CFD-Based Thermal Analysis and Experimental Validation of Pipe Materials in Earth Air Heat Exchangers for Energy-Efficient Buildings

The Earth Air Heat Exchanger (EAHE) is a passive energy system that utilizes the thermal energy of the ground to reduce cooling and heating loads in buildings. This study investigates the thermal performance of EAHE systems constructed with different pipe materials through both computational and experimental approaches. A CFD analysis using ANSYS Fluent was conducted to simulate airflow and heat transfer within buried pipes under steady-state conditions. The simulation results were validated with experimental data obtained from a test rig installed in Ajmer, India. The thermal efficiency of helical pipe configurations made from various materials was assessed using CFD, focusing on changes in air temperature, the extent of heat exchange between the air and surrounding soil, and the thermal performance at the knee point. During heating mode, a maximum air temperature rise of 13.56℃ was observed for air through copper and steel pipes, while a minimum temperature rise of 12.32℃ was achieved by air through an asbestos cement pipe. On the other hand, during the cooling of air maximum temperature drop of 19.68℃ was observed through the steel pipe, whereas a minimum temperature drop of 17.91℃ was observed for air through the asbestos pipe. The study demonstrates that the thermal performance of Earth Air Heat Exchanger (EAHE) systems is significantly influenced by the choice of pipe material. Both CFD simulations and experimental data confirm that metallic pipes, particularly steel and copper, offer superior heat exchange efficiency compared to non-metallic alternatives like asbestos cement.