Study of the design of an earth-to-air heat exchanger for low energy air cooling and heating of a school in desert climate

This work aims at designing two Earth to Air Heat Exchangers (EAHX) for air cooling and heating of a primary school in Arfoud city Morocco, which is located in the South-East of Morocco and characterized by a desert climate. The school is constituted of two independent buildings. The Earth to Air Heat Exchangers should supply cool or warm air at a temperature of around 26°C and 20°C respectively. A total airflow rate of around 2000 m3/h is required for each building. The objective here is to identify the best EAHX parameters combination based on these requirements. For this purpose, a parametric study is performed using the well-validated TYPE 460 of TRNSYS software. Intermittent operation mode from 7 am to 6 pm during the school days (Monday to Saturday) is considered. The identification of the best combinations of the EAHX parameters is based on maximum and minimum EAHX exit temperature for cooling and heating purpose respectively, total cooling and heating capacity and the total pressure drop of the air inside the pipes. It was found that the best EAHX parameters combination is constituted of 4 pipes of 100 m length and 0.195 m internal diameter each buried at 5.7 m depth and operated at 4.63 m/s air velocity.