DETERMINATION OF GROUNDWATER VELOCITY IN THERMAL RESPONSE TEST ANALYSIS C. K. Lee and H. N. Lam

A three-dimensional finite difference model was employed for the borehole ground heat exchanger to perform a thermal response test analysis using the parameter estimation technique. This allowed the groundwater velocity to be determined simultaneously together with the ground thermal conductivity and the borehole thermal resistance. It was found that the estimated groundwater velocity scattered at repeated trials with test data generated using a low groundwater velocity and a test period of 5 days. At higher groundwater flows, the groundwater velocity could be estimated with more confidence, meaning that a minimum existed above which the groundwater velocity could be estimated with confidence. For a longer test period of 30 days, this “confident minimum” could be decreased. The methodology was applied using thermal response test data provided by others, and the results agreed with those observed at site and measured in laboratory tests.