Performance analysis of helical ground heat exchangers with different configurations

Abstract

Recently, various configurations especially single U-tube ground heat exchangers have been studied to improve the thermal performance of ground heat exchangers. Although helical ground heat exchangers generally have better thermal performance than the others, only two simple types of them, a helix with an internal outlet pipe and helix with an external outlet pipe have been studied in past years. So, the novelty of this paper is comparing eight new types of helical ground heat exchangers to a single U-tube heat exchanger in terms of heat exchange rate, pressure drop, thermal resistance, effectiveness, and thermal performance capability, in order to find the best one. The considered models have the same heat transfer area, and all numerical simulations are performed by commercial CFD software. The validation of the numerical simulations is done based on experimental results. The results indicated that the triple helix heat exchanger has considerably the best thermal performance compared with other ground heat exchangers. It followed by double helix and helix (W-tube) ground heat exchangers those which approximately have the same thermal performance. In general, it can be concluded that a single U-tube heat exchanger has the worst thermal performance and the minimum pressure drop in comparison with all helical ground heat exchangers.