摘要：Thermal performance was the most important factor in the development of borehole heat exchanger utilizing geothermal *** thermal performance was affected by many different design parameters,such as configuration type and borehole size of geothermal heat *** eventually determined the operation and cost efficiency of the geothermal heat exchanger *** main purpose of this work was to assess the thermal performance of geothermal heat exchanger with variation of borehole sizes and numbers of U-tubes inside a *** this,a thermal response test rig was established with line-source *** thermal response test was performed with in-line variable input heat *** thermal conductivity and thermal resistance were obtained from the measured *** the measurement,the effective thermal conductivity is found to have similar values for twopair type(4 U-tubes)and three-pair type(6 U-tubes)borehole heat exchanger systems indicating similar heat transfer ***,the thermal resistance shows lower value for the three-pair type compared to the two-pair *** data based resistance have lower value compared to computed result from design *** comparison finds better thermal performance for the three-pair type,however,fluctuating temperature variation indicates complex flow behavior inside the borehole and requires further study on flow characteristics.