Materials with high specific heat?

[cessna7686]

Hi,

I'm looking for materials with as high a specific heat as possible that can be used as a heat sink. They have to be safe to use and not extremely hard to obtain. I know I'm being pretty vague, but can anyone help me out.

[flyboy]

dont quite kno what your asking here....like are u trying to kno which material absorbs heat?

[cessna7686]

yeah, basically. From what I know a material with a high specific heat will be a better heat sink than a material with a lower specific heat. I'm just wondering what you all think the best materials to use are.

[flyboy]

a material with a black coating or somthing on it

the color black absorbs heat but im sure not sure about materials

[labview1958]

I thought copper is normally used as a heat sink?

[[Tycho?]]

Water has a very high heat capacity, the highest of any substance I know of, and definately the highest of a substance you'll be able to get easily.

[DQW]

cessna : You are much better off describing (in as much detail as possible) your application, and allowing the solutions to evolve out of discussion. You seem to think that you know all there is to know about the required parameters for optimal heat-sink design - and maybe you do. But let me warn you that this is not a trivial problem. The specific heat is not the only parameter. I speak from a little bit of experience in heat-sink design.

 

Another important parameter (besides the heat capacity) is often the thermal conductivity - especially if the power dissipated by the device (being heat-sunk) is highly time-varying. Then there's geometric and other considerations.

 

Yes, copper is often used for heat-sinking, thanks to its excellent thermal conductivity and not terrible heat capacity. Aluminum is also very popular, due to its high specific heat capacity, good thermal conductivity and high strength-to-weight ratio.

 

In general, the specific heat capacity of a metal goes inversely with its molar mass - thanks to Dulong and Petit. Hence, the lighter metals like Mg, Al, Be, B, Li, etc. have a high specific heat capacity.

[labview1958]

"Yes, copper is often used for heat-sinking, thanks to its excellent thermal conductivity and not terrible heat capacity"

 

Is heat capacity more useful as a heat sink then heat conductivity? If heat conductivity is high the heat will immediately be dissipated elsewhere in the equipment. On the other hand if heat capacity is high it will absorb more heat.

[Evangelante]

You could also use alumnium from alumnium cans. I'm too much of an improviser though.

Is heat capacity more useful as a heat sink then heat conductivity? If heat conductivity is high the heat will immediately be dissipated elsewhere in the equipment. On the other hand if heat capacity is high it will absorb more heat.

When a heat sink is on a CPU you don't want the heat capacity to rise and accumulate. That would only fry the CPU. Instead, you want the heat to dissipate with a conductor to throw the heat around in different places.

[DQW]

Is heat capacity more useful as a heat sink then heat conductivity? If heat conductivity is high the heat will immediately be dissipated elsewhere in the equipment. On the other hand if heat capacity is high it will absorb more heat.

There is no universal answer to that question. It depends on the situation.

 

If you have a high heat capacity © but lousy conductivity (K), then your heat sink will not get very warm over the long term, but over short time-scales, parts of the heat-sink can get very hot (because it is incapable of dispersing the heat within itself). On the other hand, if it has a high K and very low C, then it will quickly disperse small amounts of heat but over the long term, will get hotter faster than it loses heat (convectively or radiatively).

 

But then again, it is important to also keep in mind how the heat-sink is made to lose heat to the surroundings, and designing this into the scheme (under some set of constraints) is part of the process.