Entropy generation for natural convection in a partitioned cavity, with adiabatic horizontal and isothermally cooled vertical walls, is studied numerically by both a FORTRAN code and the commercially available CFD-ACE software. Effects of the Rayleigh number, the position of the heated partition, and the dimensionless temperature difference on the local and average entropy generation rate are investigated. Proper scale analysis of the problem showed that, while fluid friction term has nearly no contribution to entropy production, the heat transfer irreversibility increases monotonically with the Nusselt number and the dimensionless temperature difference.

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Due to the difficulty in depositing conformal coatings on high aspect ratio surfaces, capillary evaporation on superhydrophilic porous structures have not been well studied. In this work, superhydrophilic hybrid wick was fabricated by coating micromembrane-enhanced microchannels with 20 nm-thick silica (SiO 2) using the atomic layer deposited (ALD) technique. Rapid ALD SiO 2 coatings improve thin film evaporation of water on hybrid wicks by up to 56%. An appreciable enhancement of critical heat flux was not obtained in this study because of a compromise between the increased capillary pressure and viscous drag resulting from superhydrophilic ALD SiO 2 coatings. V