Looking for heatsinks

[StirCrazy]

Originally Posted by DiverDude

Have you tried pricing solid aluminum plate -say, 1/2" thick ? You could make fins 1/4" deep in that with a table saw quite easily.

would be cheaper ordering from the US I think

a heat sink is not as much about mass as people think, here is a def "A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid."

a heat sink actually works on surface area not mass, the more surface area the more heat transfer. if you rely on mass then you will adsorb a lot of heat into the material but you won't be able to give it up fast enough and eventually the actual heat sink will get to hot. the fins are to increase the surface area so it can dissipate the heat faster than it builds up. fans can compensate for lower surface area, and increase efficiency as the rate of heat transfer is also a function of the difference in temp between the two mediums.

a hollow square tube 1.25 x 1.25 will disperse more heat than a solid 1.25 x 1.25 bar, because it has twice the surface area, this can even be increased further by supply fresh air with a fan which is increasing the flow over the surface also keeping the air at the surface cooler and increasing the rate of transfer.

the main reason we want to go with the single sided finned aluminum is looks. it is much easier to make it look good, but if you have some kind of enclosure in mine or are retro fitting into a hood then the square tube will work better as it will have a continuous supply of fresh air, where a fin type would be subject to the hood temp unless you vented you're hood with big fans.

the best place in Canada to find single sided finned AL, depends on where you are.. there is a couple companies in van that will bring it in.. probably charge you an arm or a leg though. same as Edmonton ect.. if you are in between like me and don't have the time or money to travel to look for it then you are stuck with metal recyclers, I have both here going to call me when they get what I am looking for in. they had some but it was double sided and I don't have a milling machine to make it single sided yet.

Steve

[DiverDude]

Originally Posted by StirCrazy

a heat sink actually works on surface area not mass, the more surface area the more heat transfer.

Yes !

But notice I said THERMAL mass. Think of it like thermal capacitance or heat capacity. In the end though, you are correct -it's about the transfer from one medium to the other. You can actually have a very small and light heat sink but at some point, as the thermal mass decreases, you'll need a fan. Whereas with a more thermally (and to an extent, physically) massive heat sink, you may get away without the fan.

[StirCrazy]

Originally Posted by DiverDude

Yes !

But notice I said THERMAL mass. Think of it like thermal capacitance or heat capacity.

ok you are using different terms than we used in thermodynamics

for instance heat capacity is how much a material will hold, which is what we don't want in this aplication as we want it to transfer it as fast as it can, not hold it.

and thermal mass is realy a measument to the resistance of temp change.. more specificaly the ability to hold heat and release it slowly, which again we don't want.

what we want is a material that has a high thermal conductivity, which means it passes on heat very easily when there is a temp difference.

so we mean the same thing I guess, but your choice of words confused the issue

Steve