Theoretical and Experimental Investigation of the Stability of an Evaporating Constrained Vapor Bubble

The major accomplishments of the experimental portion of the research were documented in Ling Zheng's doctoral dissertation. Using Pentane, he obtained a considerable amount of data on the stability and heat transfer characteristics of an evaporating meniscus. The important points are that experimental equipment to obtain data on the stability and heat transfer characteristics of an evaporating meniscus were built and successfully operated. The data and subsequent analyses were accepted by the Journal of Heat Transfer for publication in 2004 [PU4]. The work was continued by a new graduate student using HFE-7000 [PU3] and then Pentane at lower heat fluxes. The Pentane results are being analyzed for publication. The experimental techniques are currently being used in our other NASA Grant. The oscillation of the contact line observed in the experiments involves evaporation (retraction part) and spreading. Since both processes occur with finite contact angles, it is important to derive a precise equation of the intermolecular forces (disjoining pressure) valid for non-zero contact angles. This theoretical derivation was accepted for publication by Journal of Fluid Mechanics [PU5]. The evaporation process near the contact line is complicated, and an idealized micro heat pipe has been proposed to help in elucidating the detailed evaporation process [manuscripts in preparation].