Grey Correlation Analysis Of Thermal Property Parametersofclay

The soil source heat pump system is a device that utilizes the characteristics that the perennial temperature of the underground soil is relatively stable,and completes heat exchange through the buried pipe buried under the building and the interior of the building.The thermal properties of soil are important factors affecting the operating efficiency of heat pump systems.Therefore,it is an important issue to determine the thermal properties of soil(thermal conductivity,thermal diffusivity)and the analysis of soil thermal properties under different hydrogeological conditions.The soil is a complex porous multi-phase medium.In this paper,the thermal properties of soil and its internal heat transfer mechanism are introduced.The methods for determining soil thermal properties are classified according to different principles,and the factors affecting soil thermal properties are analyzed.The three-factor four-level orthogonal test method was used to test the thermal properties of soils,and the thermal properties of soil under different influencing factors were determined by DRE-III multi-function rapid thermal conductivity tester.The influencing factors are related to the thermal property parameters,and the visual extreme difference analysis method and the grey correlation analysis theory are used to investigate the influence degree of the influencing factors on the soil thermal property parameters.Provide data reference for the thermal performance of local rock and soil and the design of soil source heat pump system.The results show that the thermal properties of clay have different changes when combined with different factors and different levels.The thermal conductivity of clay increases with the increase of dry density and consolidation pressure,and the growth rate of thermal conductivity decreases with the increase of water content,and gradually stabilizes.The thermal diffusivity of clay increases exponentially with the increase of dry density.As the water content increases to 20%,the thermal diffusivity of clay will have a maximum value.Then,the thermal diffusivity tends to be stable.When the thermal property parameters are used as the reference sequence and other experimental conditions are used as the comparison sequence,the gray correlation analysis results show that the most important influence on the thermal conductivity of clay is the water content,followed by the dry density and consolidation pressure.This conclusion and orthogonal test the results of the range analysis are consistent;the thermal diffusion coefficient affecting the clay is mainly dry density,and the second is that the consolidation pressure has a stronger influence on the thermal diffusion coefficient than the water content.In the orthogonal test range analysis method,the influence of water content on the thermal diffusivity is greater than the consolidation pressure,but the main factor of the dry density on the thermal diffusivity is the most consistent with the gray correlation analysis.