Middle-shallow layer ground heat exchanger circulating liquid state prediction system and method
By establishing a three-dimensional coordinate system and thermal resistance equation system in a double U-shaped buried pipe, and generating a node equation system, the problem of calculating the temperature of the circulating liquid of the double U-shaped buried pipe is solved, and fast and accurate temperature prediction is achieved.
Patent Information
- Application Number
- CN202411870421.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2025-05-06
AI Technical Summary
When the dual U-shaped buried pipe is connected in parallel, it is difficult for the prior art to quickly and accurately detect and calculate the temperature changes of the circulation liquid, and it is necessary to collect the ground temperature information of multiple buried pipes, which is time-consuming and labor-intensive.
A method for predicting the circulating liquid state of a medium-shallow buried pipe heat exchanger is adopted. By establishing a three-dimensional coordinate system, setting nodes, and establishing a system of thermal resistance equations for buried pipes and a heat equilibrium equations, the equations for the circulating liquid nodes of pipelines are generated, and the temperatures of each node of the double U-shaped buried pipe are calculated.
The circulating liquid temperature of each node of the double U-shaped buried pipe is realized, which improves the accuracy and efficiency of the calculation.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of geothermal efficiency prediction, and in particular to a system and method for predicting the state of circulating fluid in a medium-shallow buried pipe heat exchanger. Background Art
[0002] At present, ground source heat pump technology uses geothermal energy, a renewable energy source, as a heat and cold source to meet the heating and cooling needs of buildings. The system consists of a ground pipe heat exchanger, a heat pump unit and indoor terminal equipment. The ground pipe heat exchanger is the core component of the system; the circulating fluid circulates in the ground pipe, extracts heat or cold from the underground soil or water, and then transfers it to the heat medium or refrigerant (usually water or air) transported to the room of the building through the heat pump unit. The ground pipe is usually U-shaped, and the end where the heat medium or refrigerant flows downward is called the downcomer, and the end where the heat medium or refrigerant flows upward is called the riser. The riser and the downcomer are connected at the bottom of the ground pipe. Two ground pipes can be buried in one place as double U-shaped ground pipes to provide heating or cooling for the building at the same time. The two single U-shaped ground pipes of the double U-shaped ground pipe are symmetrically arranged. For the prediction of the circulating fluid temperature of a single ground pipe heat exchanger, the temperature near the ground of the ground pipe can be collected and substituted into the node equation for calculation.
[0003] The above-mentioned prior art solutions have the following defects: currently, when double U-shaped underground pipes are connected in parallel, it is necessary to collect information such as the ground temperature of multiple underground pipes and then calculate them separately when detecting temperature changes, which is time-consuming and laborious. Summary of the invention
[0004] In order to simply and quickly calculate the temperature of the circulating fluid at each location of the double U-shaped buried pipe at each time, the present application provides a system and method for predicting the state of the circulating fluid in a medium-shallow buried pipe heat exchanger.
[0005] On the one hand, the present application provides a method for predicting the state of circulating fluid in a medium-shallow buried pipe heat exchanger using the following technical solution: A method for predicting the state of circulating fluid in a medium-shallow buried pipe heat exchanger comprises the following steps: Record the numbers of the riser and downcomer of each buried pipe, determine the number of the buried pipe main pipeline, establish a three-dimensional coordinate system, set nodes on the riser and downcomer, and record the position of each node in the three-dimensional coordinate system; Collect the temperature of the part of the downpipe extending out of the ground and the temperature of the surrounding ground corresponding to the number of the buried main pipeline, take the temperature of the surrounding ground as the initial ground temperature, take the temperature of the part of the downpipe extending out of the ground as the initial pipeline temperature, and mark the collection points on the three-dimensional coordinate system as geotechnical nodes; Divide the downcomer and the upcomer of the buried pipe into a top area, a middle area and a bottom area; Establishing a thermal resistance equation group of underground pipes, the thermal resistance equation group of underground pipes includes the thermal resistance equation between the circulating fluid in the branch pipe and the borehole wall, the thermal resistance equation between the circulating fluids in two adjacent branch pipes, and the thermal resistance equation between the circulating fluids in two diagonal branch pipes; The heat balance equations for each branch pipe are established according to the thermal resistance equations of the buried pipes; The pipeline circulating fluid node equation group is generated according to the buried pipe thermal resistance equation group and the heat balance equation group. The pipeline circulating fluid node equation group includes the node equation of the top area of the downcomer, the node equation of the middle area of the downcomer, the node equation of the bottom area of the downcomer, the node equation of the top area of the riser, the node equation of the middle area of the riser and the node equation of the bottom area of the riser. The end time is set, and the initial time temperature of the ground and the initial time temperature of the pipeline are substituted into the pipeline circulating fluid node equation group to obtain the predicted temperature of each node of the buried pipe at all times between the initial time and the end time.
