ABSTRACT
Experimental forced convection heat transfer coefficients were determined by flowing air through an annulus. The inner cylinder, centered in the annulus, was heated in the warm flowing air, while recording temperature as a function of time. The experimental heat transfer coefficients were then determined from a heat balance over the heat transfer surface, and the experimental coefficients were compared to those obtained from appropriate literature correlations. Finally, the experiment was repeated after adding a diffuser, connected to the bottom of the tube, in an attempt to minimize air turbulence.
The experimental forced convection coefficients from the flow of hot air over a brass rod centered in an annulus were 1.6–2.2 times higher than literature correlation coefficients, most likely resulting from the hair dryer jet velocity being 3.6 times higher than the annulus velocity. When the air diffuser was added, the experimental and literature heat transfer coefficients were equal for all air velocities, showing that the air diffuser was effective in minimizing turbulence in the system.
