Watercooling
Encyclopedia
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
removal from components and industrial equipment. As opposed to air cooling, water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
is used as the heat conductor. Water cooling is commonly used for cooling automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s and large industrial facilities such as steam electric power plants, hydroelectric
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
s, petroleum refineries
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
and chemical plant
Chemical plant
A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use special equipment,...
s. Other uses include cooling the barrels of machine guns, cooling of lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
oil in pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
s; for cooling purposes in heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s; cooling products from tanks or columns, and recently, cooling of various major components inside high-end personal computers. The main mechanism for water cooling is convective heat transfer
Convective heat transfer
Convective heat transfer, often referred to as convection, is the transfer of heat from one place to another by the movement of fluids. The presence of bulk motion of the fluid enhances the heat transfer between the solid surface and the fluid. Convection is usually the dominant form of heat...
.
Advantages
The advantages of using water cooling over air cooling include water's higher specific heat capacity, density, and thermal conductivityThermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
. This allows water to transmit heat over greater distances with much less volumetric flow and reduced temperature difference.
For cooling CPU cores its primary advantage is that its tremendously increased ability to transport heat away from source to a secondary cooling surface allows for large, more optimally designed radiator
Radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...
s rather than small, inefficient fins mounted directly on the heat source.
The water jacket
Water jacket
A water jacket is a water-filled void surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through the void. The flow of water to an external heating or cooling device allows precise temperature control of the device.-Applications:Water jackets...
around an engine is also very effective at deadening mechanical noises, which makes the engine quieter. However, the primary disadvantage is that it costs significantly more than an air-cooled engine system.
Open method
Open systems commonly use plain tap water
Tap water
Tap water is a principal component of "indoor plumbing", which became available in urban areas of the developed world during the last quarter of the 19th century, and common during the mid-20th century...
, but this leads to mineral deposits forming in the cooling system, due to the water evaporating and leaving behind dissolved salts and minerals that were in the water. Eventually the scale buildup can lead to clogging of pipes and pumps, blocking water flow and leading to equipment failure. Typically scale can not be removed and requires complete replacement of clogged parts. The use of distilled water
Distilled water
Distilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.-History:...
will prevent scale formation, but distilled water is expensive to use as an evaporative coolant.
Pressurization
Modern automotive cooling systems are slightly pressurized. This raises the boiling-point of the coolant and reduces evaporation.Antifreeze
The use of water cooling carries the risk of damage from freezing. Automotive and many other engine cooling applications require the use of a water and antifreezeAntifreeze
Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....
mixture to lower the freezing point to a temperature unlikely to be experienced. Antifreeze also inhibits corrosion from dissimilar metals and can increase the boiling point, allowing a wider range of water cooling temperatures. Its distinctive odor also alerts operators to cooling system leaks and problems that would go unnoticed in a water-only cooling system. The heated water can also be used to warm the air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
system inside the car, if so desired.
Other additives
Other less common chemical additives are products to reduce surface tension. These additives are meant to increase the efficiency of automotive cooling systems. Such products are used to enhance the cooling of underperforming or undersized cooling systems or in racing where the weight of a larger cooling system could be a disadvantage.Computer usage
Cray-2
The Cray-2 was a four-processor ECL vector supercomputer made by Cray Research starting in 1985. It was the fastest machine in the world when it was released, replacing the Cray Research X-MP designed by Steve Chen in that spot...
in 1982, using Fluorinert
Fluorinert
Fluorinert is the trademarked brand name for the line of electronics coolant liquids sold commercially by 3M. It is an electrically insulating, stable fluorocarbon-based fluid which is used in various cooling applications. It is mainly used for cooling electronics...
. Through the 1990s, water cooling for home PCs slowly gained recognition amongst enthusiasts, but it started to become noticeably more prevalent after the introduction of AMD's hot-running Athlon
Athlon
Athlon is the brand name applied to a series of x86-compatible microprocessors designed and manufactured by Advanced Micro Devices . The original Athlon was the first seventh-generation x86 processor and, in a first, retained the initial performance lead it had over Intel's competing processors...
processor in mid 2000. As of 2011, there are several manufacturers of water cooling components and kits, and some custom computer retailers include various setups of water cooling for their high performance systems.
Water cooling can be used to cool many computer components, but especially the CPU. Water cooling usually uses a CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
water block
Water block
A water block is the watercooling equivalent of a heatsink. It can be used on many different computer components including the central processing unit , GPU, PPU, and Northbridge chipset on the motherboard...
, a water pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
, and a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
(usually a radiator
Radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...
with a fan attached). Water cooling can allow quieter (potentially fanless) operation, or improved processor speeds (overclocking
Overclocking
Overclocking is the process of operating a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to...
), or a balance of both. Less commonly, GPUs
Graphics processing unit
A graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...
