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Free convection (Grashoft Number
(ratio : Buoyancy / force visqueuse)
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Free convection
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Nusselt Number
is the ratio of convective to conductive heat transfer across (normal to) the boundary
Natural convection is highly dependent on the geometry of the hot surface, various correlations exist in order to determine the heat transfer coefficient. A general correlation that applies for a variety of geometries is
Nu = [ Nu0^(1/2) + Ra^(1/6) x (f4 x Pr / 300)^(1/6) ] /2
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Raleight number
:question: When the Rayleigh number is below a critical value for that fluid, heat transfer is primarily in the form of conduction; when it exceeds the critical value, heat transfer is primarily in the form of convection.
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