A borehole casing structure ground heat exchanger heat transfer calculation method, device and storage medium

Abstract

The application provides a heat transfer calculation method, equipment and storage medium for a borehole casing structure ground heat exchanger, and belongs to the ground heat exchanger field, and comprises the following steps: obtaining user load data, heat exchanger system parameters and environmental parameters; setting a time step, establishing a borehole wall heat flux linear function along the depth direction, a borehole wall temperature calculation model and a fluid temperature calculation model; data initialization; in a preset time period, the borehole wall temperature distribution, the fluid temperature distribution and the borehole wall heat flux distribution in the current time step are sequentially calculated repeatedly at the set time step, and then the fluid temperature at the inlet of the ground heat exchanger is calculated according to the user load data. The borehole wall heat flux linear function is introduced, and on this basis, the borehole wall temperature calculation model for directly solving the borehole wall temperature through convolution is established, so that the integral calculation which needs to consume a large amount of calculation resources and a long calculation time is avoided, and the rapid calculation of the system heat transfer process is realized.

Description

Technical Field

[0001] This invention relates to a heat transfer calculation method, equipment, and storage medium for a buried pipe heat exchanger with an in-hole sleeve structure, belonging to the field of buried pipe heat exchangers. Background Technology

[0002] Ground source heat pump systems utilize the soil as a heat source or heat sink. They consist of a heat pump unit and a set of buried ground pipe heat exchangers. In winter, the heat exchangers extract heat from the soil to supply indoor heating, and in summer, they transfer heat from the indoors to the soil to cool the room. The design of the ground source heat exchangers largely determines the economy and operational efficiency of the system. Therefore, the design of the ground source heat pumps and heat transfer calculations are the most crucial aspects of designing a ground source heat pump system.

[0003] The buried pipe heat exchanger with an inner tube structure is a very common type of buried pipe heat exchanger. Its basic working principle is to achieve heat transfer and shift through the fluid flow between the inner and outer tubes, thereby achieving the purpose of heat energy recovery or temperature regulation.

[0004] In the existing technology, underground pipes are classified into shallow underground pipes and medium-deep underground pipes according to their drilling depth. The drilling depth is between 50 and 200 meters, which is considered shallow underground pipes, while the drilling depth is between 200 and 3000 meters underground, which is considered medium-deep underground pipes.

[0005] For buried pipe heat exchangers with in-hole casing structures, the calculation models for the heat transfer process in shallow buried pipes are mostly based on the assumption that the borehole wall temperature or heat flux density is uniformly distributed along the borehole wall. However, the design and operation control optimization of ground source heat pump systems for medium and deep buried pipes largely rely on advanced heat transfer calculation models.

[0006] Existing heat transfer calculation models for medium-deep buried pipes fall into two main categories: analytical heat transfer models and numerical heat transfer models. Analytical heat transfer models primarily employ a piecewise linear heat source model to solve the heat transfer process in the soil. This method requires treating the medium-deep buried pipe as a finite-length linear heat source and dividing it into multiple segments, each with a different pore wall heat flux density, to perform the calculation. However, when dealing with large-scale medium-deep buried pipe heat transfer, this method encounters a problem where the number of segmented heat sources increases with the number and depth of the buried pipes, significantly increasing the computational load. Numerical heat transfer models, on the other hand, require extensive meshing within a depth range of 200-3000 meters and a radius of 50 meters. In unsteady-state heat transfer calculations, the temperature of each mesh within each time step needs to be solved and updated. This method is computationally intensive and inefficient.

[0007] In summary, existing technologies for buried pipe heat exchangers with in-hole sleeve structures have the following drawbacks:

[0008] (1) The existing heat transfer model of buried pipe heat exchanger uses integral calculation, which requires a lot of computing resources and too long calculation time, resulting in low computing efficiency;

[0009] (2) There is a lack of heat transfer calculation methods that are applicable to both shallow and medium-deep buried pipe heat exchangers. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, equipment and storage medium for calculating the heat transfer of a buried pipe heat exchanger with an in-hole sleeve structure, thereby solving the problem of low calculation efficiency of existing buried pipe heat exchanger heat transfer models.

