Research on Hydraulic Characteristics of U-Tube Heat Exchanger Loop in Ground-Coupled Heat Pump System

Abstract There were two urgent problems that were reducing hydraulic losses of loop and exploring the spatial distribution of soil heat accumulation in the ground-coupled heat pump system. In order to solve these two problems, pressure drop of water loops would be analyzed in this paper. The pressure drop and the unbalance rate of the water loop were calculated while the velocity of the U-tube was calculated. It is found that the hydraulic characteristics can be improved. When pipe diameter and length are changed, their maximum pressure drops of water loop decrease by 61%. When installation method of U-tube is chosen, different flow velocity would lead that each water loop has a different pressure drop, and the increments of pressure drop are 50%, but the imbalance rate does not change. In the same condition, the velocity of the central pipe is lower than that of boundary pipe in U-tube group. This phenomenon is very similar to spatial distribution difference of soil heat accumulation.