# Which cheap metal would absorb and radiate heat well?

## Main Question or Discussion Point

I'm working on a solar heated pump project and require and suitable metal ..that'll absorb as well as radiate heat well. It should should also be cheap to use .

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fresh_42
Mentor
What's wrong with iron?

ZapperZ
Staff Emeritus
And define "cheap".

Zz.

Copper for sure, but silver would be better, yet far more spendy. Copper is used in heat exchangers everywhere, and is usually used with aluminum fins to reduce cost. I think copper has the highest heat transfer to cost ratio, and can also be purchased as a foil in hardware stores. Copper is easy to work with as well

I was an air conditioning technitian.

Copper for sure, but silver would be better, yet far more spendy. Copper is used in heat exchangers everywhere, and is usually used with aluminum fins to reduce cost. I think copper has the highest heat transfer to cost ratio, and can also be purchased as a foil in hardware stores. Copper is easy to work with as well

I was an air conditioning technitian.
I think you misunderstand his question.
Copper and silver certainly have a high thermal conductivity but like most metals pretty poor radiative properties.

I think you misunderstand his question.
Copper and silver certainly have a high thermal conductivity but like most metals pretty poor radiative properties.
you should do a wiki search of "infrared heater", then scroll down till you see "elements", which should give you an answer as complete as any you would find on here.

Nidum
Gold Member
Black anodised Aluminium .

I think you misunderstand his question.
Copper and silver certainly have a high thermal conductivity but like most metals pretty poor radiative properties.
this exerpt came from wikipedia

"Metal wire heating elements first appeared in the 1920s. These elements consist of wire made from chromel. Chromel is made from nickel and chrome and it is also known as nichrome. This wire was then coiled into a spiral and wrapped around a ceramic body. When heated to high temperatures it forms a protective layer of https://en.wikipedia.org/w/index.php?title=Chromium-oxide&action=edit&redlink=1 [Broken] which protects the wire from burning and corrosion, this also causes the element to glow."
Black anodised Aluminium .
BAA seems to be cheap and easily purchased online. Shipping might be pricy depending on how much you need.

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Thanks for all your help..I'm trying to build a kind of tank for my pumping device that can be made using a low cost metal.The metal should also have a quick absorbing and radiating property of heat. I've thought about painting the tank black from in as well as out to increase its absorbing and radiating property. I've taken Aluminium as an option , but thinking of anything much better and easily available at low cost. So that the surface of my tank absorbs the sun's heat and radiates it to the air inside so that the air gets heated and it expands.

this exerpt came from wikipedia

"Metal wire heating elements first appeared in the 1920s. These elements consist of wire made from chromel. Chromel is made from nickel and chrome and it is also known as nichrome. This wire was then coiled into a spiral and wrapped around a ceramic body. When heated to high temperatures it forms a protective layer of https://en.wikipedia.org/w/index.php?title=Chromium-oxide&action=edit&redlink=1 [Broken] which protects the wire from burning and corrosion, this also causes the element to glow."

BAA seems to be cheap and easily purchased online. Shipping might be pricy depending on how much you need.
I need this metal in large quantity to mould a cylindrical tank for my project.

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This the the look of my project..and I need a metal to make that tank to absorb heat from sun and radiate it to the air in the tank so that the air expands down the two pipes

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What's wrong with iron?
Using Iron will lead to corrosion..

fresh_42
Mentor
Using Iron will lead to corrosion..
Not with a suitable paint. If you want to paint it black anyway you could use one that prevents it from corrosion.

Not with a suitable paint. If you want to paint it black anyway you could use one that prevents it from corrosion.
Good Idea ..But when I create my tank using Iron ..it'll be easy to paint and maintain the non corrosive black painting from outside..but the inner side of the airtight tank can be painted only once and if the non corrosive layer is anyhow removed by water there will be no way to fix it..Rather using aluminium will be much more efficient I think because ..in case of aluminium reacting with water will lead to formation of a Non corrosive layer of aluminium oxide which will stop further corrosion or reaction

berkeman
Mentor
This the the look of my project..and I need a metal to make that tank to absorb heat from sun and radiate it to the air in the tank so that the air expands down the two pipes
That does not look like it will work... Where is your pump?

That does not look like it will work... Where is your pump?
I am only guessing about this but maybe he plans to use the temperature differences between day and night, to pump the water.
The expansion during the day would force air out and the contraction during the night would suck water up.
In that case one pipe would be suffiecient so i am not quite sure why there is a second one and if i am perfectly honest it would be a very inefficient idea.
To get a extremely rough estimate how much water you can pump per day(ignoring the height you have to pump it up which will probably ruin everything)
you can use a form of the ideal gas law.
$\frac{PV}{T}=constant$ and from that follows that you could pump up $(1-\frac{T_low}{T_high})$ of the volume of the container per temperature change(day).
And that under the assumption that you don't have to pump it up.

If the water was 3 meters down that type of pump would never even get a milliliter of water up.

You need a material with high heat conductivity, and then a surface treatment that promotes radiation emissivity. For example, emission is proportional to surface area (obviously) so the proper surface roughening improves emissivity. Scratches with a dimension of the wavelength of infrared radiation will do for a start.
Check NASA tech and applications briefs. This is an old problem they solved long ago.