Effective parameters on the performance of ground heat exchangers: A review of latest advances

Ground heat exchanger is a significant part of the ground source heat pumps system with environment-friendly and energy-saving. The coefficient of performance for the ground source heat pump systems is closely associated with the performance of the ground heat exchanger. Some important research development about the ground heat exchanger has been addressed over the last decades. This paper aims to overview the previous research on improving the thermal and flow performance of the ground heat exchanger. Various and special ground heat exchanger parameters factors: working fluid (gas, antifreeze solution, microencapsulated phase change slurry and nanofluid), turbulence promoter, ground tube (material, structure parameters and optimization tube), backfill materials (conventional type, controlled low strength material and phase change material), soil field (convention type, frozen soil and groundwater) and other factors (operation mode and composite systems). This paper is divided into six parts. The working fluid, the thermal conductivity of the backfill material and groundwater have the greatest impact on increasing the performance compared to other parameters. The composite system is an effective method to enhance the performance of the ground source heat pump systems.