Effect of pumping-recharge well structures on heat transfer characteristics of double-well groundwater heat pump systems considering hydrothermal coupling

Groundwater heat pump (GWHP) systems provide geothermal energy utilization and exploit groundwater energy or reuse energy stored underground. The design and construction of the aboveground part of GWHP systems is relatively mature, but that of the underground part of GWHP systems is insufficient. The objective of this paper was to explore the effect of the pumping-recharge well structure on the heat transfer characteristics of GWHP systems with a laboratory-scale GWHP system and physical experiments. With increasing pumping-recharge rate, the influence of the length of pumping and recharge well screens (LPRS) on the pumping water temperature and thermal breakthrough time gradually decreased, while that of the distance between the pumping and recharge well screens (DPRS) on the pumping water temperature gradually increased. The influence of the LPRS on the pumping water temperature was not obviously affected by the change in recharge water temperature, but that of the DPRS was positively correlated with the recharge water temperature. Additionally, the DPRS was more sensitive to the pumping water temperature than the LPRS. Therefore, the differences between the LPRS and DPRS must be considered in the design of GWHP systems. These experimental results provide a theoretical basis for improving heat transfer efficiency and the design and operation of GWHP systems.

Automated summary

Groundwater heat pump (GWHP) systems provide geothermal energy utilization, with the aboveground part being relatively mature in design and construction. However, the underground part lacks sufficient development. The experimental results show that the structure of the pumping-recharge well has an impact on the heat transfer characteristics of GWHP systems, with the length and distance between screens affecting the pumping water temperature and thermal breakthrough time. The study suggests that the differences between the length of pumping and recharge well screens and the distance between them must be considered in the design of GWHP systems to improve heat transfer efficiency.