Stack draught fluid calculations / design

[spacebeer13]

Hi,

I would like to perform some fluid calculations for a stack design and i would like to hear some opinions about my own calculations.
I've started from scrath, therefore as a start for this thread i would like you to comment my attachment with a simple natural convection situation, where i made a formula deduction to calculate the draught, based in bernouli's equation.

Hope to hear some opinions!

 

[davefitz]

The calculation is detailed in the B+W book "Steam " 41st edition page 25-6, simplified to SE( inch wc)=Z*(Da-Dg)/5.2 where Z= stack height, Da= air density, Dg= fluegas density. It becomes an issue on units that use a wet scribber, as the scrubber exhaust temp is only marginally hotter than ambient air. That situation makes is difficult to meet NFPA purge requirements following a trip of the fans.

"Whom the gods would destroy, they first make mad "