In this paper, a media evaporative cooling system installed in the gas turbines of the Fars (Iran) combined cycle power plant are modeled and evaluated. In this model, different design parameters such as inlet air velocity, geometric shape and sizes and depth of the media have been considered. Analysis of the results shows that at a constant Prandtl number, the cooler effectiveness decreases and pressure drop increases, as incoming air velocity increases. The water evaporation rate and temperature drop of the cooler have been calculated, and the effects of temperature, relative humidity and pressure of the ambient have been investigated as well. The practical and analytical results show that the output of a gas turbine of the Fars combined cycle power plant at 38 degrees C ambient temperature and 8% relative humidity is 11 MW more, and the temperature drop of the inlet air is about 19 degrees C with media evaporative cooling installations. Because of annual power augmentation of 5280 MWh and considering 2.5 Cents/kW h selling price for excess electricity generated, the payback period obtained is about four years. (c) 2006 Elsevier Ltd. All rights reserved.