Three-dimensional simulation of earth air heat exchanger for cooling application and its validation using an experimental test rig

In this study, the performance of the Earth air heat exchanger system for cooling applications has been investigated computationally using computational fluid dynamics (CFD) software, and the results have been compared to experimental results. According to the simulation results, the temperature of moving air drops continuously as pipe length increases. The temperature drops more slowly in larger diametric pipes than in smaller ones, and the drop in temperature reduces slightly as air velocity rises. The proposed computational fluid dynamics model has been validated by building an indoor experimental test rig with the same parameters used in the simulation for variable diameter sets. As a result, an experimental test rig was constructed and built at NIT Patna, India, for the climatic and soil conditions of Patna. This fabricated and demonstrated experimental set up may be used in any climate and soil type. This is very concise and portable for transport. In the experimental and 3D simulation results, the maximum deviation in the Nusselt number for 0.0285 m, 0.038 m, and 0.0485 m pipes varies by 9.5%, 10.9%, and 7.72%, respectively. Similarly, in experimental and 3D simulation results, the maximum deviation in friction factor for 0.0285 m, 0.038 m, and 0.0485 m pipes varies by 6.21%, 11.22%, and 9.45%, respectively. The maximum deviation in heat transfer rate and effectiveness between simulated results and experimental observations for 0.0285 m, 0.038 m, and 0.0485 m diametric pipes are 6.76%, 9.96% and 9.58% respectively. The cooling capacity (heat transfer rate) increases as the air velocity increases; however, the effectiveness reduces as the air velocity increases.