ABSTRACT
Experimental free convection heat transfer coefficients were determined from hot upward-facing horizontal plates and vertical plates. In both cases, the preheated plate was allowed to cool in ambient room air or hood air, while recording temperature as a function of time. The experimental heat transfer correlations were then determined by numerically integrating the heat balance using a 4th order Runga-Kutta integration, while varying the correlation coefficients to give the best fit to the experimental data. Finally, the experimental correlations were compared to literature correlations.
The literature correlations were multiplied by a constant factor to obtain the best fit of the experimental data. For the geometries tested, the multiplying factors were: Geometry Multiplying Factor
(h exp/h theory)
Cooling, Upward-Facing Horizontal Plate
1.4
Cooling, Upward-Facing Horizontal Plate (with less forced convection)
1.2
Cooling Vertical Plate
1.0
Forced convection caused the correction factors to be > 1 for the horizontal plate, although the multiplying factor was improved by minimizing air currents in the room. Any effect of forced convection on the vertical plate was offset by a lowering of the freely suspended convection coefficient, because the lower edge of the vertical plate was close to a horizontal table top; this position retarded the free convection fluid movements relative to an isolated vertical plate suspended in a very large room.
