Thermal response test method and system suitable for large-diameter energy column

Abstract

The invention discloses a thermal response test method and system suitable for a large-diameter energy column, which are characterized in that temperature field change of the large-diameter energy column and a rock-soil body around the large-diameter energy column is described based on a cylindrical surface heat source of the energy column and a dual-medium composite thermal response model, and compared with a linear heat source assumption, the thermal response test method is closer to a real situation. Secondly, a constant-heat-flow and constant-temperature dual test method is adopted, and a test result is corrected, so that the real operation state of the large-diameter energy pile is closer to that of the large-diameter energy pile.

Description

Technical Field

[0001] The present invention relates to the field of building engineering technology, and in particular to a thermal response testing system and method suitable for large-diameter energy columns. Background Art

[0002] Energy pile is a new type of low-carbon energy-saving building technology that combines ground-source heat pump technology with pile foundation construction. Energy pile is a kind of underground energy structure. By burying heat exchange pipes inside the pile foundation, heat exchange between the building structure and the rock and soil around the pile foundation is achieved.

[0003] There are many types of energy piles. The large-diameter energy piles are mostly bored cast-in-place piles, which are commonly found in the enclosure structures of large infrastructure projects. The thermal response test method of energy piles usually follows the ground source heat pump test technology. However, for large-diameter energy piles, studies have shown that the geothermal property test is quite different from the actual results. This is because the burial depth of large-diameter energy piles is generally shallower than the ground source heat pump borehole, and due to the large diameter, there are large differences in the thermal property parameters of the concrete and the rock and soil around the pile.

[0004] On the other hand, the commonly used constant heat flow method, as a transient reverse analysis thermal response test method, is more commonly used in the thermal physical parameter test of rock and soil, but it has certain defects when testing the heat exchange efficiency of a large-diameter energy pile. The constant temperature method, as a steady-state forward analysis thermal response test method, has not been widely used in the thermal physical property test of geothermal heat pumps in recent years.

[0005] Therefore, the existing thermal response test method for large-diameter energy columns has the technical problem of low accuracy. It can be seen that how to improve the accuracy of thermal response testing of large-diameter energy piles is a problem that needs to be solved in this field. Summary of the invention

[0006] In view of the technical problem that the existing thermal response testing methods for large-diameter energy columns have low accuracy, the purpose of the present invention is to provide a thermal response testing method suitable for large-diameter energy columns, which can improve the accuracy of thermal response testing of large-diameter energy columns. On this basis, a real-time thermal response testing system of the method is also provided.

[0007] In order to achieve the above object, the present invention provides a thermal response test method suitable for large diameter energy columns, and the thermal response test method comprises the following steps:

[0008] S1: Model building

[0009] This step is used to establish a composite thermal response model of the energy pile cylindrical heat source and dual medium;

[0010] S2: Constant heat flow method energy pile thermal response test

[0011] Use the electric heating method to input a constant heat flow into the energy pile to simulate the process of heat dissipation to the rock and soil around the pile in summer, and observe the temperature change characteristics of the inlet and return water. After a period of time, when the energy pile and the rock and soil around the pile are in a stable thermal equilibrium state, record the temperature, flow, and pressure change curves in the process, analyze the thermal conductivity of the energy pile, and obtain the heat exchange capacity of the energy pile.

[0012] S 3: Constant temperature method energy pile thermal response test

[0013] This step inputs constant temperature hot water into the energy pile and starts water circulation, and observes the flow change characteristics of water inlet and return. After a period of time, when the energy pile and the rock and soil around the pile are in a stable state, the flow and temperature change curves in the process are measured, the thermal conductivity of the energy pile is analyzed, and the heat exchange capacity of a single energy pile is obtained.

[0014] S4: Data Analysis

[0015] This step is used to analyze the data measured by S2 and S3 above, and compare the difference in thermal conductivity measured by the two test methods. If the mean square error is small, the test is considered valid.

[0016] Furthermore, the thermal response model of the cylindrical heat source of the energy pile in S1 divides the heat transfer space into three areas: concrete inside the steel cage, concrete outside the steel cage, and the surrounding rock and soil.

[0017] Furthermore, before conducting the thermal response test of the energy pile using the constant heat flow method, the initial temperature field of the energy pile and the rock and soil around the pile needs to be tested. This is done by inputting circulating water into the energy pile for a period of time and then observing the temperature changes of the incoming and return water during the circulation process. If the changes in the inlet and return water temperatures are no greater than the preset values, the measured temperature value can be considered to be the initial temperature of the energy pile and the soil at the pile head.

