A solution method for the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings

Abstract

The present invention discloses a method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings. The method can be used to predict the heat exchange conditions under long-term operation of the system, quantitatively evaluate the degree of influence of various parameters on heat transfer performance, and provide a numerical method for optimizing the heat transfer characteristics of the channel. The method aims at the transient heat exchange problem of large-span arched structure linings containing discrete internal heat sources, establishes a numerical model of the heat exchange process, and verifies the sufficient accuracy of the model through existing experimental data. The temperature of each measuring point along the radial direction of the channel under the design conditions, the heat exchange per unit channel length, and the distribution ratio of the heat exchange between the surrounding rock and the air side are calculated, providing a numerical solution idea for studying the heat exchange performance of buried pipes in underground engineering linings.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering heat transfer, and in particular to a method for solving a numerical model of heat transfer performance of a heat exchange tube in an underground engineering lining. Background Art

[0002] There are three ways to discharge heat from underground projects: internal reservoirs, cooling towers, and rock mass. The reservoir capacity is limited, and the cooling tower is easily exposed at the entrance, so the rock mass becomes a good heat discharge target to avoid detection. The entrance channel of the project is usually used for the entry and exit of personnel or vehicles. If the heat exchanger is buried in the channel lining structure without re-drilling, it will not bring too much additional construction volume. For the renovation project, only changes need to be made at the lining level, which can greatly save the project cost and construction period. The heat exchange form of the buried pipe in the entrance channel lining is as follows: Figure 1 shown.

[0003] In the lining at a certain distance from the entrance, serpentine heat exchange tubes are evenly arranged along the axial direction. The circulating medium in the tube absorbs the heat from the condenser of the chiller, and then exchanges heat with the air and surrounding rock outside the lining, thereby achieving the purpose of transferring the engineering heat to the environment. In this process, heat is transferred between the air in the channel, the circulating water in the pipeline and the surrounding rock through heat conduction, convection and radiation, which is a coupled heat transfer process. In order to deeply study the role of various influencing factors in the heat transfer process, it is necessary to establish a model for calculation.

[0004] There are mainly two types of existing models: analytical models and numerical models. Although the analytical method is simple and fast to calculate, it is based on the actual situation of the buried heat exchanger as multiple linear heat sources being equivalent to an internal surface heat source for calculation, and the actual arched section of the mouth channel is simplified to a circular section. This simplified method is bound to deviate from the actual situation and cannot fully reproduce the actual heat transfer process. In order to study the long-term operation of the system under different working conditions, it is necessary to establish a numerical model based on the actual cross-sectional shape of the channel for solution, but there is no ready-made numerical model for reference for this multi-parameter coupled heat transfer process. Summary of the invention

[0005] The purpose of the present invention is to address the problems existing in the above-mentioned prior art, provide a numerical model solution method for determining the heat transfer performance of a buried pipe heat exchanger in an underground engineering lining structure, establish a numerical model of a buried pipe heat exchanger in a lining, determine the optimal grid division order of each module of the model, and provide a numerical algorithm for optimizing the heat transfer characteristics of the channel.

[0006] The technical solution to achieve the purpose of the present invention is: on the one hand, a method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining is provided, and the method comprises the following steps:

[0007] Step 1, presetting simulation conditions;

[0008] Step 2, establishing a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0009] Step 3, meshing the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining using a variety of different meshing methods;

[0010] Step 4, perform grid independence analysis on the results of different grid division methods and select the optimal grid division method;

[0011] Step 5, using fluid simulation software to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method.

[0012] Furthermore, the simulation conditions in step 1 specifically include:

[0013] (1) The initial temperature field of the mouth channel and the surrounding rock is consistent everywhere;

[0014] (2) The physical properties of all materials are isotropic, uniform, and independent of temperature. They are constant values ​​that do not change with time.

[0015] (3) The lining concrete is evenly poured around the buried heat exchanger. The surrounding rock and lining are in close contact with no gap. The contact thermal resistance of each part can be ignored. The heat transfer process between the lining and the surrounding rock is heat conduction.

[0016] (4) The circulating water in the buried heat exchanger is regarded as an incompressible fluid, and the effect of gravity on the flow rate is ignored. The heat exchange between the circulating water and the tube wall is convective heat transfer;

[0017] (5) The heat transfer process between the air in the mouth channel and the inner wall of the lining is convection heat transfer;

[0018] (6) The influence of groundwater migration was not considered during the heat transfer process of the surrounding rock.

