Abstract:Shallow geothermal energy is defined in "The Standard for Evaluation of Shallow Geothermal Energy" as the heat energy which is “contained in the surface depth no more than 200 meters and not exceeds 25℃”. In addition, there is no specific requirement on the drilling depth in Technical Code for GroundSource Heat Pump System. According to the actual engineering experience and calculation, 100~120 meters has been found in common use. The influencing factors include: the formation drillability, which usually declines as the drilling goes deeper, thus increasing costs; the pipe diameter, which also affects the flow resistance, i.e. the power consumption for driving current increasing along with the increasing depth; the size of the pipe spacing, which has a great influence on the thermal short circuiting; and thermophysical parameters of backfill materials, etc. Based on the basic principle of heat transfer, this paper analyses various influence factors, and, through establishing numerical heat transfer models, figures out the heatexchange capability under certain conditions and the relationship between these parameters, to the effect that it can provide a reference for engineering designs and contribute to the?popularization and application of the shallow geothermal energy engineering.
