In article , Nick Atty
writes

Currently my thoughts are running to a loop of chrome tube, on chrome
stand-offs, so I end up with about an 8 metre run, with feed at return
at the same end. But the joints are going to have to be compression and
will look a bit nasty with 6 inline couplers as well as the elbows at
the end.

How much heat is this likely to give out?
Will 22mm tube work better than 15mm (greater surface area)?
Can anyone think of anything better at a sensible price?
Or any improvements to the idea?

Here's a heat loss table:
http://www.piping-toolbox.com/copper...oss-15_51.html

You'd need to have 4x15mm pipes to get 500W from the sort of span you
are talking.

An alternative might be to make up some flat panels in metal to act as
heat spreaders with the pipes behind in close (conductive) thermal contact.
Then you might then be able to get about a kW.

As to the fittings I'd be inclined to strip back the chrome at the ends and
use solder fittings, then use a sleeve made of larger diameter chrome pipe
to cover the joint, split & reformed if necessary.
--
fred