A Closer Look
This content was originally featured on Amdmb.com and has been converted to PC Perspective’s website. Some color changes and flaws may appear.Let’s start off by defining exactly what we expect a water-cooling system to do. In the big picture we want the waste heat that is generated by the CPU to be removed and transferred to the ambient room air. The waterblock is in direct physical contact with the CPU. Water is circulated thru the waterblock to keep it as cool as possible to maximize the Delta T and therefore the heat transfer out of the CPU and into the water. The water then transports the heat to the radiator (liquid to air heat exchanger) which uses forced convection cooling (fan) to transfer the heat out of the water and into the air. There are seven key components involved in this process.
- Waterblock – transfers heat out of CPU and into the water
- Radiator – transfers heat out of the water and into the surrounding air
- Fan – creates a differential pressure which causes air to flow thru radiator
- Pump – creates a differential pressure which causes the water to flow thru system
- Reservoir – holding tank for coolant, helps insure pump has a good reserve of water
- Water – the liquid coolant (heat transfer media)
- Tubing – creates a continuous flow path to connect all the components
All of the larger components are housed inside the HydroCool 200’s external cooling unit. This unit is protected by a smoked Plexiglas cover. Once removed, you can see how all of the internal components are securely mounted and neatly laid out. Most of the internal tubing pieces are 3/8” ID (except for the pump, which is ~3/4” ID).
Mounted to the back wall of the cooling unit is a black anodized aluminum reservoir tank. The reservoir acts as an expansion tank and provides a convenient access point to add water to the system. It includes a level sensor (under the yellow cap) that will warn the operator if the water level drops below a safe point. The reservoir also helps remove air bubbles from the system and insures the pump has a non-restricted supply of water.
A small Bosch centrifugal pump is mounted directly beside the reservoir. The pump suction line, which attaches directly into the reservoir, is large in diameter and short in length to help minimize NPSH (net positive suction head). The pump is secured to the frame via a large rubber mounting piece that should provide good vibration isolation.
Inside the pump, a DC motor spins an impeller, which creates a high-pressure area of water at the pump’s discharge port and a low-pressure area at the pump’s suction. This difference in pressure is what causes water to flow through the system.
Pressurized water flows out of the pump thru a flow-indicator and then on to the radiator. The flow-indicator is nothing more than a spinning wheel inside a clear plastic housing. It does not measure flow; it only indicates when flow is present. Because the inlet and outlet fitting IDs on most flow-indicators (including this one) are quite small and can therefore restrict flow, they are typically not used in the average PC water-cooling system.
A small incandescent light sits right below the flow indicator and illuminates the inside of the enclosure, which provides a visual indication that the system is powered on and water is moving thru the lines.
A number of right angle, 90º elbow fittings are used throughout the system. This makes for a cleaner, simpler routing of the tubing and helps prevent the tubing from collapsing during tight bends. These fittings can also produce flow restrictions, which depending on how fast the water is moving will sometimes reduce the overall system flow.
And while we are on the subject of flow restricting fittings – the quick-disconnect fittings used on the backside of the HydroCool 200 unit are also well-known flow restrictors, especially the kind that have internal check valves. They are very convenient to use, but to keep the water from running out whenever a connection is broken, they incorporate check valves. These valve mechanisms can also restrict water flow.
The well-designed radiator is mounted on one side of the enclosure and fitted with a large 120 mm x 38 mm fan. A fan shroud is used to space the fan approximately 1/4” off the face of the radiator. The fan draws outside air in thru an opening on the opposite side of the case and blows the air thru the radiator and then outside the enclosure. Depending on the system temperature, the fan will run in Whisper mode (slow speed) or Turbo mode (full speed).