Transition Boiling Heat Transfer of Droplet Streams and Sprays

Abstract

An experimental study was performed to characterize the transition boiling heat transfer rate from a surface to a stream of impinging water droplets, and to extrapolate this information to predict the transition boiling heat transfer of a dilute spray. First, transition boiling heat transfer data was gathered for a continuous stream of monodispersed water droplets striking a polished nickel surface. From this data, empirical correlations were developed to describe the heat transfer rate and heat transfer efficiency for droplet velocities between 1.0 and 7.1 m s−1, droplet diameters ranging from 0.250 × 10−3 to 1.002 × 10−3 m, and surface temperatures covering 110 to 240°C. By properly accounting for the hydrodynamic differences between a spray and a single droplet stream, the empirical single droplet stream heat transfer correlations were effectively extrapolated into a model for predicting the transition boiling heat flux of dilute sprays (Q′ ≈ 0.5 × 10−3 m3s−1m−2).