Experimental and numerical analysis of helical geothermal heat exchanger operating in hot climates

Abstract

With the onset of the warm and cold season, the temperature inside the building goes far away from the human comfort condition, the geothermal heat exchanger systems can be used to refresh the buildings. various configurations especially single U-tube ground heat exchangers have been studied to improve the thermal performance of ground heat exchangers. Although helical type has better thermal performance than the others. The present paper provides experimental and numerical analysis of helical geothermal heat exchanger tested in El-Oued region (Algeria). A PVC pipe was used as a Helicoidally Water-Air Heat Exchanger (HWAHE), with 30 m of length and 0.6 m of diameter. The HWAHE was emerged in the bottom of water well of 5 m of depth. A mathematical model was developed to test thermal efficiency of the system and a parametric analysis was carried out taking into account the length and the radius of the pipe and the velocity of the air in the pipe. The results of performance show that the inlet air temperature has significant effect mainly when the difference in temperature between the ambient air and the water borehole increases. Therefore, the gained temperature gap between the inlet and the outlet air of the exchanger increases with the increasing of air inlet temperature. However, at air velocity of 10 m/s the efficiency of the exchanger reached 89%.