[neilep (OP)]

Dearest Radiatorlogists and those studying radiatorology.

As a sheepy I of course luff radiators. radiators are my all time favourite metal panel wally things that have oil or water and radiate heat !...hey !!....what a coincidence with them being called RADIATors eh ?...I bet when the bloke who invented them called them that he did not realise the coincidental implications to the nature of their radiance practicalities !


look, here's a radiator.


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A radiator.

Now , following on from CZARCAR's thread here


Can ewe tell me why most radiators are white ?...I have seen yellow and green and blue ones too !...so why the other colour choices ?...also..would it be silly to have a black radiator ?.....Surely a black radiator would get just as hot and that heat would have to be radiated yes ? *guffaws at the name coincidence again*..*le sigh*  []


So whajafink ?


Why Are Most Radiators White ?


huggy kuggy


mwah mwah



Neil
Please do respond about radiate
Elucidate and Elaborate
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[MikeS]

Strikes me radiators are usually white as that is the normal colour of radiator paint.  I guess they would radiate more efficiently if painted black but would look awful.  Possibly the colour has little effect as central heating radiators operate at low temperatures and give off most of their heat through convection and not radiation.  Perhaps they should be called convectionators?

[CZARCAR]

maybe the white results in a more even heating of the radiator?

[Geezer]

A lot of the heat is directly coupled into the surrounding air by conduction. The heated air rises and circulates around the room by convection. I don't know what the ratio between radiation and conduction is, but I suspect most of the heat is removed by conduction. Same thing with the "radiator" in your car. Should it really be called a "conductor"?

[grizelda]

Possibly the idea is to alleviate the re-absorption of the room heat by the radiator when it is not carrying heat.

[Geezer]

Possibly the idea is to alleviate the re-absorption of the room heat by the radiator when it is not carrying heat.

Interesting idea, but you'd have to run really cold water through the radiator to remove much heat from the room. If the water is not flowing, there is nowhere for the heat to go.

[Airthumbs]

I painted one of the conductors brown in room number 6.   []

[neilep (OP)]

Strikes me radiators are usually white as that is the normal colour of radiator paint.  I guess they would radiate more efficiently if painted black but would look awful.  Possibly the colour has little effect as central heating radiators operate at low temperatures and give off most of their heat through convection and not radiation.  Perhaps they should be called convectionators?

Thanks MikeS. So, the colour makes little difference. Though, to call them convectionators would have an impact on the nomenclaturial labelling on the packaging and thus create the use of more ink and be non eco friendly [] (unless a smaller font would be used which could cause eye strain)  []

[neilep (OP)]

maybe the white results in a more even heating of the radiator?

Well this is what I thought. Thanks CZARCAR...but would another colour* make it truly uneven ?








* Note to self: ewe know 'white' is not a colour.

[neilep (OP)]

Possibly the idea is to alleviate the re-absorption of the room heat by the radiator when it is not carrying heat.

Thanks Grizelda....good thinking !!

[neilep (OP)]

Possibly the idea is to alleviate the re-absorption of the room heat by the radiator when it is not carrying heat.

Interesting idea, but you'd have to run really cold water through the radiator to remove much heat from the room. If the water is not flowing, there is nowhere for the heat to go.

So, if I wanted to..I could turn my lounge into a fridge !    [] Thanks Geezer !

[neilep (OP)]

I painted one of the conductors brown in room number 6.   []

Room 6 eh ?...well done !  []...good job it was not room 5 !..it's important ewe know !  []

[CZARCAR]

maybe the white results in a more even heating of the radiator?

Well this is what I thought. Thanks CZARCAR...but would another colour* make it truly uneven ?








* Note to self: ewe know 'white' is not a colour.

dunno, but water comes in @ 1 end & goes out the other? So I think more even + water prbly flows to rads downsream? Never seen rad like yours but it looks like 2 heated panels with a hole in the middle for convection? if so white would keep the surface facing the room not as hot so u dont burn urself as bad if touched?

[JP]

I checked out my radiators and they're all white, too!  They're the old steam-heat type.  The walls of my apartment are blue in the living room/bedroom, white in the bathroom, and yellow in the kitchen, but the radiators are white throughout.  Weird. 

I agree with Geezer that most of the heating is going to be by conduction/convection, so color isn't a big deal.  The thickness of the paint could be a factor--if you have a really thick layer of paint it will insulate your radiator a bit and make it less efficient, so you don't want to layer on too much.  But the effects of black/white paint on the thermal radiation from a normal radiator is going to be minimal--the radiator just isn't hot enough for it to be important.

[Bored chemist]

To a very good approximation, radiators don't radiate.
In particular, since they do not radiate visible light, their colour cannot matter much.
They are generally made of metal (which is quite a good conductor) and filled with flowing water (which has a high heat capacity) so their temperature is fairly even- there's a small drop in temperature between the input and the output. A radiator with a completely even temperature wouldn't be delivering any heat to the room.
People seem to like white, and it's cheap.
Grizelda's suggestion could only make sense if the room was warmer than the radiator.

[Geezer]

You can detect a bit of heat coming off them with the back of your hand. I always thought that was infrared radiation. If it is, there's not much of it.

The old fangled cast iron ones had a large surface area in a relatively compact volume and they could really chuck out the heat! However, in the UK at any rate, they gave way to the sleek, modern, pressed steel variety. I installed some "skirting board" radiators in a house because I hated the appearance of those big steel slabs. They consisted of a copper pipe that had lots of alumium* fins on it inside a natty teak and steel casing (this was in the seventies, so it had to be teak!)

*TNS preferred spelling to avoid transatlantic hostilities

[CZARCAR]

infrared gun thermometer, does the colouur of the surface affect the temp reading?

[JP]

The old fangled cast iron ones had a large surface area in a relatively compact volume and they could really chuck out the heat! However, in the UK at any rate, they gave way to the sleek, modern, pressed steel variety. I installed some "skirting board" radiators in a house because I hated the appearance of those big steel slabs. They consisted of a copper pipe that had lots of alumium* fins on it inside a natty teak and steel casing (this was in the seventies, so it had to be teak!)

The ones in our place now are the cast-iron.  It's an old Victorian-era house.  The ones where I grew up (built in 1985) had those awful copper pipe with fins.  As kids, we'd constantly bend the fins out of shape by falling into the radiators or "accidentally" smashing toys into them. 

One advantage of the fin variety is that it was much harder to burn yourself, whereas my brother managed to get a nasty burn once from a cast-iron radiator.

[JP]

Actually, I'm not convinced radiation isn't important (though the paint color is probably fairly unimportant).  A back-of-the-envelope calculation for a radiator operating at 100 C in a 20 C room shows that it could maximally emit about 680 Watts/m² radiated energy.  That's fairly significant, thought not huge.  It's peak wavelength would be at 7700 nm, which is in the infra red. 

[Geezer]

A back-of-the-envelope calculation for a radiator operating at 100 C in a 20 C room shows that it could maximally emit about 680 Watts/m² radiated energy. 

That seems to be about consistent with my back-of-the-hand measurement  []

If your bro was able to burn himself, those radiators must have been using really hot water, or even steam, like the ones in NYC. We were able to sit on top of the ones in our house in the UK.

I think I know the type of finned baseboard radiator you are referring to. Pretty ugly things, and not at all like the superior Scandinavian designed (did I mention they were enclosed in teak) variety that I installed in our bungalow in Renfrew.