Optimizing the Distance Between Boreholes with Helical Shaped Ground Heat Exchanger

Abstract

Energy use in buildings represents a major share of the overall energy used in developed countries. Ground source heat pump (GSHP) systems are becoming widespread due to their high energy efficiency both in heating and cooling mode. The installation cost and performance of GSHP systems can be greatly affected by optimal design of ground heat exchangers (GHEs). Two parameters affecting the helical shaped GHE’s performance are borehole spacing and helical configuration of the pipe. In large scale GSHP applications, more than one borehole is needed, therefore determining the distance between boreholes becomes as an important issue. In this work, the effects of distance between boreholes with helical shaped GHE on its performance (heat transfer ratio) are studied. Performance of GHE is determined and optimal distance is examined. Furthermore, the influence of the pitch between the turns of the helix on HTR is numerically studied in COMSOL environment. The available experimental results are used to validate the numerical results. It is seen that they are in a good agreement. Computational model in this study may provide useful guidance for designing the helical shaped GHE for GSHP systems.