https://www.energyvanguard.com/blog/fermi-problems-blower-doors-and-the-compressibility-of-air/ Building science knowledge, HVAC design, & fun Tue, 31 Aug 2021 00:59:11 +0000 hourly 1 https://wordpress.org/?v=6.6.2 https://www.energyvanguard.com/blog/fermi-problems-blower-doors-and-the-compressibility-of-air/#comment-7304 Wed, 09 Jul 2014 17:01:01 +0000 http://energyvanguard.flywheelsites.com/?blog_post=fermi-problems-blower-doors-and-the-compressibility-of-air#comment-7304 Bob S.:
Bob S.: Indeed, that’s one of the principles of good HVAC design. You want the air to come out of the supply vent with enough speed to have good throw. Then you get good mixing of air in the room. But you’ve got to get it just right. Use a wooden grille and you may reduce the air flow too much. ACCA’s Manual T describes the process of doing that correctly.  
 
The physics behind the principle you cite, by the way, is called the continuity equation and is stated mathematically as: 
 
A x v = constant 
 
or  
 
A1 x v1 = A2 x v2 
 
When you increase the area that a fluid flows through, the velocity decreases and vice versa.

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