Natural Convection Heat Transfer In Boiling Of Metals

Boiling heat transfer coefficients were measured for mercury, mercury plus 0.1 percent sodium, sodium-potassium alloy, and cadmium at temperatures from 670 to 1600°F and atmospheric pressure. The temperature differences were measured by thermocouples in the tube wall and in the bulk of the boiling liquid. The highest coefficients were for sodium and sodium-potassium alloys - up to 15,000 BTU per (hr) (°F) (sq. ft.). The combination of low coefficients with pure mercury and the high coefficients with addition agents are interpreted as film and nucleate boiling respectively. It follows that film boiling may be more the result of non-wetting characteristics of the surface than of heat flux or quanity of vapor evolved.