Hydrophilic zeolite coatings for improved heat transfer: A quantitative analysis

The wetting diameter and life time of a water droplet on the surface of a bare, ZSM-5 coated, and Zeolite-A coated stainless steel 304 substrate at different initial surface temperatures was experimentally studied. ZSM-5 and Zeolite-A coated SS-304 are more much more hydrophilic than bare stainless steel 304 as reflected by their contact angles (27° and 0° vs. 90°). The ZSM-5 and Zeolite-A coatings significantly outperformed the bare SS-304 by decreasing the droplet life time, increasing the heat flux and increasing the heat transfer coefficient at all initial surface temperatures studied. At the highest surface temperature studied, T0 = 200°C, ZSM-5, and Zeolite-A coatings are shown to increase the maximum heat flux on bare SS-304 by as much as 106% and 72%, respectively. At this temperature, the maximum heat transfer coefficients on ZSM-5 and Zeolite-A coatings are improved by 470% and 530% over the bare SS-304, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2008