how to calculate air flow in CFM through a half inch opening pipe & assuming a constant pressure of 6 bar?

i have to claculate air flown through an half inch opening pipe for 1 minute assuming the compressed air pressure to be constant as 6 bar ?
i have checked the air flow rate for complete plant : Q=1075 Nm3/hour
please help me with it..do i need any additional data...??
my email id : kautya_kc@yahoo.co.in

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Bill says...

Thanks so much for writing in.

You may want to look at this page on air flow through an orifice.

Good Luck!

Bill