Nucleation Site Activation in Saturated Boiling

Abstract

<p>An experimental investigation is presented for boiling of distilled water at atmospheric pressure on a copper surface having three different surface finishes of 16, 5 and 4 v inch CLA. Activation of the nucleation cavities under three different levels of heat flux for each surface was investigated. The measured active cavity radii showed good agreement with the active site radii as predicted by both the Hsu and Han and Griffith models. As a result of this investigation it was apparent that small cavities were able to entrap vapour residue and be activated by their neighbours and that the reason for incipience delay as reported in the literature was due to the nonexistence of sufficiently large cavities with the prerequisite residue of gas or vapour.</p> <p>The correlation suggested by Brown relating (N/A)rc as a function of rc in the form (N/A)rc a (l/rc)ⁿ was confirmed. On the basis of this work, it is recommended that the parameter group [2o Ts/Pv hfg(Tw-Ts)] be used to characterize a boiling surface.</p>