Question $4$

The company which you work for has developed a novel tubular reactor.

which has a bespoke $($irregular$)$ geometry to enhance internal mixing. You

have been asked to analyse the velocity and pressure profile within this

reactor.

$($i$)$ Describe ${?}^x($without actually having to carry out any calculations$)$ the

step by step procedure which you would use to carry out the above

task, demonstrating your knowledge of the Navier Stokes equations

and how these may be applied numerically to such irregular

geometries.

A $1\mathrm{.}8m$ diameter tank of standard geometry is to be used as a fermentation

vessel. The vessel will contain liquid to a depth of $1\mathrm{.}8m$ and the contents are

to be agitated using a $0\mathrm{.}6m$ diameter disk turbine impeller with a rotational

speed of $3rps.$ Air is to be admitted to the liquid through a sparger located

beneath the impeller. It may be assumed that the liquid contains cells, cell

products, nutrients and electrolytes.

$($ii$)$ Estimate the maximum allowable air flowrate for the proposed system

$($iii$)$ For a working air flowrate equal to $30\%$ of the value in $($ii$)$ above

calculate the expected gas holdup and the interfacial area.

$($iv$)$ Show that the effects of liquid composition are significant in this

application.

$**$ Please note that the use or description of commercial software

packages$/$approaches is not considered a valid response to part $($i$).$ Please

demonstrate your engineering knowledge of how this may be achieved using

first principles.

DATA:

Appropriate correlations are available.

Liquid Properties:

Density

$,1080k\frac{g}{m^3}$

Viscosity

Surface tension

$,0\mathrm{.}0015N\frac{s}{m^2}$

$,0\mathrm{.}054\frac{N}{m}$

Air Properties

Viscosity

Viscosity

$1\mathrm{.}8{10}^{-5}N\frac{s}{m^2}$