Performance evaluation of an earth air tunnel for space heating of a non air-conditioned building

SYNOPSIS The temperature under the earth's surface is a function of both depth and time: The diurnal variations get damped at larger depths. At a depth of 4 m or so the temperature variation throughout the year is within a small range, and is found to have characteristic values for different surface treatments. In New Delhi it is found to be around 17°C for a wet shaded ground, 30°C for an ordinary dry sunlit soil and about 53°C for blackened and grazed soil. In this communication, for a dry and sunlit earth surface, an underground earth air tunnel at this depth is designed for space heating using the tunnel to circulate the air from a non air-conditioned room. A theoretical model of a non air-conditioned building coupled to an earth air tunnel for heating is presented. The model takes into account the periodicity of solar intensity and ambient air temperature, recirculation of room air through the earth air tunnel as well as periodic heat transfer through the ground, walls and roof. The effect of tempora...