▪ Abstract This review examines recent advances made in predicting boiling heat fluxes, including some key results from the past. The topics covered are nucleate boiling, maximum heat flux, transition boiling, and film boiling. The review focuses on pool boiling of pure liquids, but flow boiling is also discussed briefly.
Pool boiling of saturated water at 1 atm pressure has been investigated. In the experiments, copper surfaces prepared by following a well-defined procedure were used. The cumulative number density of the cavities and their shapes were determined with an optical microscope. The surface had a mirror finish and had a surface Ra (centerline average) value of less than 0.02 μm. The wettability of the surface was changed by controlling the degree of oxidation of the surface. In the experiments with the primary surface, the wall heat flux and superheat were determined with the help of thermocouples embedded in the test block. The density, spatial distribution, local distribution, and nearest-neighbor distance distribution of active nucleation sites in partial and fully developed nucleate boiling were determined from still pictures.
In this work, Lennard-Jones liquid and water droplets are simulated adjacent to a solid surface using molecular dynamics. The contact angle is obtained by using direct simulation. The particle-particle particle-mesh method [B. Shi, S. Sinha, and V. K. Dhir, J. Phys. Chem. 124, 204715 (2006)] for long range force correction is used in the simulation. The contact angle is studied as a function of system temperature and the solid/fluid interaction potential. It is shown that the contact angle decreases with increasing system temperature and increases when the potential decreases. At high system temperature (pressure), the contact angle drops to zero. The predictions are compared with data from experiments and a reasonable agreement is found.
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