FILM BOILING ON A LONG VERTICAL SURFACE UNDER HIGH HEAT FLUX AND WATER SUBCOOLING CONDITIONS

This paper examines natural-convection film boiling of water on a long vertical surface under high heat flux and water subcooling conditions. Recent film boiling experiments performed at KTH are analyzed. The measured heat transfer coefficients are compared with the predictions of the convective vapor-film-unit model of Nishio and Ohtake. The model predictions are found to be reasonable when the predicted convective and radiative heat transfer coefficients are summed without further modification. The vapor-film-unit model is utilized to extrapolate the results to higher surface temperatures and water subcooling, and slightly elevated pressures. Thin, sub-millimeter, vapor films are predicted under highly subcooled water conditions.