[0019] Furthermore, step 2 establishes a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings, including establishing numerical models of heat exchange between the fluid in the buried heat exchanger tube and the tube wall, numerical models of heat exchange between the tube wall and the lining, numerical models of heat exchange between the lining and air and surrounding rock, and constructing initial conditions and boundary conditions.

[0020] Furthermore, the establishment of a numerical model of heat exchange between the fluid in the pipe and the pipe wall of the buried pipe heat exchanger in step 2 specifically includes:

[0021] The heat exchange process between the fluid and the pipe wall in the buried pipe heat exchanger includes two parts: one part is the heat transferred between the fluid in the pipe and the pipe wall through heat conduction, and the other part is the heat transferred between the fluid in the pipe and the pipe wall through heat convection.

[0022] The energy balance equation during fluid flow can be written as:

[0023] ;

[0024] In the formula, is the density of water in the tube of the buried heat exchanger, is the internal cross-sectional area of ​​the borehole heat exchanger, is the specific heat of water at constant pressure, are the inlet and outlet temperatures of circulating water, u is the speed of circulating water, is the heat exchange between the buried heat exchanger and the surrounding lining, expressed as:

[0025] ;

[0026] In the formula, is the average temperature of circulating water, is the external temperature of the tube wall, is the heat transfer coefficient between the circulating water and the tube wall, and the calculation formula is:

[0027] ;

[0028] In the formula, is the thermal conductivity of the circulating water in units of is the inner diameter of the underground heat exchanger in , is the Nusselt number, which is a dimensionless number.

[0029] Furthermore, under turbulent conditions, the Calculated by Gnielinski relation:

[0030]

[0031] In the formula, , v is the average flow velocity in the borehole heat exchanger; is a dimensionless constant; is the kinematic viscosity of water, in .

[0032] Furthermore, the numerical model of heat exchange between the pipe wall and the lining is specifically:

[0033]

[0034] In the formula, is the density of the lining, is the specific heat capacity of the lining, is the temperature inside the lining, including the inner wall temperature of the lining and outer wall temperature , is the thermal conductivity of the lining, express time,( , , ) is the three-dimensional coordinate of any point on the heat exchange model of buried pipes in arched channel lining.

[0035] Furthermore, the numerical model of the lining and the air is:

[0036]

[0037] The numerical model of heat transfer between lining and surrounding rock is:

[0038]

[0039] In the formula, is the convective heat transfer coefficient of air, is the air temperature in the channel, is the surrounding rock density, is the specific heat capacity of the surrounding rock, is the surrounding rock temperature, is the thermal conductivity of the surrounding rock, ( , , ) is the three-dimensional coordinate of any point on the heat exchange model of buried pipes in arched channel lining.

[0040] Furthermore, the initial condition is:

[0041]

[0042] In the formula, is the far boundary temperature of the surrounding rock, in units of , The radius of the surrounding rock The temperature at

[0043] The boundary conditions are:

[0044] .

[0045] Furthermore, the method further comprises:

[0046] Step 6, verifying the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining in step 5.

[0047] On the other hand, a solution system for a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings is provided, the system comprising the following:

[0048] The first module is used to preset simulation conditions;

[0049] The second module is used to establish a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0050] The third module is used to mesh the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining by using a variety of different meshing methods;

[0051] The fourth module is used to analyze the grid independence of the results of different grid division methods and select the optimal grid division method;

[0052] The fifth module is used to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method using fluid simulation software.

[0053] Compared with the prior art, the present invention has the following significant advantages:

[0054] (1) Aiming at the transient heat transfer problem of a large-span arched channel lining with discrete internal heat sources, a numerical model of the heat transfer process of a buried lined heat exchanger was established. Through grid independence analysis, it was found that the grid unit number of the heat exchange tube is in the thousands, the number of grid units in the body where the elbow is located and the number of grid units in the soil are in the 500,000 level, and the number of grid units in the channel lining is in the 200,000 level. This grid division scheme can minimize the number of grids while ensuring the calculation accuracy, and find the optimal grid division scheme for the same type of heat transfer problem.

[0055] (2) By solving the numerical model, the temperature of each measuring point along the radial direction of the channel under the design conditions, the heat transfer per unit channel length, and the distribution ratio of the heat transfer between the surrounding rock and the air side were obtained, which provided a data reference for studying the heat transfer performance of buried pipes in underground engineering linings.

