A method and device for testing heat exchange performance of a U-shaped ground heat exchanger based on effective buried depth

Abstract

The application discloses a kind of based on effective buried depth U-shaped buried pipe heat transfer performance test method and device, it is related to ground source heat pump and shallow geothermal energy utilization technical field, including when drilling test hole, layered temperature sensor is arranged along the direction of soil depth, with buried U-shaped pipe access constant temperature circulating water system, with thermal insulation material covering exposed pipeline;After standing, start data acquisition instrument, constant temperature water circulating system and water pump, regularly record sensor temperature data;Through adjusting circulating water pump flow and valve control U-shaped pipe inner water flow;After testing, data acquisition instrument exports invalid heat exchange depth number, according to this, judge the effective buried depth and heat exchange soil layer corresponding to U-shaped pipe.The application can obtain the effective buried pipe depth of U-shaped buried pipe by measuring the water temperature variation rate of U-shaped buried pipe inlet branch pipe depth direction and the temperature difference between corresponding layer soil and circulating water in U-shaped buried pipe inlet branch pipe, to avoid that buried pipe design depth is too deep, and invalid heat exchange depth appears.

Description

Technical Field

[0001] This invention relates to the field of ground source heat pump and shallow geothermal energy utilization technology, and in particular to a method and apparatus for testing the heat exchange performance of a U-shaped buried pipe based on effective burial depth. Background Technology

[0002] A ground source heat pump is an energy supply system that utilizes shallow geothermal resources as a heat source and cold source to provide cooling and heating to buildings through heat pump technology. Compared with traditional air source heat pumps and other systems, ground source heat pump systems have advantages such as low carbon emissions, energy saving, and high efficiency. However, they also have the disadvantage of a relatively high initial investment in buried pipes, which limits their widespread application to some extent. The design depth of the buried pipes is one of the important factors affecting the initial investment. In order to ensure the efficient operation of the ground source heat pump system and reduce the initial investment of the buried pipe system, the design depth of the buried pipes must ensure that the buried pipes can exchange heat fully with the soil during operation. That is, the buried depth of the buried pipes should be within the effective burial depth range, minimizing the ineffective heat exchange depth.

[0003] Existing ground source heat pump systems typically employ vertical U-shaped buried pipes, with their depth generally determined to be 30-150 m based on a combination of building load and empirical values. However, the heat exchange performance of U-shaped buried pipes gradually decreases with increasing burial depth. At deeper depths, some sections may lose heat exchange capacity, exceeding the effective burial depth range; conversely, shallower depths may result in insufficient heat exchange, failing to fully utilize the effective burial depth. Simultaneously, soil temperature fluctuates during heat exchange, leading to differences in heat exchange capacity at different pipe depths, and even the emergence of ineffective heat exchange layers. Therefore, determining the buried pipe depth solely based on empirical values ​​fails to account for the effective burial depth and effective heat exchange layer, and makes it difficult to reasonably match the actual operating conditions of the ground source heat pump system with the local soil thermal properties, thus affecting the initial investment and overall system performance. Therefore, a U-shaped buried pipe heat exchange testing method and apparatus are needed to test the effective burial depth and effective heat exchange range of a ground source heat pump system under different operating conditions. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the present invention is proposed.

[0005] The purpose of this invention is to provide a method and apparatus for testing the heat exchange performance of U-shaped buried pipes based on effective burial depth. The aim is to determine the effective burial depth and effective heat exchange depth range of the buried pipe system under different regions and operating conditions by using the method and apparatus based on effective burial depth. This ensures the economic efficiency of the initial investment in buried pipe depth and the high efficiency of system operation, and avoids problems such as excessive initial investment, inefficient operation, or underutilization of effective burial depth caused by mismatch between the design depth of the U-shaped buried pipe and the operating conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for testing the heat exchange performance of a U-shaped buried pipe based on its effective burial depth, comprising drilling test holes at the burial site, arranging temperature sensor measuring points, and connecting the inlet and outlet of the U-shaped buried pipe to a constant-temperature circulating water pipeline; after a certain period of settling, turning on the data acquisition and analysis instrument, the constant-temperature water, and the circulating water pump, and simultaneously recording measurement data at multiple time intervals; setting the operating parameters of the circulating water pump and the flow regulating valve to adjust the circulating water flow rate in the U-shaped buried pipe to a set value, and setting the preset conditions of the U-shaped buried pipe on the data acquisition and analysis instrument; reading the temperature sensor measuring point data on the data acquisition and analysis instrument, and calculating whether the layer where the temperature sensor measuring point is located has ineffective heat exchange; stopping the test after a period of continuous testing, and outputting the measuring point numbers marked as ineffective heat exchange depth and ineffective heat exchange layer through the data acquisition and analysis instrument, thereby determining the effective burial depth and effective heat exchange layer of the U-shaped buried pipe based on the corresponding numbers.

