Actual Cubic Feet Per Minute
Actual cubic foot per minute (ACFM) is the volume of gas flowing anywhere in a system, independent of its temperature and pressure. If the system were moving a gas at exactly the "standard" condition, then ACFM would equal SCFM. Unfortunately, this usually is not the case as the most important change between these two definitions is the pressure. To move a gas, a positive pressure or a vacuum must be created. When positive pressure is applied to a standard cubic foot of gas, it is compressed. When a vacuum is applied to a standard cubic foot of gas, it expands. The volume of gas after it is pressurized or rarefied is referred to as its "actual" volume.
SCF and ACF for any gas are related in accordance with the combined gas law:
Defining standard conditions by the subscript 1 and actual conditions by the subscript 2, then:
where is in absolute pressure units and is in absolute temperature units (i.e., either kelvins or degrees Rankine).
To be very precise when the gas is air, then the above equation should include correcting for the difference between the relative humidity of the air at the standard and the actual temperature and pressure conditions. In most cases of engineering design, the humidity correction for air is often quite small and hence often ignored.
Read more about this topic: Standard Cubic Feet Per Minute
Famous quotes containing the words actual, cubic, feet and/or minute:
“The true thrift is always to spend on the higher plane; to invest and invest, with keener avarice, that he may spend in spiritual creation, and not in augmenting animal existence. Nor is the man enriched, in repeating the old experiments of animal sensation; nor unless through new powers and ascending pleasures he knows himself by the actual experience of higher good to be already on the way to the highest.”
—Ralph Waldo Emerson (1803–1882)
“Mining today is an affair of mathematics, of finance, of the latest in engineering skill. Cautious men behind polished desks in San Francisco figure out in advance the amount of metal to a cubic yard, the number of yards washed a day, the cost of each operation. They have no need of grubstakes.”
—Merle Colby, U.S. public relief program (1935-1943)
“I embrace the common, I explore and sit at the feet of the familiar, the low. Give me insight into to-day, and you may have the antique and future worlds.”
—Ralph Waldo Emerson (1803–1882)
“For what but eye and ear silence the mind
With the minute particulars of mankind?”
—William Butler Yeats (1865–1939)