[0056] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram of the heat exchange model of the buried pipe in the arch channel lining. Figure 1 (a) and (b) are the front view and side view of the heat exchange model of buried pipes in arched channel lining, respectively.

[0058] Figure 2 The present invention is a flow chart of the analytical model solving method for determining the heat transfer performance of the buried pipe heat exchanger in the underground engineering structure.

[0059] Figure 3This is a grid diagram of a heat exchange model of an arched channel lining and buried pipes in one embodiment, wherein Figure 3 (a) is the cross-sectional view along the axial direction after the model is meshed. Figure 3 (b) is the cross-sectional view along the radial direction after the model is meshed. Figure 3 (c) is the overall mesh diagram after the model is meshed. Figure 3 (d) in the figure is a partial view of the pipe mesh of the buried heat exchanger after the model mesh is divided.

[0060] Figure 4 It is a schematic diagram of heat exchange under different grid densities in one embodiment.

[0061] Figure 5 Schematic diagram of the number of meshes in each part at different mesh densities in an embodiment.

[0062] Figure 6 Schematic diagram of the temperature of monitoring points under different grid densities in one embodiment.

[0063] Figure 7 It is a schematic diagram of the comparison results of the model results and the test results in one embodiment.

[0064] Figure 8 Schematic diagram of the temperature and heat exchange of each monitoring point under basic working conditions in an embodiment, where Figure 8 (a) is a schematic diagram of the temperature of each monitoring point at different distances from the central axis. Figure 8 (b) is a schematic diagram of heat exchange. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0066] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0067] In one embodiment, in combination Figure 2, provides a method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings, the method comprising the following steps:

[0068] Step 1, presetting simulation conditions;

[0069] Step 2, establishing a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0070] Step 3, meshing the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining using a variety of different meshing methods;

[0071] Step 4, perform grid independence analysis on the results of different grid division methods and select the optimal grid division method;

[0072] Step 5, using fluid simulation software to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method.

[0073] Furthermore, in one embodiment, the simulation conditions in step 1 specifically include:

[0074] (1) The initial temperature field of the mouth channel and the surrounding rock is consistent everywhere;

[0075] (2) The physical properties of all materials are isotropic, uniform, and independent of temperature. They are constant values ​​that do not change with time.

[0076] (3) The lining concrete is evenly poured around the buried heat exchanger. The surrounding rock and lining are in close contact with no gap. The contact thermal resistance of each part can be ignored. The heat transfer process between the lining and the surrounding rock is heat conduction.

[0077] (4) The circulating water in the buried heat exchanger is regarded as an incompressible fluid, and the effect of gravity on the flow rate is ignored. The heat exchange between the circulating water and the tube wall is convective heat transfer;

[0078] (5) The heat transfer process between the air in the mouth channel and the inner wall of the lining is convection heat transfer;

[0079] (6) The influence of groundwater migration was not considered during the heat transfer process of the surrounding rock.

[0080] Furthermore, in one of the embodiments, step 2 establishes a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings, including establishing numerical models of heat exchange between the fluid in the buried heat exchanger tube and the tube wall, numerical models of heat exchange between the tube wall and the lining, numerical models of heat exchange between the lining and air and surrounding rock, and constructing initial conditions and boundary conditions.

[0081] Preferably, in some embodiments, the establishing of a numerical model of heat exchange between the fluid in the pipe and the pipe wall of the buried pipe heat exchanger specifically includes:

[0082] The heat exchange process between the fluid and the pipe wall in the buried pipe heat exchanger includes two parts: one part is the heat transferred between the fluid in the pipe and the pipe wall through heat conduction, and the other part is the heat transferred between the fluid in the pipe and the pipe wall through heat convection.

[0083] The energy balance equation during fluid flow can be written as:

[0084]

[0085] In the formula, is the density of water in the tube of the buried heat exchanger, is the internal cross-sectional area of ​​the borehole heat exchanger, is the specific heat of water at constant pressure, are the inlet and outlet temperatures of circulating water, u is the speed of circulating water, is the heat exchange between the buried heat exchanger and the surrounding lining, expressed as:

[0086]

[0087] In the formula, is the average temperature of circulating water, is the external temperature of the tube wall, is the heat transfer coefficient between the circulating water and the tube wall, and the calculation formula is:

[0088]

[0089] In the formula, is the thermal conductivity of the circulating water in units of is the inner diameter of the underground heat exchanger in , is the Nusselt number, a dimensionless number, and its value for laminar flow is 3.66.

