GATE2012-16

If the Nusselt number (Nu) for heat transfer in a pipe varies with Reynolds number (Re) as Nu ${\displaystyle \propto }$ Re$^{0.8}$, then for constant average velocity in the pipe, the heat transfer coefficient varies with the pipe diameter D as
1. D$^{-1.8}$
2. D$^{-0.2}$
3. D$^{0.2}$
4. D$^{1.8}$