1. Expressed as inlet volume
This expression method is usually measured with an aperture meter on the air inlet side. At present, it is only used to mark the size of centrifugal air compressor. Icfm is used as the unit, but the internal loss is not included, so it is still higher than the actual air outlet.
2. Free air delivery (f.a.d for short) is used
The so-called free air outlet volume refers to the air volume compressed by the compressor, which is expressed by the free air (normal) condition (temperature, pressure, humidity, etc.) of the air inlet. That is, the volume flow representation commonly used today.
Note: the volume flow value of the air compressor does not come from the value directly measured at the exhaust port, but is converted to one of the following states after measuring the exhaust volume value
I. standard status:
Pressure (P) 1atm (101325pa), temperature (T) 0 ℃, humidity (RH) 0%.
When the volumetric flow is calculated and converted to this intake state, the unit is nm / min.
II. Reference status:
Pressure (P) 1atm (101325pa), temperature (T) 20 ℃, humidity (RH) 0%, expression method: scfm
When calculating the volumetric flow and converting it to this intake state, the unit is m ³/ min。
The reference state, also known as the specified state, is specified by national standards. In the United States, Britain, Australia and other English speaking countries, t = 15 ℃, Europe, Japan t = 0 ℃, China t = 20 ℃, but in the field of civil gas, t = 0 ℃.
III. actual situation:
Pressure (P) 14.4psi, temperature (T) 35 ℃, humidity (RH) 60%, expression method: ACFM, icfm.
If the exhaust volume of the same air compressor is marked according to the above three standards, the value is: standard state < reference state < actual state.