Soil thermal response test and analysis of influence factors based on TRNSYS

In view of many factors influencing the thermal response test in actual engineering, establishes the instantaneous model based on the duct ground heat storage model. Simulates and analyses the influences of heating power,borehole diameter, water tank volume and backfill material on the test result of the soil thermo-physical property. The model is verified by two practical thermal response tests for the same borehole under two different heating powers and durations. The results show that the thermal conductivity and borehole thermal resistance of these two tests are difference of 4.94% and 0.32% respectively, but the radius heat flux per borehole unit length deviation is 24.99%. And it is also verified that the duration for thermal response test is at least 50 h. The effect of the water tank volume on the thermal conductivity can be ignored, and it just affects the time of circulating water to achieve the stability. When the diameter of borehole is 110, 130,150 mm respectively, the change rate of thermal conductivity is diminishing with the increase of the thermal conductivity of backfill materials, and the overall growth is within 0.09 W/(m·K),which indicates that the backfill materials have a small effect on thermal response test.