[0090] Under turbulent conditions, the Calculated by Gnielinski relation:

[0091]

[0092] In the formula, , v is the average flow velocity in the borehole heat exchanger; is a dimensionless constant; is the kinematic viscosity of water, in .

[0093] Preferably, in some embodiments, when circulating water flows in the heat exchange tube, the heat released by it will be first transferred to the lining, and then transferred to the air and the surrounding rock (hereinafter also referred to as soil). The numerical model of heat exchange between the tube wall and the lining is specifically:

[0094]

[0095] In the formula, is the density of the lining, is the specific heat capacity of the lining, is the temperature inside the lining, including the inner wall temperature of the lining and outer wall temperature , is the thermal conductivity of the lining, express time,( , , ) is as follows Figure 1 The three-dimensional coordinates of any point on the buried pipe heat exchange model of the arched channel lining shown.

[0096] Preferably, in some embodiments, the numerical model of the lining and the air is:

[0097]

[0098] The numerical model of heat transfer between lining and surrounding rock is:

[0099]

[0100] In the formula, is the convective heat transfer coefficient of air, is the air temperature in the channel, is the surrounding rock density, is the specific heat capacity of the surrounding rock, is the surrounding rock temperature, is the thermal conductivity of the surrounding rock, ( , , ) is the three-dimensional coordinate of any point on the heat exchange model of buried pipes in arched channel lining.

[0101] Preferably, in some embodiments, the initial condition is:

[0102]

[0103] In the formula, is the far boundary temperature of the surrounding rock, in units of , The radius of the surrounding rock The temperature at

[0104] The boundary conditions are:

[0105] .

[0106] Illustratively, in one of the embodiments, step 3 and step 4 are described in detail.

[0107] for Figure 1 The heat transfer model of the buried pipe in the arched channel lining is shown in the figure. The mesh division is as follows: Figure 3 As shown in the figure. At the bend, the flow will produce vortices and the velocity changes dramatically, so the grid is locally encrypted here, while a non-uniform gradient grid from dense to sparse is used in the soil area. Compared with the radial direction of the channel, the heat transfer along the axial direction of the channel is less, so the nodes are evenly arranged at large equal intervals in this direction.

[0108] The larger the number of grids, the better. Too many grids will increase the amount of calculation and time, while too few grids will deviate from the actual results. Therefore, it is necessary to obtain an "economical" grid that can both ensure accuracy and save calculation time through grid independence analysis. The results of calculations with different grid densities are shown in Figure 2. Figure 4 As shown in the figure, as the number of grids increases, the total heat transfer value does not gradually approach the true value as expected, but fluctuates around the true value. Moreover, even if the total number of grid units is similar, there is a deviation in the heat transfer calculation results. The reason is that the grid allocation of each part of the model is different under different drawing methods.

[0109] Figure 5 and Figure 6 The grid distribution of each volume unit under different grid densities and the temperature values ​​of two temperature monitoring points are listed. Comparing drawing method 1 and drawing method 4, the number of grid units of the heat exchange tube is equivalent. After the body where the bend is located is encrypted, the calculation accuracy is significantly increased. It can be seen that the grid quality of the body where the bend is located is very important for the accuracy of the calculation results. Comparing drawing method 4 and drawing method 5, after the heat exchange tube is encrypted, the calculation results do not change much, which shows that the grid of the heat exchange tube does not need to be encrypted. Comparing drawing methods 2, drawing method 5 and drawing method 6, after the soil area is encrypted, the total heat and the temperature of the monitoring point are closer to the true value. Among them, drawing method 5 is almost the same as the true value, indicating that the grid density of the soil area of ​​drawing method 5 is sufficient and no further encryption is required. Comparing drawing method 3 and drawing method 5, after the channel lining is encrypted, the soil temperature is closer to the true value, indicating that the density of the channel lining cannot be too sparse, otherwise even if the total heat calculation accuracy is guaranteed, the temperature value of the monitoring point cannot be guaranteed to be accurate.

[0110] In summary, the grid unit number of the heat exchange tube is in the thousands, the number of grid units in the body where the elbow is located and the number of soil grid units are about 500,000, and the number of channel lining grid units is about 200,000. This grid division scheme can minimize the number of grids while ensuring the calculation accuracy. By comparison, it can be seen that the drawing method 4 is closest to this scheme and is an economical grid division scheme for this model, so the drawing method 4 is selected as the grid basis of the model.

