External Natural Flow for Various Geometries

External Natural Flow for Various Geometries For vertical walls, Churchill and Chu [Inf. J. Heat Mass Transfer, 18,1323 (1975)] recommend, for laminar and turbulent flow on isothermal, vertical walls with height L, 

Fluid properties for (5-36) should be evaluated at the film temperature Tf=(T, + Te)/2. This correlation is valid for all Pr and RaD. 

For horizontal flat surfaces, the characteristic dimension for the correlations is [Goldstein, Sparrow, and Jones, Inf. J. Heat Mass Transfer, 16,1025-1035 (1973)] 

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