F/S Titanium Chunk

[dr-ebert]

THATS BECAUSE IT DISSIPATES HEAT TOO QUICKLY TO BE USED AS A HEAT CONDUCTOR!!!!!

I'm sorry, that's just plain unadulterated nonsense.

Of the links, the 1st is just talk of uninformed people, the other two are ads. The third one just has "Titanium" in the name and doesn't even mention any allured superior thermal qualities.

Heat conductivity tells you how much energy is transported through a piece of material per unit time and temperature difference (the area and thickness also play a role, which is why there is a "meter" in the unit of the constant as well - area divided by length). You've got a high temperature at one end and a low one at the other, and you want heat transported away from the hot end as quickly and efficiently as possible. That's why you want high heat conductivity.

As the heat is transferred into your heat sink, it heats up. That means the temp difference to the hot end decreases, and that means the energy transport decreases as well, as the conductivity is proportional to the temp difference. A material with a high heat capacity heats up slowly if you pump a given amount of energy into it, compared to a material with a low heat capacity. So you want a high heat capacity.

In handbooks, the heat capacity is usually the specific heat capacity which is per mass unit. For heat sinks, the capacity per volume is more important, so you multiply with the density of the material, so you want a high density material.

Best is a combination of high heat conductivity and high heat capacity and high density.

The heat capacity per volume is about the same for copper and brass, for aluminium and titanium it's about 20-25% lower, not a big difference. So it's heat conductivity ALONE which determines quality for a heatsink.

In that respect, copper is very good; aluminium is about 60% of copper, brass (Aixiz modules) is only 1/3 of copper (and 1/2 of aluminium), and titanium is MUCH worse: only 1/17th of copper, 1/10 of aluminium.

Take a quote from the first link:

hahaha ... nope .. it cools so fast that if you heat one end and your hand on the other end .. before the heat gets to you already cool to the touch liao .. of course if you dumb enough to heat the same place where your hands are .. then no bet lor ..

Apart from the fact that this hardly sounds like an expert witness, the explanation is wrong. If you heat one end of a Ti rod and touch the other, the other end will feel cool not because the heat is "dissipated away"; it's because it spreads only very sluggishly. Try touching the part you heated! It will feel very hot at first. Then it will appear to cool quickly, again not because the heat is "dissipated", but because the energy from the (still hot) interior will be released (transported) only slowly to the surface. In that respect, it acts like wood.

So.... thermal conductivity, and thermal conductivity only, is what you should be looking for.

 

[dr-ebert]

[quote author=AdamR link=1240970566/0#14 date=1241034095]Just curious but if copper is so good at heat conductivity, why aren't we seeing more lasers using it in heatsinks? or is copper expensive?

it's very expensive.
Click on the link in my signature that says "copperhead".[/quote]
Actually a one-meter rod of electrolytic (pure) copper with 20mm diameter can be had for about $30; this can be turned into about 40 heatsinks. So the price for the material is of minor importance. I understand it is more difficult to shape (harder than aluminium, though much softer than iron).

 

[Eku]

Lol wut?

All I want to know is this better then alu. ;D

 

[dr-ebert]

Executive summary: NO.

 

[laser83]

[quote author=lordoflasers link=1240970566/0#22 date=1241037552]THATS BECAUSE IT DISSIPATES HEAT TOO QUICKLY TO BE USED AS A HEAT CONDUCTOR!!!!!

I'm sorry, that's just plain unadulterated nonsense.

Of the links, the 1st is just talk of uninformed people, the other two are ads. The third one just has "Titanium" in the name and doesn't even mention any allured superior thermal qualities.

Heat conductivity tells you how much energy is transported through a piece of material per unit time and temperature difference (the area and thickness also play a role, which is why there is a "meter" in the unit of the constant as well - area divided by length). You've got a high temperature at one end and a low one at the other, and you want heat transported away from the hot end as quickly and efficiently as possible. That's why you want high heat conductivity.

As the heat is transferred into your heat sink, it heats up. That means the temp difference to the hot end decreases, and that means the energy transport decreases as well, as the conductivity is proportional to the temp difference. A material with a high heat capacity heats up slowly if you pump a given amount of energy into it, compared to a material with a low heat capacity. So you want a high heat capacity.

In handbooks, the heat capacity is usually the specific heat capacity which is per mass unit. For heat sinks, the capacity per volume is more important, so you multiply with the density of the material, so you want a high density material.

Best is a combination of high heat conductivity and high heat capacity and high density.

The heat capacity per volume is about the same for copper and brass, for aluminium and titanium it's about 20-25% lower, not a big difference. So it's heat conductivity ALONE which determines quality for a heatsink.

In that respect, copper is very good; aluminium is about 60% of copper, brass (Aixiz modules) is only 1/3 of copper (and 1/2 of aluminium), and titanium is MUCH worse: only 1/17th of copper, 1/10 of aluminium.

