Coefficient for air flow through a hole (in a duct)

[carlosgw]

Anyone have any data for holes in ducts?
For example say a duct with -.25" and a 1" diameter hole. What would the air flow be?

 

[willard3]

You will have to give better data if you want an answer.

What is the pressure inside and outside the duct?

What is the air temperature inside and outside the duct?