Steel or Aluminum?

[ElPresidente408]

From a cooling standpoint, which PC case material would transfer heat the best, a steel or aluminum case? I've asked a few people and they said aluminum, but then I found this site click here and saw that steel has have the specific heat of aluminum, making it better for cooling. Am I right? Some people are insisting that aluminum is better for cooling but I think that is a misconception?

 

[MDE]

Well, steel tends to be a bit cheaper for cases, but there's a reason aluminum is used for CPU heatsinks, either lighter weight or better cooling. It's generally accepted that aluminum is better for cooling though.

 

[arcas]

Specific heat capacity only refers to how rapidly a material will warm up when exposed to heat energy. So according to that chart, if you have a 1kg block of aluminum and a 1kg block of steel, both at 30deg celsius, you can only "feed" 452 J of heat energy to the steel block before its temperature is 31deg. You can feed 900 J of heat energy to the aluminum block before its temperature will reach 31deg. So a steel computer case would warm up quicker than an aluminum case since it has half the heat capacity of aluminum. Personally, though, I can't believe that there would be much difference between identical steel and aluminum computer cases.

Thermal conductivity is more important than specific heat for heatsinks. The heatsink's job is to transfer heat energy from one reservoir (the CPU) to another (the surrounding air/water). So you want a material that readily conducts heat. This is why copper heatsinks have displaced aluminum (and steel's thermal conductivity is far worse than aluminum).

There are situations, though, where it's important to have both excellent conductivity and heat capacity. In medium- and high-power rocketry, one doesn't normally use "recovery wadding" like you do in little Estes rockets (a 5-inch diameter tube would require an enormous amount of wadding). Instead, it's better to create a baffle that absorbs and slowly dissipates the heat from the ejection charge. So you want something that'll quickly absorb the heat (good thermal conductivity) so that the gas doesn't burn your $50 parachute and you don't want the material to heat up so quickly that the material itself causes damage (or melts) so you want it to have a pretty high heat capacity.

 

[ElPresidente408]

Ah, ok that's where I messed up. I thought lower specific heat meant good thermal conductivity. Thanks.

 

[Mday]

Originally posted by: ElPresidente408
Ah, ok that's where I messed up. I thought lower specific heat meant good thermal conductivity. Thanks.

lower specific heat means that it takes less energy to raise its temperature. higher specific heat means it takes more energy to raise its temperature. it has nothing to do with thermal conductivity which is how long it takes for heat to go from poing A to point B of an extended body.

while Al does have better thermal conductivity than steel, it is fairly weak. I like steel cases simply because they are harder. though an Al frame wouldnt hurt too much. side panels would be easily scratched (depending on the finish)

 

[mechBgon]

Ask them this: If you park your car in the sun, which will help keep it cool better... for the car to have an aluminum body, or for the car to have the windows rolled down?

~ ah so, grasshoppah... wise man ventilates!

People who are relying on their case dissipating heat by passively transmitting heat through the metal, instead of by ventilating it, are trying to drive nails with a tomato. With even modest ventilation, the air in the case is going to be turned over in a matter of less than 30 seconds. How hot can the air get in 30 seconds?

Now, it's true that a case may have a stagnant area where the temperature goes up, such as the upper section of an Antec, but I've also heard from Lian-Li owners whose cases are running uncomfortably hot... and why, you ask?

~yeah! why?

Because... (drum roll) the grillework over the fans is restrictive, reducing the ventilation. I advise them to remove it and replace it with a low-restriction chromed-wire grille. In fact, I just ordered a Lian-Li PC-86 yesterday and had the vendor punch the grillework out of the Lian-Li's rear-exhaust port and also punch a second 80mm hole right below the stock one. It should approximately equal my steel Antec Plus880 in the cooling department, while looking nicer and having more drive bays available.

 

[Mday]

the only benefit i would get a case with an Al frame is to have it be lighter.

 

[GtPrOjEcTX]

Originally posted by: Mday
the only benefit i would get a case with an Al frame is to have it be lighter.

definately, but the ones I have worked with tend to bend at will too easily.

 

[calvink]

i prefer Al for 1U server applications, because airflow is extremely limited and several of the hottest components directly touch the walls.

 

[beatle]

Originally posted by: calvink
i prefer Al for 1U server applications, because airflow is extremely limited and several of the hottest components directly touch the walls.

In this case, heat would be transferred by conduction, not convection, which makes Al a good choice. Normal Al cases aren't going to give this kind of advantage.

Look at a good set of cookware. Many brands will offer aluminum or copper pans with "stay cool" stainless steel handles. Either that or there will be a stainless pan with an aluminum or copper insert in the bottom of the pan for even heat distribution. Steel conducts heat poorly.

 

[Georgeisdead]

Convection still has influence here. Remember, if heat were not transferred away from the case by convection to the surrounding air, then the case would get hotter and hotter. I am not saying your argument is wrong or invalid, just incomplete. Heat transfer can be pretty complicated, remeber to think about EVERYTHING that is going on for a particular system. Conduction is a very important part of this discussion, just remember not to forget about our old friend convection as well (and to a lesser extent radiation, but that opens up a whole new discussion).

 

[Mingon]

If you have ever machined Alu and Cu you would find that the copper gets hotter quicker and stays hotter for longer.

 

[0roo0roo]

Originally posted by: Mday
the only benefit i would get a case with an Al frame is to have it be lighter.

btw, what vendor punches out holes for you? i woudln't mind paying for a blow hole

considering the price difference is so small, look at aluminum antec/chieftec cases to their steel counterparts. only about 20 dollars dsifference most of th eime. i don't see a point in going steel its just @#% heavy!