Compounding heat

[STOPOT]

Hey,
This is more of a physics question, but relates to computer heating.

Does heat compound? Meaning, if my CPU produces heat and my cooler idles my CPU at 40C , if heat does not get out fast enough, does it grow exponentially or linear or another curve? Meaning it would be the same growth from 30C to 40C (linear) or dangerous growth from 30C to 40C (exponential) because the time it would take to heat up to that level.

As well is total heat that CPU produces equal when comparing good cooling to bad? Meaning if the air coming out from a good cooler is 30C and CPU is 30C, will a bad cooler with air output of 10C be 50C at CPU? Where total heat is same, just location is different. Thanks

 

[pepe2907]

It's somewhere in between. Basically it should be linear. But heating up the semiconductor increases it's electrical resistance, causing even more heat generation.
As cooler is your processor, as less heat it actually produces. But also taking away the heat of a cooler processor is more difficult as of a hot one due to the larger thermal gradient of the later case. So there is at least two factors working against each other.
And... your calculation isn't right... or I can't understand you. But you can't have a 30C cooler and 30C CPU, unless you have superconducting /thermal/ heatpipes. And what means an output of 10 degree? The heat is totally not the same.

 

[STOPOT]

I mean if the air coming out of the heat sink is X degrees and CPU is Y degrees, is X + Y always equal at a certain level of work, just the amounts of X and Y change but total heat output (X+Y) remains the same?

 

[pepe2907]

No. Your way of thinking is not right.
The heat is generated in the CPU. From there on, it's a matter of dissipation. And dissipation depends of two things - thermal gradient, and thermal conductivity /and there is another factor, who works on temporal basis - thermal capacity, which became especially important in variable temperature conditions/ of all elements of your cooling system. So heat pipes are good, because they increase the thermal conductivity. Water cooling is good, because water has larger capacity, so in specific temperatures a liter of water may carry /out/ much more heat as a liter of air. Cooling with cooler air is good, because it creates larger gradient on both ends of your thermal system. Etc. The formulas you may find in thermal engineering textbooks /not only computer related, they are general, applicable to every thermal system, even to internal combustion engines for ex./ or I believe somewhere in Wikipedia.

 

[STOPOT]

Thanks for the reply..So cooling devices can be divided into ones of thermal conductivity and ones of thermal capacity? So is it right to assume that air (via heat pipes) have high conductivity but lower capacity, where as water cooling (via water pipes) have low conductivity but high capacity? What I was thinking about previously was cooling efficiency in terms of total heat displacement at a certain level of work, so if total output Z (X+Y) where Y (air output temp) had a greater proportion of Z compared to X (CPU temp, it would represent the efficiency of the whole cooling system.

 

[pepe2907]

No, air have low capacity and low conductivity, but the copper alloy of the heatpipes have high capacity and conductivity. Water have both higher capacity and conductivity than air, but much lower conductivity as copper, it's capacity is also lower, but am not sure exactly how much

 

[STOPOT]

Ok. All this came about because I was feeling the temperature of air out of my case and it felt pretty cool yet RealTemp was reading 80s so I was just trying to figure out why.

 

[pepe2907]

It means that somewhere you have a problem with the conductivity. Most likely it's in contact, between your processor and your cooler. Maybe your thermal paste layer is too thick or is not uniform.

 

[STOPOT]

Fixed it. The preapplied Intel one was in a circle and was small. I reseated it with AS5 but used card method on whole CPU, idleing mid to high 30s now and load at 70