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Orifice airflow

From the cross sectional area of an opening, calculate the airflow from the pressure drop across it.

An example application would be a fan cooled enclosure. From the fan's flow rate vs pressure curve, adjust the pressure drop until the calculated flow rate matches the fan's specification.

Once you have found the flow rate, you can plug the value into the temperature rise calculator: LINK

Be sure to use the correct units and change the default values if necessary:

Orifice area:                 mm²

Flow coefficient:           Cd, default is for a square hole in a thin flat panel - what is this?

Pressure drop:              Pascal (Pa) Note: 1 mbar = 100 Pa

Air temperature:           ºC

Relative humidity:         %

Atmospheric pressure:  millibar


Note 1: This calculator does not check that the conditions entered are valid for air in it's gaseous state. At very low temperature & high pressure, air may be liquified, in which case the result returned may not be valid. At normal atmospheric pressure, air liquifies at approximately -196ºC

Note 2: Water vapour reduces the density of air, which at first may seem counter intuitive. It's because the molecular mass of water at 18g/mol is less than that for dry air; 29g/mol. The water vapour molecules displace the air molecules, reducing the overall density.