Question

For a hydrodynamically and thermally fully developed laminar flow through a circular pipe of constant cross section, the Nusselt number at constant wall heat flux $\left(N{u}_q\right)$ and that at constant wall temperature $\left(N{u}_T\right)$ are related as

• A.
  $N{u}_q=N{u}_T$
• B.
  $N{u}_q<N{u}_T$
• C.
  $N{u}_q>N{u}_T$
• D.
  $N{u}_q=(N{u}_T{)}^2$

Answer 1

The correct option is C

$N{u}_q>N{u}_T$
For fully developed laminar flow through pipes, Nusselt number value corresponding to uniform heat flux is $\mathrm{4.36.}$

Nusselt number value corresponding to uniform wall temperature is $3.66$

Hence, $N{u}_q>N{u}_T$