Experimental study of the hygrothermal behavior of an earth/porous pipe/ air heat exchanger (EPPAHE) for building cooling needs in the context of the hot and dry Saharan climate

We present in this paper a study on the evaluation of the hygrothermal performance of an earth/porous pipe /air heat exchanger (EPPAHE) for the need to improve the temperature and humidity conditions in the summer of the rooms in the Saharan zone (Adrar, South-West Algeria). This study realized a passive cooling system mainly constituted by an air pipe based on porous material (fired clay) buried in the wet soil. A prototype in the test bench representing the studied system was made at the University of Adrar. We have analyzed its hygrothermal performance by measuring the air temperature at various pipe points and the corresponding relative humidity. We have developed a representative numerical model of the thermal system under the Fortran environment, established on heat and mass transfer, for the validation objective. Thus, the results show a good correlation between the theoretical values and those obtained experimentally, with relative errors not exceeding 10 %. The results also show that using a porous material air pipe (fired clay) improves the hygrothermal performance of EAHE for a 1.5 m pipe length; we recorded a temperature drop of more than 13 degrees C and a relative humidity increase of more than 35 %. Numerical simulations were performed to optimize the efficiency of the earth/ porous pipe/air heat exchanger (EPPAHE) by modifying different parameters: pipe length, pipe diameter, air velocity, and soil moisture. The parametric study shows that for wet soil, the efficiency of EPPAHE was 75 % for evaporative cooling and 58 % for humidification.