Thermal performance of helical ground air heat exchanger under Saharan climate conditions: an experimental study

In the present research paper, the thermal performance of helical ground air heat exchanger (HGAHE) has been experimentally analyzed under Saharan climate conditions during summer season. A flexible PVC pipe with a diameter of 0.06 m and a length of 30 m has been arranged as a helical-coil layout to design the HGAHE, and it is inserted into a borehole of 5 m depth. The study acknowledges that a drop as high as 11.0 degrees C in air temperature can be achieved with an air velocity of 10 m s(-1) and an inlet air temperature of 38 degrees C. The study also revealed that, by incrementing the air velocity from 10 to 20 m s(-1), the heat exchange rate of the HGAHE system increases by 158% after 3 h of operation time; however, the efficiency of the HGAHE decreases by 21.51%. Moreover, thermal performance derating factor (TPDF) increments with increasing the operation time and air velocity. After 3 h of operation time, the highest TPDF is attained as 0.27 with a velocity of 20 m s(-1), whereas the lowest TPDF is observed as 0.14 for a velocity of 10 m s(-1).