##### Energy

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I think it’s worth taking a quick moment to talk about energy. Energy is a tangible entity with characteristics that govern its behavior. I like to equate the task of cooling a CPU to a bucket of water. The CPU converts electricity to thermal energy. This is like adding water to a bucket. Water enters the bucket at the rate the CPU consumes electricity. The water level in the bucket equates to temperature differential across the “cooling device”. The cooling device may be a conventional heat sink, a heat sink with peltier, or a water block. A hole at the bottom of the bucket allows water to escape. The size of the hole equates to the thermal efficiency of the cooling device.

In gravity water systems, velocity through a drain relates to the depth of the water. As depth increases, more flow will escape through a given drain size. In cooling, a higher temperature differential will force more heat through a given resistance.

In this analogy, the rate at which water enters the bucket must ultimately be matched by the rate at which water leaves the bucket. Variations in water flow (CPU idle vs full load) result in changes in the water depth. If the hole is very small and the water is flowing into the bucket quickly (think poor cooling of a powerful CPU), then the water level will rise. If the water reaches the top of the bucket and still hasn’t developed enough pressure for the little drain to keep up, then the bucket will overflow. Think of overflowing equal to locking the computer.

Assuming the hole is big enough that the bucket doesn’t overflow, the depth of the water becomes a function of how fast you add water to the bucket and how big the hole is. Such is the case with computer cooling. The temperature differential between the CPU and the cooling device depends upon how much heat the CPU generates and the efficiency of the cooling device.

There’s one more fact I’d like to mention. Ultimately all the heat generated by the CPU must get out of the computer case and into the room. It makes no difference if you use air cooling, water cooling, or some other form of cooling. Each form of cooling merely serves to transport the heat from the CPU to the room. What does vary between methods is how efficiently they accomplish the task.

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