extractor fan air flow increase

[mrmisior]

This is an odd one:

Instead of a standard inline extractor fan, I used a 300mm PC fan.
To adapt to 100mm ducting, I made a box with 100mm inlet and outlet.
The box sits in the loft and takes air from a roof vent via 1.5m of 100mm ducting.
It pumps the air down the house via 6m of 100mm ducting.

Effective air flow is 2 times greater than a standard £80 manrose while I paid £10 for two PC fans
Hence the DIY.

Here is the technical question:

In the aim of increasing the air flow even more, should I install the second fan in parallel or in series (one in front of the other)?

Parallel setup would force me to make twice as large housing.
Series setup seems easier.

Anyone knows the "aerodynamics" of 100mm ducting?

 

[Taylortwocities]

In parallel, or one Fan will damper the other one.

remember, if have a very large air throughput to push air OUT of a room, you must allow at least an equivalent volume of air IN to the room. If you don’t, the fans will be trying to create a vacuum. From the sound of it, you’ll need to saw the bottom 6inches off the bottom of the door!

 

[mrmisior]

In parallel, or one Fan will damper the other one.

remember, if have a very large air throughput to push air OUT of a room, you must allow at least an equivalent volume of air IN to the room. If you don’t, the fans will be trying to create a vacuum. From the sound of it, you’ll need to saw the bottom 6inches off the bottom of the door!

Thank you!
Actually, I never shut the door of this room. I can't open windows as it's a busy road...
Now to make a larger "compression chamber" for 2 fans

I am also wondering if making slopped walls on the outlet side will help?
As on the bottom "drawing" - top throw.

 

[Taylortwocities]

I am also wondering if making slopped walls on the outlet side will help?

It won’t make any difference, the pressure on the output side of the fan will be limited by the size of duct.

 

[mrmisior]

 

[mrmisior]

It won’t make any difference, the pressure on the output side of the fan will be limited by the size of duct.

I see. Thank you very much!

 

[JohnD]

I used a 300mm PC fan

Never seen a PC big enough for a 12" fan.

 

[EFLImpudence]

The heading is extractor fans and then you start talking about blowing air into the house.

Is that what you mean to have?

 

[mrmisior]

Never seen a PC big enough for a 12" fan.

rack server's fans apparently. really shift air but a bit noisy.

 

[mrmisior]

The heading is extractor fans and then you start talking about blowing air into the house.

Is that what you mean to have?

Yes, it works a treat in my home office. Fresh air right from a roof vent.
/edit:
I see, yes I titled 'extractor fan' wrongly. Should have put AHU I guess.
Then again, using 100mm ducts, the only difference is the flow direction, I think.

 

[mrmisior]

Never seen a PC big enough for a 12" fan.

Found a link to a similar one:
http://www.comairrotron.com/content/caravel-cd24b3-19031573a

and woow, >400m3 /h in relation to typical <100m3 of a regular 100mm fan