Thermal Performance Assessment of Earth Air Tunnel Heat Exchanger System Enhanced with Water Impregnation Using Computational Fluid Dynamics

Abstract

Geothermal energy offers a readily accessible and environmentally friendly source of low-grade thermal energy, particularly for building applications. Utilisation methods such as ground source heat pumps and earth-to-air heat exchangers (EATHE) have been employed to achieve energy-efficient cooling and heating. EATHE systems, which consist of underground heat exchangers utilising buried pipes, effectively exchange heat with the ground to cool or warm air passing through them. During summer and winter, hot or cold outdoor air is circulated through these pipes, exchanging heat with the surrounding soil. Consequently, the outlet air temperature from the EATHE system can significantly differ from the ambient air temperature. In the summer, if the outlet air temperature is sufficiently low after the heat exchange process, it can be directly used for space cooling, contributing to energy savings. Enhancing the moisture content of the soil can further improve the effectiveness and performance of the EATHE system. This can be achieved by introducing a wet configuration of the system. The earth-to-air heat exchanger configurations can reduce energy consumption for space conditioning, with the wet configuration enhancing the system's efficacy. The study employs computational fluid dynamics (CFD) simulations using ANSYS FLUENT software to model and analyse different configurations of the EATHE system. The results are compared and validated against experimental data, demonstrating the impact of soil moisture content and airflow velocity on the system's performance.