[0006] By adopting the above scheme, since the two U-shaped tubes of the double U-shaped buried pipe are connected in parallel, the internal circulating liquid temperatures will affect each other. When calculating the temperature of each node of the double U-shaped buried pipe at each time, it is necessary to consider the thermal resistance of the branch pipe and the influence of the thermal resistance of the double U-shaped buried pipe at different positions. Therefore, the present application divides the riser and downcomer of the buried pipe into three sections, and establishes a six-section node equation, which can simply and accurately calculate the temperature of each node of the double U-shaped buried pipe at each time.
[0007] Preferably, the step of "establishing a group of thermal resistance equations for buried pipes" further comprises: The thermal resistance equations of buried pipes are established as follows: In the formula, r e and r ei are the outer radius and inner radius of the equivalent tube respectively; r p is the outer radius of the U-tube, r i is the inner radius of the U-tube; r b k is the radius of the drill hole; p is the thermal conductivity of the U-tube, k b are the thermal conductivity of the backfill material, R 11 is the thermal resistance between the circulating fluid in the branch pipe and the borehole wall, R 12 is the thermal resistance between the circulating fluids in two adjacent branches, R 13 is the thermal resistance between the circulating fluids in the two diagonal branches, h is the convection heat transfer coefficient between the fluid and the inner wall of the double U-shaped tube, R p is the heat transfer resistance from the fluid to the outer wall of the tube.
[0008] By adopting the above scheme, the thermal resistance of the buried pipe has a great influence on the temperature of the circulating liquid in the buried pipe. The thermal resistance of each aspect can be simply calculated through the buried pipe thermal resistance equation group.
[0009] Preferably, the step of "establishing a heat balance equation group for each branch pipe according to the buried pipe thermal resistance equation group" further includes: The equivalent thermal resistance equations are established as follows: In the formula, is the equivalent thermal resistance between the borehole wall and the branch pipe, is the equivalent thermal resistance between the circulating fluids of two adjacent branches, is the equivalent thermal resistance between the circulating fluids in the two diagonal branches; The heat balance equations for each branch pipe are established as follows: Where C1 is the heat capacity per unit length of the pipe section.
[0010] Preferably, the step of "generating a pipeline circulating fluid node equation group according to the buried pipe thermal resistance equation group and the heat balance equation group" further includes: The node equation of the top area of the downcomer is established as follows: The node equation of the middle section of the downcomer is established as follows: The node equation of the bottom area of the downcomer is established as follows: The node equation of the top area of the riser is established as follows: The node equation of the middle section of the riser is established as follows: The node equation of the bottom area of the riser is established as follows: In the formula, j is the node number, nj is the maximum node number; They respectively represent the temperature of node j of the circulating fluid in each branch pipe at time p.
[0011] By adopting the above scheme, the heat node equations of the riser and the downcomer at the top, middle and bottom are different, so the heat can be calculated more accurately.
[0012] Preferably, the method further comprises the following steps: The underground heat conduction equation is established as follows: σ=ln(r / r b ); In the formula, a represents the earth's thermal diffusion coefficient, t represents the earth's temperature, τ represents the time, r represents the radial coordinate, z represents the axial coordinate, and r b Indicates the drilling radius; The node equations in the soil are established according to the underground heat conduction equation. The node equations in the soil include the surface node equations, the soil internal node equations and the soil borehole wall node equations.
[0013] By adopting the above scheme, when the soil supplies heat to or absorbs heat from the buried pipe, its own temperature will also change in response, so it is also necessary to combine the temperature of each node of the soil to comprehensively predict the state of the circulating fluid in the buried pipe.
[0014] Preferably, the step of "establishing a node equation in the soil according to the underground heat conduction equation" further comprises: Set nodes on the ground around the buried pipe according to the three-dimensional coordinate system; The surface node equations around the buried pipe are established as follows: Where i is the horizontal distance of the node from the buried pipe, and j is the node number; The surface node equation close to the buried pipe is established as follows: Substitute the initial ground temperature and the initial pipe temperature into the surface node equation to obtain the temperature of each ground node around the buried pipe at each time; The temperature of each node of the buried pipe is corrected using the surface node equation and the temperature of each node on the ground around the buried pipe at each moment.
