Natural-Convection Film-Boiling Heat Transfer : Film-Boiling from Horizontal Cylinders in Middle- and Small-Diameter Regions

Abstract

In this report, to discuss natural-convection film-boiling heat transfer around horizontal cylinders in the small-diameter region, analytical solutions are derived for subcooled film boiling with a smooth liquid-vapor interface. Next, film boiling experiments around thin horizontal wires are conducted for water and R113 at atmospheric pressure. Results of the experiments indicate that, compared with analyses assuming a smooth interface, saturated film-boiling heat transfer in the small-diameter region is enhanced by both rosary-vapor-film and thick-vapor-film effects. As for the effect of liquid subcooling on film-boiling heat transfer in the small-diameter region, it is found that the small-diameter region can be subdivided into normal and singular regions. In the singular region, heat-transfer coefficients decrease to a minimum with increasing liquid subcooling.