Unsteady theory of heat transfer and fluid flow during instantaneous transition to film boiling

The paper deals with the problem of unsteady convective heat transfer during instantaneous transition to film boiling over a flat vertical surface, when heat flux is suddenly switched on. This heat flux exceeds the critical value, which corresponds to the onset of the film boiling regime. As a result, instantaneous transition to film boiling takes place. To solve the problem, two sets of the initial and boundary conditions were used. The first set was used in the classical solution of the film condensation problem derived by Nusselt. The second set was proposed by Ellion for a stationary liquid at the vapor-liquid interface. The analytical solution of the problem enabled obtaining unsteady temperature distributions, Nusselt numbers, velocity profiles and friction coefficients. Results obtained based on the Laplace transform and the self-similar solution are analyzed. •Instantaneous transition to film boiling was considered with heat flux suddenly switched on.•Unsteady convective heat transfer in the vapor film was studied.•The analytical solution was obtained and analyzed for two sets of boundary conditions.•Laplace transform and the self-similar solutions were analyzed.