Effect of water subcooling on film boiling heat transfer from vertical cylinders

摘要

The effect of subcooling on the film boiling heat transfer of water from vertical copper cylinders has been investigated experimentally using a transient quench technique. A lumped parameter model was utilized since the Blot numbers were always less than 0.05. The amount of subcooling varied from 0 K to 70 K and the initial cylinder wall temperatures were of the order of 1100 K. Heat transfer coefficient were measured at the midpoint of the cylinders and were obtained over quench times in which they were verified to be constant. Subcooling had a significant effect on both the film boiling heat transfer coefficient and the minimum film boiling temperature. As the subcooling varied from 0 K to 70 K, the h transfer coefficient increased by a factor of five. As the subcooling varied from 0 K to 60 K, the minimum film boiling temperature increased from approximately 600 K to 1000 K. An attempt to correlate the heat transfer coefficient data with a method recently proposed by Sakurai et al. was only successful at subcooled temperature differences less than 10 K. A modified correlation is presented using the Sakurai et al. parameters which better represents the data over the complete subcooling range.