DTS TECHNOLOGY FOR THERMAL CONDUCTIVITY OF GROUND IN HEZE, SHANGDONG PROVINCE

This paper attempts to determine the underground thermal properties of a region in Heze, Shandong Province. On the basis of the theory of line source, a field thermal response test was carried out using distributed temperature sensing technology(DTS). Temperature measurement cables were used to capture distributed temperatures of the borehole during heating or cooling process, under single and double U buried pipe conditions respectively. The thermal conductivities of each layer were subsequently calculated. The experimental results show that the thermal conductivity of different strata can be accurately and reliably obtained with DTS technology in the field thermal response test, and the heat exchange capacity of each stratum can be evaluated. There is a significant improving effect of seepage on the thermal conductivity. It is also found that the results obtained by the double U-tube test are more accurate than that obtained by single U-tube test. Because of the heat accumulation effect, the longer the test time is, the smaller the thermal conductivity is. If the test time is long enough, the thermal conductivity would become a stable value. The results of this study can provide the basic basis for ground source heat pump design.