Project ForgeHeat Transfer
Convection
GATE 2015
Hard
Air (3m/s) flows perpendicular to a pipe (outer diameter 6cm, surface 100°C, air far-field 30°C). ν=18×10⁻⁶m²/s, k=0.03 W/m·K, Nu=hd/k=0.024Re^0.8. The rate of heat loss per unit length (W/m), rounded to 1 decimal place, is
251 W/m(± 6 accepted)
Explanation
Re=3×0.06/18×10⁻⁶=10000. Nu=0.024×10000^0.8=0.024×1584.9=38.04. h=Nu·k/d=38.04×0.03/0.06=19.02 W/m²K. Q/L=h·πd·ΔT=19.02×π×0.06×70=251.0 W/m.
Source: GATE CH 2015 (2015)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.