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Somehow AP Chemistry has to do with PC Cooling...

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Sniperboy

Member
Joined
Jun 9, 2002
Location
Omaha, NE/Ithaca, NY
Ok, I was doing my AP Chem homework and I came across this question:
High-quality hi-fi power amplifiers generate large amoutns of heat. To dissipate the heat and prevent damage to the electronic components, heat-radiating metal fins are used. Would it be better to make these fins out of iron or aluminium? Why? (See Table 6.1 for specific heat capacities.)

Here is the answer that the back of my book provided:
Al. Al has a higher heat capacity and a lower density than Fe. The same amount of heat could be dissipated by a smaller mass of Al.

Now, from my knowledge obtained from these forums, I was under the impression that specific heat had absolutely nothing to do with cooling capacity, because that fact always comes up whenever the aluminium vs. copper debate pops up on the forums. I thought that thermal conductivity was the only important factor. So is my textbook wrong?
 
The textbook is right. Heat Capacity, Cp, aka specific heat is how much heat a particular mass requires in order to change its temperature 1°C. Al has a higher heat capacity which means it can absorb more heat than the same mass of iron before itself begins to heat up.

Heat capacity and thermal conductivity both do play a role in cooling. I don't know why people would think heat capacity doesn't apply. Copper has a lower heat capacity than aluminum which means it will get hotter faster, but it has a higher thermal conductivity which means it will transfer that heat to air or water faster. Also in general the greater the termperature gradient the greater the heat transfer.
 
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