The pressure difference between inlet and outlet of commercial size slot plug and velocity of gas at outlet have been measured in laboratory. It is obtained that the drag coefficient of plug is approximately equal to 44/Re
the flow condition is laminar flow
the drag coefficient is function of Reynolds number which is unconcerned to roughness factor
and the resistance loss on the way is in proportion to velocity of gas at outlet. Therefore the resistance loss could be calculated to determine the pressure of gas at inlet of plug. With application in industry as pressure difference of blowing argon is moderate
the drag coefficient of slot plug is approximately equal to 0. 07.