[0015] By adopting the above scheme, the present application divides the temperature on the ground into two parts: close to the buried pipe and far away from the buried pipe, so as to accurately predict the temperature of each node on the ground.
[0016] Preferably, the step of "establishing a node equation in the soil according to the underground heat conduction equation" further comprises: Setting nodes in the soil around the buried pipe according to the three-dimensional coordinate system; The soil node equation inside the soil around the buried pipe is established as follows: The soil node equations of the soil layer around the buried pipe are established as follows: Substitute the initial ground temperature and the initial pipe temperature into the node equation in the soil to obtain the temperature of each node in the soil around the buried pipe at each moment; The temperature of each node of the buried pipe is corrected using the node equation in the soil and the temperature of each node in the soil around the buried pipe at each moment.
[0017] By adopting the above scheme, the present application divides the temperature in the soil into two parts: the soil interior and the surface layer, and can accurately predict the temperature of each node on the ground.
[0018] Preferably, the step of "establishing a node equation in the soil according to the underground heat conduction equation" further comprises: Nodes are set at various locations on the buried pipe borehole wall according to the three-dimensional coordinate system; The borehole wall node equation on the buried pipe borehole wall is established as follows: The node equation of the borehole wall at the buried pipe borehole wall layer is established as follows: The borehole wall node equation at the bottom of the buried pipe borehole wall is established as follows: The node equation of the borehole wall below the bottom of the buried pipe borehole wall is established as follows: Substitute the initial temperature of the ground and the initial temperature of the pipe into the borehole wall node equation to obtain the temperature of each node of the buried pipe borehole wall at each time; The temperature of each node of the buried pipe is corrected using the borehole wall node equation and the temperature of each node of the buried pipe borehole wall at each moment.
[0019] By adopting the above scheme, the present application divides the temperature of the borehole wall into four parts: the borehole wall, the borehole wall layer surface, the borehole wall bottom and below the bottom, so as to accurately predict the temperature of each node on the ground.
[0020] On the other hand, the present application provides a medium-shallow buried pipe heat exchanger circulating fluid state prediction device adopts the following technical solution: A device for predicting the state of circulating fluid in a medium-shallow underground pipe heat exchanger, characterized in that it includes a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and execute any of the above-mentioned methods for predicting the state of circulating fluid in a medium-shallow underground pipe heat exchanger.
[0021] On the other hand, a computer-readable storage medium provided by the present application adopts the following technical solution: A computer-readable storage medium, characterized in that it stores a computer program that can be loaded by a processor and execute any of the above-mentioned methods for predicting the state of circulating fluid in a medium-shallow buried pipe heat exchanger.
[0022] In summary, the present invention has the following beneficial effects: 1. Since the two U-shaped tubes of the double U-shaped buried pipe are connected in parallel, the internal circulating liquid temperature will affect each other. When calculating the temperature of each node of the double U-shaped buried pipe at each time, it is necessary to consider the thermal resistance of the branch pipe and the influence of the thermal resistance of the double U-shaped buried pipe at different positions. Therefore, the present application divides the riser and downcomer of the buried pipe into three sections, and establishes a six-section node equation, which can simply and accurately calculate the temperature of each node of the double U-shaped buried pipe at each time. DETAILED DESCRIPTION
[0023] Embodiment 1: This embodiment of the present application discloses a method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger, and the specific steps are as follows: S100, recording the numbers of the riser and the downcomer of each buried pipe, determining the number of the buried pipe main pipeline, establishing a three-dimensional coordinate system, setting nodes on the riser and the downcomer, and recording the position of each node in the three-dimensional coordinate system.
[0024] S200, collecting the temperature of the part of the downpipe extending out of the ground and the temperature of the surrounding ground corresponding to the number of the buried main pipeline, taking the temperature of the surrounding ground as the initial ground temperature, taking the temperature of the part of the downpipe extending out of the ground as the initial pipeline temperature, and marking the collection points on the three-dimensional coordinate system as geotechnical nodes.
[0025] S300, dividing the downcomer and the upcomer of the buried pipe into a top region, a middle region and a bottom region.
[0026] S400, establishing a thermal resistance equation group for underground pipes, wherein the thermal resistance equation group for underground pipes includes a thermal resistance equation between the circulating fluid in the branch pipe and the borehole wall, a thermal resistance equation between the circulating fluids in two adjacent branch pipes, and a thermal resistance equation between the circulating fluids in two diagonal branch pipes.
