Application of steel tube micro-piles as heat exchanging energy piles for air-conditioning system of a residential building

Abstract

Energy piles serves two purposes, namely, (1) bearing the building load and transferring it to the competent foundation soil layer and reducing settlement (2) transferring the heat (or coolness) from the air-conditioning system into the ground. Since the ground has much better heat transferring property and heat capacity than that of air, and in Thailand, the ground temperature ranges between 28-30 degrees Celsius throughout the year, the ground thus can be used to absorb the heat from condensing unit of air-conditioning system in Thailand.   In this study, the steel tube micropile (6” diameter) was used as energy pile to transfer heat from air-conditioning system of a residential house. The installation of 13 energy piles to depth of 17-18 m embedded in the sand layer was explained. The results of thermal response test indicated the thermal conductivity of about 1.49-2 Watts/m/Celsius. Based on preliminary analysis, it is expected that this set of energy piles can be used as ground source heat exchanger for 9000 BTU/hr air conditioning system without causing the temperature at the pile perimeter to rise above 6 degree Celsius for 24 hour operation time in 6 months.