Dynamic and Controlled Tuning of the Boiling Curve During Quenching

Abstract

Boiling influences many industrial processes like quenching, desalination and steam generation. Boiling heat transfer at high temperatures is limited by the formation of a vapor layer between the solid and fluid. Low thermal conductivity of this vapor layer inhibits heat transfer. Electrowetting (EW) fields can breakdown this vapor layer to promote wetting, and this concept works for many quenching media including water and organic solvents. This work studies the suppression of this vapor layer and measures the resulting heat transfer enhancement during quenching of metals. We image the fluid-surface interactions and boiling patterns in the presence of an electrical voltage. EW fields replace film boiling with periodic wetting-rewetting cycles and thus fundamentally change the heat transfer mode. The increased wettability substantially reduces the cool down time. The cooling rate can by increased by as much as 3X. The results show that electric fields can dynamically tune the classical quenching curve. This study opens up new avenues to control the metallurgy of metals via electrical control of the cooling rate.