PC water cooling
The PC water cooling is used in PCs, powerful and active technique to remove unreacted power loss into heat.
In computers , electrical energy taken from the power grid is converted into thermal energy. As the power density of modern computers increases, so too does the heating of the individual components. In earlier computers, the surrounding air was sufficient to dissipate the specific power loss, which is low in relation to the surface area, solely through radiation and natural convection , without additional heat sinks. Today, passively cooled PCs only use heat sinks ; used for actively cooled heat sinks with supportive effect by fans .
target
The aim of water cooling in a PC is to dissipate the heat generated in the PC, especially from the semiconductors that heat up strongly during operation, such as the main processor or graphics processor, as effectively and quietly as possible. The increase in the performance of the computer by operating it beyond the officially permissible specifications ( overclocking ) is also a field of application for water cooling.
The comparatively high heat capacity of the cooling medium water favors the absorption of heat from small-area heat sources, as is typical in a computer.
In addition to the improved heat dissipation, water cooling often enables quieter operation compared to other cooling concepts.
The heat flow between the semiconductor and the surface that is effective for heat transfer is ultimately limited by the finite thermal conductivity of the internal, intermediate materials. As a result, these materials represent a fixed and hardly changeable thermal resistance .
It should be noted that water cooling is only a point-based energy consumption system. This means that this method only enables a targeted decrease in temperature in certain areas. The need for total cooling of other components remains unaffected. In practice this means that the normal housing air circulation must not be interrupted, otherwise voltage converters , capacitors and other components can overheat and suffer "heat death" because the cooling medium is not exchanged. If this is undesirable, additional components with heat sinks must be integrated into the water cooling and / or connected to the housing made of aluminum or copper by means of heat pipes .
history
The cooling of PCs with water in the private sector began with a few enthusiasts who wanted to overclock their computers as much as possible around the year 2000 , or who were looking for replacements for the conventional CPU fans, which were always used at the time due to the exploding power dissipation of the CPUs more powerful and therefore louder. In addition, dual CPU boards came into fashion in the private sector, as they were previously only used in servers. Two CPU coolers with fans had to be installed on these motherboards, which further increased the volume.
The first heat sinks were made in-house - some still do that today - and the water was pumped into buckets next to the computer using aquariums and then returned to the cooling circuit.
In 2003, the Power Mac G5, the first desktop computer with standard water cooling, was launched on the market. Here the heat exchanger, radiator and pump were a complete system from Delphi Automotive .
The next stage of development were self-made radiators and expansion tanks made of Plexiglas . While the bucket solution managed without any further cooling or expansion tank due to the amount of water (the large amount of water heated up slowly and was cooled by the relatively large surface of the bucket in the room air), additional recooling of the water became necessary as the surface area decreased. Car coolers, for example, but also radiators , which, with their large effective surface, can do without active ventilation, are and were suitable for this.
Cooling principles
The cooling principles are classified according to the type of recooling of the cooling water. It can be active or passive.
With active cooling , a fan generates an air flow through the heat exchanger . A relatively small radiator, which is available as a single, dual, triple or quad version (ie for one, two, three or four fans), is sufficient, but there is no direct proportional reduction in the temperatures of the components through larger radiators expected. A triple radiator is sufficient for most cooling scenarios for all components.
In some coolers, a thermoelectric Peltier effect cooling is used in addition to air cooling (so-called "active-passive" cooling).
With passive cooling , the cooling effect on the radiator is only created by the normal air movement through the radiator ( convection ) similar to a radiator. A passively cooled radiator is usually significantly larger than an actively cooled one in order to achieve the same cooling performance. It is placed outside the housing so that air can flow through it freely. Depending on the design, the radiator can be designed either horizontally (as in the case of a convection tower with power plant coolers) or upright (as in the case of a car cooler through which the airstream flows).
