PC Water Cooling Principles and Ideas
Water Cooling Concepts:
- Water has much better heat transfer properties than air (.6 vs .025 Heat Transmission Coefficient). It absorbs the heat from the components much more effectively.
- Water has a high specific heat, which means that it takes a lot of heat energy to raise the temperature of the water one degree. It can absorb a lot of heat.
- The rate of heat dissipation is largely dependent on the flow rate of the water, and, the temperature difference between the water and the object you are trying to cool.
- Water flow is dependent on the pressure of the system and the resistance.
- The resistance is decreased exponentially (inversely to the radius to the forth power) by larger diameter conduits and fittings, and increases linearly with the distance traveled.
- Water stored above the ground has potential energy that increases with the amount and height of the water (compliments of earth's gravity).
Water Cooling Principles:
- Use a low resistance radiator and heat blocks, with good heat transfer properties
- Keep the water as cool as you can with a good radiator, and, good fans and air flow.
- Use 1/2" inside diameter (ID) tubing and fittings, instead of 3/8" ID. Avoid 90 degree turns.
- Use a high flow pump with a good head pressure.
- Use parallel flows where possible, to increase decrease resistance.
- Use a large volume of water to create a large heat sink and increase pressure.
- Place a large volume water reservoir near the top of the tower, to add pressure to the system to help drive the flow of water, and, decrease the work of the pump (if the pump is controlled by the mother board, it should run slower = free electricity).
We only used one powerful graphics card, and the GPU water block has only one outlet port, so the GPU was the first block in the loop. Since we used a radiator with 2 inlet ports, and the Swiftech Apogee HD CPU water block has multiple ports, we used two tubes from the CPU to the radiator to decrease resistance. If 2 graphics cards were used, the CPU would be first, with a line going to each GPU. Each GPU would have a tube to the radiator.
Even though the radiator is not large (length by width), it is extra thick, which increases the surface area for heat exchange. A fan mounted on each side of the radiator, with good air flow, provides plenty of cooling and the radiator barely gets warm, even during game play with intense graphics (see Mojo Game Studios Water Cooled Gaming PC).
With the low resistance water cooling loop and the reservoir high in the tower (with lots of water), the pump needs to provide very little pressure to circulate the water and runs slower. The high flow and lots of water keep the system very cool.
Ultimately, air is used to cool the system.
Air Cooling Concepts:
- Air is what is used to cool the system. Even with water cooling, air is used to cool the radiator.
- The rate of heat dissipation (cooling) is largely dependent on the rate of airflow, and, the temperature difference between the air and the object you are trying to cool. In other words, blowing 90 degree air past a 100 degree component gives you less cooling then blowing 75 degree air, unless you increase the air flow substantially.
- Air flow is disrupted by turbulence.
Air Cooling Principles:
- Maximize the flow of the coolest air possible. Avoid blowing warm air, that was used to cool one component, past another component that you are trying to cool. In other words, try to isolate components that get hot from each other, and use separate air flows (keep the radiator away from the mother board).
- Fans should be placed to minimize air flow obstructions, by placing them where there is a good air intake and output. Crossing or opposing airflow streams should be avoided, as they create a lot of turbulence.