Experimental Investigation of Developing Spray Boiling on a Flat Flake Surface with Constant Heat Flux

Experimental study on the heat transfer of water spray droplets impinging the surface of a stainless flat flake positioned in both horizontal and vertical direction has been carried under different spray flow rates and distances between nozzle outlet and the surface. A linear relationship between heat transfer coefficient and heat flux is found in the nonboiling region. The total heat flux is dominated sequentially by the single phase impinging convection and the fully developed boiling with increasing heat flux imposed. The wall temperature of the impinged-on surface rises very slowly with the increasing heat flux when it reaches around 110°C indicating a greatly enhanced boiling heat transfer coefficient. A new data reduction method is proposed since conventionally calculated heat transfer coefficient is found not physically interpretable in transition to fully developed boiling.