Coupled liquid film and solidified layer growth with impinging supercooled droplets and Joule heating

Abstract

Phase change heat transfer with incoming supercooled droplets on heated curved surfaces is examined. The processes of rime ice, transition and combined rime/glaze ice conditions are modelled. In the analysis, heat conduction equations in the ice and unfrozen water layers are solved simultaneously with the mass balance, including incoming droplets. Energy input from the heated boundary (due to electrical heat generation) affects the growth of the glaze film thickness and associated liquid runback along the ice surface. Validation of the predictive model is carried out through comparisons with experimental data [Lu et al., A semi-empirical icing model for an energized power line, Internal Report, Department of Mechanical and Industrial Engineering, University of Manitoba, Winnipeg, Canada, 1999; Mass of ice accretion from freezing rain simulations, Proceedings, 8th IWAIS, Reykjavik, Iceland, 1998] involving ice buildup on heated, non-rotating circular conductors. Close agreement is achieved between the predicted ice growth and the measured data. Additional effects of cable radius, Joule heating rate and surface curvature are presented. The heat transfer model is shown to correctly approach the dry growth limit, based on mass conservation alone, under appropriate thermal conditions when the surface heating rate is diminished sufficiently. As a result, a single formulation is provided over the entire range of rime, transition and combined rime/glaze ice conditions, including the simultaneous growth of unfrozen water and ice layers.