Another variant consists of a hose several meters long or, because of the more favorable thermal conductivity, metal piping, which is laid uninsulated along the skirting board of the room wall, similar to heating pipes mounted on the wall. The surface area that can be achieved is relatively large. There is no need for active cooling by fans. If the line with a large cross-section is led vertically as high as possible and then back again, the natural convection means that a circulation pump can be dispensed with entirely. For example, in order to dissipate 500 watts of power, an internal pipe diameter of at least 25 mm is required with a 2 meter rise and a total pipe length of 5 meters and a temperature difference of 15 K to the ambient temperature.
With "active-active" cooling, the coolant is actively cooled by means of a compressor (as in refrigerators / freezers).
construction
A currently common PC water cooling consists of
- Heat sink (at least for the main processor (CPU), partly also for the graphics card (GPU) and other components, such as northbridge , southbridge , hard disks , power supply , RAM and voltage converter)
- Pump (partly custom-made based on aquarium pumps)
- Expansion tank (to allow temperature-related expansion of the cooling medium, as well as for filling and venting)
- Radiator (heat exchanger for recooling)
- Fan (with active cooling)
- Hoses ("piping")
- Accessories like
- Mounting screws and hose connections
- Anti-kink springs (sometimes useful)
- Cooling water thermometers, flow indicators, etc.
- Cooling water additive ( corrosion protection and prevention of algae formation )
The "classic" water cooling is built into the computer on site using the above-mentioned components. This requires z. T. some effort, for example, the main board (motherboard) may have to be removed in order to be able to attach the retaining screws for the cooler, and suitable inlets and outlets for the radiator must be introduced in the housing if the housing does not have enough space for one Radiator offers.
Working method
The water in the cooling circuit is moved by the pump. In the heat sinks, it absorbs the heat from the components to be cooled and transports it to the radiator, where the heat of the cooling water is released into the ambient air. All components are hydraulically connected in series (coupled one behind the other) to ensure an even flow through all heat sinks.
In the meantime there are also systems in which the pump, radiator with fan and expansion tank are combined in one housing and only the cooler has to be installed in the computer and connected to the cooling system with hoses. Some of these systems are so small that they can be accommodated in two to three 5.25 ″ drive bays. These compact systems in particular have the disadvantage of the relatively small fans, which also have to rotate quickly and generate a corresponding background noise. The cooling performance also does not come close to that of a classically constructed water cooling system, but is sufficient for standard PC systems. External systems can be made larger and are the easiest to assemble.
Apple installed the first water cooling system suitable for mass production for the PC area in their Power Mac G5 , and the first TÜV-tested water cooling system for AMD / Intel PCs is now available. There have also been water cooling components that are small enough to be built into a mini PC for some time.
Problem
In the event of a conversion, it should be noted that the manufacturer's guarantee usually expires. Claiming the statutory warranty can be more difficult because the dealer will claim that the defect was caused by the conversion. Therefore, such a conversion will often lead to the rejection of claims, which is why there is only one way to court.
Components in detail
The picture shows such a CPU water cooling unit. The central element is the metal block , which sits on the CPU with a thermal paste. In this case, the material is excellent thermally conductive copper , with meandering milling for the water channel, with a groove for the surrounding O-ring for sealing. Then the acrylic cover with the connections for the hoses for the water supply and drainage, and with the clips for fastening the unit to the main board .
Heat sink
The heat sinks work according to the heat exchanger principle . These are made of aluminum or copper and are occasionally nickel-plated, silver-plated or even gold-plated. There are also heat sinks made of solid silver, which has the highest thermal conductivity of the metals mentioned, but is very expensive and easily corrodes or tarnishes.
While the first heat sinks simply contained a simple tube inside, possibly in a U-shape, the structure of the heat sinks became more and more sophisticated over time in order to offer the largest possible heat transfer surface to the water flowing through. For a long time, so-called core coolers, which consisted of a turned, cylindrical copper core and a shell (mostly made of aluminum, Delrin or Plexiglas), were considered to be the most powerful coolers. However, since these were very complex to manufacture and accordingly expensive, they met with little approval.
