Experimental Study of Heat Transfer in a Reduced Model of Bioclimatic Air-Soil Exchanger

Abstract

At depths ranging from 2 to 3 m, the soil maintains a stable temperature between 5 and 15℃ depending on the season and the region. In order to exploit this thermal characteristic, certain geothermal processes called climatic sinks consist in exploiting that energy to naturally cool or heat buildings. That system, which constitutes the Earth–Air Heat Exchanger (EAHE), can reduce the temperature of buildings by 5 to 8℃ for derisory electricity consumption and without any greenhouse gas emissions. The present paper aims to study the sensitivity of convective heat transfer in such exchanger. To achieve that goal, experiments have been carried out on an EAHE’s scale model using sand as soil’s sample. By varying at different values the velocity of the air and the temperature of the soil sample, a campaign of measurements has been performed. Analysis of data allowed discussing on the influence of the air’s velocity on the output temperature and on the heat transmission coefficient in the exchanger. Results revealed that the average difference in temperature of the air at the inlet and outlet as well as the heat transmission coefficient, increased respectively by 0.653℃ and 1.369 W.m-2.K-1 per unit of the speed of air in the pipe.