Analysis of the spray field development on a vertical surface during water spray-quenching using a flat spray nozzle

The aims of this study were (i) to conduct experimental spatially and time-resolved measurements of flow development on large heated surfaces during transient spray cooling operations and (ii) to investigate and discuss the influence of spray cooling mechanisms such as bubble formation and the flow field development of the cooling fluid and how this affects heat transfer. Quartz plates were heated to above 500 °C and then sprayed with pressurised water subcooled to 80 K. High speed images of the quench process were collected at a rate of 3000 Hz making it possible to track the movement of the quench front as the plate cools below the Leidenfrost temperature of the fluid at that location. Observations showed that the relative importance of droplet-surface interactions decreases once the Leidenfrost temperature is reached on the plate: It was found that once the water contacts the surface, a water pool develops rapidly which grows larger as the pool floods the heated surface. Comparisons between the spatial flow development and heat transfer on the plate are made in order to describe these interactions more accurately. This information not only provides crucial input into process simulations, but is also useful to develop theoretical models of fluid-solid interaction describing the wetting of a heated component due to water spraying. Crown Copyright © 2008