[0007] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing method based on effective burial depth of the present invention, wherein: the test hole includes the test hole of the U-shaped buried pipe and the soil temperature test hole; The arrangement of the temperature sensor measuring points refers to dividing the soil into k layers evenly along the depth direction, placing the temperature sensor measuring points on the outer surface of the soil temperature measuring tube and inside the water inlet branch of the U-shaped buried pipe, and then laying the pipe and backfilling; the measurement data includes the soil temperature, water temperature and circulating water flow rate at each measuring point.

[0008] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing method based on effective burial depth of the present invention, the preset conditions include the minimum water temperature change rate δ of the inlet branch pipe. min Minimum allowable temperature difference ΔT between soil and circulating water in the inlet branch pipe of U-shaped buried pipe min Minimum heat transfer rate per unit tube length (q) min Specific heat of circulating water, c.

[0009] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing method based on effective burial depth of the present invention, wherein: for U-shaped buried pipe, the evaluation criteria include effective burial depth and effective heat exchange layer; The evaluation criteria for the effective burial depth include the water temperature change rate δ along the depth direction of the U-shaped buried pipe inlet branch, which is the main evaluation criterion. k The temperature difference ΔT between the soil at the corresponding depth and the circulating water in the U-shaped buried water inlet branch pipe, serving as an auxiliary evaluation standard. k The evaluation criterion for the effective heat exchange layer is the heat transfer rate q per unit tube length of the layer. k .

[0010] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing method based on effective burial depth of the present invention, the step of reading temperature sensor measurement point data on a data acquisition and analysis instrument, and determining whether the layer where the temperature sensor measurement point is located is ineffective in heat exchange by calculation, includes determining whether it is an ineffective heat exchange depth and an ineffective heat exchange layer; wherein, determining whether it is an ineffective heat exchange depth includes: reading the water temperature measurement point in the water inlet branch pipe of the U-shaped buried pipe through the data acquisition and analysis instrument. Based on the data, calculate the water temperature change rate δ along the depth direction of the U-shaped buried pipe inlet branch pipe in each layer. k。

[0011] When the rate of change of water temperature δ k Less than the minimum water temperature change rate δ min , i.e. δ k <δ min At that time, output water temperature measuring point Measurement point number of the floor And record the layer number as the invalid heat transfer depth.

[0012] The water temperature change rate δ k The calculation formula is as follows: (1) in, , ) The test temperatures are the starting and ending temperatures of the k-th layer of the U-shaped underground water inlet branch pipe, respectively. , The test temperatures are at the beginning and end of the U-shaped underground water inlet branch pipe, respectively.

[0013] As a preferred embodiment of the U-shaped buried pipe heat transfer performance testing method based on effective burial depth of the present invention, the determination of whether it is an ineffective heat transfer depth also includes reading soil temperature measuring points through a data acquisition and analysis instrument. Data, calculation of soil temperature measuring points Temperature difference Δ of the layer T k When the temperature difference ΔT k Less than the minimum allowable temperature difference ΔT between soil and circulating water min That is, ΔT k <ΔT min At that time, output soil temperature measurement points Measurement point number of the floor The depth of this layer is recorded as the ineffective heat transfer depth; the temperature difference Δ between the soil and the circulating water in the U-shaped buried pipe inlet branch is recorded. T k As shown below: (2) In the formula, For the soil in the first Temperature at the measuring points of the layer; For the circulating water in the U-shaped buried water inlet branch pipe at the first Temperature at the measuring points of the layer.

