The effects of surface conditions on boiling characteristics

Abstract

A unified model relating surface variables to the nucleate pool boiling characteristics was developed. A simple vapor trapping mechanism was postulated and a geometrical model constructed for idealized conical cavities relating the effective radius for nucleation to cavity radius, cone angle and contact angle. This model for individual cavities was extended to the entire surface providing an expression for the cumulative site density in terms of geometrical parameters. A gas diffusion technique was developed to measure the effective radius for natural cavities and was used successfully to verify the nucleation criteria AT = 2T sv /h p. A transient heat conduction model was experimentally verified for watf an organics at atmospheric pressure and was incorporated into a unified expression showing explicitly the role of surface geometry and contact angle.