Any way of calculating CFM from an inline fan and bends in ducting?

[mallyone]

Just trying to figure out the best way to make a small cabinet with an inline fan venting the cabinet through a carbon filter -> cooltube or vice versa (if that makes sense?). Going through a couple designs in my head and was wondering if there was a simple way of estimating the power loss of the fan if it's vented through a couple bends in the ducting?

m1...

ps. hoping to have just one powerful fan instead of one venting the cooltube and one venting the box.

 

[eLiguL]

Not to my knowledge but if get a fan that is 2x-4x the cubic area of your box you should be good to go.

I have a 3x2x5ft cab with a 50cfm computer fan and 100cfm axial fan, my temps stay between 28-30C.

 

[Guest]

Usually a Manometer(sp) is used to measure/balance supply air in homes, businesses and commercial structures. It would be expensive to acquire the set up. Correctly sizing your inline fan should take care of it, providing you are pulling cool air through it.

TyStik

 

[Guest]

I wouldn't worry too much about the bends, it's the scrubber that's a huge restriction to air flow. Check out my rubbermaid tubs, I have a slick ventilation design that works really well.

 

[darthvapor]

can-fan max has a more streamlined flow which sometimes overcomes bends in venting. Its the next step in fans neat design.

 

[yamaha_1fan]

I have heard that every 90 degree turn reduces air flow by half

 

[Hurk]

Each 90 equals 5' of straight pipe, in the hvac trade anyway

 

[mallyone]

eLiguL:Not to my knowledge but if get a fan that is 2x-4x the cubic area of your box you should be good to go.

Nice way to guestimate cfm's, thanks eLiguL .

Ty-Stik:Usually a Manometer(sp) is used to measure/balance supply air in homes, businesses and commercial structures. It would be expensive to acquire the set up. Correctly sizing your inline fan should take care of it, providing you are pulling cool air through it.

Yeah, that's would be a bit more work than I want to put into the cab . Oversizing the fan is probably the best bet. I just remember something from another site having a kind of rule like yamaha_1fan and Hurk are mentioning. I imagine some trial and error is in my future .

Red-Greenery:I wouldn't worry too much about the bends, it's the scrubber that's a huge restriction to air flow. Check out my rubbermaid tubs, I have a slick ventilation design that works really well.

Thanks for the tip, will check it out Red .

can-fan max has a more streamlined flow which sometimes overcomes bends in venting. Its the next step in fans neat design.

"The ten-inch MAX Fan from Can-Fan is rated at 1050 CFM and designed for any system that requires maximum performance. The in-line MAX Fan is small yet powerful, efficient and quiet. If customers need to move a lot of air, this is their fan."

Sounds more like they are selling a jet engine Looks like the sheer force of that fan should be able to overcome any bends and filters a cabinet would throw at it.

Thanks for the replies everyone, I think I'm just going to go with an inline fan that is overrated for my needs, although can-fan max might be overkill even though the price is on par with fans rated at half the cfm's.

m1...

 

[Guest]

Each 90 equals 5' of straight pipe, in the hvac trade anyway

Now that's good info and very helpful.

I have heard that every 90 degree turn reduces air flow by half

Pretty much what I understand.

Air like water does not want to go around corners. The harder you push the more turbulence you're gonna get. I was initially trained to size a fan that'll provide an air exchange for the space in 2 minutes so theoretically a 4' x 4' x 8' space requires at least a 60 cfm fan. Over the years I've found the more air flow the better if you can maintain temps. Kinds, bends an line length can dramatically reduce fan effectiveness. Using a passive intake requires using an exhaust fan with a bit more oomph IMO.

I've found that 2 minute rule to be ineffective in the summer and have ended up with more like an exchange every minute or better cause I don't air cool my lights like most. I recirculate all the hot air mainly for winter time but also to justify more air flow through the room in the summer.

I've heard that can type filters can reduce air flow up to 30% but that seems a little high based on the systems I've set up.