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 ÷ 0.30 m/s; volumetric void fraction 0.996 ÷ 0.998; bubble dimensions 0.005 ÷ 0.015 m. Inclination angle of the flat surface 45°. Experimental surface was heated using electric current; surface temperature varied from 16.8 to 36.2 °C; foam flow temperature varied from 14.6 to 19.5 °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.