Thermal performance analysis of helical ground-air heat exchanger under hot climate: In situ measurement and numerical simulation

The ground air heat exchanger (GAHE) is a promising passive approach for cooling and heating buildings. In this study, thermal performance of helical ground air heat exchanger (HGAHE) has been experimentally assessed in summer season for arid climate. The findings revealed that, the outlet air temperature of the HGAHE is strongly dependent on the inlet air temperature. Furthermore, the air temperature drop and the heat exchange rate as high as 13.3 °C and 463.4 W respectively, are attained at the highest inlet temperature of 41.0 °C. Besides, a transient numerical model was established and validated through the experimental data to investigate the heat penetration into the borehole. The results acknowledge that, the borehole temperature distribution in axial direction is higher at the upper surface and then decreases with the HGAHE length. In the other hand, the borehole temperature distribution in the radial direction reduces rapidly with the distance away from the pipe surface. Moreover, when the ambient air temperature during the night shift is lower than the borehole temperature, the forced convection which helps to take the heat away via purge air circulating into the HGAHE pipe allowed the borehole to restore its cooling ability.