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What sheds heat better


Gromit
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My radiator is in for a re-core at the moment. It's getting a copper core. The guy was chatting about the rising cost of copper, due to the Chinese motor industry apparently. I didn't know that many rads are now ali, which is cheaper.

So, out of curiosity, given 2 equal rads, which will get the heat out of the water quicker? Copper or Aluminium?

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pretty sure it is copper. *

so why are radiators now may of aluminium? I had the answer to this but most likely it is cost and by redesigning the radiator, it still will shift the heat required for the given engine.

* quick googles say that is so; silver is the only common metal that is better.

note you say "given 2 equal rads" - the design of copper cored rads is different to ali; so without knowing the ins and aout, you may find that an alumimium type radaitor made from copper may not be as good as an aluminium one.

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Hmmm, how about a radiator made from Diamond?

List borrowed from wikipedia.org

Material ↓ k, [k] = W/(m*K) ↓

Air 0.025

Alcohol or oil 0.15

Aluminium 237

Copper 401

Gold 318

Lead 35.3

Silver 429

Cork 0.05

Diamond 900 – 2320

Glass 1.1

Rubber 0.16

Sandstone 2.4

Soil 0.15

Stainless steel 15

Thermal grease 0.7 – 3

Wood 0.04 – 0.4

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I would have thought diamond would be a great insulator. Intuitively, this doesn't make any sense to me!

Yes, diamond is an amazing thermal conductor.

I saw an interesting experiment - A thin disc of synthetic diamond if held between 2 fingers, can cut through an ice cube like its butter. because it conducts the body heat so well.

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My initial answer to the thread question was - timber ones !

But then I read the thread.

Hoss - Just out of interest, do you know if synthetic diamond has the same thermal conductivity as pure diamond ? If so, could synthetic diamond be used in say electronics applications to conduct heat away ?

Adrian.

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Diamond is strange - usually, thermal conductivity and electrical conductivity are closely related (both dependent on 'free electrons') but diamond is a good electrical insulator while being an excellent thermal conductor - I don't remember why. I don't see radiators being made out of it for a while though ;) Also don't forget that for water-to-air heat exchange, convection efficiency is important too.

do you know if synthetic diamond has the same thermal conductivity as pure diamond ? If so, could synthetic diamond be used in say electronics applications to conduct heat away ?

Diamond is already used in mounts for semiconductor laser chips among other applications - not sure if it's typically synthetic or natural though.

small sheds heat better - with a big fire in them.

Very good - reminds me of a crossword clue I saw once - something like 'illuminate the outbuilding?' (= 'shed light on') :D

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Copper will be better at conducting the heat - however it is not a significat factor in the efficiency of the radiator.

The rate at which heat is transferred from the water to the rad and from the rad to the air is far more significant.

I doubt you would be able to tell the difference between the two in operation - and the Ali one is lighter - so that would be my choice.

Si

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The rate at which heat is transferred from the water to the rad and from the rad to the air is far more significant.

Is this rate not determined by the conductivity of the radiator material though?

or do you mean that the design of the rad (in terms of water/rad and rad/air surface area etc.) is more significant?

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Is this rate not determined by the conductivity of the radiator material though?

or do you mean that the design of the rad (in terms of water/rad and rad/air surface area etc.) is more significant?

It is, but the transfer of heat between a surface and air is very poor. It therefore does not make very much difference what it's made from so long as the rate it can conduct the heat between it's two surfaces is greater than the rate it can dissipate the heat into the air. It's like having a constriction in a pipe. The flow through the pipe is determined more by the constriction than the rest of the pipe so long as the constriction is significantly smaller than the pipe.

This is why radiators have a large surface area where it is in contact with air but a smaller area in contact with water.

Si

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I understood that copper is the better conductor of heat, and would make a substantially better radiator than Ali. However, the copper core is attached to the copper fins with lead solder, and it's the lead that's a poor conductor of heat and lets the whole system down, meaning overall, the Ali radiators are more efficient conductors.

Paul :)

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Here we go, found the article that I referred to earlier. As usual, it is some stuff off the web that may or may not be true but seems reasonable going by the trend of using aluminium instead of copper (still reckon cost is a big factor too).

While it is true that brass and copper radiators offer thermal conductivity advantages over aluminium radiators, they are limited to a maximum coolant tube diameter of 5/8 to ¾ inch.

Since brass and copper are very soft, larger tubes cannot handle the pressure. Aluminium radiators, can be built with tubes up to 1-½ inches in diameter. The larger tubes allow the radiator manufacturer to place more fins-per-inch, which improves the radiator’s thermal efficiency. That reduces the hickness (and weight) of the radiator and also improves airflow through the radiator.

For example, an aluminum radiator with two rows of 1-½-inch coolant tubes is probably more efficient than a four-row brass/copper radiator. Not only would the brass/copper radiator be heavier, but its added thickness would present a more restrictive path for the air to travel, especially at low vehicle and engine speeds.

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Isn't copper a better conductor of heat...and aluminium is a better dissipator...ie it cools down quicker.

I have an Aluminium Radiator in my 130 and noticed an immediate benifit over the old copper one...apart from the price...1000 quid verses 200. (it's the man hours required to tig the thing together that puts the prices up)

It's lighter too.

I'm told that strength wise the ali rad is better because the copper braized components aren't as strong as the tig welded aluminium ones.

Our boy Mark Powell (Desert Dog) would know better...he works for Serck Services out here...they make them on a daily basis.

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Copper rads cool things down alot better but going from many reports from the renault turbo lads they also block up alot quicker as the copper corrodes inside the rad and then you start to get problems.

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you can get ali rads capable of overcooling a chevy 5.7 V8 for cricuit racing from Summit for around the £110 mark+ VAT and shipping. A much cheaper option than recoring a range rover item and has a lot more cooling too. a 4000cfm leccy fan with shroud to cover the whole of the rad was around the same price.

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Copper rads cool things down alot better but going from many reports from the renault turbo lads they also block up alot quicker as the copper corrodes inside the rad and then you start to get problems.

Never heard that one, surely the corrosion inhibitors in anti-freeze stop that sort of thing? I've not had a rad fail due to gunk inside it, usually due to damage from outside.

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Huge Yank racing company- very well known in racing and modding circles as they seem to stock just about everything at a good price- often appear on overhaulin' (if you watch it)

web adress is http://www.summitracing.com/ and they are happy to ship to the UK- the website is easy to use ONCE you've got the hang of it. Best to make international orders by credit card over the phone as the website doesn't seem to like international internet orders!

Have had 2 or 3 orders off them and the parts have been correct, well packaged and well looked after every time. They sent me a free baseball cap too last time so you can't say fairer than that.

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