Effect of surface coating on defrosting water drainage characteristics of vertical-fin microchannel frosting evaporator

Abstract

Vertical-fin microchannel heat exchanger has better frosting and defrosting performance owing to its better water drainage along vertical fins. Effect of hydrophilic and superhydrophobic coatings on frosting and defrosting performance is experimentally compared and drainage performance is investigated by dynamic dip testing and simulation. Results show that since water has smaller adhesive force on superhydrophobic fins, defrosting water carries some frost while is separated from the evaporator in form of frost-water mixture. Hence, the superhydrophobic vertical-fin microchannel evaporator has shorter defrosting duration by 9.8%. Both hydrophilic and superhydrophobic samples have satisfactory cyclic repeatability without obvious capacity attenuation. During defrosting, most water can flow down the leading edge extension. The residual water of the superhydrophobic sample is 61 g/m2, which is 19.6% less than that of hydrophilic one.