[0014] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing method based on effective burial depth of the present invention, the determination of whether it is an ineffective heat exchange layer specifically involves reading the flow rate and water temperature measurement points of the electromagnetic flowmeter on a data acquisition and analysis instrument. Data, calculate water temperature measurement points Heat transfer rate per unit tube length in the layer q k ;like q k ≤ q min Then output water temperature measurement point Measurement point number of the floor And record that the layer is an ineffective heat transfer layer; the heat transfer rate per unit tube length of the layer q k The calculation formula is as follows: (3) In the formula, q k Δh represents the heat transfer rate per unit length of the k-th layer of the U-shaped buried water inlet branch pipe, in W / m; c represents the specific heat capacity of the circulating water, in J / (kg·K); m represents the mass flow rate of the circulating water, in kg / s; and Δh represents the layer thickness.

[0015] Another objective of this invention is to provide a heat exchange performance testing device for U-shaped buried pipes based on effective burial depth. To solve the above-mentioned technical problems, this invention also provides the following technical solution: a heat exchange performance testing device for U-shaped buried pipes based on effective burial depth, comprising a soil temperature measurement unit, including a data acquisition and analysis instrument, a soil temperature measurement tube, and multiple soil temperature sensors, wherein the soil temperature sensors are connected to the data acquisition and analysis instrument via signal transmission lines; The water circulation unit includes a constant-temperature water area, a circulating water pump, a flow regulating valve, an electromagnetic flow meter, a U-shaped underground pipe, and multiple U-shaped underground pipe circulating water temperature sensors. The circulating water pump and the flow regulating valve are sequentially installed in the inlet pipe of the circulating water pipe connecting the U-shaped underground pipe and the constant-temperature water area, and the electromagnetic flow meter is installed in the outlet pipe. The U-shaped underground pipe circulating water temperature sensors and the electromagnetic flow meter are connected to the data acquisition and analysis instrument through signal transmission lines.

[0016] As a preferred embodiment of the U-shaped buried pipe heat exchange performance testing device based on effective burial depth according to the present invention, wherein: the soil temperature measuring pipe and the U-shaped buried pipe are buried at the same depth, and both the soil temperature measuring pipe and the U-shaped buried pipe are uniformly divided into n layers along the depth direction to correspondingly arrange temperature sensor measuring points; the temperature sensor measuring points include soil temperature measuring points. and water temperature measuring point , .

[0017] As a preferred embodiment of the present invention: the soil temperature measuring point A soil temperature sensor is set up at the corresponding water temperature measuring point. A U-shaped buried pipe circulating water temperature sensor is correspondingly installed; the soil temperature measuring point With the water temperature measuring point The soil and water temperatures are uniformly distributed along the depth direction within the aforementioned n layers, with one measuring point at the beginning and end of the inlet branch pipe in each layer to monitor changes in soil and water temperature. With the water temperature measuring point One-to-one correspondence along the depth direction.

[0018] The beneficial effects of the U-shaped buried pipe heat exchange performance testing device based on effective burial depth of the present invention are as follows: (1) By measuring the water temperature change rate in the depth direction of the U-shaped buried pipe inlet branch and the temperature difference between the corresponding soil layer and the circulating water in the U-shaped buried pipe inlet branch, the effective burial depth of the U-shaped buried pipe can be obtained, thereby avoiding the problem of excessively deep buried pipe design, resulting in ineffective heat exchange depth, causing excessively high initial investment or shallow burial depth and insufficient utilization of effective burial depth, which can provide a basis for optimizing the design depth of buried pipe. (2) By measuring the circulating water temperature change rate in the depth direction of the U-shaped buried pipe inlet branch, the heat exchange rate per unit pipe length in the depth direction can be obtained, thereby obtaining the heat exchange status of U-shaped buried pipes at different depths, identifying ineffective heat exchange layers, and determining the high-efficiency heat exchange layers and low-efficiency heat exchange layers within the depth range of the buried pipe, which can provide a reference for the optimized design of U-shaped buried pipes. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the heat exchange performance testing device for U-shaped buried pipes based on effective burial depth in this invention.

[0020] Figure 2 This is a schematic diagram showing the arrangement of temperature measuring points in the k-th soil layer along the depth direction in this invention. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Example 1 Reference Figure 1 This is the first embodiment of the present invention, which provides a method for testing the heat transfer performance of a U-shaped buried pipe based on its effective burial depth, including... S1: Drill test holes at the buried pipe site, set up temperature sensor measuring points, and connect the inlet and outlet of the U-shaped buried pipe 205 to the constant temperature water circulation pipe 201.

