I need to estimate the dP when a gas exits a header and flows through 3/4" TOL.  This is for a very low-pressure gas sparger assembly.  How much error do you think I'll introduce if I calculate the dp across the TOL by assuming it's a sharp-edged orifice and use the usual procedure for an orifice, e.g. the procedure in Crane TP410?  Or would I be better off just assuming it's a sharp-edged pipe exit with a very short length of straight pipe?  I know this sounds like hair-splitting but the design of this sparger is critical (and expensive since it's made from 316L).

Thanks in advance for any help, comments, ideas, cat-calls, etc.

Thanks!
Pete