Heat Transfer and Fluid Flow Experiments With a Tube Fed by a Plenum Having Nonaligned Inlet and Exit

Local turbulent heat transfer coefficients for airflow were measured in a tube situated downstream of a cylindrical plenum chamber in which the inflow was radial and the outflow was axial. Pressure drop measurements and flow visualization were performed to supplement the heat transfer experiments. The plenum length and diameter were varied systematically during the experiments, and the Reynolds number ranged from 10,000 to 60,000. Substantially higher Nusselt numbers in the tube were encountered for the present nonaligned plenum inlet/exit configuration than for a plenum with axially aligned inlet and exit or for an upstream hydrodynamic development section. For a given Reynolds number, the Nusselt numbers corresponding to the present plenum configuration were quite insensitive to the investigated geometrical parameters. The thermal development length was found to be substantially elongated due to swirl carried into the tube from the plenum; the presence of the swirl was confirmed by flow visualization. The net pressure loss due to the presence of the plenum was about 1.75 velocity heads and was guite insensitive to the geometrical parameters and to the Reynolds number.