Studying the effect of design parameters on the performance of earth-air heat exchangers

Nowadays, energy is a vital issue. Earth to Air Heat Exchanger (EAHE) is a technique that promotes energy saving. EAHE is a non-conventional technique that utilizes the thermal potential of the geothermal energy for space cooling/heating. In this study, a transient implicit computational fluid dynamics model is developed to simulate the thermal performance of EAHEs. The developed model is validated against available experimental and numerical studies in the literature. Good agreement between simulated results and experimental data is obtained. The model is then used to evaluate the effects of operating parameters, i.e., air velocity, EAHE pipe diameter, and EAHE pipe length, on the thermal performance of EAHE. As a cases study, a 50m EAHE is considered to provide cooling in the range of 1–5.17 ℃ and heating in the range of 6.2–8.65 ℃ for the flow velocities 2-5 m/s. It is demonstrated that the length of the buried pipes significantly affects the performance of EAHE, and the amount of cooling and heating capacity generally increases with increasing pipe length. The results show that increasing pipe diameter increases the amount of cooling and heating capacity. The results also revealed that condensation happening through the pipes does not considerably affect the outlet air humidity. Thus, this technology can be effectively used for ventilation in mild climates.