[0011] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0012] In a first aspect, the present invention provides a method for calculating the heat transfer of a buried pipe heat exchanger with an in-hole sleeve structure, comprising:

[0013] S1: Obtain load data from the user side, system parameters of the buried pipe heat exchanger, and environmental parameters;

[0014] S2: Set the time step and initialize the heat flux density distribution, temperature distribution, and fluid temperature distribution within the borehole of the buried pipe; wherein, the fluid temperature distribution includes: the fluid temperature at the inlet of the buried pipe and the fluid temperature at the outlet of the buried pipe.

[0015] S3: Establish a linear function of the heat flux density of the borehole wall along the depth direction inside the buried pipe and initialize the coefficients; construct a borehole wall temperature calculation model based on the finite length heat source model, and construct a fluid temperature calculation model based on the heat transfer differential equation;

[0016] S4: Obtain the orifice wall temperature distribution within the current time step based on the linear function of orifice wall heat flux density and the orifice wall temperature calculation model from the previous time step. The linear function of orifice wall heat flux density is:

[0017]

[0018] in, The heat flux density at the orifice wall. The z-axis coordinate of the point heat source. These are the first and second coefficients of the linear function of the heat flux density at the orifice wall, respectively.

[0019] The calculation model for the orifice wall temperature is as follows:

[0020]

[0021] in,

[0022]

[0023] In the formula, For convolution calculation, The temperature of the hole wall. As the first intermediate quantity, As the second intermediate quantity, As the third intermediate quantity, It is the fourth intermediate quantity. This is the fifth intermediate quantity. The thermal diffusivity of the soil, For time, To calculate the z-axis coordinates of the point, For time step, For soil density, The specific heat capacity of soil, The radius of the underground pipe drilling well. This is the minimum distance between the buried pipe and the ground surface. Let be the maximum distance between the buried pipe and the ground surface, exp be an exponential function, and erf be a Gaussian error function. Soil temperature distribution;

[0024] S5: Obtain the fluid temperature distribution within the current time step based on the temperature distribution of the inner wall of the borehole at the current time step, the fluid temperature at the inlet of the buried pipe at the previous time step, and the fluid temperature calculation model.

[0025] S6: Obtain the orifice wall heat flux density distribution within the current time step based on the orifice wall temperature distribution and fluid temperature distribution within the current time step, and perform linear fitting on the coefficients of the orifice wall heat flux density linear function in combination with the orifice wall heat flux density distribution within the current time step to obtain the orifice wall heat flux density linear function within the current time step.

[0026] S7: Calculate the fluid temperature at the inlet of the buried pipe at the current time step based on the load data on the user side and the fluid temperature at the outlet of the buried pipe at the current time step.

[0027] S8: Output the orifice wall temperature distribution, fluid temperature distribution, and linear function of orifice wall heat flux density within the current time step to the terminal device and store them in a preset variable container;

[0028] Within a preset time period, S4 to S8 are executed repeatedly at a set time step to obtain the corresponding heat transfer data of the buried pipe heat exchanger.

[0029] In conjunction with the first aspect, optionally, the fluid temperature calculation model is applicable to two operating modes: outer pipe inlet and inner pipe outlet, and inner pipe inlet and outer pipe outlet, including:

[0030]

[0031]

[0032] In the formula, The volumetric specific heat capacity of the fluid in the inlet pipe is calculated by multiplying the volume of the fluid per unit length in the inlet pipe by the density and specific heat capacity of the fluid. The volumetric specific heat capacity of the fluid in the outlet pipe is calculated by multiplying the volume of the fluid per unit length in the outlet pipe by the density and specific heat capacity of the fluid. This represents the temperature of the fluid in the inlet pipe; This represents the temperature of the fluid in the outlet pipe; Represents the temperature of the borehole wall; This represents the thermal resistance between the inlet and outlet pipes. This represents the thermal resistance between the outer sleeve and the hole wall; The direction of fluid movement. This indicates that the fluid flows from the outer pipe to the inner pipe. This indicates that the fluid flows in through the inner pipe and out through the outer pipe. Represents the operating flow rate of the fluid; Specific heat capacity of the fluid; This represents the cross-sectional area of ​​the water inlet pipe; This represents the cross-sectional area of ​​the outlet pipe; denoted as , where is the thermal conductivity of the fluid.

