Method for testing performance of deep geothermal water conveying pipeline

Abstract

The invention discloses a deep geothermal water conveying pipeline performance testing method, a deep geothermal water conveying pipeline comprises an inner layer pipe, a middle winding layer and an outer layer pipe, the inner layer pipe is made of extrusion-molded PE or PERT, the middle winding layer is made of a high-thermal-conductivity material wound on the outer pipe wall of the inner layer pipe, and the outer layer pipe is made of a high-thermal-conductivity material wound on the outer pipe wall of the middle winding layer. The high thermal conductivity material is a natural graphite film, an artificial graphite film, a graphene composite film or a graphite composite film, and the outer layer pipe is PE or PERT. According to the detection method, firstly, cold water is input into the deep underground for heat exchange, after the cold water is heated to be close to the temperature of the deep position, water is pumped out through the deep geothermal water conveying pipeline, and the water outlet temperature is measured. The deep geothermal water conveying pipeline can meet the hot water conveying requirement of a deep geothermal pipe, has the heat insulation effect, and enables more medium-deep layer heat to be conveyed to the ground for use.

Description

Technical Field

[0001] The invention belongs to the field of deep geothermal pipelines, and in particular relates to a method for testing the performance of deep geothermal water transportation pipelines. Background Art

[0002] At present, the deep geothermal field of renewable energy is receiving extensive attention. The utilization of deep geothermal requires extracting hot water from a well more than 2,500 meters underground, and transporting the deep underground heat energy to the ground for use through heat exchange. In actual use plans, foamed insulated pipes are the main pipe products, and their derivative products also include foamed composite pipes, core foamed pipes, etc. However, the pressure resistance of the foaming layer in general foamed pipes is low, especially in a high-temperature and high-pressure water medium environment of 2,500 meters. The pores in the pipe and the foaming layer will be subjected to great pressure, causing the pores to be squeezed and deformed, and even the pores to rupture and enter water, greatly reducing the thermal insulation performance. At the same time, a certain degree of heat exchange is required in the deep water medium environment to better transport heat energy to the ground. The reduced thermal conductivity of the foaming pipe is not conducive to heat exchange in the deep area. In order to improve the strength of the foamed pipe, some patents CN1105743C mention adding rigid ions such as calcium carbonate and talcum powder into the foaming system to improve its rigidity. However, under the high pressure of 25MPa, the bubbles are easily squeezed, and it is still difficult to achieve good results in the deep geothermal field.

[0003] The present invention no longer uses foaming to reduce thermal conductivity to achieve the effect of heat preservation of deep geothermal hot water in the pipeline. By adding a layer of ultra-high thermal conductivity in the plane in the pipeline, while the thermal conductivity in the vertical plane direction is relatively low and can be more than an order of magnitude different, the heat in the pipeline can be mostly conducted along the axial direction of the pipeline by using the heat conduction, heat dissipation and insulation principle of thermal management of electronic products. The design idea of ​​realizing deep geothermal pipe hot water transportation through anisotropic high thermal conductivity materials is to make a three-layer composite pipeline, the inner and outer layers are PE or PERT with good heat resistance, and the middle layer is natural graphite film, artificial graphite film, graphene film, graphene composite film and graphite composite film with ultra-high thermal conductivity of more than 400W / mK in the plane, but their thermal conductivity in the vertical plane is only 10 to 20W / mK, with very good anisotropy, which can make more heat conduct in the plane. On the basis of extruding a certain thickness of inner pipe PE or PERT material, the high thermal conductivity membrane material is compounded to the pipe through hot melt adhesive, and then a layer of hot melt adhesive is further extruded on the outer layer to bond the outer PE or PERT material and shape it, so that the high thermal conductivity layer is well compounded to the middle layer of the pipe material. This reduces the amount of heat dissipated to the environment outside the pipe during the hot water transportation of the floor heating pipe in the area where the temperature is lower than the hot water temperature in the pipe, and at the same time does not affect the heat conduction to the water in the pipe in the high temperature area in the deep environment with high temperature. Through the design concept of thermal management, the deep geothermal heat can be more efficiently transported to the ground for use. Summary of the invention

