Experimental and theoretical investigation of an evaporative cooler using patented diabatic contacting device with high surface density, 410to 550 m2 / m3, will be presented in this paper. Heat and mass transfer coefficients have been reported. High surface density of the heat andmass transfer surface helps keep the unit compact and air flow parallel the wavy surface of the rotating disks helps achieve high heat and masstransfer coefficients while keeping the pressure drops low. Carryover of liquid in to the air stream is also avoided in this design.

The diabatic contacting device involves multiple disks assembled on a non-circular shaft rotated at 5 to 40 rpm using a low speed lowwattage rotor motor. Multi stage contacting is possible with several diabatic contacting devices assembled in series. Cooling capacity of theassembly can be increased by increasing the number of parallel trays or increasing the length of each contacting tray. Assembly of the rotatingdisks dips in the water in the trough as it rotates and then comes in contact with the air passing perpendicular to the shaft. Evaporation of watercools the remaining water in the trough and this in turn cools the fluid being passed through the passages of the diabatic co ntacting device. Thiscooling effect has been used to cool liquids, condense refrigerant or process vapours which simultaneously aerating and / or evaporating effluentstreams in a once through flow arrangement.

The system is economically viable and involves less maintenance cost. The analysis presented in the paper confirms the benefi t of indirectevaporative coolers for hot and humid climate conditions.