Correct Answer - Option 2 : Natural convection
Explanation:-
\(\rm Grashoff\;number = \frac{{{\rm{Buoyancy\;Force}}}}{{{\rm{Viscus\;Force}}}}\)
\(Gr = {\rm{\;}}\frac{{{\rm{g\beta \Delta T}}{{\rm{L}}^3}}}{{{{\rm{\nu }}^2}}}\)
g = acceleration due to gravity, β = isobaric volume expansion coefficient of fluid, ΔT = temperature difference, L = characteristic dimension of body,ν = kinematic viscosity
Some important points regarding Grashoff number
- The role played by the Reynolds number in forced convection is played by the Grashoff number in natural convection.
- The flow in Free convection Heat Transfer is decided as laminar or turbulent based on the value of (Gr Pr) product that is Rayleigh number (Ra)
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(Gr Pr) < 109
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Flow is laminar
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(Gr Pr) > 109
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Flow is turbulent
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Other important dimensionless numbers are:
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Biot number → Ratio of internal conductive resistance to external convective resistance.
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Grashoff number → Ratio of buoyancy to viscous force
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Prandtl number → Ratio of momentum diffusivity to thermal diffusivities
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Reynolds number → Ratio of inertia force to viscous force.