[0025] S1.1: Drill test holes for U-shaped buried pipe 205 and soil temperature test holes at the buried pipe site according to design requirements. Based on site conditions, the soil is layered along the depth direction. The temperature sensor measuring points are arranged on the outer surface of the soil temperature measuring pipe 102 and inside the water inlet branch pipe of the U-shaped buried pipe 205 as required. Then, the pipe is laid and backfilled as required.

[0026] S1.2: Connect the U-shaped underground pipe 205 to the inlet and outlet of the constant temperature water circulation pipe 201, and insulate the exposed pipe with insulation material.

[0027] S1.3: Connect the inlet and outlet of the U-shaped underground pipe 205 to the circulating water pipe of the constant temperature water area 201, and insulate the exposed pipe with insulation material.

[0028] Specifically, both the soil temperature measuring pipe 102 and the U-shaped buried pipe 205 are PE pipes, and they are buried at the same depth, which can be 30~200m depending on the actual site conditions. The horizontal spacing between them is 2~3m. Both the soil temperature measuring pipe 102 and the U-shaped buried pipe 205 are evenly divided into n layers along the depth direction to arrange temperature sensor measuring points. The depth of each layer can be 3~5m depending on the site conditions.

[0029] S2: After standing for at least 48 hours, turn on the data acquisition and analysis instrument 101, the constant temperature water area 201 and the circulating water pump 202, and record the measurement data at different time intervals.

[0030] Specifically, the measurement data includes soil temperature, water temperature, and circulating water flow rate at each measuring point.

[0031] S3: Set the operating parameters of the circulating water pump 202 and the flow regulating valve 203, use the flow regulating valve 203 to adjust the circulating water flow in the U-shaped buried pipe 205 to the set value, and set the preset conditions of the U-shaped buried pipe 205 on the data monitoring and analysis unit 1.

[0032] Specifically, the preset condition is the minimum water temperature change rate δ in the inlet branch pipe. min Minimum allowable temperature difference ΔT between soil and circulating water in the inlet branch of U-shaped buried pipe (205) min Minimum heat transfer rate per unit tube length (q) min Specific heat of circulating water, c.

[0033] S4: Read the temperature sensor measurement point data on the data acquisition and analysis instrument 101, and determine whether the layer where the temperature sensor measurement point is located is an ineffective heat transfer depth and an ineffective heat transfer layer by calculation.

[0034] The evaluation criteria for U-shaped buried pipe 205 include effective burial depth and effective heat exchange layer. The evaluation criteria for effective burial depth include, as the primary evaluation criterion, the water temperature change rate δ along the depth direction of the U-shaped buried pipe 205 inlet branch pipe. k The temperature difference ΔT between the soil at the corresponding depth and the circulating water in the U-shaped buried pipe 205 inlet branch pipe, serving as an auxiliary evaluation standard. k The evaluation criterion for the effective heat exchange layer is the heat transfer rate q per unit tube length of the layer. k .

[0035] S4.1: Determining whether a heat transfer depth is ineffective includes the following steps: S4.1.1: Read the water temperature measurement point in the inlet branch pipe of the U-shaped underground pipe 205 using the data acquisition and analysis instrument 101. Based on the data, calculate the water temperature variation rate δ along the depth direction of the 205 U-shaped buried pipe inlet branch pipe of each layer. k。

[0036] S4.1.2: When the rate of change of water temperature δ k Less than the minimum water temperature change rate δ min , i.e. δ k <δ min At that time, output water temperature measuring point Measurement point number of the floor And record the layer number as the invalid heat transfer depth; Water temperature change rate δ k The calculation formula is as follows: (1) in, , ) The test temperatures are the starting and ending temperatures of the k-th layer of the U-shaped underground water inlet branch pipe, respectively. , The test temperatures are at the beginning and end of the U-shaped underground water inlet branch pipe, respectively.

