Numerical and experimental investigation on the transient behavior of an earth air heat exchanger in continuous operation mode

Abstract

The main objective of the present study is to investigate the thermal performances of an earth air heat exchanger (EAHE) under transient conditions in cooling mode. This work was performed experimentally in the University of Biskra, Algeria. For that, a PVC pipe of 53.16 m long and 110 mm diameter buried at 3 m depth is used. Tests of the experimental setup were carried out in continuous operation mode for 71 hours with high inlet temperatures. Besides, a mathematical model was presented for EAHE by using the finite differences method applying the energy balance equations with forced convection. In addition of the horizontal portion on soil surface, the two vertical portions of 3m each one connected to the horizontal portion were considered in the modeling in order to present a fairly complete study of the EAHE. It was found that the continuous operation mode have no remarkable effect on the outlet air temperature and thus on the EAHE performances during all 71 hours. Results of the theoretical predictions were validated with the measured air temperatures along the EAHE and showed satisfactory qualitative and quantitative agreement.