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Evaporative cooling is an economic and environment-friendly technique for air cooling. This technique may involve air cooling with humidification (direct evaporative cooling) or sensible air cooling only (indirect evaporative cooling). In this study, the saturation efficiency of direct evaporative cooling (DEC) was investigated with rigid media cellulose (RMC) pads and compared with that of wood straw pads. Face air velocity on pads was varied between 0.5 and 3.0 m·s-1. The time change of ambient air dry-and wet-bulb temperatures, water temperature, and outlet air dry-bulb temperature were measured. For cellulosic pad, the experimental data showed that the saturation efficiency reached 71% of its steady state value in the first 100 seconds of operation and the final steady state value was reached after 600 seconds. The saturation efficiency decreases with the increase in the air velocity. It could be shown that the DEC is more efficient with wood straw pads compared to RMC pads. Predicted data using the published literature underestimated the saturation efficiency of DEC by about 18%.

RMC pads --- Wood straw pads --- Evaporative cooling --- Saturation efficiency --- Adiabatic saturation