On the Discharge Coefficient of Orifice Meter for Plastic Fluids

Abstract

The discharge coefficient of orifice meter in a commercial 1/2" gas pipe for plastic fluid was calculated and C vs. Re diagrams were drawn.
The concentrations of sludge tested were 4.1, 10.8, 15.0, 17.5, 23.1, 26.6, 31.2, in wt. % and the ratios of the orifice areas to the sectional area of the pipe were 0.096, 0.247, 0.348, 0.467, 0.652.
The results of the experiments were as follows:
(1) The limits of the concentration for measurable flow rates are,
m=0.247, up to 31wt.% or more. m=0.467, up to 26wt.%
m=0.348, up to 31wt.% m=0.652, up to 17wt.%
(2) The drag coefficient C increases rapidly when Reynolds number Re is less than 10⁴, and after having reached maximum value, it decreases as Re decreases.
The more the value of m becomes the greater is the value of C_max., and tbe steeper is the slope of the curve.
(3) The more the concentration of sludge becomes the smaller is the value of Re at the point where C reaches maximum.
(4) When m is constant, C approaches a constant regardless of concentrations of sludge within the range for Re>2×10⁴.