(V) Flow effects on the transient behavior of vapor film and bubbles during forced-convective quenching experiments

The transient behavior of boiling phenomena during quenching of an AISI 304 stainless steel, conical-end, cylindrical probe in flowing water at 60 °C was studied. Two free-stream velocities (0.2 and 0.6 m/s) and two initial probe temperatures (850 and 950 °C) were investigated.

From high-speed video recordings, perturbations of the vapor film that appear periodically and propagate in the direction of the flow stream were observed. After the collapse of the vapor film, a wetting front is formed which consists of many small bubbles that coalesce rapidly in a small area while fewer and larger bubbles nucleate and grow below it.

The initial temperature has a marginal effect on the size and half-life of the large bubbles. However, the water flow rate produces larger values of maximum diameter and half-life time for water flowing at 0.2 m/s than their equivalents for 0.6 m/s.