There are now systems with fine channels, needles or even a honeycomb structure ( nozzle cooler ). Thus, the water surface and flow speed are increased many times over at this point, so that a turbulent flow is reliably achieved. This ensures an increased heat transfer with a higher pressure loss in the system.
In order to avoid corrosion, which reduces the heat transfer, an anti-corrosive agent is added to the cooling medium; commercially available agents from the automotive sector are absolutely sufficient. The heat sinks are adapted to the respective processor, its fastening system and the hose system within the cooling system.
Since the further development of graphics chips is accompanied by increasing waste heat, water heat sinks for graphics cards are playing an increasingly important role. A basic distinction can be made between coolers that are only intended for the graphics chip (GPU) and so-called complete coolers that cool both the GPU and the RAM as well as the voltage converters of the graphics card. In the case of coolers that only cool the graphics chip, however, there is a risk that the service life of the graphics card will be reduced if the airflow over other components of the graphics card of the original fan is eliminated. Mounting a water cooler on graphics cards is also often associated with loss of warranty.
When cooling other components (chipset, hard drives, etc.), the coolers are kept simple due to the relatively low waste heat so that they do not unnecessarily slow down the flow.
There are now also heat sinks for game consoles .
pump
The pumps used were high-quality aquarium pumps that are continuously operational and very quiet. While the pumps used to require their own 230 V supply and had to be switched on separately from the computer (but there is a risk of forgetting to switch on the pump), there are now control units that are dependent on the computer's power supply and can be connected directly to the power supply 12 V pumps. With a pump, not only the delivery rate (liters per hour), but also the maximum delivery head ( meters of water column , mWS) is an important criterion, as these data represent a measure of the performance of the pump. The pump must overcome the flow resistance or pressure loss of the entire cooling circuit, which is determined, among other things, by hose diameters, angles and the structure of the heat sink and radiator. The pressure drop is given either in bar or mWS (10.19 mWS = 1 bar). Differences in height in the filled cooling system with inflow and outflow at the same level are not important, as the water is only circulated.
surge tank
The expansion tank offers sufficient space for the cooling medium when it expands due to heating and is used for simple filling and venting of the water cooling. It usually consists of plexiglass or aluminum and is also available in exclusive and high-quality versions in which the water can be viewed through a porthole, for example, or in which the water is illuminated with light-emitting diodes, which is partly supported by fluorescent water additives. Nowadays, pumps are also manufactured that sit directly in the expansion tank and thus take up less space in the housing.
radiator
The radiators usually consist of a copper pipe that is in contact with many thin metal lamellas or fine water channels with thin metal bars between them. The second variant is the more powerful, but also more expensive, due to the larger cooling surface. The radiator size is determined by the maximum heat output of all computer components to be cooled. This heat output is measured in watts.
A large part of today's active radiators fit fans with a wheel diameter of 120 mm or 140 mm, which due to their size can work at a relatively low speed and thus quietly in order to generate the required air flow. Such radiators for 1–18 fans are available on the market, some radiators being supplied with fans.
Hoses and connections
Hoses and connections are considered together, because not every type of connection is suitable for every hose (and vice versa).
Hose dimensions are specified for the specific application as "plug diameter × wall thickness". The second diameter specification (depending on the system, i.e. inside or outside diameter) is calculated by adding (ESV system) or subtracting (plug-in system) twice the wall thickness from the nominal diameter.
The most common connection system are the so-called ESV connections (screw-in fittings): Here the hose is attached and held in place by a union nut. The hoses used are usually manufactured with a wall thickness of 1 mm, depending on the design of the system. The most common type of tubing used with these connectors is made of polyvinyl chloride (PVC). Tygon is now widely used: these hoses are more elastic and flexible thanks to special plasticizers and are therefore easier to lay.
The minimum laying radii are around 40 to 60 mm, depending on the hose. The ESV connections are mostly made of metal (MS-Ni) and are quite small, so they look very high quality and are hardly bulky. They are also quite inexpensive at around 1 euro per connector.