[0033] In conjunction with the first aspect, optionally, the inner and outer pipes of the buried pipe heat exchanger can be divided into n equal parts from top to bottom, and the fluid temperature in the inlet pipe can be... Temperature of fluid in the outlet pipe ;

[0034] At any given moment, the fluid temperature calculation model satisfies the following boundary conditions:

[0035]

[0036]

[0037]

[0038] In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe. Let be the fluid temperature at the nth node in the inlet pipe. Let be the fluid temperature at the nth node in the outlet pipe.

[0039] In conjunction with the first aspect, optionally, obtaining the orifice wall heat flux density distribution within the current time step based on the orifice wall temperature distribution and fluid temperature distribution within the current time step specifically involves:

[0040]

[0041] In the formula, The heat flux density is the heat flux density at the orifice wall.

[0042] In conjunction with the first aspect, optionally, S7 includes:

[0043] S71: The load on the ground source side of the buried pipe is calculated based on the energy efficiency coefficient of the heat pump unit and the user-side load. The calculation formula is as follows:

[0044]

[0045] In the formula, The coefficient of performance (COP) of a heat pump unit. For the load on the ground source side of the buried pipe;

[0046] S72: The fluid temperature at the inlet of the buried pipe is calculated based on the fluid temperature at the outlet of the buried pipe and the load on the ground source side of the buried pipe. The calculation formula is as follows:

[0047]

[0048] In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe. The operating flow rate of the fluid; is the specific heat capacity of the fluid.

[0049] In conjunction with the first aspect, optionally, the energy efficiency coefficient of the heat pump unit is calculated based on the fluid temperature at the outlet of the buried pipe, and the calculation formula is as follows:

[0050]

[0051] In the formula, These are the coefficients obtained by fitting the measured performance of the corresponding model of heat pump unit.

[0052] In a second aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure described in the first aspect.

[0053] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the steps of the heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure described in the first aspect.

[0054] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0055] (1) The heat transfer calculation method of the buried pipe heat exchanger with the in-hole sleeve structure provided by the present invention adopts the finite length line heat source model to construct the hole wall temperature calculation model, and introduces the linear function of the heat flux density of the buried pipe hole wall for the first time. On this basis, the buried pipe hole wall temperature is solved by direct convolution, no longer relying on integral calculation that consumes a lot of computing resources and takes too long to calculate, thus realizing the rapid calculation of the heat transfer state of the buried pipe heat exchanger at each moment in the dynamic analysis of system heat transfer;

[0056] (2) The fluid temperature calculation model provided by the present invention can be applied to both shallow and medium-deep buried pipe heat exchangers, as well as to the two operating modes of buried pipe heat exchangers with in-hole sleeve structure, namely the outer pipe water inlet and inner pipe water outlet mode and the inner pipe water inlet and outer pipe water outlet mode. This overcomes the problem that two independent calculation models need to be established for the two operating modes in the prior art, and avoids the problem of switching models in actual use. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a buried pipe heat exchanger with an inner sleeve structure in the mode of water inlet through outer pipe and water outlet through inner pipe in Embodiment 1 of the present invention.

[0058] Figure 2 This is a schematic diagram of a buried pipe ground source heat pump system in the mode of water inlet through outer pipe and water outlet through inner pipe in Embodiment 1 of the present invention;

[0059] Figure 3 This is a schematic diagram of a buried pipe ground source heat pump system in the inner pipe water inlet and outer pipe water outlet mode in Embodiment 1 of the present invention;

[0060] Figure 4 This is a schematic diagram of the vertical buried pipe of the buried pipe heat exchanger with an in-hole sleeve structure in Embodiment 1 of the present invention. Detailed Implementation

[0061] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Example 1

[0062] Figure 1 The internal sleeve structure of the buried pipe heat exchanger is shown, such as... Figure 1 As shown, the inner and outer sleeves are arranged coaxially. The inner sleeve is the heat source side of the heat pump, extracting heat energy from deep underground, while the outer sleeve is the heat carrier side, responsible for heat exchange. Its working principle is to utilize the underground stored heat energy to complete the heat exchange between the heat source and the heat carrier, achieving a balance of heat energy.

