Mixed convection in a horizontal square duct with local inner heating

Numerical analyses were performed for the effect of local inner heating on the mixing flow in a horizontal square duct. Three-dimensional governing equations were solved for Re = 100, Pr = 0.72 and six kinds of inner heating sizes in a duct, with insulated walls or uniform temperature walls. Local inner heating induced the local buoyancy force and produced four recirculating flows across a section in a thermally insulated duct. In a horizontal square duct with uniform wall temperature, the interaction of the buoyancy induced flows by temperature difference between the fluid and the local inner heating and between the fluid and the walls reduced the maximum intensity of the secondary flow. Two recirculating flows were generated in a downward region. Heat transfer was locally enhanced or depressed corresponding to the flow situation. (author)