Thermal response testing method for rock-soil thermal conductivity distribution

Abstract

The invention provides a thermal response testing method for rock-soil thermal conductivity distribution. The method is used for testing the thermal conductivity of rock soil in different underground depth layers. The method comprises the following steps: firstly, establishing a multi-dimensional transient heat transfer model of a buried pipe heat exchanger by considering heat transfer in the depth direction of rock soil, simulating a longitudinal temperature distribution curve of fluid in the heat exchanger, then testing temperature distribution data of the fluid at different depths in the heat exchanger through experiments, and finally using a multi-objective optimization algorithm and directly adopting fluid temperature distribution data to predict rock soil thermal conductivity distribution data in multiple spatial layers at the same time. The rock soil thermal conductivity distribution tested by the method has high precision, the problem of poor convergence during layered testing of a traditional method can also be solved, meanwhile, the testing precision is not affected by depth, and the method is wide in applicability and high in testing efficiency.

Description

technical field [0001] The invention relates to the technical field of ground source heat pump thermal response testing and the technical field of soil thermophysical property testing, in particular to a thermal response testing method for thermal conductivity distribution of rock and soil. Background technique [0002] The thermal conductivity of rock and soil is the main factor affecting the underground heat transfer of the ground source heat pump system, and it is the key design parameter of the ground source heat pump load and the buried pipe heat exchanger. Because the thermal response test can avoid the errors caused by the laboratory method being divorced from the actual geological conditions, it has gained widespread attention and application, and has now developed into the most important method for thermal physical property testing in ground source heat pump systems. However, in the process of implementation, it is usually necessary to assume that the thermal physic...

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Problems solved by technology

[0004] 1. The current technology uses the average temperature of the fluid to test the thermal conductivity distribution of rock and soil. As the depth of the heat exchanger increases, the estimation error of the average fluid temperature also increases significantly, which eventually leads to the test error of the thermal conductivity distribution increasing with the increase of the depth of the heat exchanger. The depth of the heat exchanger increases significantly

[0005] 2. The test theoretical models are all based on the classic line heat source or column heat source model. Since the classic model has a large error during the short-term thermal response test, in order to obtain reliable thermal physical property test results, the existing technology usually requires long-term testing ( >10 hours), while early temperature data are usually discarded during testing

[0006] 3. The theoretical model of the test is based on a one-dimensional analytical model, ignoring the heat transfer in the depth direction of the rock and soil. The test of the thermal physical property distribution of the rock and soil is only to apply the traditional thermal response test method to each single layer, that is, ignoring the mutual influence between layers However, the thermal conductivity of each layer is tested separately, which eventually leads to large deviations and poor convergence of test results under different layering conditions.

[0007] In summary, the current thermal response testing methods for thermal conductivity distribution of rock and soil have obvious defects in accuracy and efficiency.

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