On Sun, 28 Jan 2007 10:01:56 GMT someone who may be
wrote this:-

Axial fans are cheaper and generally work fine with short ducts with
few bends. Centrifugal fans are more expensive, but work with longer
ducts with bends because they develop higher pressures. Which is
better? It depends on what you want to do.

Getting steam out as quickly as possible!

In long ducts: no question, it has to be centrifugal, but which moves
the most air along a short duct?

Neither. It depends on the design specification. However, for a
given flow rate along a short duct people tend to go for the
cheapest (and neatest if mounted on the surface).

Also note that if you get a fan with integral back draught shutters,
generally the more expensive ones, then the outlet can be a simple
grille.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54