Film Boiling of Saturated Nitrogen Flowing in a Vertical Tube

Abstract
A study is made of film boiling of a saturated nitrogen flowing upward through a uniformly heated tube. Visual experimental observations demonstrate that the annular flow regime which exists at very low qualities is broken up at higher qualities to form a dispersed flow of liquid droplets in a vapor matrix. Analysis of experimentally determined tube wall temperature distributions shows that a significant amount of vapor superheat is present throughout the film-boiling process. A method is presented by which both an upper bound and an estimated value of the heat-transfer coefficient for the dispersed flow regime may be calculated.