[0027] S401, establish a buried pipe thermal resistance equation group, the buried pipe thermal resistance equation group is as follows: In the formula, r e and r ei are the outer radius and inner radius of the equivalent tube respectively; r p is the outer radius of the U-tube, r i is the inner radius of the U-tube; r b k is the radius of the drill hole; p is the thermal conductivity of the U-tube, k b are the thermal conductivity of the backfill material, R 11 is the thermal resistance between the circulating fluid in the branch pipe and the borehole wall, R 12 is the thermal resistance between the circulating fluids in two adjacent branches, R13 is the thermal resistance between the circulating fluids in the two diagonal branches, h is the convection heat transfer coefficient between the fluid and the inner wall of the double U-shaped tube, R p is the heat transfer resistance from the fluid to the outer wall of the pipe. The thermal resistance of the buried pipe has a great influence on the temperature of the circulating fluid in the buried pipe. The thermal resistance of each aspect can be simply calculated through the buried pipe thermal resistance equation group.
[0028] S500: Establish a heat balance equation group for each branch pipe according to the buried pipe thermal resistance equation group.
[0029] S501, establish an equivalent thermal resistance equation group, the equivalent thermal resistance equation group is as follows: In the formula, is the equivalent thermal resistance between the borehole wall and the branch pipe, is the equivalent thermal resistance between the circulating fluids of two adjacent branches, It is the equivalent thermal resistance between the circulating fluids in the two diagonal branches.
[0030] S502, establish a heat balance equation group for each branch pipe, the heat balance equation group is as follows: Where C1 is the heat capacity per unit length of the pipe section.
[0031] S503, establish the node equation of the top area of the downcomer, the node equation is as follows:
[0032] S504, establish the node equation of the middle area of the downcomer, the node equation is as follows:
[0033] S505, establish the node equation of the bottom area of the downcomer, the node equation is as follows:
[0034] S506, establish the node equation of the top area of the riser, the node equation is as follows:
[0035] S507, establish the node equation of the middle section of the riser, the node equation is as follows:
[0036] S508, establish the node equation of the bottom area of the riser, the node equation is as follows: In the formula, j is the node number, nj is the maximum node number; They represent the temperature of the circulating fluid node j in each branch at time p. The heat node equations of the riser and downcomer are different at the top, middle and bottom, which can calculate the heat more accurately.
[0037] S600. Generate a pipeline circulating fluid node equation group according to the buried pipe thermal resistance equation group and the heat balance equation group. The pipeline circulating fluid node equation group includes the node equation of the top area of the downcomer, the node equation of the middle area of the downcomer, the node equation of the bottom area of the downcomer, the node equation of the top area of the riser, the node equation of the middle area of the riser and the node equation of the bottom area of the riser.
[0038] S700, establish an underground heat conduction equation, which is as follows: σ=ln(r / r b ); In the formula, a represents the earth's thermal diffusion coefficient, t represents the earth's temperature, τ represents the time, r represents the radial coordinate, z represents the axial coordinate, and r b Indicates the drilling radius.
[0039] S800. Establish soil node equations based on underground heat conduction equations. The soil node equations include surface node equations, soil internal node equations, and soil borehole wall node equations. When the soil supplies heat to or absorbs heat from the buried pipe, its own temperature will also change in response. Therefore, it is also necessary to combine the temperatures of various nodes in the soil to comprehensively predict the state of the circulating fluid in the buried pipe.
[0040] S801. Setting nodes on the ground around the buried pipe according to the three-dimensional coordinate system.
[0041] Establish the surface node equation around the buried pipe. The surface node equation is as follows: Where i is the lateral distance of the node from the buried pipe, and j is the node number.
[0042] S802, establish a surface node equation close to the buried pipe, the surface node equation is as follows: Substitute the initial ground temperature and the initial pipe temperature into the surface node equation to obtain the temperature of each ground node around the buried pipe at each moment.
[0043] The temperature of each node of the underground pipe is corrected using the surface node equation and the temperature of each node on the ground around the underground pipe at each moment. This application divides the temperature on the ground into two parts, close to the underground pipe and far away from the underground pipe, and can accurately predict the temperature of each node on the ground.
[0044] S803. Setting nodes in the soil around the buried pipe according to the three-dimensional coordinate system.
[0045] The soil node equations inside the soil around the buried pipe are established. The soil node equations are as follows:
[0046] The soil node equations of the soil layer around the buried pipe are established as follows: Substitute the initial ground temperature and the initial pipe temperature into the node equation in the soil to obtain the temperature of each node in the soil around the buried pipe at each moment.
