We'll begin by looking at air cooling, the most common method of cooling the processor, and watercooling, probably the second most common. They have one thing in common; they use a constant medium, which means that no transformation takes place (no material changes form from i.e. solid to liquid or liquid to gas form).

Air cooling
An ordinary heatsink with fan, the most occuring form of cooling. The heatsink leads the heat from the processor to a larger number of fins with a significantly larger surface area than the processor itself. A fan blows (in some cases suck) air over/through the fins that are cooled and hot air flows out.

Water cooling
Water cooling has a certain advantage. Water is first and foremost a better medium than air when it comes to transferring and storing heat. We can use water to transport the heat away from the processor faster, and we transfer the water to a radiator, a heatsink for the water that can be a lot bigger than there is space for if you make sure it would have been seated directly on the processor.

Phase change
Now we're getting to something here. Here we can get below the room/ambient temperature, which isn't possible with air nor water. How is this possible then? We use the larger amount of energy required to make matter pass from liquid to gas. Here's a simple experiment to understand. Wave strong with your hand in the air. It will get cooler. Put some acetone on your hand and wave. Feels pretty cool, doesn't it? acetone boils off pretty fast (evaporates is a more common word) and when it does (going from liquid to gas form), the acetone uses heat energy from your hand, which gets cold. It works with water aswell, but it's a significant difference with acetone, which feels a bit cold even when you're not waving with your hand. In a compressor cooling device acetone isn't used, but some different cooling mediums such as R404 and R507, mediums that have a boiling point in the lower subzero area.

So you "pour" a liquid onto your processor, or more precise in the cooling head that is fastened to the processor where the liquid boils off and becomes a gas form. This is the process that cools your processor. For the whole thing to work in a sealed system you have to make the gas revert to liquid form so that you can "pour" it again. This is where the compressor comes in. It compresses the gas under pressure. Under pressure, the gas gets warm and we cool it off with the condensator (the radiator) which makes it pass to liquid again which once again goes to the processor. A simplified principal sketch looks like this:

[Editor's note: CPU -> Compressor -> Condenser]

Of course there's a little more than this that makes a compressor cooling device, like capillary tubes, the proper cooling mediums, effect and so on, but we'll stop here and get back to compressor cooling devices in the future.
Enough about the introduction and background information. It's time to take a closer look at Vapochill XE II!