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Cooling hardware

Evgenie Rudometov, Victor Rudometov.
authors@rudometov.com

Article is grounded on substances of books PC: customisation, optimisation and dispersal — 2 izd., the reslave. And dop. — SPb: BHV, 2000, 336 and "the Arrangement of the multimedia computer".

For support reliable and a quiescent operation of modern, high-powered units and computer subsystems in regular and especially in the forced modes it is necessary to provide their effective cooling.

Modern high-powered units and computer sites are characterised by a considerable heat release that demands the adequate resources providing temperature functional modes recommended by implementators of accessories.

The choice of hardware of support of necessary temperature modes is expedient for starting from computer tank. For the architecture of modern computers the optimal are tanks of standard ATX. Thus, considering a high heat release of the units maintained in forced modes, it is expedient to be oriented to type tanks mini ATX or even more volume midi ATX, providing the best temperature mode for accessories of all system.

It is useful to supply the selected tank of the computer with additional fans which provide lowering of temperature of air in used tank. It raises an overall performance of local resources of cooling of electronic parts of the computer. Heat sinks and the cooling fans installed, for example, on the central processor unit, a chip set, videoadapter chips concern such local resources.

Since processors 486DX2/66 heat sinks (heatsinks) became the integral data attribute of units. It is linked by that together with growth of computational capability of processors their heat release, as a rule, grows. According to it it is necessary to increase the size and effective square of the heat sink. But, despite all reasonable efforts, the processing techniques of semiconducting production linked to improvement and perfection of the architecture of chips, a heat release of high-powered units increases fast rates. Therefore already from Pentium processors in addition to traditional heat sinks began to mount special cooling fans. Such resources often name as coolers (from English cooler — the cooling arrangement).

Further the tendency of usage of the coolers providing maintenance of a necessary temperature mode of maintenance of high-powered units, has captured also the videoadapters which basis is made by video chip sets. It is necessary to mark, that on internal complexity the newest video chip sets concedes to modern processors a little. Created on similar processing techniques, they, as well as processors, also demand intensive cooling without which their maintenance, as a rule, is impossible.

It is necessary to mark, that in addition to the specified resources for improvement of the thermal contact electrode of tank of a cooled unit with the heat sink attached to it it is expedient to use the special thermopastes released as the domestic industry (for example, КПТ-8), and foreign (for example, Arctic Silver). Alternatively or additions to thermopastes can be used appropriate thermofilms. The given resources — thermopastes and thermofilms eliminate an air slot between tank of a cooled unit and its heat sink. It promotes the best transmission of heat from a protected unit to the heat sink and accordingly more effective cooling of the given unit.

So, usage of heat sinks provides the best temperature mode of maintenance of electronic parts. Heat sinks increase heat exchange of cooled units, for example, the processor, a video chip set, etc . With a surrounding medium. It is carried out at the expense of substantial growth of square of a cooled surface in comparison with square of tank of an electronic unit. The more the heat sink square, the dissipates through it of warmly cooled unit in environing space more intensively. There are the various manufacturing techniques of heat sinks influencing its quality. However it is necessary to mark, that qualitative products, as a rule, are not only effective, but accordingly and rather expensive units. But, as a rule, such units are the optimal components of systems of cooling.

Heat sinks are usually made of aluminium — the cheap substance well leading heat. Copper, of course, — is better, but this substance essentially is more expensive. Besides, a specific gravity of copper it is considerable above, that leads to increase in weight of the heat sink and complicates a problem of its mount.

From physics it is known, that bodies of dark colours ray heat better the light. For this reason at a choice of the heat sink it is necessary to give preference to heat sinks of black colour though for giving to the products of more advantageous sort manufacturers use colours of gold and silver. But black colour is optimal. However it is necessary to pay attention that black colour is reached as a result of application of the special processing techniques linked to etchback in chemical, a sputtering of special substances, etc . And, of course, the due result cannot be reached by means of usual black colour which is faster a thermal insulator, than an explorer though there is also such coating. Certainly, it concerns bad quality products, as a rule, from unknown manufacturers.

