Hydrodynamic and thermal effects in moving water layers uniformly heated from below

Convective heat transfer processes in a water layer flowing over a heated heated plate and the effects of buoyancy on hydrodynamic and thermal conditions in the water were studied. The experimental apparatus consisted of a water channel with a test section that was uniformly heated from below. Three different means of flow visualization were used and included the hydrogen bubble, dye injection and shadowgraph techniques. The results indicate that buoyancy forces induced by heating from below will disturb the flow to the point of hastening the occurrence of transition from laminar to turbulent conditions, and will enhance mixing in the turbulent flow regime. For a given flow condition, these effects increase with increasing bottom heat flux; for a given heat flux, the effects increase with decreasing mean flow velocity. Convective heat transfer coefficients were also inferred from temperature measurements, and the results indicate that heat transfer is significantly enhanced by the effects of buoyancy.