Thermal properties of deep ground are important data for designing geothermal heat exchangers in ground source heat pump (GSHP) systems. The values of the thermal properties have great influence on the number and depth of boreholes; thereby influence the initial cost of GSHP systems. To determine the thermal properties of deep ground soil/rock, the authors have designed an insitu system to measure the heat flux imposed on the ground loop heat exchanger and temperature Variation of the circulating fluid in t...