I doubt that's a significant factor in this application. You have a large surface area, coated with paint, and then transferring heat to air. So I strongly suspect the difference in the thermal resistance of steel vs alli is negligible compared with the other thermal resistances in the heat path.
Worth paying extra aluminium radiators?
- Thread starter bobgroups123
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My only experience of ally rads is leaks at the badley corroded valve connections. The rate of heat transfer is faster through ally than steel even with it's thicker profile. This means a smaller rad can do the same job.the flow rate will be the same if sized correctly. If you have limited space this could be useful but you can get steel triple panel rads. I would not pay the extra or take a gamble in my own house.
I find that very hard to believe. Do you have evidence?
You could do a heat loss calc for a room as a comparison. Any vessel rad or room made from a material with a higher conductivity rate will pass heat more quickly if the temperature within is greater than the temperature externally. If the rate of transfer is faster it's surface can be smaller. Ie a small conservatory losses more heat than an ordinary room of the same size. glass is a better conductor than brick. Qed.
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i think you'll find that the limiting factor is the surface-air interface - that's why they go to such lengths to increase the surface area with multiple panels and lots of fins. if the thermal resistance of the casing was a significant factor, then we would have rads where the surface temp was significantly below that of the water inside, but I don't belive that is normally the case.
Blimey there is some waffle here.
Once a red is hot, it matters not a shlt what its made if. The amount/rate of heat convected into the room is a product of surface area and difference between surface and air temperature.
The difference in heat up rate of the read between Ali and steel will so small as to be laughable.
Once a red is hot, it matters not a shlt what its made if. The amount/rate of heat convected into the room is a product of surface area and difference between surface and air temperature.
The difference in heat up rate of the read between Ali and steel will so small as to be laughable.
Aly rads maximise their surface area with fins similar to steel rads. don't have time a working but look up the heat out put of a steel v an aluminium rad. Would be a to know.
I did look up the ones mentioned, and found the output to be fairly similar to that of a similar sized steel rad. If they have better finning, and hence higher output for a given size, then that's a matter of the extra surface area rather than a difference in thermal conductivity of the metal.
Better finning due to complex shaped that can be cast rather than pressed from sheet is likely to be the major differentiator.
Better finning due to complex shaped that can be cast rather than pressed from sheet is likely to be the major differentiator.
I value of steel is 50 w/m2 per degree c aluminium is 160. If the rate of heat transfer is not a factor we needn't do heat loss calculations.
that'll be a "no" then.
The values are expressed as relation ship of energy per m2 per degree centigrade therefore 1m2 steel at sets t 60 = 50 Watts. Compared to 1m2 of aluminium = 160 Watts
The values are expressed as relation ship of energy per m2 per degree centigrade therefore 1m2 steel at delta t 60 = 60 x 50 Watts. Compared to 1m2 of aluminium = 60 x 160 .Watts. The relation ship is always 3 x greater per m2.
I find that very hard to believe. Do you have evidence?
or did you mean 1% smaller or something?
You have of course considered the heat transference from rad to air, as well as from water to rad.
1/UA=1/h1A1+dxw/KA+1/h2 A2
u= w/m2 I aluminium = 160 and steel = 50
A = m2
K = w/mk steel 16_24 aly 205_250
h= w/m2k water 500_10000 air 10_100
dxw = wall thickness m
Try working it out. This is the formula do calculating the heat transfer through a heat exchanger or radiator.
u= w/m2 I aluminium = 160 and steel = 50
A = m2
K = w/mk steel 16_24 aly 205_250
h= w/m2k water 500_10000 air 10_100
dxw = wall thickness m
Try working it out. This is the formula do calculating the heat transfer through a heat exchanger or radiator.
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