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The following table gives flow rate Q such that friction loss per unit length Δp / L (SI kg / m 2 / s 2) is 0.082, 0.245, and 0.816, respectively, for a variety of nominal duct sizes. The three values chosen for friction loss correspond to, in US units inch water column per 100 feet, 0.01, .03, and 0.1.
Round duct is made using a continuous spiral forming machine which can make round duct in nearly any diameter when using the right forming die and to any length to suit, but the most common stock sizes range evenly from 4" to 24" (10-60 cm) with 6"-12" (15-30 cm) being most commonly used. Stock pipe is usually sold in 10' (300 cm) joints.
where the pressure loss per unit length Δp / L (SI units: Pa/m) is a function of: ρ {\displaystyle \rho } , the density of the fluid (kg/m 3 ); D H {\displaystyle D_{H}} , the hydraulic diameter of the pipe (for a pipe of circular section, this equals D ; otherwise D H = 4A/P for a pipe of cross-sectional area A and perimeter P ) (m);
For some usage examples, consider the conversion of 1 SCCM to kg/s of a gas of molecular weight , where is in kg/kmol. Furthermore, consider standard conditions of 101325 Pa and 273.15 K, and assume the gas is an ideal gas (i.e., =).
Rectangular cement plant duct stiffeners are 15 to 20% times duct plate weight. Power plant ductwork is often larger. Power plant ductwork is usually rectangular, with stiffener weights of 50% (or more) times duct plate weight. (this is based on personal experience, and my vary with loads, duct size, and industry standards)
Actual cubic feet per minute (ACFM) is a unit of volumetric flow. It is commonly used by manufacturers of blowers and compressors. [1] This is the actual gas delivery with reference to inlet conditions, whereas cubic foot per minute (CFM) is an unqualified term and should only be used in general and never accepted as a specific definition without explanation.
Typically, mass air flow measurements are expressed in the units of kilograms per second (kg/s) or feet per minute (fpm), which can be converted to volume measurements of cubic metres per second (cumecs) [1] or cubic feet per minute (cfm). [2]
where is in absolute pressure units and is in absolute temperature units (i.e., either kelvins or degrees Rankine). This is only valid when at a pressure and temperature close to standard conditions. For non-ideal gasses (most gasses) a compressibility factor "Z" is introduced to allow for non-ideality. To introduce the compressibility factor ...
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