[0018] Furthermore, the analysis of the test data in S2 and S3 in S4 includes the following steps:

[0019] S41: Analyze the test data in S2 and S3 respectively to obtain the test results of thermal conductivity, heat exchange per linear meter, and heat exchange of a single energy pile.

[0020] S42: Compare the difference in thermal conductivity measured by the two test methods. If the mean square error is small, the test is considered valid, and the mean of the two tests is taken as the final test value of the energy pile.

[0021] In order to achieve the above-mentioned purpose, the present invention provides a thermal response testing system suitable for large-diameter energy columns, comprising a model building module, a constant heat flow method thermal response testing module, a constant temperature method thermal response testing module and a data acquisition module. The model building module is used to establish a composite thermal response model of a cylindrical heat source of an energy pile and a dual medium. The constant heat flow method thermal response testing module and the constant temperature method thermal response testing module respectively interact with data of a data acquisition module to transmit the tested data to the data acquisition module respectively. The data acquisition module stores and analyzes the collected data.

[0022] Further, the constant heat flow method thermal response test module includes a compensation water tank, a first heater, a second heater, a heat pump, a first pressure sensor, a first flow sensor, a first temperature sensor, a second temperature sensor and a second temperature sensor;

[0023] The water in the compensation water tank is transported to the energy pile through the water delivery pipeline and then returned to the compensation water tank through the return water pipeline after passing through the energy pile, thereby forming a water circulation system;

[0024] The heat pump is arranged on the water delivery pipeline to pump the water in the compensation water tank, and the first heater and the second heater are arranged at both ends of the heat pump to heat the water delivered to the energy pile;

[0025] The first temperature sensor, the first flow sensor and the first pressure sensor are used to measure the temperature, flow rate and pressure of the incoming water respectively;

[0026] The second temperature sensor and the second pressure sensor are respectively arranged on the return water pipeline, and are used to measure the temperature and pressure of the return water respectively.

[0027] Further, the constant temperature method thermal response test module includes a constant temperature water tank, a variable flow heat pump, a third temperature sensor, a second flow sensor, a third pressure sensor, a control valve, a fourth temperature sensor and a fourth pressure sensor;

[0028] The water in the constant temperature water tank is transported to the energy pile through the water delivery pipeline and then returned to the constant temperature water tank through the return water pipeline after passing through the energy pile, thereby forming a water circulation system;

[0029] The variable flow heat pump is arranged on the water delivery pipeline, and is used to pump the water in the constant temperature water tank and can adjust the flow rate;

[0030] The third temperature sensor, the second flow sensor, and the third pressure sensor are used to measure the temperature, flow rate, and pressure of the incoming water, respectively;

[0031] The fourth temperature sensor and the fourth pressure sensor are respectively arranged on the return water pipeline, and are used to measure the temperature and pressure of the return water respectively.

[0032] Furthermore, the data acquisition module includes an automated data acquisition unit, a data storage unit and a data analysis unit; the automated data acquisition unit is used to automatically acquire data from the constant heat flow method thermal response test module and the constant temperature method thermal response test module;

[0033] The data storage unit interacts with the automatic data collection unit to store the data collected by the automatic data collection unit;

[0034] The data analysis unit interacts with the data storage unit to analyze the data measured by the constant heat flow method thermal response test module and the constant temperature method thermal response test module.

[0035] The present invention provides a thermal response test method and system suitable for large-diameter energy columns, which describes the temperature field changes of large-diameter energy piles and the rock and soil around the piles based on the cylindrical heat source of the energy pile and the dual-medium composite thermal response model, and is closer to the actual situation than the linear heat source assumption.

[0036] Secondly, a dual testing method of constant heat flow and constant temperature is adopted, and the test results are corrected to be closer to the actual operating status of large-diameter energy piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0038] Figure 1 Schematic diagram of the process of the thermal response test method applicable to large-diameter energy columns.

