SINOPSIS

Various aspects of forced convective boiling in vertical channels are discussed, with emphasis on deviations from the classical behaviour. These deviations arise from influence of relaminarisation, from instability effects at near-zero quality and from the influence of multi-component mixtures, hi high quality forced convective boiling, me annular flow regime is reached and, here, droplets are entrained from the liquid film and flow with the gas core. Thus, any prediction methodology for this region must, per force, take account of the behaviour of these droplets. Here, two aspects of droplet behaviour are reviewed, namely the magnitude of the fraction of liquid entrained as droplets at the onset annular flow and the influence of heat flux on entrainment and deposition of droplets. In all these areas, there are significant challenges to the present and future research investigator.