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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.
To further confuse the issue, a centrifugal fan is a constant CFM device or a constant volume device. This means that, provided the fan speed remains constant, a centrifugal fan will pump a constant volume of air. This is not the same as pumping a constant mass of air. Again, the fan will pump the same volume, though not mass, at any other air ...
An air flow meter is a device similar to an anemometer that measures air flow, i.e. how much air is flowing through a tube. It does not measure the volume of the air passing through the tube, it measures the mass of air flowing through the device per unit time, though Thus air flow meters are simply an application of mass flow meters for the ...
Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
If the unit had no variable geometry, there would be handling problems, because the surge line would be very steep and cross the working line at part-flow. During a slam-acceleration from a mid-throttle setting, the compressor working line will move rapidly towards surge and then slowly approach the steady state operating point, further up the map.
This means that the air velocity in a system is the same even though mass flow rate through the fan is not. See also Standard conditions for temperature and pressure; Standard cubic foot; MMSCFD; External links ACFM versus SCFM for ASME AG-1 HEPA Filters; SCFM (Standard CFM) vs. ACFM (Actual CFM) (Specifically for air flows only)
These motors are sometimes called DC motors, sometimes EC motors and occasionally DC/EC motors. DC stands for direct current and EC stands for electronically commutated.. DC motors allow the speed of the fans within a fan coil unit to be controlled by means of a 0-10 Volt input control signal to the motor/s, the transformers and speed switches associated with AC fan coils are not required.
Too bad there is no Cubic Feet per Minute (CFM) article, even though there is a whole article on ACFM. Unfortunately, this ACFM article claims to be the more standard unit, whereas on planet Earth it is CFM that is the standard unit and is used probably over a hundred times to describe product capabilities for 1 time that ACFM is used!