[0039] Figure 2 It is a schematic diagram of the structure of the existing large-diameter energy column;

[0040] Figure 3 This is a structural cross-sectional view of an existing large-diameter energy column;

[0041] Figure 4 This is a schematic diagram of the equipment structure for the thermal response test using the constant heat flow method in the thermal response test system for large-diameter energy columns;

[0042] Figure 5 This is a schematic diagram of the equipment structure for constant temperature thermal response testing in the thermal response testing system suitable for large diameter energy columns. DETAILED DESCRIPTION

[0043] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0044] The constant temperature method in the existing thermal response test method for energy columns is a thermal response test method for steady-state forward analysis. In recent years, it has not been widely used in geothermal property tests of geothermal heat pumps. However, since it can simulate the operating state of the air-conditioning system under the stable operating state of the energy pile, it can be used to correct the test results of the constant heat flow method and improve the accuracy of the heat exchange rate test of the energy pile. Therefore, the present invention proposes a constant heat flow and constant temperature dual measurement method based on the cylindrical heat source of the energy pile and the dual-medium composite thermal response model, which can improve the accuracy of the thermal response test of large-diameter energy piles.

[0045] The thermal response test method for large diameter energy columns provided by the present invention is described in detail in Figure 1 , including the following steps:

[0046] Step 1: Model building

[0047] This step is used to establish a composite thermal response model of the energy pile cylindrical heat source and dual media, and to obtain the temperature field change of the energy pile heat exchange power test.

[0048] The heat exchange pipes of the energy pile are arranged in the steel cage. Due to the strong thermal conductivity of concrete, the concrete inside the cage and the concrete outside the cage together form a cylindrical heat source. The energy pile is a large-diameter, shallow-buried bored pile enclosure structure, and the heat exchange pipes are arranged close to the soil.

[0049] The present invention fully considers the difference in thermal properties between the concrete outside the cage and the surrounding rock and soil, and divides the heat transfer space into three areas by the heat source position: concrete inside the steel cage, concrete outside the steel cage and surrounding rock and soil, and their corresponding temperatures and distribution powers are Ti and qi (i = 1, 2, 3) respectively. The radii of the areas are r1 and r2 respectively, such as Figure 2-Figure 3 shown.

[0050] The thermal response model of the cylindrical heat source of the energy pile is based on the following assumptions: the concrete medium is a uniform material with constant physical properties, the initial ground temperature of the overall temperature field is T0, and the heat source is in close contact with the medium.

[0051] The excess temperature at each point in the heat transfer space is θi = Ti(t) - T0, satisfying the heat transfer equation of formula (1):

[0052]

[0053] Among them, T0 is the initial temperature (℃); θi is the excess temperature (℃); aj is the thermal diffusion coefficient (m2 / s); qi is the heat transfer power (W / m); t is the heat conduction time (s); r is the heat transfer position (m), i=1,2,3; j=i,0.

[0054] Assuming that the heat transfer center of the energy pile is an adiabatic boundary, at r1, heat is transferred to both sides at a constant power q1. The energy conservation equation can be obtained as

[0055]

[0056] Where kj is the thermal conductivity (W m / °C).

[0057] The energy conservation law at the interface position of r2 can be described as

[0058]

[0059] By solving the above equations using Laplace transform, we can obtain the analytical expression of the excess temperature of the rock and soil outside the energy pile:

[0060]

[0061] Among them, J0 and J1 are the 1st order and the first kind Bessel functions respectively; Y0 and Y1 are the 0th order and the 1st order Bessel functions respectively.

[0062] Based on the energy pile cylindrical heat source and dual-medium composite thermal response model, the temperature field change of the energy pile heat exchange power test can be obtained.

[0063] S2: Constant heat flow method energy pile thermal response test

[0064] This step can be used for the initial temperature field test of the energy pile and the rock and soil around the pile, as well as for the test conditions simulating summer cooling and winter heating, and for the heat exchange test of the energy pile.

[0065] S21: Initial temperature field test of energy pile and surrounding rock and soil

[0066] It inputs circulating water into the energy pile for a period of time and then observes the temperature changes of the incoming and return water during the circulation process.

[0067] If the circulation time is ≥ 3h and the change in the inlet and return water temperatures is no more than 0.3℃, it is considered that the circulation loop has reached the stable state of the initial temperature field, which can be considered as the initial temperature T0 of the energy pile and the pile head soil.

[0068] S22: Heat transfer test of energy pile

[0069] The electric heating method is used to input a constant heat flux into the energy pile to simulate the process of heat dissipation to the rock and soil around the pile in summer, and the temperature change characteristics of the inlet and return water are observed. After a period of time, when the energy pile and the rock and soil around the pile are in a stable thermal equilibrium state, the temperature, flow rate, and pressure change curves of the process are recorded.