, Northbridges
Northbridge (computing)
The northbridge has historically been one of the two chips in the core logic chipset on a PC motherboard, the other being the southbridge. Increasingly these functions have migrated to the CPU chip itself, beginning with memory and graphics controllers. For Intel Sandy Bridge and AMD Fusion...
, Southbridges
Southbridge (computing)
The southbridge is one of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In Intel chipset...
, hard disk drives
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
, memory, voltage regulator module
Voltage regulator module
A voltage regulator module or VRM, sometimes called PPM , is a buck converter that provides a microprocessor the appropriate supply voltage, converting +5 V or +12 V to a much lower voltage required by the CPU. Some are soldered to the motherboard while others are installed in an open slot...
s (VRMs), and even power supplies
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
can be water-cooled.
Water coolers for desktop computers were, until the end of the '90s, homemade. They were made from car radiators
Radiator (engine cooling)
Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine....
(or more commonly, a car's heater core
Heater Core
A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air...
), aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
pumps and home-made water block
Water block
A water block is the watercooling equivalent of a heatsink. It can be used on many different computer components including the central processing unit , GPU, PPU, and Northbridge chipset on the motherboard...
s, laboratory-grade PVC and silicone tubing and various reservoirs (home made using plastic bottles, or constructed using cylindrical acrylic or sheets of acrylic, usually clear) and or a T-Line
T-Line
A T-line is a simple alternative to a pressure tank, air-trap or any other filling, bleeding, and draining device. It is constructed by plumbing a "Tee" connector into an existing tube thus creating an alternate flow-path...
. More recently a growing number of companies are manufacturing water-cooling components compact enough to fit inside a computer case. This, and the trend to CPUs of higher power dissipation, has greatly increased the popularity of water cooling, although only a very small minority of computers are water-cooled.
Dedicated overclockers occasionally use vapor-compression refrigeration
Vapor-compression refrigeration
Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...
or thermoelectric coolers in place of more common standard heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s. Water cooling systems in which water is cooled directly by the evaporator coil of a phase change system are able to chill the circulating coolant below the ambient air temperature (impossible with a standard heat exchanger) and, as a result, generally provide superior cooling of the computer's heat-generating components. The downside of phase-change or thermoelectric cooling is that it uses much more electricity, and antifreeze must be added due to the low temperature. Additionally, insulation, usually in the form of lagging around water pipes and neoprene pads around the components to be cooled, must be used in order to prevent damage caused by condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
of water vapour from the air on chilled surfaces. Common places from which to borrow the required phase change systems are a household dehumidifier
Dehumidifier
A dehumidifier is typically a household appliance that reduces the level of humidity in the air, usually for health reasons. Humid air can cause mold and mildew to grow inside homes, which pose various health risks. Very humid climates or air make some people extremely uncomfortable, causing...
or air conditioner.
An alternative cooling system, which enables components to be cooled below the ambient temperature, but which obviates the requirement for antifreeze and lagged pipes, is to place a thermoelectric device
Thermoelectric cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...
(commonly referred to as a 'Peltier junction' or 'pelt' after Jean Peltier
Jean Charles Athanase Peltier
Jean Charles Athanase Peltier ]] – October 27, 1845, in Paris) was a French physicist.He discovered the calorific effect of electric current passing through the junction of two different metals...
, who documented the effect) between the heat-generating component and the water block
Water block
A water block is the watercooling equivalent of a heatsink. It can be used on many different computer components including the central processing unit , GPU, PPU, and Northbridge chipset on the motherboard...
. Because the only sub-ambient temperature zone now is at the interface with the heat-generating component itself, insulation is required only in that localized area. The disadvantage to such a system is that pelts typically dissipate a lot of power, and the water cooling system must remove this heat in addition to that generated by the component.
Another possible danger is damaging condensation, due to the ambient air right around the pelt being cold. A proper installation requires that the Peltier be "potted" with silicone epoxy. The epoxy is applied around the edges of the device, preventing air from entering or leaving the interior.
Apple's Power Mac G5
Power Mac G5
The Power Mac G5 is Apple's marketing name for models of the Power Macintosh that contains the IBM PowerPC G5 CPU. The professional-grade computer was the most powerful in Apple's lineup when it was introduced, widely hailed as the first 64-bit PC, and was touted by Apple as the fastest personal...
was the first mainstream desktop computer to have water cooling as standard. Dell
Dell
Dell, Inc. is an American multinational information technology corporation based in 1 Dell Way, Round Rock, Texas, United States, that develops, sells and supports computers and related products and services. Bearing the name of its founder, Michael Dell, the company is one of the largest...
followed suit by shipping their XPS computers with liquid cooling, using thermoelectric cooling
Thermoelectric cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...
to help cool the liquid. Currently, Dell's only computers to offer liquid cooling are their Alienware
Alienware
Alienware is an American computer hardware subsidary of Dell, Inc. It mainly assembles third party components into desktops and laptops with custom enclosures for high-performance gaming. These products also support graphically intense applications such as video editing, simulation, and audio editing...
desktops.
