Question

Water (Prandtl number =6) flows over a flat plate which is heated over the entire length. Which one of the following relationship between the hydrodynamic boundary layer thickness $\left(\delta \right)$ and thermal boundary layer thickness $\left({\delta }_t\right)$ is true

• A.
  ${\delta }_t=\delta$
• B.
  ${\delta }_t<\delta$
• C.
  ${\delta }_t>\delta$
• D.
  Can not be predicted

Answer 1

The correct option is B

${\delta }_t<\delta$
Given, Pr = 6

$\Rightarrow \frac{\delta }{{\delta }_t}$$=P{r}^{1/3}=(6{)}^{1/3}=1.82$

Hence $\delta >{\delta }_t$