Structure optimization design of ground heat exchanger by topology method to mitigate the geothermal imbalance

Abstract

Intensive thermal interference between adjacent buried pipes and heat buildup around the surrounding soil lead to the deterioration of thermal performance of ground heat exchanger (GHE). The study aims at designing an optimized structure for GHE to accelerate releasing rate of the accumulating heat and mitigate the degree of thermal interference. In this paper, the topology optimization method is proposed to the design of highly conductive GHE and the optimization result is obtained. Moreover, the rules of generation and evolution of optimization results are studied by exploring the influences of volume fraction and different boundary conditions. Finally, a comparison study between thermal performance of optimized GHE and conventional serpentine GHE is carried out. Taking the minimum dissipation of heat transport potential capacity as the optimization objective, the topology optimization result presents a symmetrical tree-shaped structure. The tree-structure GHE yields a lower standard deviation of soil temperature and a smaller maximum soil temperature. Compared with conventional serpentine GHE, the tree-structure GHE can efficiently accelerate the releasing heat rate and improve heat transfer performance by about 25.3%, which provides a new way to design GHE to avoid heat accumulation.