[0111] Furthermore, in one embodiment, the method further comprises:

[0112] Step 6, verifying the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining in step 5.

[0113] For example, Figure 7 The comparison chart of the numerical calculation results and experimental results of the constructed model is shown in Table 1. Figure 7 It can be seen that among the three temperature measurement points, the two measurement points in the soil are highly consistent with the test data, while the simulated value of the temperature measurement point on the outer wall of the lining on the water inlet side is lower than the measured value, but the trend is the same. The reason for this is that there is a deviation between the coordinates of the monitoring point on the outer wall of the lining of the model and the coordinates of the points on the outer wall of the lining measured. The placement of the temperature sensor of the test bench is done manually, and its position may not be exactly the same as the position in the model. Moreover, the layout position of the buried heat exchanger in the lining needs to be fixed on the steel cage when it is actually placed, which may not be exactly the same as the position of the test schematic diagram. This causes the actual relative position between the temperature monitoring point of the test bench and the buried heat exchanger to deviate from the relative position in the numerical model, and this deviation will cause a difference in the temperature transfer time between the two. Now the results show that the simulated value is low, so it can be inferred that the straight-line distance between the temperature measurement point on the outer wall of the lining of the test bench and the buried heat exchanger is closer than the model distance. In summary, the calculation results of this model are highly consistent with the actual test results, and it can be considered that the model has sufficient accuracy.

[0114]

[0115] In one embodiment, a method for calculating heat exchange performance of buried pipes in underground engineering lining is provided, the method comprising:

[0116] Based on the solution results of the solution method of the numerical model of the heat transfer performance of the heat exchange pipes in the underground engineering lining, the heat exchange performance of the buried pipes in the underground engineering lining is calculated.

[0117] For example, the heat transfer performance is as follows Figure 8 shown.

[0118] In one embodiment, a system for solving a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings is provided, the system comprising:

[0119] The first module is used to preset simulation conditions;

[0120] The second module is used to establish a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0121] The third module is used to mesh the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining by using a variety of different meshing methods;

[0122] The fourth module is used to analyze the grid independence of the results of different grid division methods and select the optimal grid division method;

[0123] The fifth module is used to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method using fluid simulation software.

[0124] Furthermore, the system further comprises:

[0125] The sixth module verifies the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings in the fifth module.

[0126] The specific limitations of the solution system for the numerical model of the heat transfer performance of heat exchange tubes in underground engineering linings can be found in the limitations of the solution method for the numerical model of the heat transfer performance of heat exchange tubes in underground engineering linings above, which will not be repeated here. Each module in the solution system for the numerical model of the heat transfer performance of heat exchange tubes in underground engineering linings can be implemented in whole or in part through software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0127] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following is achieved:

[0128] Step 1, presetting simulation conditions;

[0129] Step 2, establishing a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0130] Step 3, meshing the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining using a variety of different meshing methods;

[0131] Step 4, perform grid independence analysis on the results of different grid division methods and select the optimal grid division method;

[0132] Step 5, using fluid simulation software to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method;

[0133] Step 6: Verify the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining in step 5.

[0134] For the specific limitations of each step, please refer to the limitations of the solution method for the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings mentioned above, which will not be repeated here.

[0135] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the computer program implements:

[0136] Step 1, presetting simulation conditions;

[0137] Step 2, establishing a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings;

[0138] Step 3, meshing the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining using a variety of different meshing methods;

[0139] Step 4, perform grid independence analysis on the results of different grid division methods and select the optimal grid division method;

[0140] Step 5, using fluid simulation software to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method;

[0141] Step 6, verifying the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining in step 5.

[0142] For the specific limitations of each step, please refer to the limitations of the solution method for the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings mentioned above, which will not be repeated here.