Alternatively, there are connector systems. Basically, this system also comes from the field of pneumatics. In addition to the Festo Quick Star system , a structurally equivalent system from the French manufacturer Legris is also used. These connections are significantly larger than pneumatic connections and require special, thick-walled and therefore very rigid hose (mostly made of polyurethane (PUR)), which also requires larger laying radii of 60 to 80 mm. Here the hose is simply plugged into the connection, held in place by metal clips and sealed with a rubber ring. To release the connection, an externally attached ring is pressed into the connection and presses the retaining clips apart.
Problems arise if the minimum bending radii are not reached, if the hose sits at an angle in the connection or if it is slightly deformed into an oval cross-section. In this case, leakage problems often arise. In addition, the hoses must be cut as straight as possible.
The elbow fittings designed for pneumatic applications have small deflection radii, which are to be regarded as unfavorable for water applications. In addition, the price for individual purchases is from 2.50 to over 5 euros.
There are two different thread types: conical with Teflon seal (designation for example R 1 ⁄ 4 ″) and straight with rubber seal (designation for example G 1 ⁄ 4 ″). The first variant with a conical thread (R thread) is not suitable for direct screw connections with plastic and Plexiglas, as the seal is made in the thread and the forces that occur during assembly can damage the cooler. The cylindrical version, on the other hand, can be used anywhere without any problems.
Hose nozzles are rarely used on the European market except as connectors and actually only have disadvantages compared to the aforementioned systems, above all the greater risk of leaks if they are not installed carefully. Hose clamps or cable ties often have to be used to prevent the hose from loosening.
In the American market, on the other hand, nozzles are widespread, as larger hose diameters ( 1 ⁄ 2 ″ and more) are often used, which means that the systems are designed for high flow rates. In the meantime, this trend is also gradually gaining acceptance on the European market, as standard garden hoses can be used by using 1 ⁄ 2 ″ nozzles.
In summary, the ESV connections are quite easy to handle in practice. Assembly errors can hardly occur due to the design. This system is safe to use even with frequent dismantling. In addition to the disadvantage of the necessary larger bending radii, connector systems also have the disadvantage that the necessary rigid hoses exert higher forces on the components, which can lead to contact problems with VGA cards, for example. After dismantling, the hoses used should be shortened or replaced, as the metal clamps of the bracket can cause scratches on the hose if dismantled carelessly, which can lead to leaks when reassembling.
The details of the connections always relate to the plug diameter:
- ESV system: thread / inner diameter / wall thickness, for example: G 1 ⁄ 4 inches - 8 × 1, the hose here has the dimensions 8 mm inside and 10 mm outside
- Connector systems: thread / outer diameter / wall thickness, for example: G 1 ⁄ 4 inch, 10 × 1 hose has dimensions of 8 mm inside and 10 mm outside. Despite the other information, they are the same hoses.
- In the case of sleeve systems, the outer diameter of the sealing lips of the sleeve is usually specified (for example 14 mm), according to which the hose to be used must have a slightly smaller inner diameter (for example 12 mm) so that the hose is tight enough to be able to seal. The outside diameter and the wall thickness are irrelevant.
For example, the designation 8 ⁄ 6 is also common for hoses with an outer diameter of 8 mm and an inner diameter of 6 mm, which results in a wall thickness of 1 mm. The designation 8 × 1 is also common for these hoses. If the reference diameter is not specified (for example 8a × 1), there is a risk of confusion with 8i × 1 hoses, which then have an inner diameter of 8 mm and an outer diameter of 10 mm , especially when using hoses and connections from more than one manufacturer.
Water addition
Corrosion protection with the aid of water additives primarily has the purpose of protecting the water cooling system from biological activity and its consequences, as well as from corrosion. In addition, the addition also takes over the lubrication of the pump. Modern cooling water additives meanwhile allow ordinary tap water to be used in the cooling circuit. Another desirable side aspect is often the lowering of the surface tension of the water, which in particular facilitates the ventilation of the cooling circuit.
