The Earth to Air Heat Exchanger for Reducing Energy Consumption in South Algeria

Abstract

In Algeria, the construction sector accounts for 30% of the country's final energy consumption. The integration of passive or semi-passive cooling/heating systems in construction is now essential for the reduction of energy consumption while improving thermal comfort. Amongst the systems used is the air-to-ground exchanger. It consists of tubes buried at a depth of 2 to 4 m in which the ambient air is pushed in order to be cooled/heated in contact with the ground whose temperature is almost constant throughout the year. This temperature, which is highly dependent on weather conditions, is about 24℃ in Bechar, a region located in south- west of Algeria. The cooled/heated air was blown into the building. The objective of the present study is to highlight the possibility of installing and using this system in arid regions. The mathematical model established to calculate the temperature at the outlet of the exchanger, based on the k-ε turbulence equations and the energy equation, discretized by the finite volume method. For the temperature distribution in the soil, a simple analytical solution is developed. The parameters of (1) the length diameter ratio (alpha), (2) the Reynolds number, and (3) the depth of burial was studied. The results obtained are validated with the experimental device installed at the University of Biskra, a region in the south- east of Algeria. Sand, as a soil type, gives a constant annual temperature of 21℃ at a depth of 3m. For Reynolds equals 7500 and the ratio, alpha=250 gives a temperature at the outlet of the ground air exchanger equal to 24℃. An optimal solution was chosen for the installation of the ground air exchanger in south-western Algeria.