Calculating ductwork air leaks

[LvCoug]

I'm trying to find a formula to calculate air leakage INTO a flue gas duct prior to our induced draft fan on a biofuel power boiler.

The conditions are as follows:

- Sucking air at atm pressure and temp
- Pressure inside the duct will be vacuum (up to - 15" H20)

We have some significant leaks and are seeing impacts to steaming rate due to the extra volume of air that the fan is having to move. We are fan limited due to the leaks.

Just for kicks, I want to run a calc using a 2" hole. I can scale up from there for larger (or multiple) leaks. I'm looking to be able to calculate this so I can present to management what we're actually losing through these leaks.

 

[STYMIEDPIPER]

You may consider posting in 'Local Exhaust Ventilation' forum since the response to your inquiry reuires determination of capture velocity and/or slot velocity.

 

[quark]

Blank off after the portion where you feel you have leakage and run the blower. Check cfm at fan suction. You can approximately calculate the leakrate from SMACNA formulae but they are valid upto 10" static.