Project ForgeHeat Transfer
Convection
GATE 2012
Medium
If the Nusselt number (Nu) for heat transfer in a pipe varies with Reynolds number (Re) as Nu∝Re^0.8, then for constant average velocity in the pipe, the heat transfer coefficient varies with the pipe diameter D as
- AD⁻¹·⁸
- D⁻⁰·²
- CD⁰·²
- DD¹·⁸
Explanation
Nu=hD/k∝Re^0.8. Since Re=ρVD/μ, at constant V, Re∝D, so Nu∝D^0.8. Then hD/k∝D^0.8 ⟹ h∝D^(0.8−1)=D^(−0.2).
Source: GATE CH 2012 (2012)
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