Question

For a fluid with a Prandtl Number of 1000.0, the hydrodynamic layer is thinner than the thermal boundary layers. a) True b) False

Answer 1

(b)False

Step-by-step explanation:

Given:

Prandtl number(Pr) =1000.

We know that
`Pr=(\\u )/(\alpha )`

Where
`\\u` is the molecular diffusivity of momentum

`\alpha` is the molecular diffusivity of heat.

Prandtl number(Pr) can also be defined as

`Pr=\left ((\delta )/(\delta _t)\right )^3`

Where
`\delta` is the hydrodynamic boundary layer thickness and
`\delta_t` is the thermal boundary layer thickness.

So if Pr>1 then hydrodynamic boundary layer thickness will be greater than thermal boundary layer thickness.

In given question Pr>1 so hydrodynamic boundary layer thickness will be greater than thermal boundary layer thickness.

So hydrodynamic layer will be thicker than the thermal boundary layer.