Thermal Performance of Earth–Air Heat Exchanger Using an Experimental Test Rig

This study describes the results of an experimental investigation of an earth–air heat exchanger for heating and cooling in Patna India, using an experimental test rig. An experimental test rig was constructed and built for the climatic and soil conditions of Patna. In the test rig, three horizontal polyvinyl chloride (PVC) pipes of equal length with a diameter of 0.0285, 0.038, and 0.0485 m were installed. The tests were conducted with ambient air entering at various speeds of 2, 3.5, 5, and 6.5 m/s. The result of the experiments shows that the temperature rises and falls in the larger diametric pipe are lesser than those in the smaller ones, and it decreases slightly as the velocity of air increases. So, a smaller diametric pipe with a lower airflow velocity shows a maximum rise and fall in temperature. The cooling and heating capacity (heat transfer rate) increases with increased inlet velocity. In both heating and cooling applications, the effectiveness of an earth–air heat exchanger decreases as the velocity of the moving air increases. Also, the larger diametric pipe has less effectiveness than the smaller diametric pipe. The maximum heating and cooling effectiveness of 0.63 and 0.61, respectively, was observed for 28.5 mm diameter pipes when the inlet air speed was 2 m/s.