Industrial usage
Cooling tower
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or in the case of closed circuit dry cooling towers rely...
s may use river water, coastal water (seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
) or well water as their source of fresh cooling water. The large mechanical induced-draft or forced-draft cooling towers in industrial plants continuously circulate cooling water through heat exchangers and other equipment where the water absorbs heat. That heat is then rejected to the atmosphere by the partial evaporation of the water in cooling towers where upflowing air is contacted with the circulating downflow of water. The loss of evaporated water into the air exhausted to the atmosphere is replaced by "make-up" fresh river water or fresh cooling water. Since the evaporation of pure water is replaced by make-up water containing carbonates and other dissolved salts, a portion of the circulating water is also continuously discarded as "blowdown" water to prevent the excessive build-up of salts in the circulating water.
High grade industrial water (produced by reverse osmosis
Reverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...
) and potable water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
is sometimes used in industrial plants requiring high-purity cooling water.
Some nuclear reactors use heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
as cooling. Heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
is employed in nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s because it is a weaker neutron absorber. This allows for the use of less enriched fuel. For the main cooling system, normal water is preferably employed through the use of a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
as heavy water is much more expensive. Reactors that use other materials for moderation (graphite) may also use normal water for cooling
RBMK
RBMK is an initialism for the Russian reaktor bolshoy moshchnosti kanalniy which means "High Power Channel-type Reactor", and describes a class of graphite-moderated nuclear power reactor which was built in the Soviet Union. The RBMK reactor was the type involved in the Chernobyl disaster...
.
Environmental impacts
On very large rivers, but more often at coastal and estuarine sites, "direct cooled" systems are often used instead. These industrial plants do not use cooling towers and the atmosphereAtmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
as a heat sink but put the waste heat to the river or coastal water instead. These once-through cooling (OTC) systems thus rely upon a good supply of river water or seawater for their cooling needs. The warmed water is returned directly to the aquatic environment, often at temperatures significantly above the ambient receiving water. Thermal pollution
Thermal pollution
Thermal pollution is the degradation of water quality by any process that changes ambient water temperature.A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers...
of rivers, estuaries and coastal waters is an issue which needs to be addressed when considering the siting of such plants.
Other impacts include "impingement" (the capture of larger organisms such as fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
on screens
Fish screen
A fish screen is designed to prevent fish from swimming or being drawn into an aqueduct, cooling water intake, dam or other diversion on a river, lake or waterway where water is taken for human use. They are built to supply debris-free water without harming aquatic life...
protecting the small bore tubes of the heat exchangers from blockage) and "entrainment" (the combined effects of temperature, pressure, biocide residual and turbulence/shear on smaller organisms entrained with the cooling water and then expelled back to the aquatic environment in the effluent). The cooling water in such heat exchange cycles is often treated with a biocide
Biocide
A biocide is a chemical substance or microorganism which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means. Biocides are commonly used in medicine, agriculture, forestry, and industry...
to prevent fouling
Fouling
Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms or a non-living substance...
in heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s like condensers
Condenser (heat transfer)
In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant...
and other equipment, but in some instances such control can be exercised instead through frequent cleaning, antifouling paints (both toxic-release and non-toxic), or heat treatment.
Industrial cooling water regulations
The U.S. Clean Water Act
Clean Water Act
The Clean Water Act is the primary federal law in the United States governing water pollution. Commonly abbreviated as the CWA, the act established the goals of eliminating releases of high amounts of toxic substances into water, eliminating additional water pollution by 1985, and ensuring that...
requires the Environmental Protection Agency (EPA) to issue regulation
Regulation
Regulation is administrative legislation that constitutes or constrains rights and allocates responsibilities. It can be distinguished from primary legislation on the one hand and judge-made law on the other...
s on industrial cooling water intake structures. EPA issued final regulations for new facilities in 2001 (amended 2003). Other EPA regulations for existing facilities were challenged in litigation and EPA issued new proposed regulations in March 2011.
See also
- Cooling pondCooling pondA cooling pond is a man-made body of water primarily formed for the purpose of supplying cooling water to a nearby power plant or industrial facility such as a petroleum refinery, pulp and paper mill, chemical plant, steel mill or smelter...
- Deep lake water coolingDeep lake water coolingDeep lake water cooling uses cold water pumped from the bottom of a lake as a heat sink for climate control systems. Because heat pump efficiency improves as the heat sink gets colder, deep lake water cooling can reduce the electrical demands of large cooling systems where it is available...
- Full immersion cooling
- Heat pipeHeat pipeA heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces....
cooling - Oil coolingOil coolingOil cooling refers to a process whereby heat is displaced from a 'hotter' object, into a cooler oil and is the principle behind oil cooler devices. The oil carrying the displaced heat usually passes through a cooling unit such as a radiator or less commonly a gas decompresser...
- Peltier cooling
- ThermosiphonThermosiphonThermosiphon refers to a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump...
(passive heat exchange)