James Murrays site had some good articles about chimneys
Try here - http://www.onland.info/cgi-bin/mt/mt-search.cgi?tag=chimney&blog_id=1
Its quite detailed as it is really for producing accurate constructional drawings, but still maybe useful to you.
If it's just for a simple chimney effect, try using the niche library part, along with a few multi-storey walls as the actual chimney flue/breast/stack.
Thanks. Just to say that i'm a newbie to AC11 and just trying to complete some academic work. So its only the effect that i'm after rather than any detailed drawings.