For reasons of cost, anti-freeze from the automotive sector ( e.g. Glysantin ) is often used . In addition, the additives contained therein have a corrosion-inhibiting effect on mixed metal installations. If the anti-freeze property is not required, less high doses can be used. A mixing ratio of around 1:10 is then common. In principle, however, the conditions in a PC water cooling circuit are much more conducive to microorganisms, since the coolant is not regularly "boiled" here as in a combustion engine, but is mostly in a temperature range that is optimal for bacterial growth (between 30 ° C and 40 ° C) so that further antibiological additives may be necessary.
The cooling water can also be colored by adding color additives, which creates an additional optical effect with transparent hoses. Commercially available food coloring is theoretically sufficient for this, but is not long-term stable and therefore unsuitable from a technical point of view. Ultraviolet (UV) reactive colors light up in connection with a built-in UV lamp, the so-called black light . However, hoses made of UV-resistant material should then be installed. It is also common to observe that many plastic parts (including those on the mainboard) become discolored or hardened after months of UV exposure. The coloring of the cooling water has no additional use and should, if at all, only be done for a short time and the system should then be thoroughly cleaned. Color additives can reduce the cooling capacity of the system or attack seals, pump bearings and coolers.
Installation
The placement of the radiator is of great importance when installing water cooling. In the case of passively cooled systems, it is only possible to place them outside the housing, on the one hand for reasons of space, because passive radiators often compensate for a lack of ventilation through size, and on the other hand because additional fans would have to transport the heat from the radiator out of the housing when installed inside the housing which contradicts the concept of the passive radiator.
Alternatively, it can be attached to the rear wall. Usually only a single radiator can be attached in this way. Other installation locations are also possible, such as the side, housing front or floor. The housing and pump size play an important role in the installation of the pump and expansion tank. Some expansion tanks have suitable brackets with which they can also be attached to the outside of the housing (for example at the rear). The advantages here are that they are not a hindrance in the housing and the housing does not have to be opened to fill the cooling system.
After successful installation, the system is filled and vented. Distilled or demineralized water with an anti-algae additive is usually used. It is often recommended to assemble the complete water cooling system outside of the computer, to fill it up and to check it for leaks. However, this only makes sense if it can then be installed without being dismantled again. Coolant can escape when bleeding. A test of the built-in water cooling while the pump is running and the computer is de-energized can reveal possible leaks and contribute to venting the cooling circuit.
When installing inside the housing, a housing that is too small can prevent the installation of a dual or triple radiator. If the radiator is attached outside of the housing, the choice of housing is not restricted. It can then, for example, be attached to the housing with the aid of a corresponding bracket; the bracket leaves a distance between the radiator and the housing. A triple radiator with a midi tower can also be used.
If the radiator is to be attached to the rear, but the housing does not offer space for the 120 mm variant, there are also 80 mm wide heat exchangers. Particularly when the radiator is attached to the front, bottom or side, additional housing ventilation (rear panel or cover) may be required.
Integrated systems
There are also solutions that integrate the components of a water cooling system in a small space. The unit shown here was sold to be built on AMD Athlon processors. A water pump is integrated in the aluminum body of this unit. The water runs through the blue plastic shafts to the copper pipe cooler. There, the coolant is cooled by an air flow generated by a fan between the aluminum body and the copper cooler.
The problem with such units is the lack of information about the need to replenish the coolant. If the circulation no longer works, it is only a matter of time before the high processor heat also affects the plastic. These systems are neither more powerful nor quieter than good conventional air coolers or water cooling systems made up of individual components. In addition, it does not solve the basic problem that the waste heat from the processor remains in the PC housing and has to be dissipated in some other way.
Web links
Individual evidence
- ↑ https://www.hardwareinside.de/phononic-praesentiert-gigantische-cooling-power-dank-thermoelektischer-peltier-effekt-kuehler-19545/
- ↑ http://www.pcgameshardware.de/Overclocking-Thema-98540/News/Kompressorkuoice-im-PC-machts-moeglich-Stark-uebertaktete-CPU-und-Grafikkarten-bleiben-extrem-kuehl-1113510/