[0004] In view of some deficiencies of existing medium-deep geothermal pipelines in the prior art, the purpose of the present invention is to provide a performance testing method for deep geothermal water transportation pipelines.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for testing the performance of a deep geothermal water transportation pipeline, the deep geothermal water transportation pipeline comprising an inner layer pipe, an intermediate winding layer and an outer layer pipe, the inner layer pipe is extruded PE or PERT, the intermediate winding layer is a high thermal conductivity material wound on the outer wall of the inner layer pipe, the high thermal conductivity material is a natural graphite film, an artificial graphite film, a graphene composite film or a graphite composite film, and its in-plane thermal conductivity is 400-1200 W / mK, and its vertical thermal conductivity is 10-20 W / mK; when the high thermal conductivity material is wound on the outer wall of the inner layer pipe, the angle between the high thermal conductivity material and the central axis of the inner layer pipe is 50°-60°, and the thickness of the intermediate winding layer is 0.5mm-3.00mm; the outer layer pipe is extruded PE or PERT coated on the outside of the intermediate winding layer;

[0007] A layer of hot melt adhesive is provided between the inner tube and the middle winding layer, and between the middle winding layer and the outer tube. The hot melt adhesive is PE hot melt adhesive or acrylic adhesive, and the thickness of the hot melt adhesive is 0.05-0.15 mm.

[0008] The test method comprises the following steps: injecting low-temperature water from above the ground into the deep underground through the deep geothermal water delivery pipeline, so that the injected cold water exchanges heat in the deep underground, the inlet temperature of the cold water is the pipe inlet temperature of 20°C, the geothermal gradient is 3°C / 100m, and the maximum temperature reaches 95°C at 2500m. After the injected cold water is heated to a temperature close to that at the deep layer through heat exchange, the deep water is pumped out through the deep geothermal water delivery pipeline, the pumping pressure at the inner pipe outlet is 0.7Mpa, the average outlet flow rate is 1m / s, and the comprehensive flow rate is 25m 3 / h, detect the outlet water temperature of the pipe.

[0009] Furthermore, in the structure of the deep geothermal water delivery pipeline, the thickness of the hot melt adhesive is 0.1 mm.

[0010] Furthermore, the method for preparing a deep geothermal water delivery pipeline comprises the following steps:

[0011] 1) The PE or PERT inner layer pipe raw material is melt-extruded by a single screw extruder, the barrel zone temperature is 180-200°C, the die zone temperature is 190-200°C, and then vacuum sizing and cooling;

[0012] 2) Extruding and coating a layer of hot melt adhesive on the outside of the cooled PE or PERT inner layer tube, and then wrapping and coating a layer of high thermal conductivity material to form an intermediate winding layer, and then extruding and coating another layer of hot melt adhesive;

[0013] 3) Using a single screw extruder, a layer of PE or PERT outer layer pipe material is finally extruded and coated on the outer side of the pipe obtained in step 2), the temperature of the barrel zone is 180-200° C., the temperature of the die zone is 190-200° C., and after extrusion and coating, the pipe is shaped and cooled before being taken off the line.

[0014] The beneficial effects achieved by this application are:

[0015] The deep geothermal water transportation pipeline prepared by the present invention can achieve the premise of not affecting the pressure resistance of the pipe material and not reducing the thermal conductivity of the entire pipeline. By enhancing the thermal conductivity of the pipeline middle layer material along the pipeline axis, the heat loss of the pipeline when transporting hot water in an area with lower ambient temperature close to the ground is reduced. The effect of thermal insulation is achieved through thermal management, so that more heat from the middle and deep layers can be transported to the ground for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A process flow chart for preparing a deep geothermal water delivery pipeline according to the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of the deep geothermal water delivery pipeline of the present invention;

[0018] Figure 2 Middle: 1-outer tube, 2-in-plane high thermal conductivity layer, 3-inner tube. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0020] Example: Control Figure 2

[0021] A deep geothermal water transportation pipeline comprises an inner tube 3, an intermediate winding layer (i.e., an in-plane high thermal conductivity layer 2) and an outer tube 1, wherein the inner tube is extruded PE or PERT, the intermediate winding layer is a high thermal conductivity material wound on the outer tube wall of the inner tube, and the high thermal conductivity material is a natural graphite film, an artificial graphite film, a graphene composite film or a graphite composite film, and its in-plane thermal conductivity is above 400 W / mK and its vertical thermal conductivity is below 20 W / mK; the outer tube is extruded PE or PERT coated on the outside of the intermediate winding layer.

