Sorry, didn't get what OP was asking the first time around.
Provided there's ample cross sectional area in the tubes, I'd agree with LittleInch; why would there be very much pressure differential at all between the steam admission box and the condensate collection box?
And why steam in the tubes? Is this a vertical unit?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]