Correlation of the experimental data

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There is a recommended correlation (from Churchill) for free convection heat transfer from a sphere:

[Graphics:../Images/thermal_bl_gr_80.gif] = 2 + [Graphics:../Images/thermal_bl_gr_81.gif].

(See page 504 of I &D.)

The Nusselt and Rayleigh numbers are based on the sphere diameter.  Thus this correlation does have [Graphics:../Images/thermal_bl_gr_82.gif]  in agreement with the scaling of the boundary-layer equations. Note that Ra≡ Gr Pr.  

Converted by Mathematica      April 30, 2000