[0063] This embodiment provides a method for calculating the heat transfer of a buried pipe heat exchanger with an in-hole sleeve structure, including:

[0064] Step 1: Obtain load data from the user side, system parameters of the buried pipe heat exchanger, and environmental parameters;

[0065] Specifically, user-side load data includes: the operating flow rate of the buried pipe, the number of hours it operates per year, the user-side heating and cooling loads, and the energy consumption coefficient of the heat pump equipment. System parameters of the buried pipe heat exchanger include: fluid density, specific heat capacity, and thermal conductivity; the drilling radius of the buried pipe; the length and diameter dimensions of the inner and outer pipes; the thermal properties of the pipe material; the thermal resistance between the inner and outer pipes; the thermal resistance between the outer casing and the borehole wall; the distance from the top and bottom of the buried pipe to the ground; and the number of segments in the inner and outer pipes along the depth direction. Environmental parameters include: the soil's thermal diffusivity, soil density, and soil specific heat capacity.

[0066] Step 2: Set the time step and initialize the heat flux density distribution, temperature distribution, and fluid temperature distribution of the borehole wall inside the buried pipe. The fluid temperature distribution includes the fluid temperature at the inlet of the buried pipe and the fluid temperature at the outlet of the buried pipe.

[0067] As is generally known, the time step refers to the time interval between two adjacent time steps, primarily used to determine the update frequency of the system state and its impact on numerical stability. A smaller time step implies more frequent updates, while a larger time step may lead to numerical instability.

[0068] In this embodiment, the time step can be set according to actual needs, such as 1 minute, 5 minutes or 1 hour.

[0069] Before performing heat transfer calculations, it is necessary to set initial values ​​for the fluid temperature at the inlet of the buried pipe, the heat flux density distribution on the borehole wall inside the buried pipe, the borehole wall temperature distribution, and the fluid temperature distribution.

[0070] Step 3: Establish a linear function of the heat flux density of the borehole wall along the depth direction inside the buried pipe, and initialize the coefficients.

[0071] Specifically, based on the finite-length heat source model, a system is established that correlates the location of the point heat source with the heat source location. The linear function of the heat flux density along the depth direction of the borehole wall directly related to the underground pipe is expressed as follows:

[0072] in, The heat flux density at the orifice wall. The z-axis coordinate of the point heat source. These are the first and second coefficients of the linear function of the heat flux density at the pore wall, respectively.

[0073] It is important to note the first coefficient of the linear function of the heat flux density at the pore wall. Second coefficient It is not a fixed value, but a coefficient that is continuously updated after fitting the linear change of the heat flux along the depth direction of the inner wall at each time step, i.e., the first coefficient. Second coefficient These are variables that change over time. Before performing heat transfer calculations, initial values ​​need to be set for the first and second coefficients.

[0074] The above are the preparatory steps before performing heat transfer calculations. Next, the heat transfer calculations for the buried pipe heat exchanger will be performed, including: repeating steps 4 to 8 below at a set time step within a preset time period to obtain the corresponding heat transfer data of the buried pipe heat exchanger.

[0075] Step 4: Obtain the orifice wall temperature distribution in the current time step based on the linear function of orifice wall heat flux density in the previous time step and the pre-built orifice wall temperature calculation model.

[0076] In some specific embodiments, before performing heat transfer calculations, a hole wall temperature calculation model is pre-constructed based on a linear function of the hole wall heat flux density and a finite-length heat source model. Specifically:

[0077]

[0078] in,

[0079]

[0080] In the formula, For convolution calculation, The temperature of the hole wall. , , , , As an intermediate quantity, The thermal diffusivity of the soil, For time, To calculate the z-axis coordinates of the point, For time step, For soil density, The specific heat capacity of soil, The radius of the underground pipe drilling well. This is the minimum distance between the buried pipe and the ground surface. Let be the maximum distance between the buried pipe and the ground surface, exp be an exponential function, and erf be a Gaussian error function. This represents the soil temperature distribution.

[0081] It should be noted that, as Figure 4 As shown, and The value is directly related to the vertical burial depth of the underground pipe. Meanwhile, when calculating the temperature distribution of the borehole wall at the first time step, the initialized linear function of the borehole wall heat flux density is used.

[0082] Step 5: Based on the current time step borehole wall temperature distribution obtained in Step 4, the fluid temperature at the inlet of the buried pipe in the previous time step, and the pre-built fluid temperature calculation model, obtain the fluid temperature distribution within the current time step.

