Laboratory Thermal Performance Tests on a Model Heat Exchanger Pile in Sand

Pile-anchored geothermal systems are increasingly being implemented as an innovative and sustainable method of harvesting shallow geothermal energy. With a view of characterizing heat exchange through geothermal piles in sand, this paper describes and analyzes results from a series of laboratory thermal performance tests on a model geothermal pile in sand. Heat carrier fluid was circulated through a U-shaped circulation tube embedded within the model concrete pile. The effects of fluid circulation velocity and initial temperature difference between soil and circulation fluid (at the inlet point) on heat transfer performance of the model pile is investigated. Temperature measurements were obtained at several locations within the test setup and data collected during the thermal tests are further used to characterize time-dependent heat exchange behavior of the model pile. Moreover, soil thermal conductivity values obtained from element thermal conductivity tests are compared with equivalent soil thermal conductivity values derived from thermal performance tests on the model pile.