Abstract
Pool boiling heat transfer during quenching in subcooled water at atmospheric pressure was investigated on stainless steel rodlets with a superhydrophilic surface. It was shown that both the surface superhydrophilicity and degree of subcooling can accelerate significantly the quenching process. Under saturated condition, the quenching time is reduced by 50% for the superhydrophilic surface in comparison to the untreated one, due to the remarkable heat transfer enhancement with the critical heat flux being increased by 128%. The increase of the degree of subcooling can further reduce the quenching time. Frequent and intensive liquid-vapor interface fluctuations were observed visually during the initial phase of quenching for both saturated and subcooled conditions, indicating the absence of stable film boiling regime even though film-boiling-like boiling curves were obtained for the subcooled cases. Through visualized observations, the quench front was found to propagate upwards from the bottom of both the untreated and superhydrophilic rodlets. The propagation velocity could be accelerated noticeably with increasing the degree of subcooling. In addition, good durability and stability of the superhydrophilicity were exhibited by consecutive quenching tests up to 100 times.
Published Version
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