CFM to MPH????
Posted 20 August 2007 - 04:29 PM
this is a bit of a strange question but this is my last place to turn.
Ok High output fans or any fan really is measured by CFM (Cubic feet ,Minute)
Ok now what i am interested in is how to convert a fans CFM to actual WINDSPEED MPH
I am sure some variables would include the following.
Size of Area, Resistance, CFM, and possibly other things.
But is there a way to calculate this or is that something that is just impossible. and i would just have to build a wind tunnel and run a fan with X CFM coming out of it in a specific area and then measure windspeed.
i would hope not, i would like to think that is a way to mathmatically figure it out
thanks for anyone here who can help with this,
And what the basis of this question is for is wind tunnel testing.
THanks for your time and reading this post and hopefully and informative answer.
Posted 20 August 2007 - 04:41 PM
i assume you can do basic unit conversion. change cubic feet per minute into cubic miles per hour and area into square miles and plug them into the equation. numbers are going to be horrible. but thats the imperial system for you.
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Posted 20 August 2007 - 05:05 PM
Say you have a box fan 4 foot square that puts out 21120 CFM. 21120/4 means that in each square foot there are 5280 CFM or that each individual cubic foot travels 5280 feet per minute. 5280 * 60 is 316,800 feet per hour which is 60 MPH...
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Posted 21 August 2007 - 12:36 PM
<?php $cfm = 1900; $length = 30; $width = 10; $height = 10; $minute_seconds = 60; $hour = 60; $mile = 5280; $squarefoot = $length * $width * $height; echo "<br> total cfm = $cfm <br>"; echo " <br> square foot $squarefoot<br>"; $minute_air_speed = $squarefoot / $cfm; // per minute air speed echo " <br> minute aire speed: $minute_air_speed <br>"; $feet_per_second = $minute_seconds / $minute_air_speed; $mph = ($mile / ($minute_air_speed * $hour)); echo " <br> feet per second: $feet_per_second <br>"; echo " <br> MPH= $mph "; ?>
the above script will produce this following output
total cfm = 1900
square foot 3000
minute aire speed: 1.5789473684211
feet per second: 38
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