The influence of groundwater seepage on the performance of ground source heat pump system with energy pile

Abstract

Both initial cost and land area can be saved while ground source heat pump (GSHP) system employs energy pile as the ground heat exchanger (GHE), and the energy pile exchanges heat with the surrounding underground medium. Groundwater seepage exerts influence on the heat transfer, and this is because the convection of groundwater alleviates the heat or cold accumulation around pile and then improves the heat transfer effect of energy pile. The existing researches regards the velocity of groundwater seepage as the one-dimensional vector, or the available models are not accurate enough though three-dimensional groundwater seepage is considered. The paper describes the spiral line heat source models with three-dimensional groundwater velocity, and the analytical solutions of temperature response are obtained. Afterwards, the performance of GSHP system is studied based on the proposed models, and the factors that have impacts on the coefficient of performance (COP) of heat pump unit are explored. The differences are explained while every factor employs different cases, but the common results of all cases are that the COP is indeed improved by groundwater seepage, and therefore the advantages of groundwater seepage should be noted. The researches of the paper attach importance to the seepage role, and the findings of the paper are favorable for the further development of GSHP technology.