Direct evaporative cooling is one of the efficient traditional strategies to provide summer comfort in a building or air-conditioning in storage rooms. The present paper concerns a new mathematical approach to analyse the influence of the effective parameters on the performance of direct evaporation from a porous layer. The ambient air flows over a porous material, fed with water. The evaporation of an amount of water into the air reduces its temperature and, at the same time, raises the air's humidity. A mathematical model that accounts for simultaneous heat and mass transfer characteristics in the ambient air and water flow in corporating non-Darcian model in the porous region within vertical parallel walls is presented. The solution of the mathematical model is based on the finite volume method and the velocity-pressure coupling is treated with the SIMPLE algorithm. The results showed that the porous evaporative cooler could satisfy the cooling requirements in arid climates. An average drop of 15 degrees C of air temperature below the ambient temperature can be reached at the considered conditions. Therefore, the ambient air is satisfactorily cooled. Furthermore, the better cooling performance can be achieved for a high porosity with a thick porous medium and lower air velocity at the entrance. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.