COOLING OF HIGH-TEMPERATURE CYLINDRICAL SURFACES USING A WATER-AIR SPRAY

In materials processing such as heat treating, metal extrusion, forgin g, etc., control of the surface heat flux rate contributes to better p roducts. Spray cooling using a mixture of water and air is studied for these applications. It is shown that the heat transfer rate depends o n the mass fraction of liquid and that it can be adjusted to a desired value. Experimental heat flux data are presented for different liquid mass fractions, and at surface temperatures up to 1000 degrees C. Two distinct hear transfer regions above the dry wall temperature are rec ognized: radiation-dominated and convection-dominated, where droplets evaporate in the boundary layer. In between these two regions is a tra nsition region. The inverse thermal conduction technique based on the Monte Carlo simulation is used to provide surface temperature and subs equently to compute heat flux.