Toshiyuki Misumi

Fluid Flow and Heat Transfer of Combined Convection Adjacent to Vertical Heated Plates Placed in Uniform Horizontal Flow of Air

Experiments have been carried out for combined convective flows of air adjacent to the vertical heated plates in the uniform horizontal forced flows to investigate relationships between the flow and the heat transfer. The experiments cover the ranges of the Reynolds and modified Rayleigh numbers as; ReL=160-2300 and Ra*L=4.3×105-2.0×108. The flow fields over plates are visualized with particles and smoke. The results show that the stagnation point moves downward away from the center of the plates when the surface heat flux is beyond a critical value. The condition where the stagnation point begins to move is expressed with the non-dimensional parameters as; Gr*L/Re2.5L=0.15. Profiles of measured local heat transfer coefficients are smooth even at the stagnation points in all cases examined. When the buoyancy effect is sufficiently weak, the coefficients agree well with those of the wedge flow. With increasing the surface heat flux, the coefficients are augmented to approach asymptotically the boundary layer solution of natural convection along a vertical heated plate. Finally, forced, natural and combined convective flow regimes are classified by the nondimensional parameter (Gr*L/Re2.5L).

Heat Transfer Enhancement of Turbulent Natural Convection Adjacent to Vertical Heated Plate.

Enhancement of heat transfer was investigated experimentally on natural convection adjacent to a vertical heated plate. In order to promote heat transfer from the heated plate, a V-shaped diverter plate of which the edge faced upstream was attached onto the surface of the vertical plate. The diverter plate redirects high-temperature fluids toward both sides of the plate and introduces low temperature ambient fluids behind the plate instead. These two mechanisms enhance heat transfer, in particular, in the region behind the diverter plate. Local heat transfer coefficients around the diverter plate were measured using water as a test fluid. The coefficients behind the diverter plate reached 2.5 times of those without the diverter plate. The optimum heights and angles of the the diverter plate that make the heat transfer maximum were also studied experimentally.