[0047] The temperature of each node of the buried pipe is corrected using the node equation in the soil and the temperature of each node in the soil around the buried pipe at each moment. This application divides the temperature in the soil into two parts: the soil interior and the surface, and can accurately predict the temperature of each node on the ground.
[0048] S804, setting nodes at various locations on the buried pipe borehole wall according to the three-dimensional coordinate system.
[0049] The borehole wall node equation on the buried pipe borehole wall is established as follows:
[0050] The node equation of the borehole wall at the buried pipe borehole wall layer is established as follows:
[0051] The borehole wall node equation at the bottom of the buried pipe borehole wall is established as follows:
[0052] The node equation of the borehole wall below the bottom of the buried pipe borehole wall is established as follows:
[0053] Substitute the initial ground temperature and the initial pipe temperature into the borehole wall node equation to obtain the temperature of each node of the buried pipe borehole wall at each moment.
[0054] The temperature of each node of the buried pipe is corrected using the borehole wall node equation and the temperature of each node of the buried pipe borehole wall at each moment. This application divides the temperature of the borehole wall into four parts: the borehole wall, the borehole wall layer, the bottom of the borehole wall, and below the bottom, which can accurately predict the temperature of each node on the ground.
[0055] S900, setting the end time, substituting the ground initial time temperature and the pipeline initial time temperature into the pipeline circulating fluid node equation group to obtain the predicted temperature of each node of the buried pipe at all times between the initial time and the end time.
[0056] The implementation principle of a method for predicting the circulating liquid state of a shallow buried pipe heat exchanger in an embodiment of the present application is as follows: since the two U-tubes of the double U-shaped buried pipe are connected in parallel, the internal circulating liquid temperatures will affect each other. When calculating the temperature of each node of the double U-shaped buried pipe at each time, it is necessary to consider the thermal resistance of the branch pipe and the influence of the thermal resistance of the double U-shaped buried pipe at different positions. Therefore, the present application divides the riser and downcomer of the buried pipe into three sections, and establishes a six-section node equation, which can simply and accurately calculate the temperature of each node of the double U-shaped buried pipe at each time.
[0057] The embodiments of the present application disclose a method for predicting the state of circulating fluid in a medium-shallow buried pipe heat exchanger. The embodiments of this specific implementation method are all preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger, characterized in that: The following steps are involved: Record the numbers of the riser and downcomer of each buried pipe, determine the number of the buried pipe main pipeline, establish a three-dimensional coordinate system, set nodes on the riser and downcomer, and record the position of each node in the three-dimensional coordinate system; Collect the temperature of the part of the downpipe extending out of the ground and the temperature of the surrounding ground corresponding to the number of the buried main pipeline, take the temperature of the surrounding ground as the initial ground temperature, take the temperature of the part of the downpipe extending out of the ground as the initial pipeline temperature, and mark the collection points on the three-dimensional coordinate system as geotechnical nodes; Divide the downcomer and the upcomer of the buried pipe into a top area, a middle area and a bottom area; Establishing a thermal resistance equation group of underground pipes, the thermal resistance equation group of underground pipes includes the thermal resistance equation between the circulating fluid in the branch pipe and the borehole wall, the thermal resistance equation between the circulating fluids in two adjacent branch pipes, and the thermal resistance equation between the circulating fluids in two diagonal branch pipes; The heat balance equations for each branch pipe are established according to the thermal resistance equations of the buried pipes; The pipeline circulating fluid node equation group is generated according to the buried pipe thermal resistance equation group and the heat balance equation group. The pipeline circulating fluid node equation group includes the node equation of the top area of the downcomer, the node equation of the middle area of the downcomer, the node equation of the bottom area of the downcomer, the node equation of the top area of the riser, the node equation of the middle area of the riser and the node equation of the bottom area of the riser. The end time is set, and the initial time temperature of the ground and the initial time temperature of the pipeline are substituted into the pipeline circulating fluid node equation group to obtain the predicted temperature of each node of the buried pipe at all times between the initial time and the end time.
