Performance of Single Pass Earth-Tube Heat Exchanger: An Experimental Study

A single pass earth-tube heat exchanger (ETHE) was installed to study its performance in cooling and heating mode. ETHE is made of 50 m long ms pipe of 10 cm nominal diameter and 3 mm wall thickness. ETHE is buried 3 m deep below surface. Ambient air is pumped through it by a 400 w blower. Air velocity in the pipe is 11 m/s. Air temperature is measured at the inlet of the pipe, in the middle (25 m), and at the outlet (50 m), by thermisters placed inside the pipe. Cooling tests were carried out three consecutive days in each month. On each day system was operated for 7 hours during the day and shut down for the night. Heating tests were carried out at night in January. Test results are presented in summary form for each month. Detailed analysis is presented for two months only -- May for cooling and January for heating. ETHE cools the ambient air in May by as much as 14oC. It heats the ambient air in January nights also by similar amount.