the_constructor wrote:
snip
Can you explain difference between axial and centrifugal etc.

Axial - think boat propeller. Air comes in the front and goes out the back.

http://www.bobstevenson.co.uk/images..._axial_fan.jpg

Where this type comes into its own is when the flow needs to be capable
of being reversed.

Centrifugal - think spin drier. Air comes in at the centre and leaves at
the edge.

http://img.alibaba.com/photo/5054968...ved_Blades.jpg

Where this type comes into its own is when operating against back
pressure, eg a long delivery tube or trunking.


--
Sue