[0070] Then, the data post-processing software is used to perform reverse analysis and calculation on the thermal conductivity of the energy pile and the heat exchange of a single pile.

[0071] S3: Constant temperature method energy pile thermal response test

[0072] This step inputs constant temperature hot water into the energy pile and starts water circulation, and observes the flow change characteristics of water inlet and return. After a period of time, when the energy pile and the rock and soil around the pile are in a stable state, the flow and temperature change curves in the process are measured.

[0073] Then, the data post-processing software is used to perform reverse analysis and calculation on the thermal conductivity of the energy pile and the heat exchange of a single pile.

[0074] This method can directly obtain the heat exchange capacity of a single energy pile under corresponding working conditions. Compared with the constant heat flow test method, the constant temperature test is more intuitive and avoids the influence of unstable heat transfer.

[0075] S4: Data Analysis

[0076] This step is used to analyze the data measured by S2 and S3 above, and the analysis process includes the following steps:

[0077] S41: The test data in S2 and S3 are analyzed respectively, and the inverse analysis is performed on the energy pile cylindrical heat source and dual-medium composite thermal response model constructed based on formulas 1-6 to obtain the test results of thermal conductivity, heat exchange per linear meter, heat exchange of a single energy pile, and the correction result of the heat exchange of a single energy pile.

[0078] S42: Compare the difference in thermal conductivity measured by the two test methods. If the mean square error is small, the test is considered valid, and the mean of the two tests is taken as the final test value of the energy pile.

[0079] Based on the thermal response test method suitable for large-diameter energy columns constructed by the above-mentioned scheme, this scheme also provides a thermal response test system suitable for large-diameter energy columns, which includes a model building module, a constant heat flow method thermal response test module, a constant temperature method thermal response test module and a data acquisition module.

[0080] The model building module in this system is used to establish the energy pile cylindrical heat source and dual-medium composite thermal response model.

[0081] The model building module is configured to execute the above model building steps to realize corresponding functions.

[0082] The constant heat flow method thermal response test module in this system can be used for the initial temperature field test of the energy pile and the rock and soil around the pile, as well as the test conditions for simulating the heat transfer process of the energy pile, and for the heat transfer test of the energy pile, see Figure 4 The constant heat flow method thermal response test module includes a compensation water tank 11, a first heater 13, a second heater 14, a heat pump 12, a first pressure sensor 17, a first flow sensor 16, a first temperature sensor 15, a second temperature sensor 20 and a second pressure sensor 21.

[0083] The water in the compensation water tank 11 is transported to the energy pile through the water delivery pipeline and then returned to the compensation water tank 11 through the return water pipeline after passing through the energy pile, thereby forming a water circulation system.

[0084] The heat pump 12 is disposed on the water delivery pipeline for pumping the water in the compensation water tank 11 . The first heater 14 and the second heater 13 are disposed at both ends of the heat pump 12 for heating the water delivered to the energy pile.

[0085] A first control valve 18 is provided on the water delivery pipeline, and the first control valve 18 is used to control the opening and closing of the water delivery pipeline.

[0086] The first temperature sensor 15 , the first flow sensor 16 and the first pressure sensor 17 are used to measure the temperature, flow rate and pressure of the incoming water respectively.

[0087] The second temperature sensor 20 and the second pressure sensor 21 are respectively disposed on the return water pipeline to measure the temperature and pressure of the return water respectively.

[0088] A second control valve 19 is provided on the return water pipeline, and the opening and closing of the return water pipeline are controlled by the second control valve 19.

[0089] The constant heat flow method thermal response test module constructed by the above scheme can realize the initial temperature field test of the energy pile and the rock and soil around the pile, as well as the test condition simulating the heat transfer process of the energy pile, which is used for the heat exchange test of the energy pile.

[0090] Among them, the initial temperature field test is to turn off the heating device, start the circulating water flow, and observe the temperature change characteristics during the circulation process. After the circulation time is ≥3h and the change of the inlet and return water temperatures is no more than 0.3℃, it is considered that the circulation loop has reached the stable state of the initial temperature field, which can be regarded as the initial temperature T0 of the energy pile and the pile head soil.

