Performance Investigation of Multiple-Tube Ground Heat Exchangers for Ground-Source Heat Pump

Abstract

The present study aims to investigate the performance of multiple-tube ground heat exchangers (GHEs). The multiple-tube GHEs with a number of pipes installed inside the borehole were simulated. Thermal interferences between the pipes and performance of multiple-tube GHEs are discussed. Increasing the number of inlet tube in the borehole increases the contact surface area and then leads to increase of heat exchange with the ground. However, ineffective of heat exchange in the outlet tube caused by thermal interferences from the inlet tube reduces the heat exchange rate for the GHEs. The GHE performances increase of 9.1 % for three-tube, of 13.6 % for four-tube, and of 20.1 % for multi-tube compared with that of the U-tube. The four-tube and multi-tube GHEs which consist of four pipes as heat exchange pipes where the multi-tube GHE provides better performance than that of the four-tube GHE. This fact indicates that thermal interferences between the pipes affect the performance. Thermal interferences between the pipes should be considered.