Confined and unconfined FC72 and FC87 boiling on a downward-facing disc

Abstract This paper presents new results for confined and unconfined boiling of FC72 and FC87 at atmospheric pressure and low and moderate heat fluxes—lower than 45 kW/m 2 —on a downward-facing disc placed at 0.2, 0.5, 1 and 13 mm distance from the base of a boiling chamber, corresponding to Bond numbers 0.28, 0.69, 1.38 and 17.95. The experimental results showed enhanced boiling as the main trend for the cases with s  = 0.2 and 0.5 mm compared with those with s  = 1 and 13 mm and a higher heat-transfer coefficient for FC72 boiling compared with FC87, with a wall superheating of 7.7–8 K higher for FC87.