please clarify me this points?

[bloch2006]

hi friends:

i have got room its flow rate of air is: 21.562 cfm
i want install exhaust fan and door grille what is the flow rate of exhaust fan i must installed and the dimention of door grille?

if i want install supply fan is there size will be equal exhaust fan or bigger if this in what percent?

i want install duct system for garage what is suitable material and duct shape for this application : round or square)

any articles i will be appressiate

best regards

 

[johnp]

Keep your life simple - you will never be able to measure 0.562 cfm - so call it 22 cfm close enough.

What comes in must go out. If you want 22 cfm to go in, you need a fan which can handle 22 cfm. That is a tiny domestic baby.

The door grille should be sized on about 400 fpm. That makes a hole about 3 inch square. You will just about get that in leaks around the door, or by undercutting the bottom of the door by about a quarter of an inch.

For this amount of ducting you can use any material - steel, plastic, plumbing fittings - whatever you can find in a hardware store. Round is great. There is no advantage going for rectangular.

Propeller fans don't like a lot of pressure. Talk to your fan supplier and ask for advice. I doubt if you are looking at more that one inch pressure loss in your ducting.

 

[LSA]

JohnP has summed it up pretty well.
However, in my opinion...I dont know what good it will do to ventilate 22cfm in a garage. I would consider increasing the amount to 50cfm. The undercut of the door can still support 50 cfm of transfer air from the adjacent space.

for this small exhaust system...use 4" flexible ducting. This will be cheapest. (similar to the dryer vent duct).