radiator output formula and finless rad specs
John Stumbles
found a formula which gives a reasonable approximation so one can
calculate output from dimensions (and v.v.)
Heat Output = (Height + 12) * Length * FACTOR
(Watts) (cm) (cm)
where FACTOR is (for Delta-T 50°C)
* 0.13 for SC
* 0.19 for DP
* 0.24 for DC
See
http://wiki.diyfaq.org.uk/index.php?title=Central_Heating_Radiators
It might be useful[1] to be able to calculate the output of old-fashioned
radiators without convection fins. Anyone have any data sheets on these?
[1] or at least, marginally interesting :-)
--
John Stumbles
I'd give my right arm to be ambidextrous
Roger
from John Stumbles <john.s...@ntlworld.com> contains these words:
> It might be useful[1] to be able to calculate the output of old-fashioned
> radiators without convection fins. Anyone have any data sheets on these?
As I mentioned in another thread recently I have some documentation from
Ravensbourne Heating. The older catalogue (which I think dates to the
mid 70s) has data on radiators from Stelrad, Potterton, International,
Harcal and even Finrad. The later catalogue (circa 1988) is a much
thinner affair with Barlo as the only standard radiator offering. Heat
output in both cases is in btus/hour.
To go off on something of a tangent while flicking through some of the
rubbish I have accumulated over the years I came across a leaflet for
the Trisave condensing boiler which, unlike all the other stuff I have
retained, was actually dated - February 1989.
IIRC Trisave was the first condensing boiler on the British market and
was (in retrospect) notoriously unreliable. It was (perhaps thankfully)
no longer available when I came to replace my gas boiler a couple of
years later so I ended up fitting a conventional fanned flue model which
is still working well.
--
Roger Chapman
Roger Mills
John Stumbles <john.s...@ntlworld.com> wrote:
It is certainly useful to be able to estimate the output of existing
(obsolescent) radiators - and the question is often asked here by those who
are re-jigging their central heating systems, or just doing a sanity check
on what they've got.
I don't still have the catalogues which I used back in the late 60's - but I
have still got my calculations, from which I developed my own formula -
having converted from imperial to metric units. The figues which I use - at
a Delta-T of 60 degC are:
Single Panel: 1280 watts/M^2
Double Panel: 2170 watts/M^2
This would equate to 1020 and 1730 respecively at a Delta-T of 50 degC.
This would be 0.102 and 0.173 watts/cm^2 to compare with your 'factors' -
except that my calculations just take the projected area without adding
anything to the height. What is the rationale of your +12 bit?
What sort of radiator is your 'DC'?
--
Cheers,
Roger
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John Stumbles
> This would be 0.102 and 0.173 watts/cm^2 to compare with your 'factors'
> - except that my calculations just take the projected area without
> adding anything to the height. What is the rationale of your +12 bit?
Looking at the Myson & Kudox specs it was apparent that their outputs were
not linearly related to heights, so that a 600mm high rad was less than
twice the output of a 300. I didn't plot the values but I'd guess it's a
curve of some sort. Approximating it to an offset as I've done gives a
pretty good agreement with the published values.
Intuitively it makes sense that doubling the height wouldn't double the
output: since 'radiators' are actually convectors then a greater
quantity of warm air has to come off a taller rad, so I'd expect greater
resistance from the surrounding air.
What sort of heights were the rads you arrived at your figures for?
> What sort of radiator is your 'DC'?
Double Convector - like 2 single convectors sandwiched together. Explained
in the wiki article (tsk!, you haven't read it? :-))
--
John Stumbles
Procrastinate now!
John Stumbles
> As I mentioned in another thread recently I have some documentation from
I recalled such a discussion but couldn't remember anything else about the
thread!
> Ravensbourne Heating. The older catalogue (which I think dates to the
> mid 70s) has data on radiators from Stelrad, Potterton, International,
> Harcal and even Finrad. The later catalogue (circa 1988) is a much
> thinner affair with Barlo as the only standard radiator offering. Heat
> output in both cases is in btus/hour.
Any chance of a scan of some of the specs?
--
John Stumbles
I forgot to take my amnesia medecine again
Roger Mills
John Stumbles <john.s...@ntlworld.com> wrote:
>
> What sort of heights were the rads you arrived at your figures for?
>
They were all either 24" or 30" high.
Looking at some modern catalogues, it looks as if *very* low radiators (e.g.
300 high) punch above their weight in heat output terms but - although I
haven't done the sums in detail - my impression is that, once you get above
a certain height, the output is linear. So my formula probably gives
pessimistic results for low rads.
>> What sort of radiator is your 'DC'?
>
> Double Convector - like 2 single convectors sandwiched together.
> Explained in the wiki article (tsk!, you haven't read it? :-))
Mea Culpa! On reading the Wiki item and looking again at your previous post,
it seems that I misunderstood what you initially said. When you said it
might be useful to calculate the output of old unfinned rads, I initially
thought that you were offering that as the reason for the figures you had
quoted - which I had assumed to apply to unfinned rads. I now realise that
you were suggesting looking at unfinned rads *in_addition* to what you had
quoted. The figures I gave *were* for unfinned.
Having cleared that up, my complete list - with outputs in Watts/M^2 is:
TYPE Output at Delta-T=60
Output at Delta-T=50
Single unfinned 1280
1021
Single finned 2020
1612
Double unfinned 2170
1732
Double with single fins 2790
2226
Double with double fins 3575
2853
Roger
from John Stumbles <john.s...@ntlworld.com> contains these words:
> > As I mentioned in another thread recently I have some documentation from
> I recalled such a discussion but couldn't remember anything else about the
> thread!
> > Ravensbourne Heating. The older catalogue (which I think dates to the
> > mid 70s) has data on radiators from Stelrad, Potterton, International,
> > Harcal and even Finrad. The later catalogue (circa 1988) is a much
> > thinner affair with Barlo as the only standard radiator offering. Heat
> > output in both cases is in btus/hour.
> Any chance of a scan of some of the specs?
I will see what I can do. Is you address genuine?
--
Roger Chapman
John Stumbles
> I will see what I can do. Is you address genuine?
Yup. Just don't put V14GR4 in the subject line ;-)
--
John Stumbles
I'm less competitive than you
Geo
wrote:
>It might be useful[1] to be able to calculate the output of old-fashioned
>radiators without convection fins. Anyone have any data sheets on these?
Sent you an email with a url of some zipped scans on Stelrad units circa 1979
including a couple of graphs.
Geo