Vacuum - Expanded Air Ratio
Converting standard air volume flow to actual air volume flow
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Standard air volume flow - SCFM - can be converted to actual air volume flow - ACFM - with the expanded air ratio equation
EAR = (30 / P) ((T + 460) / 520) (1)
where
EAR = ACFM / SCFM = expanded air ratio - ratio between actual air volume flow - ACFM - and standard air volume flow - SCFM
P = absolute vacuum pressure (inches Hg) where 29.92 inches Hg is normal atmospheric pressure and 0 inches Hg is absolute vacuum
T = temperature (oF)
Actual air volume flow can be calculated by multiplying standard air volume with the expanded air ratio.
Expanded air ratios for temperatures 60oF (15.5oC) are indicated in the diagram below:
The diagram above can be used to calculate air flow in SI-units where
- actual air flow - al/s
- standard air flow - sl/s
The relation between vacuum in % and other pressure units are indicated in
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Related Topics
- Gas and Compressed Air - Gas properties, capacities of pipelines, sizing of relief valves - air, LNG, LPG and more
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Related Documents
- Vacuum - Vacuum is defined as air pressure below atmospheric pressure
- Vacuum - Evacuation Time - Vacuum pumps - calculating flow rate and required evacuation time
- Vacuum Pipes - Velocities - Vacuum pipes - air velocity diagrams
- Vacuum Pressure - Converting Units - Vacuum converting units - % vacuum - mm Mercury - psi - torr - micron - kPa
- Vacuum and Flow Measurement - Measuring volume flow in vacuum
