Quote:
Originally Posted by gasman
I haven't found an example where it has been tried with the purpose of reducing drag, so the results don't really apply (they didn't measure what I needed measured... at least that I could find publicly).
If I'm right, though, it might be a moot point. It would be a pretty involved install (cutting a big hole in the firewall and other obstructions, making it water-tight, keeping the ducting out of the way, etc.).
man I wish I had access to a wind tunnel...
I just might have to build one of these (low-speed wind tunnel, courtesy of NASA)... I checked it out and I have everything except the plexiglass and fan... and I can just adapt a computer power supply and computer fans to go in place of that... hmmm...  |
Since you've done HVAC work,let me throw some at you in HVAC terms:
* At 60 mph,a vehicle of 22 sq-ft frontal area( typical mid-size car ) is displacing 116,160 cubic feet per mile,or,116,160 cfm.
* From your ASHRAE Manual it should indicate that to avoid unacceptable duct friction losses for the 'air handler' velocities should be kept below 1,200 fpm.
* If you were to shunt all the vehicles air through your duct at 1,200 fpm it would require a throat size of 96.8 sq-ft,or 9.838 on a side for a square duct or 11.1 ft dia. round duct.This is obviously larger than the vehicle itself.
* If you make the duct smaller to accommodate seats,passengers,engine,powertrain,etc.,the duct losses would be larger.