[0083] like Figure 2 and Figure 3 As shown, the underground pipe heat exchanger with an inner-shell structure has two operating modes. The first is the inner pipe inlet and outer pipe outlet mode. In summer, hot water enters the ground through the inner pipe, releases heat, cools, and then flows back into the outer pipe, completing the underground heat energy storage. The second is the outer pipe inlet and inner pipe outlet mode. In winter, cold water extracts the underground stored heat from deep underground through the outer pipe, heats it, and then transfers it to the heat pump to provide the heat required for heating.

[0084] Similar to existing technologies, the fluid temperature calculation model is based on the heat transfer differential equation. However, the fluid temperature calculation model in this embodiment introduces a parameter representing the direction of fluid flow into the differential equation. To implement a system of differential equations to calculate the fluid temperature under two different operating modes, specifically:

[0085]

[0086]

[0087] In the formula, The volumetric specific heat capacity of the fluid in the inlet pipe is calculated by multiplying the volume of the fluid per unit length in the inlet pipe by the density and specific heat capacity of the fluid. The volumetric specific heat capacity of the fluid in the outlet pipe is calculated by multiplying the volume of the fluid per unit length in the outlet pipe by the density and specific heat capacity of the fluid. This represents the temperature of the fluid in the inlet pipe; This represents the temperature of the fluid in the outlet pipe; Represents the temperature of the borehole wall; This represents the thermal resistance between the inlet and outlet pipes. This represents the thermal resistance between the outer sleeve and the hole wall; The direction of fluid movement. This indicates that the fluid flows from the outer pipe to the inner pipe. This indicates that the fluid flows in through the inner pipe and out through the outer pipe. Represents the operating flow rate of the fluid; Specific heat capacity of the fluid; This represents the cross-sectional area of ​​the water inlet pipe; This represents the cross-sectional area of ​​the outlet pipe; denoted as , where is the thermal conductivity of the fluid.

[0088] When solving for the fluid temperature distribution, the inner and outer pipes of the buried pipe heat exchanger are divided into n equal parts from top to bottom. The fluid temperature in the inlet pipe is... Temperature of fluid in the outlet pipe ;in, Let be the fluid temperature at the nth node in the inlet pipe. Let be the fluid temperature at the nth node in the outlet pipe.

[0089] It should be noted that the fluid temperature at the first node of the outlet pipe... This refers to the fluid temperature at the outlet of the buried pipe.

[0090] In some specific embodiments, at any given time, the fluid temperature calculation model satisfies the following boundary conditions:

[0091]

[0092]

[0093]

[0094] In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe.

[0095] It should also be noted that when calculating the fluid temperature distribution within the first time step, the initial fluid temperature at the inlet of the buried pipe is used for the calculation.

[0096] Step 6: Obtain the orifice wall heat flux density distribution within the current time step based on the orifice wall temperature distribution and fluid temperature distribution within the current time step, and perform linear fitting on the coefficients of the orifice wall heat flux density linear function in combination with the orifice wall heat flux density distribution within the current time step to obtain the orifice wall heat flux density linear function within the current time step.

[0097] In some embodiments, the calculation method for the orifice wall heat flux density distribution within the current time step is as follows:

[0098]

[0099] In the formula, The heat flux density is the heat flux density at the orifice wall.

[0100] After obtaining the heat flux density distribution of the orifice wall within the current time step, it is necessary to perform linear fitting on the coefficients of the linear function of the orifice wall heat flux density based on the obtained heat flux density distribution, and update the first and second coefficients of the linear function of the orifice wall heat flux density for use in the calculation of the next time step.

[0101] Step 7: Calculate the fluid temperature at the inlet of the buried pipe at the current time step based on the load data on the user side and the fluid temperature at the outlet of the buried pipe at the current time step.

[0102] In some embodiments, the load on the ground source side of the buried pipe is first calculated based on the energy efficiency coefficient of the heat pump unit and the user-side load. The specific calculation formula is as follows:

[0103]

[0104] In the formula, The coefficient of performance (COP) of a heat pump unit. For the load on the ground source side of the buried pipe, This indicates winter operating conditions, while This indicates summer operating conditions.

[0105] Next, the fluid temperature at the inlet of the buried pipe is calculated based on the fluid temperature at the outlet of the buried pipe and the load on the source side of the buried pipe. The calculation formula is as follows:

[0106]

[0107] In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe. The operating flow rate of the fluid; is the specific heat capacity of the fluid.

