Influences of structure parameters on performance of tree-shaped ground heat exchanger

Abstract

During long-term operation of ground source heat pump (GSHP) system, heat accumulation is a common problem leading to the increase of soil temperature and the degradation of operating efficiency. The tree-shaped ground heat exchanger (GHE) showed great potential to eliminate heat accumulation and maintain soil temperature. In this paper, the influences of structure parameters on flow and heat transfer performance of GHE are explored. The results indicate that the diameter ratio adopting design method of minimum flow resistance has better comprehensive performance than that of minimum thermal resistance. For two sub-tubes, the comprehensive performance of GHE increases as the rise of asymmetry ratio and reaches maximum when the sub-tube is symmetric. Meanwhile, for tree-shaped GHE with bifurcation level of 1, the optimal length ratio is 1.