Experiments on Film Boiling Heat Transfer around a Vertical Finite-Length Cylinder (Effect of Bottom and Top Surfaces Configurations)

摘要

The film boiling heat transfer around vertical finite-length silver cylinders was investigatedexperimentally for quiescent water at atmosphereric pressure. The configurations of bottom andtop surfaces of silver cylinders are (1) flat bottom and flat top, (2) curved bottom and flat topand (3) flat bottom and curved top, where “flat” refers to “horizontal” and “curved” to “convexhemispherical”. The experiments have been carried out by a quenching method. The diameter ofthe test cylinder is 32mm and the lateral length is 32mm. The test cylinder was heated to about600°C in an electric furnace and then cooled in saturated and subcooled water with the immersiondepth of about 100mm. The temperature is measured using a K-type thermocouple inserted intothe center of the test cylinder. The degree of liquid subcooling was varied from 0 to 35K. The effectof bottom and top surfaces configurations on the degree of superheating and the wall heat flux atthe lower limit of film boiling was discussed.