# Using 4awg wire as a "heat pipe" to a heatsink



## mds82 (Jun 26, 2013)

Hi All, Been doing some thinking about a way to attach a heatsink remotely from a LED fixture. the LED Fixture is in a very small space with limited room for a heatsink. I was wondering if its possible to attach a 4awg stranded wire like the one below to the LED and the other end to a heatsink. Of course the LED would be on a MCPCB , attached to a copper plate, with the wire soldered to the copper plate. 

I can handle all the logisitics of making sure all the connections are proper between everything. I just want to know if a 4awg or even 2awg wire would conduct enough heat. I would be looking to only go 6-10 inches with the wire.


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## bshanahan14rulz (Jun 26, 2013)

Test it and see  As a random thought, I wonder how well it'd work as a heatsink if you soldered one end to the copper plate and then opened up the other end and started unstranding all the bundles and strands? 

I once had a micro build where I used an amc7135 regulator chip. No board, just the chip floating between the two wires with the appropriate connections. I filled the rest of teh space I had with some insulated solid core copper wire, and soldered the middle of it to the tab on the regulator for a bit of extra thermal mass. So, in my use I was using it to hold heat that would otherwise just build up in the tab of the tiny chip. Your use would be transporting much more heat from one place to another.


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## mds82 (Jun 26, 2013)

I'm thinking it should work. 2 awg wire is almost 0.25 inches in diameter so that should be able to conduct enough heat. I will be running roughly 10-20 watts of LED's so ye it is a decent amount of heat.


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## Steve K (Jun 26, 2013)

solder to 4AWG wire? How big is your soldering iron??
I think it might be easier to clamp to the wire, honestly.


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## DIWdiver (Jun 26, 2013)

Nope. 

A pure copper solid rod 1/4" diameter by 10" long conducting 10W axially would develop a 157K temperature differential from end to end. Assuming your cold end is 25C, that would be 182C at the junction to the star. 

A true heat pipe could get that down quite a lot.


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## sn0wBLiND (Jun 26, 2013)

Why not use a proper thermal solution, something like Amec Thermasol: 
http://www.amecthermasol.co.uk/product412.php?url=1&page=282&ty=30&gr=30&fg=148

Thickness is about the same as the MCPCB, length up to 500mm.


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## Optical Inferno (Jun 27, 2013)

You could always do the flip flop, and use a large core plastic fiber optic to pipe the beam where you need it to be. Most fiber optic lighting guys usually have end fixtures that work with the fiber to produce beam patterns.


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## mds82 (Jun 27, 2013)

DIWdiver said:


> Nope.
> 
> A pure copper solid rod 1/4" diameter by 10" long conducting 10W axially would develop a 157K temperature differential from end to end. Assuming your cold end is 25C, that would be 182C at the junction to the star.
> 
> A true heat pipe could get that down quite a lot.



Unfortunately i need soemthing that is quite flexible and a solid heat pipe wouldnt be a viable option. Also just wondering how you came up with that equation? 



Optical Inferno said:


> You could always do the flip flop, and use a large core plastic fiber optic to pipe the beam where you need it to be. Most fiber optic lighting guys usually have end fixtures that work with the fiber to produce beam patterns.



That would be wonderful, however it woulnt be cost effective to make something like that. It might be something i look into though..


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## jason 77 (Jun 27, 2013)

mds82 said:


> Unfortunately i need soemthing that is quite flexible and a solid heat pipe wouldnt be a viable option. Also just wondering how you came up with that equation?
> 
> 
> 
> That would be wonderful, however it woulnt be cost effective to make something like that. It might be something i look into though..



I don't know what your budget is but have you looked into liquid cooling, try searching "Aluminum Cooling Block F CPU" on ebay. They have a lot of the pieces, cooling block, radiator, pumps for not too much money?


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## mds82 (Jun 27, 2013)

Small budget. I'm actually looking to mass product a product so cost is one of the largest factors. Thats why i was thinking using a 2 or even 0 awg wire because the cost is little to nothing on that.


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## DIWdiver (Jun 27, 2013)

mds82 said:


> Unfortunately i need soemthing that is quite flexible and a solid heat pipe wouldnt be a viable option. Also just wondering how you came up with that equation?


 

A well-known formula from thermodynamics, completely analogous to the voltage equation from electronics:
dT = rho * P *l/A, where 

dT is temperature differential across a uniform body, 

rho is thermal resistivity, 1/conductivity, 

P is power input, 

l (lower case "L") is the length of the thermal path, 

A is the cross sectional area of the thermal path. 

I know the conductivity of copper is 400W/m-K, so I converted 1/4" to 0.0063 meters, 10" to 0.25m, and get: 

dT = 0.0025 m-K/W * 10W * 0.25m/(0.0063m)^2 = 157K


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## 127.0.0.1 (Jun 27, 2013)

stranded wire has too much air gap between strands, traps heat, useless as a sink unless fanned out like a mushroom


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## hellokitty[hk] (Jun 28, 2013)

Right a solid bar of copper is not too bad.


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## mds82 (Jun 28, 2013)

THanks all for the feedback. DIWdiver - thanks for that calculation. the only thing that would really make sense is a .3-.4 inch thcik bar at 4 inches or so. I dont think i'd be able to get a solid bar in there, so there goes that idea.


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## Epsilon (Jun 28, 2013)

Why not buy a heatpipe? I can buy them for around 15euro a piece. 10cm long 6mm thick (4in long 0.25thick). 

0.3K/W over those 10cm. 

Link:
http://www.conrad.nl/ce/nl/product/180985


Edit: sorry, missed the part that is has to be flexible .


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## Ken_McE (Jul 2, 2013)

I believe it is worth hooking one up just to see.


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