In the present study, a special test setup was designed to evaluate the performance of a fan-pad evaporative cooling system under different climatic conditions in Saudi Arabia. Weather data for Riyadh representing arid climate, Jeddah representing humid climate and Abha representing moderate climate were analyzed. These data contained hourly readings for air temperature, relative humidity and solar radiation. An evaporative cooler consisting of a 10 cm thick cooling pad, suction fan and water

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... mp was used. The cooling pad was installed in a 1080mm high, horizontal duct of square cross-section insulated by 50mm polyurethane. The duct cross-section measures 1000mm ×1000mm. A variable speed suction fan was fitted at one end and the pad was designed so that the inlet air passed through the wetted pads. Air temperature and relative humidity of the inlet air were changed to simulate dry, humid and moderate climatic conditions of Saudi Arabia. The inlet air was heated by two types of electrical heater. The heaters were fixed in a contractioncone-profile that is mounted in the air duct. The inlet air temperature was controlled by a PID temperature controller. Electrical high pressure steam boiler was used to produce low pressure steam for heating and humidifying the inlet air stream. The boiler capacity is 57 kg/h steam at a pressure of 5.5 bar. The weather data analyses showed that cooling of agricultural structures in Riyadh and Jeddah is very essential. The mean monthly temperature during summer in Riyadh area varies between 31.5 o C and 36 o C, and the relative humidity is between 14.4% and 20%. These conditions encourage the use of evaporative cooling.