[0091] The heat exchange test of the energy pile is carried out by turning on the heater, setting the water pump flow rate and flow, circulating the water flow, and observing the temperature change characteristics of the inlet and return water. After the circulating water flow reaches 50 hours and the measured temperature is in a stable state, it can be considered that the energy pile and the rock and soil around the pile have reached a stable state, and the temperature, flow, and pressure change curves of this process are saved, and the test is ended.

[0092] The constant temperature thermal response test module of this system is used for the heat exchange test of energy piles. It uses the heat pump system and the constant temperature water tank to provide hot water with constant temperature for the energy piles, directly simulating the heat exchange of a single energy pile.

[0093] See also Figure 5The constant temperature thermal response test module includes a constant temperature water tank 22, a variable flow heat pump 23, a third temperature sensor 24, a second flow sensor 25, a third pressure sensor 26, a fourth temperature sensor 29 and a fourth pressure sensor 30.

[0094] The water in the constant temperature water tank 22 is transported to the energy pile through the water delivery pipeline and then returned to the constant temperature water tank through the return water pipeline after passing through the energy pile, thereby forming a water circulation system.

[0095] The variable flow heat pump 23 is arranged on the water delivery pipeline, and is used to pump the water in the constant temperature water tank 22 and to adjust the flow rate.

[0096] A third control valve 27 is provided on the water delivery pipeline, and the opening and closing of the water delivery pipeline are controlled by the third control valve 27 .

[0097] The third temperature sensor 24, the second flow sensor 25, and the third pressure sensor 26 are used to measure the temperature, flow rate, and pressure of the incoming water, respectively.

[0098] The fourth temperature sensor 29 and the fourth pressure sensor 30 are respectively disposed on the return water pipeline to measure the temperature and pressure of the return water respectively.

[0099] A fourth control valve 28 is provided on the return water pipeline, and the opening and closing of the return water pipeline are controlled by the fourth control valve 28 .

[0100] The constant temperature method thermal response test module constructed by the above scheme sets the inlet water flow temperature to ensure the constant temperature of the heat flow at the inlet of the energy pile, then starts the variable flow water pump and the constant temperature water tank, circulates the water flow and observes the flow change characteristics of the inlet and return water. After the circulating water flow reaches 50 hours and the flow reaches a stable state without obvious fluctuations, it is confirmed that the energy pile and the soil around the pile have reached a stable state, and the flow and temperature change curves of this process are saved, and the test ends.

[0101] The data acquisition module is used to collect, analyze and store the test results obtained by the above two test modules, and includes an automatic data acquisition unit, a data storage unit and a data analysis unit.

[0102] The automatic data acquisition unit is used to automatically acquire data from the above two test modules.

[0103] The data storage unit interacts with the automatic data collection unit and is used to store the data collected by the automatic data collection unit.

[0104] The data analysis unit interacts with the data storage unit to analyze the data measured by the constant heat flow method thermal response test module and the constant temperature method thermal response test module, respectively, to obtain test results of thermal conductivity, heat exchange per linear meter, and heat exchange of a single energy pile.

[0105] Then the difference in thermal conductivity obtained by the two test methods is compared. If the mean square error is small, the test is considered valid, and the mean of the two tests is taken as the final test value of the energy pile.

[0106] This solution preferably uses the communication interface of the measurement and control equipment to achieve data connection between the system and the host computer. The data acquisition system develops an automated data acquisition, data storage and analysis program, and has remote observation and control functions. The system collects data every 30 seconds and automatically records and saves it, without the need to manually record each measurement value, which improves test efficiency.

[0107] Based on the thermal response test method and system suitable for large-diameter energy columns constructed by the above-mentioned scheme, the following examples illustrate its working process in specific applications. It should be noted that the working process here is only an example and does not constitute a limitation to this scheme.

[0108] Firstly, a composite thermal response model of the cylindrical heat source and dual medium of the energy pile is established, taking into full account the heat transfer differences between the concrete media inside the heat exchange tube of the large-diameter energy pile and the steel protective layer, as well as the differences in the thermal physical properties between the pile concrete and the rock and soil around the pile. Fourier transform is performed in Laplace space to obtain the analytical expression of the heat transfer of the model.