[0037] S4.1.3: Read soil temperature data from measurement points using data acquisition and analysis instrument 101. Data, calculation of soil temperature measuring points Temperature difference Δ of the layer T k ; S4.1.4: When the temperature difference ΔT k Less than the minimum allowable temperature difference ΔT between soil and circulating water min That is, ΔT k <ΔT min At that time, output soil temperature measurement points Measurement point number of the floor And record the layer number as the invalid heat transfer depth; The temperature difference Δ between the soil and the circulating water in the 205 U-shaped buried water inlet branch pipe T k As shown below: (2) In the formula, For the soil in the first Temperature at the measuring points of the layer; For the circulating water in the U-shaped buried water inlet branch pipe at the first Temperature at the measuring points of the layer.

[0038] S4.2: Determining whether the heat exchange layer is invalid involves reading the flow rate and water temperature data from the electromagnetic flowmeter 204 on the data acquisition and analysis instrument 101. Data, calculate water temperature measurement points Heat transfer rate per unit tube length in the layer q k ;like qk ≤ q min Then output water temperature measurement point Measurement point number of the floor And record the layer number as an invalid heat exchange layer; Heat transfer rate per unit tube length in stratified layers q k The calculation formula is as follows: (3) In the formula, q k Δh represents the heat transfer rate per unit length of the k-th layer of the U-shaped buried water inlet branch pipe, in W / m; c represents the specific heat capacity of the circulating water, in J / (kg·K); m represents the mass flow rate of the circulating water, in kg / s; and Δh represents the layer thickness.

[0039] S5: After continuous testing for about 72 hours, the test is stopped. The measurement point number marked as invalid heat transfer depth and invalid heat transfer layer is output by the data acquisition and analysis instrument 101. The effective burial depth and effective heat transfer layer of the U-shaped buried pipe 205 are determined according to the corresponding number.

[0040] In summary, this embodiment, by measuring the water temperature change rate along the depth direction of the U-shaped buried pipe inlet branch and the temperature difference between the corresponding soil layer and the circulating water inside the U-shaped buried pipe inlet branch, can obtain the effective burial depth of the U-shaped buried pipe. This avoids the problem of excessively deep buried pipe design, resulting in ineffective heat exchange depth and excessively high initial investment, or insufficient burial depth and underutilization of the effective burial depth. It can provide a basis for optimizing the design depth of buried pipes. Furthermore, by measuring the circulating water temperature change rate along the depth direction of the U-shaped buried pipe inlet branch, the heat transfer rate per unit pipe length in the depth direction can be obtained. This allows for the assessment of the heat transfer status of the U-shaped buried pipe at different depths, identification of ineffective heat transfer layers, and determination of high-efficiency and low-efficiency heat transfer layers within the buried pipe depth range. This can provide a reference for the optimized design of U-shaped buried pipes.

[0041] Example 2 Reference Figure 1 and Figure 2 This is the second embodiment of the present invention. Based on the first embodiment, this embodiment is formed to further provide a U-shaped buried pipe heat exchange performance testing device based on effective burial depth, including a soil temperature measurement unit 100, including a data acquisition and analysis instrument 101, a soil temperature measurement tube 102 and multiple soil temperature sensors 103. The soil temperature sensors 103 are connected to the data acquisition and analysis instrument 101 through a signal transmission line.

[0042] The water circulation unit 200 includes a constant temperature water area 201, a circulating water pump 202, a flow regulating valve 203, an electromagnetic flow meter 204, a U-shaped underground pipe 205, and multiple U-shaped underground pipe circulating water temperature sensors 206. The circulating water pump 202 and the flow regulating valve 203 are sequentially installed in the inlet pipe of the circulating water pipe connecting the U-shaped underground pipe 205 and the constant temperature water area 201, and the electromagnetic flow meter 204 is installed in the outlet pipe. The U-shaped underground pipe circulating water temperature sensors 206 and the electromagnetic flow meter 204 are connected to the data acquisition and analysis instrument 101 through signal transmission lines.

[0043] Specifically, the soil temperature measuring tube 102 and the U-shaped buried pipe 205 are buried at the same depth, and both the soil temperature measuring tube 102 and the U-shaped buried pipe 205 are uniformly divided into n layers along the depth direction to correspondingly arrange temperature sensor measuring points; the temperature sensor measuring points include soil temperature measuring points. and water temperature measuring point , .

