Numerical Investigation for the Cooling Performance of Circular and Rectangular Ground-Coupled Heat Exchangers with Different Geometrical Layouts

Ground-coupled heat exchangers use geothermal energy storage to provide a sustainable solution for heating, ventilation, and air conditioning. In this study, the performance of circular- and rectangular-cross-section ground-coupled heat exchangers with four layouts (simple horizontal, U-shaped, helical, and slinky) is numerically simulated. It has been found that the rectangular GCHE maintains a more stable air temperature and achieves the maximum temperature drop at a shorter length across all layouts. The temperature at the exit of a circular GCHE with horizontal, U-shaped, helical, and slinky layouts is found to be 302.159 K, 301.586 K, 300.647 K, and 300.20 K, respectively, while the same temperatures are achieved in rectangular GCHEs with corresponding layouts at sections of 18.82 m, 17.46 m, 16.09 m, and 15.43 m, respectively. The length of the slinky layout with a circular cross-section GCHE is reduced by 17%, 13%, and 6% relative to the horizontal, U-shaped, and helical layouts, respectively. In comparison, reductions of 23%, 19%, and 8% are observed for the rectangular cross-section in the corresponding layouts. The inlet velocity significantly impacts the thermal performance of the GCHE, with the maximum temperature reduction occurring at a flow rate of 1 m/s. The average cooling capacity of rectangular cross-sectional GCHE is more than 40% higher than that of circular GCHE for all the layouts studied. The maximum cooling capacity is observed at a higher inlet air temperature of 323 K for a rectangular GCHE with a slinky layout. The friction factor and pressure drop are found to increase with the increase in the Reynolds number. The rectangular GCHEs provides 19.8% – 40.34% higher cooling capacity compared to circular GCHEs at air velocity increases from 1 m/s to 5 m/s.