Dissertation

A composite heat transfer model of the film boiling regime

Farmer, Mitchell Theodore

1988

Overview

An approximate set of coupled ordinary differential equations are developed which describe the temporal evolution of the vapor domes and film over a flat plate heater surface during film boiling for the general case of a subcooled bulk liquid. Given these results, a phenomenological model is then developed to describe the intermittent surface wetting process observed to occur in the film boiling regime. Assuming that the heater surface has been locally wetted, equations are developed to predict the time-dependent heat flux during contact and the subsequent duration of the liquid dryout period. Additionally, assuming that liquid propagation along the surface is terminated at the inception of nucleate boiling, an expression is developed to predict the wetted area of contact at a given node site. The hydrodynamic and surface interaction results are then combined to obtain an expression for the composite heat flux in the film boiling regime. A comparison of the local liquid-solid contact model with the experimental data available in the literature indicates that the model adequately predicts the wetted area fraction in a large neighborhood of the minimum film boiling point for an aluminum-water system. The model slightly underpredicts the wetted area fraction for methanol on the same surface. A comparison of the overall energy balance to the experimental data indicates that the model reasonably predicts the film to transition boiling progression for a wide class of heater surface/bulk liquid systems.

• Publisher: ProQuest Dissertations & Theses
• Subject: Nuclear engineering / Nuclear physics
• ISBN: 9798207012858