On Saturday, February 16, 2013 4:01:07 PM UTC, Andrew Gabriel wrote:

Convection forces are very important. The hot water rises instantly in

the first channel, and the rest of the radiator behaves as TBOE, with

the hot water descending uniformly down all the other channels, as it

cools, and remains stratified almost equally across them all. See

http://www.paceplumbing.co.uk/images...r-flushing.png

I'm starting to change my mind on this. That image does seem to show all the hot water (white area) going straight up the first channel. Presumably the waterways are oversized (relative to a pipe) for the flow rate that is going through them.

I'm not wholly convinced since the 'before' picture on that site does not show what I'd expect from a sludged-up radiator. There are numerous thermal images of radiators on the internet, but none as 'black & white' as this one; they've probably chosen an image that best suited their sales patter.

TBOE connections would seem to be a waste of time unless you want the valves high up. The extra heat is probably due to the extra pipe.