Film boiling heat transfer of droplet streams and sprays

This paper presents an empirical approach to determining film boiling heat transfer of a spray from extrapolation of the heat transfer characteristics of an isolated droplet stream. First, an experimental investigation of film boiling heat transfer from a polished nickel surface to a continuous stream of monodispersed water droplets was performed for surface temperatures up to 490 degrees C. Empirical correlations are presented for film boiling heat transfer rate and droplet heat transfer efficiency over a wide range of operating conditions. These single droplet stream correlations were then employed to predict film boiling heat transfer rates of both multiple droplet streams and sprays of uniform droplet size and velocity. By correctly accounting for differences in volumetric flux and droplet heat transfer efficiency, it is shown how the single droplet stream correlations facilitate the prediction of film boiling heat transfer of a dilute spray. (C) 1997 Elsevier Science Ltd.