Numerical study on ground-air heat exchanger performance in a hot climate under different inlet air temperatures

The present study includes a numerical assessment of air-cooling by EAHE (i.e., Earth to Air Heat Exchanger) on hot days in Baghdad city. EAHE consists of pipes buried in a certain depth in the soil, where the temperature is moderate throughout the year. The effect of different input air temperatures at day and night on the EAHE performance has been studied, taking into account the change in soil temperature due to continuous passing of hot air causing an increase in soil temperature and lowers its cooling capacity. In Baghdad (i.e. capital of Iraq), the hot days are extended from mid-April to mid-October. During these months, the weather is characterized by the high solar intensity at day with a daily range exceeding 15 ͦ C. Ambient air temperature varies greatly through spring, summer, and autumn. The various ambient temperatures recorded and documented for Baghdad are used as the inlet temperatures of EAHE in the present study. Besides, the pressure drops and power losses through pipes have been studied, too. The simulated results indicates that the use of EAHE gives the accepted outlet temperature for space cooling (about 26 ℃) on hot days of spring and autumn. In addition, the decrease of ambient temperature less than soil temperature at night leads to lessening the heat storage in soil.