2. The method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 1, characterized in that: The step of "establishing a group of thermal resistance equations for buried pipes" also includes: The thermal resistance equations of buried pipes are established as follows: In the formula, r e and r ei are the outer radius and inner radius of the equivalent tube respectively; r p is the outer radius of the U-tube, r i is the inner radius of the U-tube; r b k is the radius of the drill hole; p is the thermal conductivity of the U-tube, k b are the thermal conductivity of the backfill material, R 11 is the thermal resistance between the circulating fluid in the branch pipe and the borehole wall, R 12 is the thermal resistance between the circulating fluids in two adjacent branches, R 13 is the thermal resistance between the circulating fluids in the two diagonal branches, h is the convection heat transfer coefficient between the fluid and the inner wall of the double U-shaped tube, R p is the heat transfer resistance from the fluid to the outer wall of the tube.
3. The method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 2, characterized in that: The step of "establishing a heat balance equation group for each branch pipe according to the buried pipe thermal resistance equation group" also includes: The equivalent thermal resistance equations are established as follows: In the formula, is the equivalent thermal resistance between the borehole wall and the branch pipe, is the equivalent thermal resistance between the circulating fluids of two adjacent branches, is the equivalent thermal resistance between the circulating fluids in the two diagonal branches; The heat balance equations for each branch pipe are established as follows: Where C1 is the heat capacity per unit length of the pipe section.
4. The method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 3 is characterized in that: The step of "generating pipeline circulating fluid node equations according to the buried pipe thermal resistance equations and the heat balance equations" also includes: The node equation of the top area of the downcomer is established as follows: The node equation of the middle section of the downcomer is established as follows: The node equation of the bottom area of the downcomer is established as follows: The node equation of the top area of the riser is established as follows: The node equation of the middle section of the riser is established as follows: The node equation of the bottom area of the riser is established as follows: In the formula, j is the node number, nj is the maximum node number; They respectively represent the temperature of node j of the circulating fluid in each branch pipe at time p.
5. The method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 4, characterized in that: The following steps are also included: The underground heat conduction equation is established as follows: σ / ln(r / r b )4 In the formula, a represents the earth's thermal diffusion coefficient, t represents the earth's temperature, τ represents the time, r represents the radial coordinate, z represents the axial coordinate, and r b Indicates the drilling radius; The node equations in the soil are established according to the underground heat conduction equation. The node equations in the soil include the surface node equations, the soil internal node equations and the soil borehole wall node equations.
6. A method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 5, characterized in that: The step of "establishing the node equation in the soil according to the underground heat conduction equation" also includes: Set nodes on the ground around the buried pipe according to the three-dimensional coordinate system; The surface node equations around the buried pipe are established as follows: Where i is the horizontal distance of the node from the buried pipe, and j is the node number; The surface node equation close to the buried pipe is established as follows: Substitute the initial ground temperature and the initial pipe temperature into the surface node equation to obtain the temperature of each ground node around the buried pipe at each time; The temperature of each node of the buried pipe is corrected using the surface node equation and the temperature of each node on the ground around the buried pipe at each moment.
7. A method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 6, characterized in that: The step of "establishing the node equation in the soil according to the underground heat conduction equation" also includes: Setting nodes in the soil around the buried pipe according to the three-dimensional coordinate system; The soil node equation inside the soil around the buried pipe is established as follows: The soil node equations of the soil layer around the buried pipe are established as follows: Substitute the initial ground temperature and the initial pipe temperature into the node equation in the soil to obtain the temperature of each node in the soil around the buried pipe at each moment; The temperature of each node of the buried pipe is corrected using the node equation in the soil and the temperature of each node in the soil around the buried pipe at each moment.
8. The method for predicting the state of circulating fluid in a medium-shallow underground heat exchanger according to claim 1, characterized in that: The step of "establishing the node equation in the soil according to the underground heat conduction equation" also includes: Nodes are set at various locations on the underground pipe borehole wall according to the three-dimensional coordinate system; The borehole wall node equation on the buried pipe borehole wall is established as follows: The node equation of the borehole wall at the buried pipe borehole wall layer is established as follows: The borehole wall node equation at the bottom of the buried pipe borehole wall is established as follows: The node equation of the borehole wall below the bottom of the buried pipe borehole wall is established as follows: Substitute the initial temperature of the ground and the initial temperature of the pipe into the borehole wall node equation to obtain the temperature of each node of the buried pipe borehole wall at each time; The temperature of each node of the buried pipe is corrected using the borehole wall node equation and the temperature of each node of the buried pipe borehole wall at each moment.
9. A circulating fluid state prediction device for a medium-shallow underground heat exchanger, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and executes any one of the methods of claims 1 to 8.
10. A computer-readable storage medium, characterized in that: A computer program is stored which can be loaded by a processor and execute the method according to any one of claims 1 to 8.