[0108] In some specific embodiments, the coefficient of performance (COP) of the heat pump unit is calculated based on the fluid temperature at the outlet of the buried pipe, using the following formula:

[0109]

[0110] In the formula, These are the coefficients obtained by fitting the measured performance of the corresponding model of heat pump unit.

[0111] Step 8: Output the orifice wall temperature distribution, fluid temperature distribution, orifice wall heat flux density linear function and heat pump unit energy efficiency coefficient within the current time step to the terminal device and store them in the preset variable container.

[0112] The heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure in this embodiment introduces a linear function of the heat flux density of the buried pipe hole wall for the first time. Based on the linear function of the heat flux density of the hole wall and the finite-length line heat source model, a hole wall temperature calculation model that can directly solve the hole wall temperature of the buried pipe by convolution is constructed, replacing the integral calculation in the prior art. This avoids consuming a lot of computing resources and excessive computing time, and realizes the rapid calculation of the heat transfer state of the buried pipe heat exchanger at each moment in the dynamic analysis of heat transfer in the ground source heat pump system. Example 2

[0113] This embodiment describes the process of constructing a borehole wall temperature calculation model based on a finite-length line heat source model:

[0114] First, a position is... After a point heat source instantaneously releases heat in an infinitely large area of ​​soil, the calculation point... Excess temperature at time The formula is:

[0115]

[0116] in, The intensity of a point heat source; Soil density; The specific heat capacity of the soil; This represents the thermal diffusivity of the soil.

[0117] If we integrate along the length of the buried pipe from this point heat source and transform the computational coordinate system into a cylindrical coordinate system, we can obtain:

[0118]

[0119] in: The excess temperature representing the location of the calculation point; For time step, The radius of the underground pipe drilling well. This is the minimum distance between the buried pipe and the ground surface. Let be the maximum distance between the buried pipe and the ground surface, and exp be an exponential function.

[0120] Further calculation of the integral in the above formula yields the excess temperature at the calculation point. Matrix expression:

[0121]

[0122] in,

[0123]

[0124] In the formula, erf is the Gaussian error function. , , , , This is an intermediate quantity.

[0125] To simplify the calculation, the excess temperature at any point in the soil at any time can be quickly calculated using convolution:

[0126]

[0127] Based on this, a convolutional model is also used to construct a calculation model for the hole wall temperature at any time point, specifically:

[0128]

[0129] In the formula, For convolution calculation, The temperature of the hole wall. This represents the soil temperature distribution. Example 3

[0130] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure as described in Embodiment 1 or Embodiment 2. Example 4

[0131] This embodiment provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the steps of the heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure as described in Embodiment 1 or Embodiment 2.

[0132] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0133] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for calculating the heat transfer of a buried pipe heat exchanger with an in-hole sleeve structure, characterized in that, include: S1: Obtain load data from the user side, system parameters of the buried pipe heat exchanger, and environmental parameters; S2: Set the time step and initialize the heat flux density distribution, temperature distribution, and fluid temperature distribution within the borehole of the buried pipe; wherein, the fluid temperature distribution includes: the fluid temperature at the inlet of the buried pipe and the fluid temperature at the outlet of the buried pipe. S3: Establish a linear function of the heat flux density of the borehole wall along the depth direction inside the buried pipe and initialize the coefficients; construct a borehole wall temperature calculation model based on the finite length heat source model, and construct a fluid temperature calculation model based on the heat transfer differential equation; S4: Obtain the orifice wall temperature distribution within the current time step based on the linear function of orifice wall heat flux density and the orifice wall temperature calculation model from the previous time step. The linear function of orifice wall heat flux density is: in, The heat flux density at the orifice wall. The z-axis coordinate of the point heat source. These are the first and second coefficients of the linear function of the heat flux density at the orifice wall, respectively. The calculation model for the orifice wall temperature is as follows: in, In the formula, For convolution calculation, The temperature of the hole wall. As the first intermediate quantity, As the second intermediate quantity, As the third intermediate quantity, It is the fourth intermediate quantity. This is the fifth intermediate quantity. The thermal diffusivity of the soil, For time, To calculate the z-axis coordinates of the point, For time step, For soil density, The specific heat capacity of soil, The radius of the underground pipe drilling well. This is the minimum distance between the buried pipe and the ground surface. Let be the maximum distance between the buried pipe and the ground surface, exp be an exponential function, and erf be a Gaussian error function. Soil temperature distribution; S5: Obtain the fluid temperature distribution within the current time step based on the temperature distribution of the inner wall of the borehole at the current time step, the fluid temperature at the inlet of the buried pipe at the previous time step, and the fluid temperature calculation model. S6: Obtain the orifice wall heat flux density distribution within the current time step based on the orifice wall temperature distribution and fluid temperature distribution within the current time step, and perform linear fitting on the coefficients of the orifice wall heat flux density linear function in combination with the orifice wall heat flux density distribution within the current time step to obtain the orifice wall heat flux density linear function within the current time step. S7: Calculate the fluid temperature at the inlet of the buried pipe at the current time step based on the load data on the user side and the fluid temperature at the outlet of the buried pipe at the current time step. S8: Output the orifice wall temperature distribution, fluid temperature distribution, and linear function of orifice wall heat flux density within the current time step to the terminal device and store them in a preset variable container; Within a preset time period, S4 to S8 are executed repeatedly at a set time step to obtain the corresponding heat transfer data of the buried pipe heat exchanger.

