Selection of wetted media for pre-cooling of air entering natural draft dry cooling towers

The performance of natural draft dry cooling towers (NDDCTs) can be improved by wetted-medium evaporative pre-cooling. However, the pre-cooling benefit is season dependent and is significantly affected by wetted media. To further investigate the effect of wetted medium type on pre-cooling performance, the current study simulates a pre-cooled NDDCT using two typical types of wetted media, i.e., film (Cellulose7060 and PVC1200) and trickle (Trickle125 and Trickle100). A MATLAB program was developed and was validated against published data. The model was then used to carry out case study of a 120 m-high NDDCT pre-cooled using the selected wetted media with fixed thickness of 300 mm. Both the medium performance and pre-cooled NDDCT performance were compared to recommend the characteristics of wetted media promising for evaporative pre-cooling. Simulation finds that the media with high or low cooling efficiencies and pressure drops are not promising for the studied pre-cooling case while those media with middle cooling efficiencies and pressure drops intend to produce much performance enhancement and Cellulose7060 is a representative of such kind of medium. For the 120 m-high NDDCT, the wetted-medium pre-cooling can raise the heat rejection rate of the tower without pre cooling from 45 MW to 92 MW, 76 MW, 68 MW and 65 MW by Cellulose7060, PVC1200, TricIde125 and Tricldel 00, respectively at ambient temperature of 50 degrees C and humidity of 20%. (C) 2016 Elsevier Ltd. All rights reserved.