[0143] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings, characterized in that: The method comprises the following steps: Step 1, presetting simulation conditions; Step 2, establishing a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings; Step 3, meshing the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining using a variety of different meshing methods; Step 4, perform grid independence analysis on the results of different grid division methods and select the optimal grid division method; Step 5, using fluid simulation software to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method; Step 2 establishes a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings, including establishing numerical models of heat exchange between the fluid in the buried heat exchanger tube and the tube wall, numerical models of heat exchange between the tube wall and the lining, numerical models of heat exchange between the lining and air and surrounding rock, and constructing initial conditions and boundary conditions; The establishment of a numerical model for heat exchange between the fluid in the tube and the tube wall of the buried tube heat exchanger specifically includes: The heat exchange process between the fluid and the pipe wall in the buried pipe heat exchanger includes two parts: one part is the heat transferred between the fluid in the pipe and the pipe wall through heat conduction, and the other part is the heat transferred between the fluid in the pipe and the pipe wall through heat convection. The energy balance equation during fluid flow can be written as: ； In the formula, is the density of water in the tube of the buried heat exchanger, is the internal cross-sectional area of ​​the borehole heat exchanger, is the specific heat of water at constant pressure, are the inlet and outlet temperatures of circulating water, u is the speed of circulating water, is the heat exchange between the buried heat exchanger and the surrounding lining, expressed as: ； In the formula, is the average temperature of circulating water, is the external temperature of the tube wall, is the heat transfer coefficient between the circulating water and the tube wall, and the calculation formula is: ； In the formula, is the thermal conductivity of the circulating water in units of is the inner diameter of the underground heat exchanger in , is the Nusselt number, which is a dimensionless number; Said Calculated by Gnielinski relation: ； In the formula, , v is the average flow velocity in the borehole heat exchanger; is a dimensionless constant; is the kinematic viscosity of water, in ; The numerical model of heat transfer between the tube wall and the lining is specifically: ； In the formula, is the density of the lining, is the specific heat capacity of the lining, is the temperature inside the lining, including the inner wall temperature of the lining and outer wall temperature , is the thermal conductivity of the lining, express time,( , , ) is the three-dimensional coordinate of any point on the heat exchange model of buried pipes in arched channel lining; The numerical model of the lining and air is: ； The numerical model of heat transfer between lining and surrounding rock is: ； In the formula, is the convective heat transfer coefficient of air, is the air temperature in the channel, is the surrounding rock density, is the specific heat capacity of the surrounding rock, is the surrounding rock temperature, is the thermal conductivity of the surrounding rock, ( , , ) is the three-dimensional coordinate of any point on the heat exchange model of buried pipes in arched channel lining; The initial conditions are: ； In the formula, is the far boundary temperature of the surrounding rock, in units of , The radius of the surrounding rock The temperature at The boundary conditions are: 。 2. The method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining according to claim 1 is characterized in that: The simulation conditions described in step 1 specifically include: (1) The initial temperature field of the mouth channel and the surrounding rock is consistent everywhere; (2) The physical properties of all materials are isotropic, uniform, and independent of temperature. They are constant values ​​that do not change with time. (3) The lining concrete is evenly poured around the buried heat exchanger. The surrounding rock and lining are in close contact with no gap. The contact thermal resistance of each part can be ignored. The heat transfer process between the lining and the surrounding rock is heat conduction. (4) The circulating water in the buried heat exchanger is regarded as an incompressible fluid, and the effect of gravity on the flow rate is ignored. The heat exchange between the circulating water and the tube wall is convective heat transfer; (5) The heat transfer process between the air in the mouth channel and the inner wall of the lining is convection heat transfer; (6) The influence of groundwater migration was not considered during the heat transfer process of the surrounding rock.

3. The method for solving the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining according to claim 1 is characterized in that: The method further comprises: Step 6, verifying the numerical model of heat transfer performance of heat exchange tubes in underground engineering lining in step 5.

4. A solution system for the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings based on the method according to any one of claims 1 to 3, characterized in that: The system comprises: The first module is used to preset simulation conditions; The second module is used to establish a numerical model of heat transfer performance of heat exchange tubes in underground engineering linings; The third module is used to mesh the numerical model of heat transfer performance of heat exchange tubes in the underground engineering lining by using a variety of different meshing methods; The fourth module is used to analyze the grid independence of the results of different grid division methods and select the optimal grid division method; The fifth module is used to solve the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings corresponding to the optimal grid division method using fluid simulation software.

5. A solution system for the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings according to claim 4, characterized in that: The system further comprises: The sixth module verifies the numerical model of heat transfer performance of heat exchange tubes in underground engineering linings in the fifth module.

6. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 2 is implemented.

7. The computer device according to claim 6, characterized in that: The processor also executes the method of claim 3.

8. A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method according to any one of claims 1 to 2.

9. The computer-readable storage medium according to claim 8, wherein: When the computer program is executed by a processor, the method according to claim 3 is also implemented.

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