[0109] Second, the preparation before the test

[0110] (1) Before the test, confirm that the energy pile construction time exceeds 3 months, and there is no large-volume concrete construction such as water-stop curtain around the pile body within 3 months, to eliminate the possibility that the initial temperature field of the initial rock and soil body is disturbed by the heat of concrete hydration. At the same time, it is necessary to confirm that there is no abnormal seepage in the energy pile test site, which will affect the accuracy of the test.

[0111] (2) When conducting the fluidity test of the heat exchange tube of the energy pile, use a large-lift water pump to flush the pre-buried heat exchange tube in the energy pile at high speed, and try to shorten the flushing time to avoid affecting the initial temperature field, until the bubbles and sediment in the heat exchange tube are discharged.

[0112] (3) Set up a constant heat flow method thermal response tester. The heating power of the tester should be less than 3000k and equipped with a large-lift circulating water pump. Connect the test loop and wrap the exposed part with insulation cotton.

[0113] Then, the energy pile thermal response test is carried out

[0114] (1) Determination of initial temperature field of energy pile and rock and soil

[0115] Turn off the heating device, start the circulating water flow, and observe the temperature change characteristics during the circulation process. When the circulation time is ≥3h and the change of the inlet and return water temperatures is no more than 0.3℃, it is considered that the circulation loop has reached the stable state of the initial temperature field, which can be considered as the initial temperature T0 of the energy pile and the pile head soil.

[0116] (2) Constant heat flow method thermal response test

[0117] Turn on the heater, set the water pump flow rate and flow, circulate the water, and observe the temperature change characteristics of the inlet and return water. After the circulating water reaches 50 hours and the measured temperature is in a stable state, it can be considered that the energy pile and the rock and soil around the pile have reached a stable state, save the temperature, flow, and pressure change curves of this process, and end the test.

[0118] (3) Initial temperature field recovery

[0119] Seal the heat exchange tube of the energy pile and let it stand for more than 14 days to restore the energy pile and the soil around the pile to their original state.

[0120] (4) Constant temperature thermal response test

[0121] Set up the test equipment, turn on the constant temperature water tank and the variable flow heat pump at the same time, and adjust the flow. Set the outlet temperature of the thermal response test device to the steady-state temperature value of the constant heat flow method operation condition in the previous stage to ensure that the temperature of the heat flow at the inlet of the energy pile is constant. When the temperature remains constant, the flow change value during the test cycle can be measured by the measuring device. After the circulating water flow reaches 50 hours and the flow reaches a stable state without obvious fluctuations, confirm that the energy pile and the soil around the pile have reached a stable state, save the flow and temperature change curves of this process, and end the test.

[0122] Finally, data analysis

[0123] The test data was analyzed to obtain the test results of thermal conductivity, heat exchange per linear meter, and heat exchange of a single energy pile. The differences in thermal conductivity were compared. If the mean square error was small, the test was considered valid, and the mean of the two tests was taken as the final test value of the energy pile.

[0124] The thermal response test method and system of large-diameter energy columns formed by the above-mentioned scheme describe the temperature field changes of large-diameter energy piles and the rock and soil around the piles based on the cylindrical heat source of the energy pile and the dual-medium composite thermal response model, which is closer to the actual situation than the linear heat source assumption.

[0125] Secondly, a dual testing method of constant heat flow and constant temperature is adopted, and the test results are corrected to be closer to the actual operating status of large-diameter energy piles.

[0126] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. 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, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A thermal response test method suitable for large diameter energy columns, characterized in that: The thermal response testing method comprises the following steps: S1: Model building This step is used to establish a composite thermal response model of the energy pile cylindrical heat source and dual media, and to obtain the temperature field change of the energy pile heat exchange power test. S2: Constant heat flow method energy pile thermal response test Use the electric heating method to input a constant heat flow into the energy pile to simulate the process of heat dissipation to the rock and soil around the pile in summer, and observe the temperature change characteristics of the inlet and return water. After a period of time, when the energy pile and the rock and soil around the pile are in a stable thermal equilibrium state, record the temperature, flow, and pressure change curves in the process, analyze the thermal conductivity of the energy pile, and obtain the heat exchange capacity of the energy pile. S 3: Constant temperature method energy pile thermal response test This step inputs constant temperature hot water into the energy pile and starts water circulation, and observes the flow change characteristics of water inlet and return. After a period of time, when the energy pile and the rock and soil around the pile are in a stable state, the flow and temperature change curves in the process are measured, the thermal conductivity of the energy pile is analyzed, and the heat exchange capacity of a single energy pile is obtained. S4: Data Analysis This step is used to analyze the data measured by S2 and S3 above, and compare the difference in thermal conductivity measured by the two test methods. If the mean square error is small, the test is considered valid.

