Local Film Thickness During Transient Voiding of a Liquid-Filled Channel

Using a recently developed method, measurements were obtained of local film thicknesses during transient voiding of a liquid-filled channel. The liquid film remaining on the channel walls was found to vary in thickness over a range of 0.015–0.15 times channel diameter. In a Lagrangian coordinate system, the film thickness at a fixed distance from the head of the void was found to increase with increasing void acceleration. In an Eulerian system, the film thickness at a fixed location on the channel wall was found to decrease with increasing acceleration, when measured at the same time after passage of the head of the void. In all cases, film thickness monotonically decreased with increasing distance from the head of the void. Complete film breakage (dryout) was not observed in these experiments. These experimental measurements of local film thicknesses during transient voiding conditions are pertinent to thermal analyses for reactor safety studies.