Fluid flow and heat transfer of opposing mixed convection adjacent to vertical heated plates

Opposing mixed convective flows induced around heated vertical plates were investigated experimentally. The experiments have been carried out with air and test plates of 100 mm and 200 mm long. The flow fields over the heated plates were visualized and the local heat transfer coefficients of the plates were measured for a wide range of Reynolds and Rayleigh numbers; ReL = 7 × 102−1.5 × 104, Ra = 9 × 106−8 × 108. The visualization experiments showed that the separation of the boundary layer appears first at the trailing edge of the plate when the non‐dimensional parameter of (Gr /Re ) = 0.35, and that the separation point reaches the leading edge when (GrL*/ReL2.5) = 1.0. The heat transfer experiments showed that the above flow separation retards the heat transfer significantly from that of pure forced convection. It was also revealed that the flows over the heated plates can be categorized into forced, natural, and combined convection using the above parameter, (Gr /Re ), as (Gr /Re ) < 0.2, (Gr /Re ) > 3 and 0.2 < (Gr /Re ) < 3, respectively.