Film evaporation from a micro-grooved surface - An approximate heat transfer model and its comparison with experimental data

An analytical model is presented that can be used to predict the heat-transfer characteristics of film evaporation on a microgroove surface. The model assumes that the liquid flow along a V-shaped groove channel is driven primarily by the capillary pressure difference due to the receding of the meniscus toward the apex of the groove, and the flow up the groove side wall is driven by the disjoining pressure difference. It also assumes that conduction across the thin liquid film is the dominant mechanism of heat transfer. A correlation between the Nusselt number and a nondimensional parameter ¥ is developed from this model which relates the heat transfer for the microgroove surface to the fluid properties, groove geometry, and the constants for the disjoining pressure relation. The results of a limited experimental study of the heat transfer during vaporization of a liquid coolant on a microgroove surface are also reported. Film-evaporation transfer coefficients inferred from these experiments are found to correlate fairly well in terms of Nusselt number and ¥ parameter format developed in the model. The results of this study suggest that disjoining pressure differences may play a central role in evaporation processes in microgroove channels.