Experiments on Film Boiling Heat Transfer around a Vertical Finite-Length Cylinder with Convex Hemispherical Bottom and Top Surfaces

摘要

The film boiling heat transfer around a vertical finite-length silver cylinder with convex hemispherical bottom and top surfaces was investigated experimentally for quiescent water at at-mosphereric pressure. The experiments have been carried out by a transient method, i.e., quenching method. The diameter of test cylinder is 32mm and the total length is 64mm with 32mm length of vertical lateral part. The test cylinder was heated to about 600°C in an electric furnace and then cooled in saturated and subcooled water with the immersion depth of about 100mm. The degree of liquid subcooling was varied from 0 to 35K. The film boiling heat transfer increased in terms of heat flux by 240% with 30K increase in liquid subcooling at the wall superheating of 300K. The wall superheating and heat flux at the lower limit of film boiling increased with an increase in liquid subcooling.