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In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, [1] i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in non-dimensional form that relates the Darcy–Weisbach friction factor f D, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.
The key quantities are then the pressure drop along the pipe per unit length, Δp / L , and the volumetric flow rate. The flow rate can be converted to a mean flow velocity V by dividing by the wetted area of the flow (which equals the cross-sectional area of the pipe if the pipe is full of fluid). Pressure has dimensions of energy per ...
For air with a heat capacity ratio =, then =; other gases have in the range 1.09 (e.g. butane) to 1.67 (monatomic gases), so the critical pressure ratio varies in the range < / <, which means that, depending on the gas, choked flow usually occurs when the downstream static pressure drops to below 0.487 to 0.587 times the absolute pressure in ...
h f = head loss in meters (water) over the length of pipe; L = length of pipe in meters; Q = volumetric flow rate, m 3 /s (cubic meters per second) C = pipe roughness coefficient; d = inside pipe diameter, m (meters) Note: pressure drop can be computed from head loss as h f × the unit weight of water (e.g., 9810 N/m 3 at 4 deg C)
The area required to calculate the volumetric flow rate is real or imaginary, flat or curved, either as a cross-sectional area or a surface. The vector area is a combination of the magnitude of the area through which the volume passes through, A , and a unit vector normal to the area, n ^ {\displaystyle {\hat {\mathbf {n} }}} .
The ratio of length to radius of a pipe should be greater than 1/48 of the Reynolds number for the Hagen–Poiseuille law to be valid. [9] If the pipe is too short, the Hagen–Poiseuille equation may result in unphysically high flow rates; the flow is bounded by Bernoulli's principle, under less restrictive conditions, by
For flow in a pipe of diameter D, experimental observations show that for "fully developed" flow, [n 2] laminar flow occurs when Re D < 2300 and turbulent flow occurs when Re D > 2900. [ 15 ] [ 16 ] At the lower end of this range, a continuous turbulent-flow will form, but only at a very long distance from the inlet of the pipe.