THE PARAMETERS OPTIMIZING OF THE EARTH-TO-AIR HEAT EXCHANGER

physics

The main objective of this work is the exploitation of geothermal energy contained in the soil. It is therefore a study related to an air / ground heat exchanger. Thus, we have established an analytical model that allows us to describe the behavior of the air temperature along the interchange, assumed to be located in Toliara and in a region that has weather data and soil characteristics similar of our soil in Toliara, in the south western region of Madagascar. The calculation, related to the temperature leaving the exchanger, is based on the Bessel function and the periodic resolution of the signal. As in the majority of the practical cases, we resorted to empirical relations which are based on the simplifying hypotheses such as the admission of a constant average value of this parameter for the whole surface of transfer. For the simulation of the parameters determining the functioning, we have written computer programs under MATLAB, which comprise two main programs. The first program was used to estimate the soil temperature in order to know the variation of the soil temperature at several levels of depth as a function of time. The soil temperature mainly affects the performance of such a phenomenon because the soil, at a certain depth, becomes the primary factor for heat exchange between the air circulating inside the exchanger and the environment. which surrounds it.The second program concerns the calculation of the air temperature while varying the thermal design parameters of the exchanger. These sizing parameters concerning the characteristic quantities of the earth-to-air heat exchanger are: length, diameter and the velocity of air flow in the buried tube.

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