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In Europe, the standard temperature is most commonly defined as 0 °C, but not always. In the United States, the EPA defines standard conditions for volume and volumetric flow as a temperature of 293 K (68 °F) and a pressure of 101.3 kilopascals (29.92 in. Hg), [1] although various industry users may use definitions from 60 °F to 78 °F.
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.
An actual volume can be converted to a standard volume using the following equation: [6] [7] V s = V a × F p × F t × (F pv) 2. Where, V s: standard volume V a: actual volume (sometimes shown as V r for registered volume) F p: pressure factor (sometimes shown as P m for pressure multiplier)
For example, such a regulation might limit the concentration of NOx to 55 ppmv in a dry combustion exhaust gas corrected to 3 volume percent O 2. As another example, a regulation might limit the concentration of particulate matter to 0.1 grain per standard cubic foot (i.e., scf) of dry exhaust gas corrected to 12 volume percent CO 2.
Note that the m³ gas conversion factor takes into account a difference in the standard temperature base for measurement of gas volumes in metric and imperial units. The standard temperature for metric measurement is 15 degrees Celsius (i.e. 59 degrees Fahrenheit) while for English measurement the standard temperature is 60 °F.
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
CFM is an often confusing term because it has no single definition that applies to all instances. In the most basic sense, CFM means cubic feet per minute. Sounds simple enough right? Unfortunately, air is a compressible gas. To further confuse the issue, a centrifugal fan is a constant CFM device or a constant volume device.
Volumetric flow rate is defined by the limit [3] = ˙ = =, that is, the flow of volume of fluid V through a surface per unit time t.. Since this is only the time derivative of volume, a scalar quantity, the volumetric flow rate is also a scalar quantity.