The Characteristic Analysis Of Uncertain Factors In Soil Thermal Properties For GSHP

In comparison to conventional air source heat pump systems, ground source heatpump systems can achieve a higher coefficient of performance(COP). During the designof ground source heat pump systems, how to accurately and efficiently determine soilthermal properties(thermal conductivity and heat capacity) is a key problem.Soil is a kind of complex porous media with multiphase. Physical properties of soilitself and heat transfer mechanism within it are introduced first, followed by the overallclassification of uncertain factors in soil thermal properties according to direct and indirectrelation and the characteristic analysis of every uncertain factor. The analytical models ofeffective soil thermal conductivity proposed by international and domestic scholars aresummarized and an effective thermal conductivity model is then presented. Finally, thesingle factor regression analysis is conducted for every uncertain factor respectively andthe primary and secondary characters of these uncertain factors are analyzed by using theorthogonal test.The analysis result shows that the effective soil thermal conductivity is positivelycorrelated with solid phase thermal conductivity of saturated and unsaturated soil andsaturation degree; it is negatively correlated with porosity of saturated and unsaturated soiland the depth of water table; it has linear relationship s with saturation degree and thedepth of water table and has power function relationships with other4uncertain factors;the porosity of unsaturated soil has the most obvious effect on the effective soil thermalconductivity, followed by the saturation degree, porosity of saturated soil, solid phasethermal conductivity of unsaturated soil, solid phase thermal conductivity of saturated soiland the depth of water table.