International Journal of Heat and Mass Transfer, Vol.69, 230-236, 2014
Experimental investigation of heat transfer from inclined flat surface to aqueous foam
Paper presents the results of the experimental investigation of heat transfer process between the inclined flat surface and the longitudinal upward macrofoam (foam) flow. Investigation was performed on the special laboratory stand using macrofoam, which was generated inside the channel on the perforated plate. Foaming solution was made from the 0.5% concentration of the washing powder (TIDE Absolute) solution in water and gas (air). Macrofoam parameters: velocity 0.10 divided by 0.30 m/s; volumetric void fraction 0.996 divided by 0.998; bubble dimensions 0.005 divided by 0.015 m. Inclination angle of the flat surface 45 degrees. Experimental surface was heated using electric current; surface temperature varied from 16.8 to 36.2 degrees C; foam flow temperature varied from 14.6 to 19.5 degrees C. Investigation showed that the heat transfer rate depends on the foam flow characteristics (velocity and volumetric void fraction) and on the drained liquid film parameters (film thickness, film flow velocity and direction). It was stated that the heat transfer rate increases with the increase of the foam flow velocity up to the critical value. When the foam flow velocity exceeds the critical value, the thickness of the drained liquid film begins to grow and heat transfer rate decreases. Further augmentation of the foam flow velocity forms a concurrent drained liquid flow and heat transfer intensity increases again. The experimental results were compared with the results obtained for the vertical flat surface and for the different types of the tube bundles as well. (C) 2013 Elsevier Ltd. All rights reserved.
Keywords:Experimental investigation;Macrofoam flow;Heat transfer;Inclined flat surface;Drained liquid film