[0044] The soil temperature sensor 103 includes several soil temperature measuring points evenly arranged on the outer surface of the soil temperature measuring tube 102 along the depth direction. And each soil temperature measuring point Each of the U-shaped buried pipes is equipped with a soil temperature sensor 103; the U-shaped buried pipe circulating water temperature sensor 206 includes several water temperature measuring points evenly placed inside the inlet branch pipes of the U-shaped buried pipe 205 along the depth direction. And each water temperature measuring point Each of the soil temperature measuring points is equipped with a U-shaped buried pipe circulating water temperature sensor 206; A soil temperature sensor 103 is correspondingly installed at the water temperature measuring point. A U-shaped underground pipe circulating water temperature sensor 206 is installed accordingly.

[0045] Furthermore, soil temperature measuring point 103-1 and water temperature measuring point 206-1 are evenly arranged along the depth direction within the above-mentioned n layers, and one measuring point is arranged at the beginning and end positions of the water inlet branch pipe of each layer to monitor the changes in soil temperature and water temperature of that layer; the positions of soil temperature measuring point 103-1 and water temperature measuring point 206-1 along the depth direction correspond one-to-one.

[0046] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise changed, and the nature or number or position of discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0047] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0048] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for testing the heat transfer performance of a U-shaped buried pipe based on effective burial depth, characterized in that: Includes the following steps: Drill test holes at the buried pipe site, set up temperature sensor measuring points, and connect the inlet and outlet of the U-shaped buried pipe (205) to the constant temperature water (201) circulating water pipeline; After a certain period of time, the data acquisition and analysis instrument (101), the constant temperature water body (201) and the circulating water pump (202) are turned on, and the measurement data at multiple times are recorded at certain time intervals. Set the operating parameters of the circulating water pump (202) and the flow regulating valve (203) to adjust the circulating water flow in the U-shaped underground pipe (205) to the set value, and set the preset conditions of the U-shaped underground pipe (205) on the data acquisition and analysis instrument (101); The temperature sensor measurement point data is read on the data acquisition and analysis instrument (101), and the layer where the temperature sensor measurement point is located is determined by calculation to determine whether the heat exchange is ineffective. After continuous testing for a period of time, the test is stopped. The measurement point number marked as ineffective heat transfer depth and ineffective heat transfer layer is output by the data acquisition and analysis instrument (101). The effective burial depth and effective heat transfer layer of the U-shaped buried pipe (205) are determined according to the corresponding number. The test holes include test holes for the U-shaped buried pipe (205) and soil temperature test holes; The arrangement of the temperature sensor measuring points refers to dividing the soil into k layers evenly along the depth direction, arranging the temperature sensor measuring points on the outer surface of the soil temperature measuring pipe (102) and inside the water inlet branch pipe of the U-shaped buried pipe (205), and then laying the pipe and backfilling. The measurement data includes soil temperature, water temperature, and circulating water flow rate at each measuring point; The preset conditions include the minimum water temperature change rate δ of the inlet branch pipe. min Minimum allowable temperature difference ΔT between soil and circulating water in the inlet branch of U-shaped buried pipe (205) min Minimum heat transfer rate per unit tube length (q) min Specific heat of circulating water, c; For U-shaped buried pipes (205), the evaluation criteria include effective burial depth and effective heat exchange layer; The evaluation criteria for the effective burial depth include the water temperature change rate δ in the depth direction of the U-shaped buried pipe (205) inlet branch pipe, which is the main evaluation criterion. k The temperature difference ΔT between the corresponding depth of soil and the circulating water in the U-shaped buried pipe (205) inlet branch pipe, which serves as an auxiliary evaluation standard. k The evaluation criterion for the effective heat exchange layer is the heat transfer rate q per unit tube length of the layer. k ; The process of reading temperature sensor measurement point data on the data acquisition and analysis instrument (101) and determining whether the layer where the temperature sensor measurement point is located is ineffective in heat transfer by calculation includes determining whether it is an ineffective heat transfer depth and an ineffective heat transfer layer. The determination of whether a heat transfer depth is ineffective includes: The water temperature measurement point in the inlet branch pipe of the U-shaped buried pipe (205) is read by the data acquisition and analysis instrument (101). Based on the data, calculate the water temperature change rate δ along the depth direction of the U-shaped buried pipe (205) inlet branch pipe of each layer. k ; When the rate of change of water temperature δ k Less than the minimum water temperature change rate δ min , i.e. δ k <δ min At that time, output water temperature measuring point Measurement point number of the floor And record the layer number as the invalid heat transfer depth; The water temperature change rate δ k The calculation formula is as follows: （1） in, , The test temperatures are the starting and ending temperatures of the kth layer of the U-shaped buried pipe water inlet branch pipe, respectively. , The test temperatures are at the beginning and end of the U-shaped underground water inlet branch pipe, respectively. Determining whether a heat transfer depth is ineffective also includes, Soil temperature readings were obtained from the data acquisition and analysis instrument (101) at the measuring points. Data, calculation of soil temperature measuring points Temperature difference Δ of the layer T k ; When the temperature difference ΔT k Less than the minimum allowable temperature difference ΔT between soil and circulating water min That is, ΔT k <ΔT min At that time, output soil temperature measurement points Measurement point number of the floor And record that layer as an ineffective heat transfer depth; The temperature difference Δ between the soil and the circulating water in the U-shaped buried pipe (205) inlet branch pipe T k As shown below: （2） In the formula, For the soil in the first Temperature at the measuring points of the layer; For the circulating water in the U-shaped buried water inlet branch pipe at the first Temperature at the measuring points of the layer; Determining whether a heat exchange layer is invalid involves reading the flow rate and water temperature data from the electromagnetic flowmeter (204) on the data acquisition and analysis instrument (101). Data, calculate water temperature measurement points Heat transfer rate per unit tube length in the layer q k ;like q k ≤ q min Then output water temperature measurement point Measurement point number of the floor And record that the layer is an ineffective heat exchange layer; The heat transfer rate per unit tube length of the layered tube q k The calculation formula is as follows: （3） In the formula, q k Δh represents the heat transfer rate per unit length of the k-th layer of the U-shaped buried pipe inlet branch pipe, in W / m; c represents the specific heat capacity of the circulating water, in J / (kg·K); m represents the mass flow rate of the circulating water, in kg / s; and Δh represents the layer thickness.