Qualitative characteristics of heat sinks are thermal conduction coefficient (thermal conductivity) and thermoresistance coefficient (thermal resistance). The thermoresistance  is a value, return thermal conductions, substantially depends on a substance of which the heat sink is made. For this parametre dimension S/Vt uses. It is necessary to mark, that the value of the given parametre influences not only a heat sink substance, but also its sizes, the form etc ., and also processing technique and quality of manufacture of the heat sink. The thermoresistance shows the value on which the temperature of the heat sink concerning an ambient temperature will raise at dispersion by a cooled unit, for example, the processor of power of 1 W. For example, at a thermoresistance in 2  With/Vt and power disseminated by the processor in 15 W the temperature will raise on 30 s. Values of this parametre usually are in limits from 0,3 to 2 s/Vt. By the way, the big role plays so much size, how many a heat sink construction. Therefore the big sizes of the heat sink at all do not mean, that it is better than what is less.

The best cooling properties the construction consisting of the heat sink and the fan possesses. The fan (fan) is usually installed over the heat sink having the thermal contact electrode to the cooled object. The fan is intended for a vending of warm air from the heat sink and simultaneous feed in it of colder stream of air.

There are some types of fans which differ type of used bearings: sliding bearings (sleeve bearings) and-or bearings kachenija (ball bearings). It is Thus better, if the bearings used in a construction of a cooler, will be bearings kachenija. It is linked by that sliding bearings, as a rule, are less reliable and usually possess more high level of noise. Fans on the basis of bearings kachenija work on the average twice longer their clones on sliding bearings. Both types often use. It is better, if bearings kachenija — double ball bearing cooler use only . In this case period of maintenance of the fan increases, at least, in one and a half time, in comparison with a variant providing simultaneous usage of both types of bearings.

Period of maintenance of fans makes usually 2-3 years. However follows periodically, as a rule, not less often than an once in a year to clear cooling fan of the accumulated dust. In due course the dust, settling on fan blades, can not only is essential worsen parametres of the arrangement of cooling, but also serve as the reason of a stop of the fan, mortality of a cooled unit, for example, the processor, the video chip, etc. can be result of that . It is necessary to mark, that for preventing of an overheat of the processor from a stop of the cooling fan, in a construction of the processor, the motherboard, BIOS, the system software of modern computers the whole system of hardware-software warning facilities and protection is provided. Such system incorporates the various sensors which are carrying out the control over temperature and supply voltages. About existence of the given resources it is necessary to be convinced at an analysis stage and a choice of accessories of the computer before their acquisition.

There are some key parametres characterising productivity of the fan. The given parametres are designated as CFM, LFPM and RPM.

Parametre CFM (cubic feet per minute) characterises speed of feed of air, i.e. Shows how many cubic foots of air blows the fan for one minute. Typical values of this parametre for modern fans make 10-15.

Parametre LFPM (linear feet per minute) characterises a linear velocity of a stream of air in foots a minute. Typical values — 500-800. Having increased LFPM value on square of a stream of air created by the fan, it is possible to receive option value CFM.

Parametre RPM (rotations per minute) shows speed of rotation of the fan in turns in a minute. Typical values of this parametre — 4000-6000 rpm.

The more each of described parametres CFM, LFPM and RPM, the above productivity of the fan, that it is better as a unit of system of cooling.

The sizes of fans for modern processors make usually 50 50 10 mm.

The level of noise gauged in decibels (db), characterises operation qualities of the fan. The high level of noise, as is known, badly influences nervous system of the user, irritates and tyres. Fans with level of noise of an order 20-25 db (less — better, more — is worse) are good   . Quite often raised level of noise is called by vibrations of its construction. Therefore one more of tags of the qualitative fan is an absence of considerable vibrations. If from the fan working in a hand any vibrations this fan not so excellence and is better to pay the attention to another are felt.

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