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# Condensate from stack

## Condensate from stack

(OP)
Hello all,

I am looking for a way to calculate the amount of condensation formed in the air discharge stack. There will be two air streams exiting the stack:

1) 20,000 ACFM, 137F, Saturated, 3' Diameter Duct
2) 40,000 ACFM, 162F, 50% RH, 3.5' Diameter Duct

For calculation purposes I want to consider the minimum ambient temperature to be 41F.

After mixing the air continues for 50' before exiting the stack, the stack diameter is 6'6".

Any points in the right direction would be helpful, I am having a difficulty incorporating the time in the stack into the equation as it very brief.

Best,

Danny B

### RE: Condensate from stack

(OP)
Ok so my Heat & Mass teacher would be embarrassed at my previous question, I found the necessary information using Nusselt Equations for Heat Transfer to Fluids with Phase Change.

However if anyone has a more practical rule of thumb for stack condensation I would love to hear about it.

Also we realized that the Pollution control company butchered the stack design by adding the two inlet duct circumferences together to determine the duct diameter rather than calculating it based on velocity. So the exit velocity is only 30 ft/sec (9 m/s) which is very low compared to the 22 m/s that I have been reading about. Any comments about this would also be helpful.

Thanks,

Danny B

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