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Physics question

post #1 of 8
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I'm hoping someone better educated than me can answer this for me:

Will water cooling your CPU and GPU (single loop) result in less heat exchanged than air cooling?

I've noticed my water cooled case seems to heat the room just as much as when I had everything air cooled. Of course, it's quieter and the temps on the GPU and CPU are lower.

So my guess is that regardless if the GPU or CPU is at 80 degrees or 50 degrees, it's still generating the same heat that needs to be cooled, right? Thus, whether I'm using air or water cooling, the system will generate the same heat that needs to be cooled?
post #2 of 8
Quote:
Originally Posted by grit View Post

I'm hoping someone better educated than me can answer this for me:

Will water cooling your CPU and GPU (single loop) result in less heat exchanged than air cooling?

No it won't. You're going to be pulling the same power from the wall, and that waste energy has to go somewhere. Water is just better at removing heat than air is.
Quote:
Originally Posted by grit View Post

So my guess is that regardless if the GPU or CPU is at 80 degrees or 50 degrees, it's still generating the same heat that needs to be cooled, right? Thus, whether I'm using air or water cooling, the system will generate the same heat that needs to be cooled?

Correct.
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post #3 of 8
Quote:
Originally Posted by grit View Post

Will water cooling your CPU and GPU (single loop) result in less heat exchanged than air cooling?

Simple answer; no.

Complex answer; kinda maybe.


Heat (power) and temperature are two different and largely independent things. The example I usually use is a cigarette lighter compared to a radiator. A cigarette lighter will burn you, but it won't heat a room (high temperature, low heat). A radiator will not burn you, but it will heat a room (low temperature, high heat).

Heat transfer is driven by temperature difference, the higher the temperature difference the higher the heat transfer for a given system. With water cooling you can transfer the heat more efficiently than with air, meaning a lower temperature difference is needed to drive the heat transfer. This results in your GPU running cooler, even though it is still generating the same amount of heat.

So you are right in that heat is heat, it really doesn't matter how you cool a 300W heat source, you will be moving 300W of heat (in steady state), all you change is the temperature difference.


However this is where it gets a little more complex. Electronics generate heat through electrical resistance, and the resistance of an electrical component depends on its temperature. Therefore the cooler you can keep your GPU, the less power it will produce in terms of heat. Tests were done on a GTX 480 back in the day that show this to be true.

So if you don't push your system harder than you did on air, you will probably be dumping less heat into the room due to the lower resistance of the electrical components.

Outside of a lab this is fairly unnoticeable, and most people take the opportunity to get a little more performance out of their systems anyway, negating this effect.


So yes - your room will reach essentially the same temperature on air or water.
Edited by GingerJohn - 6/28/16 at 2:00pm
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post #4 of 8
Essentially the same. You are also heating up the water (higher specific heat than air) slightly in the case of water cooling. If your room is the same temp and your components are lower temps, then this is probably where the extra heat is going. Of course to know exactly, it would be hard to tell. The water is still going through the heat exchanger and dumping that energy in the air and that is why your room is still heating up.
Edited by mtrapuzz - 6/28/16 at 3:47pm
post #5 of 8
Quote:
Originally Posted by grit View Post

I'm hoping someone better educated than me can answer this for me:

Will water cooling your CPU and GPU (single loop) result in less heat exchanged than air cooling?

I've noticed my water cooled case seems to heat the room just as much as when I had everything air cooled. Of course, it's quieter and the temps on the GPU and CPU are lower.

So my guess is that regardless if the GPU or CPU is at 80 degrees or 50 degrees, it's still generating the same heat that needs to be cooled, right? Thus, whether I'm using air or water cooling, the system will generate the same heat that needs to be cooled?

Energy cannot be created or destroyed, only changed in form. Since heat is energy, and since energy cannot just simply disappear, then the temperature in your room will rise the same regardless of how you draw that heat from your components.
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post #6 of 8
Your computer produces the same amount of heat either way. What changes is how efficient the system is at removing that heat from the computer and dumping it into the environment (the room).
post #7 of 8
Thread Starter 
Thank you for all the replies. I had initially hoped and wished for cooler temperatures. Somewhere in my head, it initially made sense that if the graphics card was running at 50 degrees Celsius you would dissipate less heat in my room then if it was running at 80 degrees Celsius. From a comprehension point of view, the lit cigarette or match analogy help me understand it best.

Unfortunately, it seems that if I'm not going to overclock the only real advantage to water cooling is a decrease in ambient noise. I suppose one could argue that the life of the components would be extended from operating at a lower temperature however I'm more likely to replace them long before they were out at normal temperatures. Of course, athletics to play a role too, but in the end water cooling is quite costly.
post #8 of 8
Quote:
Originally Posted by grit View Post

Thank you for all the replies. I had initially hoped and wished for cooler temperatures. Somewhere in my head, it initially made sense that if the graphics card was running at 50 degrees Celsius you would dissipate less heat in my room then if it was running at 80 degrees Celsius. From a comprehension point of view, the lit cigarette or match analogy help me understand it best.

Yeah that comes from a misunderstanding of heat vs. temperature. Though they are related, they aren't the same. Another analogy that might help is this:

Let's say you have a cup of water and a swimming pool. Both are at room temperature (say 20°C). Now let's say we take a small heating element that only needs 10 watts of power and put it to the cup of water. After a few seconds the temperature of the water in the cup will rise significantly (let's just say 80°C as a wild guess). Now take that same heating element and stick it in the swimming pool. Do you think it will change the temperature very much? Nope. The heating element has the same amount of heat emanating from it (10 watts) in both cases, but it doesn't cause the same change in temperature of both bodies of water. Why? It's easy to understand why if you visualize it this way. The water in the cup has such a small volume and surface area that it doesn't take much heat to change the temperature. Also, a swimming pool and a cup of water that are the same temperature will not have equal hotness. The swimming pool contains much more heat than the cup even though they are the same temperature.

Another example is that an iceberg has more total heat than a boiling pot of water. Even though the iceberg is below freezing in temperature, it still is hotter (total thermal energy) than a pot of boiling water.

So temperature, it turns out, is just the average heat in a system.
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