2. A thermal response test method suitable for large diameter energy columns according to claim 1, characterized in that: The thermal response model of the cylindrical heat source of the energy pile in S1 divides the heat transfer space into three areas: concrete inside the steel cage, concrete outside the steel cage, and the surrounding rock and soil.

3. A thermal response testing method suitable for large diameter energy columns according to claim 1, characterized in that: Before conducting the thermal response test of the energy pile using the constant heat flow method, the initial temperature field of the energy pile and the rock and soil around the pile needs to be tested. This is done by inputting circulating water into the energy pile for a period of time, and then observing the temperature changes of the incoming and return water during the circulation process. If the changes in the inlet and return water temperatures are no greater than the preset values, the measured temperature value can be considered to be the initial temperature of the energy pile and the soil at the pile head.

4. A thermal response testing method applicable to large diameter energy columns according to claim 1, characterized in that: The analysis of the test data in S2 and S3 in S4 includes the following steps: S41: Analyze the test data in S2 and S3 respectively to obtain the test results of thermal conductivity, heat exchange per linear meter, and heat exchange of a single energy pile; S42: Compare the difference in thermal conductivity measured by the two test methods. If the mean square error is small, the test is considered valid, and the mean of the two tests is taken as the final test value of the energy pile.

5. A thermal response test system suitable for large diameter energy columns, characterized in that: It includes a model building module, a constant heat flow method thermal response test module, a constant temperature method thermal response test module and a data acquisition module. The model building module is used to establish a composite thermal response model of an energy pile cylindrical heat source and a dual medium. The constant heat flow method thermal response test module and the constant temperature method thermal response test module interact with the data acquisition module respectively to transmit the tested data to the data acquisition module respectively. The data acquisition module stores and analyzes the collected data.

6. A thermal response test system suitable for large diameter energy columns according to claim 5, characterized in that: The constant heat flow method thermal response test module includes a compensation water tank, a first heater, a second heater, a heat pump, a first pressure sensor, a first flow sensor, a first temperature sensor, a second temperature sensor and a second temperature sensor; The water in the compensation water tank is transported to the energy pile through the water delivery pipeline and then returned to the compensation water tank through the return water pipeline after passing through the energy pile, thereby forming a water circulation system; The heat pump is arranged on the water delivery pipeline to pump the water in the compensation water tank, and the first heater and the second heater are arranged at both ends of the heat pump to heat the water delivered to the energy pile; The first temperature sensor, the first flow sensor and the first pressure sensor are used to measure the temperature, flow rate and pressure of the incoming water respectively; The second temperature sensor and the second pressure sensor are respectively arranged on the return water pipeline, and are used to measure the temperature and pressure of the return water respectively.

7. The thermal response test system suitable for large diameter energy columns according to claim 5, characterized in that: The constant temperature method thermal response test module includes a constant temperature water tank, a variable flow heat pump, a third temperature sensor, a second flow sensor, a third pressure sensor, a control valve, a fourth temperature sensor and a fourth pressure sensor; The water in the constant temperature water tank is transported to the energy pile through the water delivery pipeline and then returned to the constant temperature water tank through the return water pipeline after passing through the energy pile, thereby forming a water circulation system; The variable flow heat pump is arranged on the water delivery pipeline, and is used to pump the water in the constant temperature water tank and can adjust the flow rate; The third temperature sensor, the second flow sensor, and the third pressure sensor are used to measure the temperature, flow rate, and pressure of the incoming water, respectively; The fourth temperature sensor and the fourth pressure sensor are respectively arranged on the return water pipeline, and are used to measure the temperature and pressure of the return water respectively.

8. The thermal response test system for a large diameter energy column according to claim 5, characterized in that: The data acquisition module includes an automated data acquisition unit, a data storage unit and a data analysis unit; the automated data acquisition unit is used to automatically acquire data from the constant heat flow method thermal response test module and the constant temperature method thermal response test module; The data storage unit interacts with the automatic data collection unit to store the data collected by the automatic data collection unit; The data analysis unit interacts with the data storage unit to analyze the data measured by the constant heat flow method thermal response test module and the constant temperature method thermal response test module.

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