Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

Abstract A system of borehole heat exchangers (BHEs) combined with pumping–injection wells is established in areas where the groundwater shallow and seepage velocity weak. The pumping injection are set on both sides BHEs. According to three-dimensional unsteady-state transfer model aquifer, convection–dispersion analytical solution excess temperature derived that considers groundwater-forced thermal dispersion effects axial effect Then, we use dimensional analysis method similarity criteria build a controllable forced sandbox. software FEFLOW 7.1 adopted simulation results validated by theoretical indoor experiment test. On this basis, numerical used explore influence different flow volume Darcy aquifer BHEs located, as well average efficiency rates depth. show when increases from 200 m 3 day −1 1200 , correspondingly about 10 times. coefficient increased 11.5% cooling stage, 7.5% heating stage. When 400–600 increment reaches 12.8–17.9 W 3.6–4.2 per unit depth during stage respectively, then decreases gradually.