Dr of BBQ
I've seen a lot of 12 volt exhaust fans on street vendor carts here, they use old car radiator fans, hooked up to a 12 V battery, anyway here's a couple links that may help.
Do you know how to use the math in the formula? If so can you engineer all that needs done to figure the protective cone that BAB is trying to build?Or is it your impression that it's no big deal?
Here's a second formula for calculating the capture air velocity that is used in the first. http://www.engineeringtoo...ust-outlet-d_1008.html
With the known CAV you can then enter the other variables in the first calculation I referenced.
Here are some references to designing hoods, one big thing you need to consider is the make up air. Take a look at the following links and pdf's. They explain in some detail about how to feed make up air into the area.
Think of make up air as the air that you take out with your hood has to be replaced with makeup air, and how that air is supplied to the area is very important.
As far as your cone is concerned I don't think I'd worry too much about it as the temps are probably not high enough to worry about. More important is how your grease filtering works to insure the air leaving thru the hood has most of the grease filtered out already.
When you design your fan into the plenum I'd make it a modular type unit that you can just slide out of a slot in the plenum sort of like a drawer. That way you don't have to take the world apart to replace a fan. http://www.google.com/url...4YEA3CY5K77NC6bqSjyvng http://www.google.com/url...xdlyO_Y2Poq2r3ZqcaJOXQ http://www.energy.ca.gov
Kosonen Risto, Mustakallio PanuAnalysis of Capture and Containment Efficiency of a Ventilated Ceiling.
Reading engineering documents can be quite boring or make you look up a lot of terms and associated data, but its all in the realm of learning something new.
I'll try and help with questions, I'm no hvac expert, but we've got experience in doing simpler type designs. I believe in learn by doing so dig into this and other sources on the web, theres a vast amount of information out there, just takes some time to find it.
I'm in and out and away from my time on forums quite a bit so if I don't get back to someone its because I'm tied up and away from these sites.
Hope this helps