2. A device for testing the heat transfer performance of a U-shaped buried pipe based on effective burial depth, characterized in that: Including the method for testing the heat transfer performance of U-shaped buried pipes based on effective burial depth as described in claim 1; and, The soil temperature measurement unit (100) includes a data acquisition and analysis instrument (101), a soil temperature measurement tube (102), and multiple soil temperature sensors (103). The soil temperature sensors (103) are connected to the data acquisition and analysis instrument (101) via signal transmission lines. The water circulation unit (200) includes a constant temperature water area (201), a circulating water pump (202), a flow regulating valve (203), an electromagnetic flow meter (204), a U-shaped underground pipe (205), and multiple U-shaped underground pipe circulating water temperature sensors (206). The circulating water pump (202) and the flow regulating valve (203) are sequentially installed in the inlet pipe of the circulating water pipe connecting the U-shaped underground pipe (205) and the constant temperature water area (201), and the electromagnetic flow meter (204) is installed in the outlet pipe. The U-shaped underground pipe circulating water temperature sensor (206) and the electromagnetic flow meter (204) are connected to the data acquisition and analysis instrument (101) through a signal transmission line.

3. The U-shaped buried pipe heat transfer performance testing device based on effective burial depth as described in claim 2, characterized in that: The soil temperature measuring tube (102) and the U-shaped buried pipe (205) are buried at the same depth, and both the soil temperature measuring tube (102) and the U-shaped buried pipe (205) are evenly divided into n layers along the depth direction to correspondingly arrange temperature sensor measuring points; the temperature sensor measuring points include soil temperature measuring points. and water temperature measuring point , .

4. The U-shaped buried pipe heat transfer performance testing device based on effective burial depth as described in claim 3, characterized in that: The soil temperature measuring point A soil temperature sensor (103) is correspondingly installed at the water temperature measuring point. A U-shaped buried pipe circulating water temperature sensor (206) is installed accordingly. The soil temperature measuring point With the water temperature measuring point The soil and water temperatures are uniformly distributed along the depth direction within the aforementioned n layers, with one measuring point at the beginning and end of the inlet branch pipe in each layer to monitor changes in soil and water temperature. With the water temperature measuring point One-to-one correspondence along the depth direction.

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