Ground thermal conductivity for (ground source heat pumps) GSHPs in Korea

• We evaluate the characteristic thermal properties of 208 thermal response test data sets in Korea.
• The acceptance criterion of the calculated ground thermal conductivity is highly dependent on the evaluation periods.
• The ground thermal conductivities in Korea were investigated statistically.
• The differences between the ground thermal conductivity and the bedrock thermal conductivity measured were analyzed statistically.

The aim of this study is to evaluate the characteristic thermal properties of 208 (thermal response test) TRT data sets collected in Korea. In the evaluation, the line-source model is used in conjunction with the step-wise evaluation to validate the applicability of the model. The applicability of the step-wise evaluation is classified focusing on the convergence criterion of ground thermal conductivities. The ground thermal conductivities were evaluated in the range of 1.73 and 8.56 W/m·K with the mean of 2.55 W/m·K. The corresponding borehole thermal resistances were also obtained in the range between 0.06 and 0.20 m·K/W with the mean 0.13 m·K/W. In order to investigate the availability of the thermal conductivity of the test sites from the geothermal database in Korea, the ground thermal conductivity obtained by TRTs was compared with the mean bedrock thermal conductivity. Comparison of the four major bedrocks in the test sites indicated that the mean differences are 0.34, 0.53, 0.22 and 1.39 W/m·K at the bedrocks of the granite, geneiss, tuff and sandstone areas, respectively.