Take a quote from the first link:

hahaha ... nope .. it cools so fast that if you heat one end and your hand on the other end .. before the heat gets to you already cool to the touch liao .. of course if you dumb enough to heat the same place where your hands are .. then no bet lor ..

Apart from the fact that this hardly sounds like an expert witness, the explanation is wrong. If you heat one end of a Ti rod and touch the other, the other end will feel cool not because the heat is "dissipated away"; it's because it spreads only very sluggishly. Try touching the part you heated! It will feel very hot at first. Then it will appear to cool quickly, again not because the heat is "dissipated", but because the energy from the (still hot) interior will be released (transported) only slowly to the surface. In that respect, it acts like wood.

So.... thermal conductivity, and thermal conductivity only, is what you should be looking for.[/quote]

Very informative, thanks. More posts like this and I might start thinking you have an actual Ph.D.  

As to lord of lasers, did you buy a piece from ebay and drill a hole in it? Piece of titanium for sale on ebay :-?  Great to put on the name of any golf clubs granted, as people think it's some "super metal" and will pay extra.

whats a kryton :-?

You seriously don't know? Just the name of a host that is made out of aluminum alloy. Do a search, I'm telling you to do a search too amusing.  
Here's what one looks like.

 

[Tech_Junkie]

[quote author=John Lawson link=1240970566/20#20 date=1241036239]whats a kryton :-?

You seriously don't know? Just the name of a host that is made out of aluminum alloy. Do a search, I'm telling you to do a search too amusing.  
Here's what one looks like.[/quote]

Its more amusing that you actually believed him ;D ;D ;D ;D ;D

 

[laser83]

[quote author=laser83 link=1240970566/20#36 date=1241104803][quote author=John Lawson link=1240970566/20#20 date=1241036239]whats a kryton :-?

You seriously don't know? Just the name of a host that is made out of aluminum alloy. Do a search, I'm telling you to do a search too amusing.  
Here's what one looks like.[/quote]

Its more amusing that you actually believed him  ;D ;D ;D ;D ;D

[/quote]

Enjoy it while it lasts buddy...     Got me good there I'll give you that. John owes me an RPL for this joke, does that sound fair?  ;D I bet now he doesn't know what an "RPL" is either.  ;D

 

[Tech_Junkie]

Enjoy it while it lasts buddy...

What does that mean? ;D Its a joke man, lighten up. Throw one back at me..it will make you feel better.

 

[laser83]

[quote author=laser83 link=1240970566/20#38 date=1241106783]Enjoy it while it lasts buddy...

What does that mean? ;D Its a joke man, lighten up. Throw one back at me..it will make you feel better. [/quote]

I just meant you only caught me offguard while I'm still a semi-newb I was kidding too that's why I put this wink.

I was pretending I was angry, the wink was so you would know it's a joke. It can be tricky to make humor clear in writing even with the emoticons.

Just thinking I have a half dollar sized 99% silver bullion coin (non-historical) that could be made into a heatsink, wonder how much more efficient that would be?

 

[dr-ebert]

The numbers are on Wikipedia. Heat capacity per volume is similar to Al (~20% lower than Cu), Heat conductivity is the best of all metals but still only 5-10% better than Cu (different sources have different values). Not really worthwhile...

Also take into account that improving your heatsink will have diminishing returns. You can't improve the heat transport from the diode through the diode mount into the heatsink.

 

[Bionic-Badger]

Lord of lasers, your links are of very questionable authority.

The first is some link to a blog post (i.e. very low credibility) where some guy is ranting about the ability of titanium to heatsink based on anecdotal "evidence" which could be explained by other things (i.e. no heat ever made it into the titanium to begin with).

The second link is some truncated press release about some hard drive enclosure, using some titanium alloy. Though it mentions a little bit about heat dissipation, most of the use of the titanium is to make the enclosure light. Why it would be any better than enclosures of other materials--which don't need fans either--is not explained at all.

The third link is to some RAM modules with some "titanium mirrored XTC heatspreaders" which really don't explain anything in why the titanium in it does anything at all. More than likely it was used just to make a "titanium" brand of memory that sounded cool, and maybe the material is strong as well.

These "citations" are dubious at best. A quick search of other literature on the web related to titanium used for heatsinking turned up nothing. Most uses of titanium in thermal applications are related to its low corrosivity in such systems as well as its strength.

The material facts also do not add up, since titanium has a very low thermal conductivity (essential for removing heat), and a low heat capacity. The basic idea behind a heatsink is to remove heat as quickly as possible from the target device, and once that is accomplished get rid of the heat into some other medium (like air). Since air has such a low thermal conductivity, you want a high surface area to improve overall head conduction. The heatsink featured in this BST post is just a big round piece of metal, hardly suited towards dissipating heat into the air, even if the material it was made from was a decent conductor to begin with.