2. The heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure according to claim 1, characterized in that, The fluid temperature calculation model is applicable to two operating modes: outer pipe inlet and inner pipe outlet, and inner pipe inlet and outer pipe outlet, including: In the formula, The volumetric specific heat capacity of the fluid in the inlet pipe is calculated by multiplying the volume of the fluid per unit length in the inlet pipe by the density and specific heat capacity of the fluid. The volumetric specific heat capacity of the fluid in the outlet pipe is calculated by multiplying the volume of the fluid per unit length in the outlet pipe by the density and specific heat capacity of the fluid. This represents the temperature of the fluid in the inlet pipe; This represents the temperature of the fluid in the outlet pipe; Represents the temperature of the borehole wall; This represents the thermal resistance between the inlet and outlet pipes. This represents the thermal resistance between the outer sleeve and the hole wall; The direction of fluid movement. This indicates that the fluid flows from the outer pipe to the inner pipe. This indicates that the fluid flows in through the inner pipe and out through the outer pipe. Represents the operating flow rate of the fluid; Specific heat capacity of the fluid; This represents the cross-sectional area of ​​the water inlet pipe; This represents the cross-sectional area of ​​the outlet pipe; denoted as , where is the thermal conductivity of the fluid.

3. The heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure according to claim 2, characterized in that, The inner and outer pipes of the buried pipe heat exchanger are divided into n equal parts from top to bottom. The fluid temperature in the inlet pipe is... Temperature of fluid in the outlet pipe ; At any given moment, the fluid temperature calculation model satisfies the following boundary conditions: In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe. Let be the fluid temperature at the nth node in the inlet pipe. Let be the fluid temperature at the nth node in the outlet pipe.

4. The heat transfer calculation method for a buried pipe heat exchanger with an in-hole sleeve structure according to claim 2, characterized in that, The process of obtaining the orifice wall heat flux density distribution within the current time step based on the orifice wall temperature distribution and fluid temperature distribution within the current time step specifically involves: In the formula, The heat flux density is the heat flux density at the orifice wall.

5. The heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure according to claim 1, characterized in that, S7 includes: S71: The load on the ground source side of the buried pipe is calculated based on the energy efficiency coefficient of the heat pump unit and the user-side load. The calculation formula is as follows: In the formula, The coefficient of performance (COP) of a heat pump unit. For the load on the ground source side of the buried pipe; S72: The fluid temperature at the inlet of the buried pipe is calculated based on the fluid temperature at the outlet of the buried pipe and the load on the ground source side of the buried pipe. The calculation formula is as follows: In the formula, This refers to the fluid temperature at the inlet of the buried pipe. This refers to the fluid temperature at the outlet of the buried pipe. The operating flow rate of the fluid; is the specific heat capacity of the fluid.

6. The heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure according to claim 5, characterized in that, The energy efficiency coefficient of the heat pump unit is calculated based on the fluid temperature at the outlet of the buried pipe. The calculation formula is as follows: In the formula, These are the coefficients obtained by fitting the measured performance of the corresponding model of heat pump unit.

7. An electronic device, characterized in that, The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the heat transfer calculation method for the buried pipe heat exchanger with an in-hole sleeve structure as described in any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the heat transfer calculation method for the buried pipe heat exchanger with the in-hole sleeve structure as described in any one of claims 1 to 6.

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