In article <1kv4peu.1vkvc9kwwc1sN%alan@darkroom.+.com>,
alan@darkroom.+.com (A.Lee) writes:
> <
orion....@virgin.net> wrote:
>
>> Anyone know if this format is as efficient as the conventional,
>> rectangular one?
>
> Define efficiency?
Precisely.
The only definition I can think of which makes any sense is heat
transfer into the room versus size of the radiator, in which case
which dimension are you interested in being minimised (width,
height, thickness)?
Working from most efficient (on this basis) to least...
Most efficient will be fanned units, if you count them as
radiators - they can be made very many times smaller for
the same heat output, and hidden in kickspaces.
Next will be regular finned utility radiators. When I looked at
the datasheets 12 years back when I installed mine, for a given
surface area of the front, a taller one has higher output than a
wider one, which I presume is due to a longer chimney effect
drawing a larger airflow over the panels/fins.
Obviously, single panel, 1.5 panel, double panel, triple panel
increase output for any given front surface area, but that depends
how you feel about radiator thickness.
After these come radiators with integral side panels and top grills,
which slightly reduce the output for any given size.
Unfinned radiators come next.
Finally, designer radiators are the least efficient of all, with
the metalic finishes (e.g. chromed) being the worst of all, but
this is often made up for by designer radiators being much bigger
anyway, partly from a style point of view, but also because they
would otherwise be completely useless.
> All radiators come with a BTU (or similar) rating, so they will put out
> that amount of heat, whether they are horizontal or vertical.
When comparing data sheets, make sure you are comparing outputs
at the same rated delt-T, and also note that these figures are
almost never based on ideal condensing boiler operating conditions,
which you should compensate for by oversizing if you want the best
_system_ efficiency.
> Where that heat goes is different though. A radiator low down is likely
> to heat up a room more than one that touches the ceiling, as heat rises,
> it'll warm the room as it rises, one that is high up will warm the
> ceiling a lot more, and the room above it.
They're normally placed near the floor, but I've seen instructions
that say they should be no closer to the finished floor level (e.g
top of the carpet) than the horizontal distance from the wall to the
front face, or that gap will reduce airflow through them.
Most radiator mounting brackets have two mounting positions for
spacing the radaitor near or far from the wall. I would assume the
far from wall setting would be marginally better, but never seen
any figures.
There's also a technique one manufacturer is trying with double
panel radiators, where the water first circulates through the
front panel, and is then transferred to the rear panel. The idea
here is to generate more radiative heat from the front (facing
into the room) than from the rear (facing the wall). Part of
the claim here is that with a cooler wall behind, less heat will
be lost out through the wall.