Performance analysis of oval and circular cross-sections single U-tube ground heat exchangers: A simulation-based comparison

Abstract

The heat transfer performance of vertical Ground Heat Exchangers (GHEs) is an important criterion for this key component of Ground Source Heat Pump (GSHP) systems. This paper examines the thermal efficiency of oval cross-section single U-tube GHE compared to circular cross-section single U-tube GHE to evaluate the geometrical configurations and physical properties of the oval cross-section single U-tube GHE. The impact of key operating and design parameters on the thermal performance of the GHEs is also investigated, followed by a detailed sensitivity analysis. The analysis is performed by means of a three-dimensional numerical model. Experimental data from the literature are used to validate the adopted numerical model. The results showed that the maximum and average heat transfer rate of the oval cross-section GHE could be increased by 26.41% and 12.26% compared with circular cross-section GHE. The results of the sensitivity analysis revealed that flow rate, GHE material's thermal conductivity, GHE length, and tube cross-section area have the highest impact on the thermal performance of the oval cross-section GHE. Therefore, these parameters should be carefully designed. However, the effects of these parameters are dominant early in the heat exchange operation. The outcomes of this study can substantially give guidance for the favorable configuration from the heat transfer performance perspective.