Rewetting Theory and the Dryout Heat Flux of Smooth and Grooved Plates With a Uniform Heating

Abstract

The evaporation and condensation of thin liquid films are of significant importance in a wide variety of problems ranging from specific applications in the heat pipe field to more general ones in the chemical, nuclear, and petrochemical industries. Although several investigations have been conducted to determine the rewetting characteristics of liquid films on heated rods, tubes, and flat plates, no solutions are yet available to describe the rewetting process of a hot plate subjected to a uniform heating. A model is presented to analyze the rewetting process of such plates with and without grooves. Approximate analytical solutions are presented for the prediction of the rewetting velocity and the transient temperature profiles of the plates. It is shown that the present rewetting velocity solution reduces correctly to the existing solution for the rewetting of an initially hot isothermal plate without heating from beneath the plate. Numerical solutions have also been obtained to validate the analytical solutions. Finally, a simple method is presented to predict the dryout heat flux of a liquid film flowing over a heated smooth or grooved plate. The results of the prediction are found to be in reasonable agreement with the existing experimental data.