[0022] A layer of hot melt adhesive is arranged between the inner tube and the middle winding layer, and between the middle winding layer and the outer tube. The hot melt adhesive is PE hot melt adhesive or acrylic adhesive, and the thickness of the hot melt adhesive is 0.5-1.5 mm.

[0023] When the high thermal conductivity material is wound on the outer wall of the inner tube, the angle between it and the central axis of the inner tube is 30°

[0024] -85°, preferably 50°-60°; the thickness of the middle winding layer is 0.05mm~5.00mm, preferably 0.5mm~3.00mm.

[0025] The graphene composite film in Example 1 of the present application was purchased from Changzhou Sixth Element Materials Technology Co., Ltd., and the graphene composite film in Example 2 was purchased from Shanghai Enren New Materials Technology Development Co., Ltd.

[0026] Embodiment 1:

[0027] A method for preparing a deep geothermal water transmission pipeline (process flow as shown in FIG. Figure 1 ), including the following steps:

[0028] 1) Inner layer extrusion: PE pipe is extruded by single screw extruder, the temperature of barrel area is 180℃, the temperature of die area is 190℃, then it is sized by vacuum, the vacuum degree is 0.1MPa, and cooled;

[0029] 2) Coating of the middle high thermal conductivity layer: Use a coating machine to extrude and coat a layer of hot melt adhesive on the outside of the PE inner tube. The coating machine temperature is set to 160°C, and then wrap and coat a layer of 1mm graphene composite film. The angle between the graphene composite film and the central axis of the inner tube is 50°. Its thermal conductivity in the plane is 1200W / mK, and its thermal conductivity in the vertical direction is 10W / mK. Then extrude and coat a layer of 0.1mm hot melt adhesive on the outside of the graphite composite film layer. The hot melt adhesive is PE hot melt adhesive, and the coating thickness of the hot melt adhesive is 0.2mm.

[0030] 3) Outer layer extrusion coating: A single screw extruder is used to extrude and coat a layer of PE outer layer pipe material on the outer side of the pipe obtained in step 2) at a temperature of 180°C in the barrel zone and 190°C in the die zone. After extrusion coating, the pipe is shaped and cooled before being taken off the line.

[0031] The size of the composite pipe prepared in Example 1 is DN110*SDR11, the overall outer diameter is 110 mm and the overall wall thickness is about 10 mm, wherein the thickness of the inner PE pipe is 2 mm.

[0032] Embodiment 2:

[0033] A method for preparing a deep geothermal water transmission pipeline (process flow as shown in FIG. Figure 1 ), including the following steps:

[0034] 1) Inner layer extrusion: PERT II type pipe is extruded by a single screw extruder, the temperature of the barrel zone is 185°C, the temperature of the die zone is 195°C, and then vacuum sizing is performed with a vacuum degree of 0.1MPa and cooling;

[0035] 2) Coating of the middle high thermal conductivity layer: Use a coating machine to extrude and coat a layer of hot melt adhesive on the outside of the PE inner tube. The coating machine temperature is set to 160°C, and then a 2mm graphite composite film layer is wrapped and coated. The angle between the graphite composite film layer and the central axis of the inner tube is 55°. Its thermal conductivity is 800W / mK in the plane and 15W / mK in the vertical direction. Then extrude and coat a layer of hot melt adhesive of 0.1mm on the outside of the graphite composite film layer. The hot melt adhesive is PE hot melt adhesive, and the coating thickness of the hot melt adhesive is 0.2mm.

[0036] 3) Outer layer extrusion coating: A single screw extruder is used to extrude and coat the outer side of the pipe obtained in step 2) with a layer of PERT II type pipe. The temperature of the barrel zone is 180° C., and the temperature of the die zone is 190° C. After extrusion coating, the pipe is shaped and cooled before being taken off the line.

[0037] The size of the composite pipe prepared in Example 2 is DN110*SDR11, the overall outer diameter is 110 mm and the overall wall thickness is about 10 mm, wherein the thickness of the inner PE pipe is 2 mm.

[0038] Actual performance test:

[0039] It is known that the flow through the bottom of the geothermal well is poor and there is a certain dead zone, which means that in the area with the highest temperature at the bottom, the heat transfer is mainly heat conduction, and there is less heat convection. Under the pumping pressure, the flow rate at the outlet is the largest, up to 1.06m / s, and the flow rate decreases with increasing depth. From 800m down, it tends to a stable laminar state, with an average flow rate of about 0.2m / s.

