Natural-Convection Film-Boiling Heat Transfer : Saturated Film Boiling with Long Vapor Film

Abstract

This paper presents a simple model for natural-convection film boiling heat-transfer in staturated liquids for inclined plates. The model assumes that a vapor film has two-dimensional laminar vapor-film units that line up in the longitudinal direction of the plate. To determine the pitch of these units, the model uses the Kelvin-Helmholtz instability analysis. The model agrees with experimental results on heat-transfer coefficient as for the effects of the parameters : fluid properties, surface superheat, surface height, and surface inclination. Besides being applicable to flat surfaces, the model can be successfully extended to the case of saturated film-boiling around large horizontal cylinders. The paper also examines by an experiment in saturated liquid nitrogen the validity of the assumptions made in the analysis, concerning the interfacial behavior of film boiling on a vertical flat plate.