Performance investigation of earth air heat exchanger: A synergistic approach of 3D simulation and its experimental validation for heating mode

Abstract

This study investigates the thermal performance of Earth air heat exchanger (EAHE) systems for heating purposes through a combination of 3D simulations and corresponding experimental analyses. EAHE systems hold potential for enhancing thermal comfort in various settings, such as residential buildings, offices, and laboratories. However, field experiments are constrained by factors like uncontrolled environments, limited repeatability, and extensive land requirements. Therefore, a laboratory test setup featuring variable diameters was constructed, and experiments were carried out to assess system performance across different climatic zones. The study reveals that smaller pipes exhibit the most significant rise in outlet temperature at lower air velocities, while the effectiveness of EAHE diminishes with increasing airflow velocity. Furthermore, smaller-diameter pipes outperform larger ones. The simulated results were validated with experimental data, indicating disparities in Nusselt numbers and friction factors among the pipes. The maximum differences observed were 9.18%, 10.9%, and 11.2% for Nusselt numbers and 6.21%, 11.22%, and 9.45% for friction factors, respectively, for smaller, medium, and larger diametric pipes. These variations between simulation and experimentation can be attributed to human errors, procedural discrepancies, and environmental influences. Therefore, these slight variations between the results indicate a satisfactory level of agreement between them.