[0040] We tested and compared the pipe materials under the conditions of 20℃ pipe inlet temperature (principle explanation: low-temperature water is injected from above the ground into the deep underground, the temperature of the deep underground is about 95℃, the injected cold water is heated to a temperature close to the deep outlet temperature through heat exchange, and then returned to the ground to achieve the heating effect. Therefore, this is the inlet of cold water, and the outlet is hot water to meet the heating demand), geothermal gradient 3℃ / 100m, and the maximum temperature of 95℃ at 2500m. For the flow field, the pumping pressure at the inner pipe outlet is about 0.7Mpa, the average outlet flow rate is 1m / s, and the comprehensive flow rate is 25m 3 / h. The same specifications of PE and PERT pipes (two geothermal pipes DN110 and SDR11 produced by Zhejiang Weixing New Building Materials Co., Ltd.) were reduced from 95°C to 42°C and 41°C at the deep geothermal temperature, respectively, while the outlet temperature of the pipe in Example 1 was reduced to 58°C, and the outlet temperature of the pipe in Example 2 was reduced to 55°C. Other mechanical properties can meet the requirements of deep geothermal pipe hot water transportation.

[0041] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A method for testing the performance of a deep geothermal water pipeline, characterized in that The deep geothermal water transportation pipeline comprises an inner tube, an intermediate winding layer and an outer tube, the inner tube is extruded PE or PERT, the intermediate winding layer is a high thermal conductivity material wound on the outer wall of the inner tube, the high thermal conductivity material is a natural graphite film, an artificial graphite film, a graphene composite film or a graphite composite film, and its in-plane thermal conductivity is 400-1200 W / mK, and the vertical thermal conductivity is 10-20 W / mK; when the high thermal conductivity material is wound on the outer tube wall of the inner tube, the angle between the high thermal conductivity material and the central axis of the inner tube is 50°-60°, and the thickness of the intermediate winding layer is 0.5mm-3.00mm; the outer tube is extruded PE or PERT coated on the outside of the intermediate winding layer; A layer of hot melt adhesive is provided between the inner tube and the middle winding layer, and between the middle winding layer and the outer tube. The hot melt adhesive is PE hot melt adhesive or acrylic adhesive, and the thickness of the hot melt adhesive is 0.05-0.15 mm. The test method comprises the following steps: Low-temperature water is injected from above the ground into the deep underground through the deep geothermal water delivery pipeline, so that the injected cold water exchanges heat in the deep underground. The inlet temperature of the cold water is 20°C, the inlet temperature of the pipe, and the geothermal gradient is 3°C / 100m. The maximum temperature reaches 95°C at 2500m. After the injected cold water is heated to a temperature close to that at the deep layer through heat exchange, the deep water is pumped out through the deep geothermal water delivery pipeline. The pumping pressure at the inner pipe outlet is 0.7Mpa, the average outlet flow rate is 1m / s, and the comprehensive flow rate is 25m 3 / h, and detect the outlet water temperature of the pipe.

2. A method for testing the performance of a deep geothermal water pipeline as claimed in claim 1, characterized in that In the structure of the deep geothermal water delivery pipeline, the thickness of the hot melt adhesive is 0.1 mm.

3. A method for testing the performance of a deep geothermal water pipeline as claimed in claim 1, characterized in that The method for preparing a deep geothermal water delivery pipeline comprises the following steps: 1) The PE or PERT inner layer pipe raw material is melted and extruded by a single screw extruder, the barrel zone temperature is 180~200℃, the die zone temperature is 190~200℃, and then vacuum sizing and cooling; 2) Extrude and coat a layer of hot melt adhesive on the outside of the cooled PE or PERT inner tube, then wrap and coat a layer of high thermal conductivity material to form an intermediate winding layer, and then extrude and coat another layer of hot melt adhesive; 3) Using a single screw extruder, a layer of PE or PERT outer layer pipe material is finally extruded and coated on the outer side of the pipe obtained in step 2), the temperature of the barrel zone is 180-200°C, the temperature of the die zone is 190-200°C, and after extrusion and coating, the pipe is shaped and cooled before being taken off the line.

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