absorbed by the phase change heat storage material 25 arranged in the hot water storage tank 12, and part of the heat enters the heat storage well 4 through the hot water pipe 8 and the heat storage return pipe 9; the phase change temperature of the phase change heat storage material in the hot water storage tank 12 is 70-80°C.

[0022] The water extraction and recharging depths of the plurality of water extraction wells or recharging wells are arranged in a multi-level stepped layered manner, and are divided into shallow water extraction wells 2 and deep water extraction wells 11. It should be noted that the shallow water extraction wells 2 and the deep water extraction wells 11 are also equipped with recharging pipes 3, so the depths of the water extraction wells and the recharging wells can be set to the same structure. The purpose of this structural setting is to ensure water extraction and recharging at the same water level, so as to avoid cross-contamination of water quality and soil in different underground water layers.

[0023] The horizontal branch pipe 41 in the heat storage well is composed of a branch pipe outer casing 411 and a branch pipe inner casing 412. The distal end of the branch pipe outer casing 411 is provided with an outer sealing plate 413; the distal end of the inner casing 412 is provided with an inner sealing plate 423; the heat storage well riser 42 is composed of an outer riser 421 and an inner riser 422. The bottom end of the outer riser 421 is provided with a casing lower sealing plate 47 and an eyelet 48; the bottom end of the inner riser 422 is also provided with an inner pipe lower sealing plate 46; the casing lower sealing plate 47 is provided with an eyelet 48.

[0024] The described heat storage water tank 12 is provided with interfaces connected to the solar water heater 6, the cold water pipe 7 and the hot water pipe 8, and completes the transfer and storage of heat through the circulation pump 10, the cold water pipe 7 and the hot water pipe 8; the described heat storage water tank 12 is provided with interfaces connected to the heat storage well 4, the heat storage outlet pipe 5 and the return pipe 9, and completes the transfer of heat from the heat storage well 4 and heat storage through the water extraction pump 21, the heat storage return pipe 9 and the heat storage outlet pipe 5.

[0025] The described heat storage water tank 12 is provided with connection components such as a circulation pump 10, a heat coupling return pipe 13, a heat coupling supply pipe 14 and valves connected to the ground source heat pump machine room 15 for combined heating of solar energy and geothermal energy.

[0026] The several U-shaped vertical buried pipes 22 include a return pipe and a water outlet pipe, which are respectively connected to the inside of the ground source heat pump machine room 15 through a horizontal return pipe, a horizontal water inlet pipe and a main pipeline.

[0027] Preferably, the regional heat insulation board 1 can be a hollow heat insulation structure with adjustable height and detachable, and is arranged on the upstream and downstream sides of the underground aquifer in the "thermal island" area; when the ground source heat pump machine room 15 operates under the refrigeration condition in summer, the regional heat insulation board 1 loses its heat insulation and heat isolation functions to ensure a higher refrigeration COP value of the ground source heat pump machine room 15.

[0028] Furthermore, the recharge water level of the same-layer water extraction and recharge well is less than the water intake level of the water extraction well by 1-3 m, which is beneficial to forming or increasing the head difference of the runoff water in the upstream and downstream soils of the U-shaped vertical buried pipe 22, increasing the groundwater runoff velocity V, and improving the passive and enhanced heat exchange effect of the U-shaped vertical buried pipe 22.

[0029] In this embodiment, the well completion technologies of the U-shaped vertical buried pipe 22, the water extraction well, the recharge well, and the heat storage well, the water extraction or booster pump and the conveying pipeline connected thereto are all existing conventional technologies, and no more technical descriptions will be given here; the above-mentioned horizontal buried pipe, U-shaped vertical buried pipe 22 and their connectors are all made of PE or HDPE materials; In this embodiment, the circulation pump 10 is a centrifugal pipeline pump, and the water extraction pump 21 is a submersible pump or a multi-stage centrifugal pump.

[0030] In summary, the present invention can effectively increase the temperature of the shallow soil and aquifer in the crust variable temperature zone by setting vertical heat insulation boards and heat storage wells in the crust daily variable temperature zone soil and annual variable temperature zone soil, reasonably optimizing the water runoff velocity in the aquifer soil around the U-shaped vertical buried pipe, and adopting forced and passive heat exchange methods, effectively improving the heat exchange efficiency of the U-shaped vertical buried pipe in the variable temperature zone, reducing or eliminating the phenomenon of "geothermal imbalance or cold accumulation", thereby increasing the heating COP value of the ground source heat pump unit and the operation stability of the system, meeting the requirements of energy conservation, high efficiency, low carbon and environmental protection.

Claims

1. A shallow underground heat exchanger energy efficiency improvement system, characterized by: A closed or semi-closed thermal storage area unit is enclosed by area insulation panels; The heat storage area unit includes a plurality of heat storage wells, a plurality of shallow water extraction wells, a plurality of deep water extraction wells, a plurality of solar water heaters, a heat storage tank, a plurality of U-shaped vertical buried pipes, a water extraction pump, a circulation pump, a water extraction pipeline, a recharging pipeline, a water delivery pipeline and a ground source heat pump room; The buried depth of the regional thermal insulation board is set in the soil of the constant temperature zone of the earth's crust, and passes through the daily temperature zone and the annual temperature zone of the earth's crust from top to bottom. The buried depth H≥H2+0.5~1m, and the H2 is the depth of the annual temperature zone; The heat storage well is an inner and outer sleeve type hollow structure with a plurality of horizontal branch pipes in a "cross" or "well" shape, and the horizontal branch pipes are arranged in the soil of the annual temperature zone and the constant temperature zone of the earth's crust; the buried depth of the upper horizontal branch pipe is H≥H1+0.5~1m, and the buried depth of the lower horizontal branch pipe is H≥H2+0.5~1m; the H1 is the depth of the daily temperature zone, and H2 is the depth of the annual temperature zone; Phase change heat storage material is arranged in the horizontal branch pipe of the heat storage well; and phase change heat storage material is arranged in the hot water storage tank.

2. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The shallow water extraction well has the same depth as the shallow recharging well, and the deep water extraction well has the same depth as the deep recharging well.

3. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The solar water heater is a light tube, flat plate or groove type solar water heater collector.

4. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized in that: The heat storage tank is provided with an interface connected with the cold water pipe and the hot water pipe of the solar water heater, and completes the heat transfer and heat storage through the circulation pump, the cold water pipe and the hot water pipe.

5. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The heat storage tank is provided with an interface connected to the heat storage well, and completes the transfer and heat storage of the heat storage well through a water pump, a heat storage return pipe, and a heat storage outlet pipe.

6. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The plurality of U-shaped vertical buried pipes include a U-shaped water return riser and a U-shaped water outlet riser, which are respectively connected to the interior of the ground source heat pump room through a horizontal water return pipe, a horizontal water inlet pipe and a main pipe.

7. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The water intake and water recharging positions of the shallow water extraction well and the shallow recharging well are arranged in the water-bearing soil layer in the variable temperature zone or constant temperature zone within 15 to 30 m from the ground.

8. The shallow underground heat exchanger energy efficiency improvement system according to claim 1 is characterized by: The water intake and water recharging positions of the deep water extraction well and the deep recharging well are set in the water-bearing soil layer in the warming zone 30 to 100 meters below the ground.

9. The shallow underground heat exchanger energy efficiency improvement system according to claim 1, characterized in that: The water intake and water recharging positions of the shallow water extraction well and shallow recharging well or the deep water extraction well and deep recharging well are arranged in multiple steps in different underground water-bearing soil layers, and the gradient height is greater than 15 to 20 meters.

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