Effect of the behavior of generated vapor on the minimum-heat-flux point during rapid quenching of a thin horizontal wire

Heat transfer characteristics and minumum-heat-flux point (MHF point) condition during rapid quenching of a thin horizontal wire were studied both experimentally and theoretically. Experiments were conducted with ethanol as a quenching liquid. The wire was either fixed or moving downward at a constant speed in an ethanol bath. When the wire was heated instantly to a high temperature, bead-like bubbles were formed along the wire. This was in contrast to the previous results for a heated wire that was dipped into the ethanol bath at a relatively high velocity, where a vapor sheet was formed in the wake of the wire. Consideration was given to the effect of film boiling mode on the MHF point condition. A linear stability analysis of vapor film for natural convection film boiling on a horizontal cylinder was presented. The theoretical prediction of the critical vapor film thickness compared well with the measured value at the MHF point for the fixed wire.