Numerical Simulation of the Thermal Performance and Thermal Influencing Radius of a Heat-Transfer Pipe in a Backfill Body

Abstract

The horizontal ground heat exchanger has been extensively employed to collect geothermal energy from mine backfill bodies. A novel method for avoiding thermal interference using the thermal influencing radius coupling pipe spacing was investigated. Thermal interference between adjacent heat-transfer pipes can be neglected when D40°C=2R40°C is used as the pipe spacing. The comprehensive impacts of heat-transfer fluid and backfill body on the heat-transfer efficiency and thermal influencing radius of the horizontal single pipe were investigated. The growth ratio of heat-transfer capacity can be as high as 227.3% when thermal conductivity increases from 0.5 kJ/(kg·°C) to 2 kJ/(kg·°C). The heat-transfer capacity increases by 4% for every 1°C reduction in inlet temperature. The thermal influencing radius is significantly influenced by specific heat capacity and thermal conductivity. This study can provide theoretical recommendations for the design and improvement of heat-transfer pipes in the backfill body.