Pool boiling heat transfer during quenching on a superhydrophilic surface in dilute aqueous saline solutions: Effects of the solution concentration and type of salts

Abstract

The durability of a superhydrophilic surface upon consecutive quenching in dilute aqueous saline solutions was studied, with emphasis on the effects of the solution concentration (up to 0.01 mol/L) and the type of salts. It was shown that the quenching process slows down, as a result of the deteriorated pool boiling heat transfer, during consecutive quenching runs in the saline solutions. Progressive changes in the surface morphology and wettability were observed on the superhydrophilic surface, due to the accumulative deposition of the dissolved salts during quenching. The deteriorated quenching performance of the superhydrophilic was found to become more significant upon increasing both the solution concentration and the number of consecutive quenching runs. Comparison was also made among three different dissolved salts at a constant concentration of 0.0025 mol/L, in order to reveal the effects of both cation and anion. It was observed that the KCl and NaCl solutions decelerate significantly the quenching process, whereas the K2SO4 solution only has a slight impact. Through the morphological and elementary analysis on the quenched surfaces, the rational surface deposition mechanisms are hypothesized. It was concluded that the chloride salts are prone to deposition due to their stronger corrosive ability than the sulfate salts.