Types

All cooling works on the same basic principle: Transfer heat from one place to somewhere else. There are four categories of cooling solutions used in modern computers.

Convection Heatsink

Based on pure speculation and a little bit of informal survey taking, it is pretty safe to conclude that at least 90% of all desktop computers in operation today utilize a cooling method commonly called “air-cooling”. If you have ever seen inside of a computer and noticed a weird metal-looking thing with spikes or fins on it, chances are pretty good that you have a standard convection heatsink.

When your processor, or any powered part on your computer for that matter, is subjected to an electric current, it heats up. Depending on how efficient that particular part is, it can produce varying amounts of heat. This has to do with the first Law of Thermodynamics, also known as the Law of Conservation of Energy. In the case of a transistor, the energy being fed into the system is being used to open and close the electrode gates. When the gate opening is small, energy is forced through a smaller channel than normal, creating resistance, and the buildup of energy produces heat. This is true for all electrical components unless the current is passing through a perfect conductor, which does not exist. There is no way around it: heat is just a byproduct of computer operation and the flow of current itself.

So, we have this heat building up in our computers’ components and we don’t have any way to stop it. That is where heat transfer comes in. Imagine the following if you will: You wake up in the morning and it is fiercely cold, so you put on a sweatshirt. You go to class or work, and when you’re back outside in midday, the temperature has risen substantially. Now you’ve exerted yourself and the sun is higher in the sky, so you’re hot. What do you do? You take off your sweatshirt. But how does the sweatshirt affect your internal temperature?

When you put on a sweatshirt, the sweatshirt does not intrinsically make you warmer by transferring heat to you. The reason you feel warmer when wearing a sweatshirt is because it insulates you; it keeps the heat you already have in your body from leaving. If your body temperature is warm (which it should be if you’re alive), heat will naturally want to diffuse out through your skin, into the atmosphere. The process through which it does this is called convection (Granted, heat loss through the skin is far from being this simple, but in effect, it is convection). The mechanism of convection is equilibrium, the driving force behind all heat transfer. So, if the heat needs to get out of your body and through your skin to maintain equilibrium, and the only parts of you that are not covered up are your face and hands, then there is relatively little surface area from which the heat can be transferred, leading to a buildup of heat between your skin and your clothing, thus making you warm. Surface area plays a tremendous role in the ability of an object to transfer heat. Imagine, instead of just taking off your sweatshirt, you stripped down to your underwear. You would get cooler much faster!

Increasing surface area leads to better cooling, and engineers throughout the world employ this concept when designing a heatsink. A heatsink is simply a device that is capable of absorbing heat from an object that is in thermal contact with it. On your body, skin is the heatsink. You can find applications of heatsinks everywhere you go, usually when there is some sort of electrical equipment nearby, such as power generation facilities, transformers, and wall heaters. As I mentioned, the type of heatsink most commonly used in computers is the forced convection heatsink. In forced convection, warmth transferred from the thermal-generating object to the heatsink is then forced away by some kind of moving medium. So, in a computer, the medium that flows around the heatsink is air, which is being propelled by directional fans. If the air was not moving, the heatsink could probably still do a decent job at keeping the temperatures down for the component that it was meant to cool. However, this is less true for the heatsink on a CPU or GPU as it is for the something like the Northbridge chip on your motherboard, or the DRAM chips on your memory DIMMs. This video illustrates the effect moving air has on the heat dispersion ability of a forced convection heatsink.