cooling system, apparatus employed to keep the temperature of a structure or device from exceeding limits imposed by needs of safety and efficiency. If overheated, the oil in a mechanical transmission loses its lubricating capacity, while the fluid in a hydraulic coupling or converter leaks under the pressure created. In an electric motor, overheating causes deterioration of the insulation. The pistons in an overheated internal-combustion engine may seize (stick) in the cylinders. Cooling systems are employed in automobiles, industrial plant machinery, nuclear reactors, and many other types of machinery. (For a treatment of cooling systems used in buildings, see air-conditioning.)
The cooling agents customarily employed are air and a liquid (usually water or a solution of water and antifreeze), either alone or in combination. In some cases, direct contact with ambient air (free convection) may be sufficient; in other cases, it may be necessary to employ forced-air convection, created either by a fan or by the natural motion of the hot body. Liquid is typically moved through a continuous loop in the cooling system by a pump.
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construction: Heating and cooling
In a transmission, if the surface area of the housing (container) is sufficiently large compared with the power lost, or if the transmission is in a moving vehicle, there is usually adequate free convection and no need for artificial cooling. To augment the cooling effect by increasing the surface area, the housing may be provided with thin metal fins. On some stationary mechanical transmissions, it may be necessary to circulate the lubricating oil through pipes surrounded by cold water or to use a fan to blow air through pipes surrounded by the oil in the reservoir. On many electric motors, a fan is attached to the rotating element to create a current of cooling air through the housing.
In an automobile, the motion of the vehicle provides sufficient forced-convection cooling for the transmission and the gears in the rear axle; in the engine, however, so much energy is released that, except for some early models and certain small cars with low-powered engines, air cooling is inadequate, and a water cooling system (radiator) is required.
A typical automotive cooling system comprises (1) a series of channels cast into the engine block and cylinder head, surrounding the combustion chambers with circulating liquid to carry away heat; (2) a radiator, consisting of many small tubes equipped with a honeycomb of fins to convect heat rapidly, that receives and cools hot liquid from the engine; (3) a water pump, usually of the centrifugal type, to circulate the liquid through the system; (4) a thermostat to control temperature by varying the amount of liquid going to the radiator; and (5) a fan to draw fresh air through the radiator.
To prevent freezing, an antifreeze solution is either added to or substituted for water. To raise the boiling point of the solution, the cooling system is usually pressurized by means of a pressure cap on the radiator with valves that open outwardly at a prescribed pressure and inwardly to prevent a vacuum as the system cools.
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Learn MoreThe following pages are intended to provide you with a better understanding of Koolance products and liquid cooling in general.
As transistor sizes continue to decrease, chip manufacturers pack even more on to the processor. In 1992, a 486/DX2 66Mhz CPU consumed about 7W of power (with 1.2 million transistors). It didn't even require a cooling fan. Today, processors can range from 50-200W depending upon the core type and load.
Most high-end video cards now exceed the total power consumption of today's processors. Other components have also followed this tendency toward higher heat outputs with each consecutive generation.
Koolance has long believed liquid to be the next evolutionary phase in computer cooling systems. Major processor and video card manufacturers have been devising water-based concepts for years, anticipating the point when air cooling would simply reach its limit.
Heat-producing devices in a typical computer are cooled by air. Generally, this involves mounting a heat sink and fan to each component. Heat generated from your CPU is transferred into a metal heat sink, where a fan blows air across its wider surface area.
While altering a heat sink's size and makeup can improve the effectiveness, it is still limited because air absorbs and transfers heat very slowly. To help counteract this, the fan can be run at a higher speed, but most people know what that means: high performance has become equated with high noise. As systems continued to be upgraded, required heat sinks got larger and louder.
Of liquids, water (after mercury) conducts heat the fastest. Its thermal conductivity is about 30 times greater than that of air. And not only that, it holds a lot more heat. It takes over 4 times as much heat to raise the temperature of water as it does air.
These basic physical attributes give liquid cooling a considerable advantage in cooling, but the benefits don't end there.
Next: The Basics of Heat Transfer