TRANSIENT POOL BOILING FROM DOWNWARD-FACING CURVED SURFACES

Quenching experiments were performed to investigate the effects of wal l thickness on pool bailing from downward-facing curved surfaces in wa ter. Experiments employed three copper sections of the same diameter ( 50.8 mm) and surface radius (148 mm), but of different thicknesses (12 .8, 20 and 30 mm). Local and average pool boiling curves were obtained at saturation and 5, 10 and 14 K subcooling. The maximum and minimum film boiling heat fluxes, which increased with increased subcooling, w ere independent of wall thickness >19 mm and Blot number >0.8 and 0.00 8, respectively, indicating that boiling curves for the 20 and 30 mm t hick sections were representative of quasi steady-state, but not those for the 12.8 mm thick section. When compared to that of a flat surfac e section of the same material and dimensions, the average pool boilin g curve for the 12.8 mm thick section showed significant increases in the maximum heat Bur (from 0.21 to 0.41 MW m(-2)) and the minimum film boiling heat flux (from 2 to 13 kW m(-2)) and about 11.5 and 60 K inc rease in the corresponding wall superheats, respectively.