Air Flow Measurement Formula

Air changes per hour abbreviated acph or ach or air change rate is a measure of the air volume added to or removed from a space normally a room or house divided by the volume of the space.

Air flow measurement formula.

25 cfm for 1 5 inches 3 8 cm 35 cfm for 2 inches 5 1 cm 48 cfm for 2 5 inches 6 4 cm cfm stands for cubic feet per minute which is how airflow is measured. Normally we do not have an online density measurement. The air flow in cfm is 6 128 ft min air flow in cfm q flow velocity in feet per minute v x duct cross sectional area a air flow in cfm q 3 468 ft min x 1 77 ft 6 128 cfm. Consult factory for your specific condition.

Volume flow is usually measured in cubic feet per minute cfm. This is also inaccurate for extremely low flow or elevated pressure. The average air velocity is then multiplied by the area of the duct in square feet. The answer to this formula is airflow in cfm.

Orifice meters require pressure temperature compensation formula when we use them to measure steam or gas flow in pipes with variable operating pressure and temperature. Pressure temperature compensation flow measurement formula. Cfm duct area sq ft x velocity standard air 70f 29 92 hg mercury 1 cubic foot of standard air 0 075 pounds 13 3 cubic feet of standard air 1 pound. If you have any questions about this procedure please call your bapi representative.

By multiplying air velocity by the cross section area of a duct you can determine the air volume flowing past a point in the duct per unit of time. Volume flow is usually measured in cubic feet per minute cfm. Of course there are a host of conditions that must be met in order for the traverse to be accurate. Multiply the flowrate indicated on the meter by the correction factor.

This will equal an approximation of the flowrate of the gas being used. This correction factor is only accurate within 10. The default calculation involves air passing through a medium sized orifice in a 4 pipe with answers rounded to 3 significant figures. To calculate the flowrate of a fluid passing through an orifice plate enter the parameters below.

By multiplying air velocity by the cross section area of a duct you can determine the air volume flowing past a point in the duct per unit of time. Measure how far in inches the card swings inward to get a sense of the fan s airflow.