ISSN Online: 2377-424X
ISBN Print: 0-89116-559-2
International Heat Transfer Conference 8
HEAT TRANSFER REGIMES IN FORCED-CONVECTION FILM BOILING ON SPHERES
Abstract
Heat transfer rates have been measured for nickel-plated copper spheres at temperatures ≤ 540 °C, moving downwards at velocities ≤ 1.8 ms−1 and in natural convection in water at 607−100 °C. Stable film boiling occurs at high wall temperatures in saturated or slightly subcooled water; the low rate of heat transfer is independent of velocity until the separation point of the vapour wake reaches the mid-point of the sphere. In water subcooled by more than 20K and at wall temperatures of 430−540 °C heat is transferred at a high rate in the microbubble regime. With decreasing wall temperature, these regimes transform to disturbed film boiling with a jump in heat flux (upwards from stable film boiling, downwards from microbubble boiling).