Experimental study of a water-mist jet issuing normal to a heated flat plate

Abstract

A parametric experimental study on the development of a round jet spray impacting a smooth, heated, flat plate has been accomplished. The main objective of this effort was to provide information characterizing the flow structure of a developing mist jet, issuing vertically towards an upward facing, horizontal heated plate, by means of simultaneous droplet size and velocity measurements. Phase Doppler anemometry was used, providing also information on liquid volume flux. The fine spray of small atomized droplets (0.5-5.0 μm), was generated using a medical nebulizer. Two low Reynolds number jets (Re =2952 and 3773) issuing from a cylindrical pipe have been tested. The distance between the jets exit and the plate was 50 cm. A stainless steel non-magnetic flat plate of dimensions 1000 mm × 500 mm × 12 mm was used as target wall. Constant heat flux boundary conditions were established during measurements. Results indicate that the heat flux from the plate is influencing the evolution of the spray jet, diminishing its velocity and turbulence. Average droplet sizes are affected little by the heat flux, although for the non-heated sprays, droplet sizes increase at locations very close to the plate. A significant effect on droplet volume flow rate is also reported.