26 de janeiro de 2010

COOLING PC PROBLEM DESCRIPTION

Inside of computer cabinet there is always a metallic box named energy-source, which contains several electronic-components in a circuit-board (semiconductors, converters, rectifiers, resistors, condensers, inductors and transformers). Several kinds of electric devices, either industrial and domestic need an energy-source. The electric resistance of the energy-source electronic components causes natural loss of electrical energy in the form of heat that increases the components temperature. Each electronic-component is a particular physical system. Each temperature value corresponds to a particular system state with different physical variable values. Thus, changing the component's temperature modifies its electric behavior. On the other hand, high temperatures can cause irreversible chemical reactions and permanent material deformations in the component's insulation. When an energy-source model is tested, and increases its temperature above the operational limit, it needs to be cooled to avoid damage, and the electrical engineer adds a proper fan in its project.

A standard commercial energy-source-box with fan was used to assemble the first personal-computer prototypes. However prototypes are only rustic solutions and may have some imperfection. Probably in order to gain time when assembling their prototypes, engineers ventilated the CPU cabinet only with the energy-source fan, pushing or pulling the cooling air directly inside the CPU, because they were mounting prototypes in some laboratory with clean conditioned air.

Several electronic and electromechanical devices can be assembled in the cabinet of a computer central processing unit, CPU. Beyond the electric energy source, inside the cabinet of the CPU, there is a motherboard with on-board-devices, and controllers. Finally, the hard-disks and the media drives are connected by suited electric cables both to the energy source, and to the external bus. When the computer works, the energy-source supplies the suited energy to all devices connected to the motherboard. During the machine operation the processor and some other electronic chips, and electromechanics devices can generate heat inside the CPU cabinet.

To avoid troubles caused by increasing temperature, the most heated electronic components are connected to some metallic fin arrangement named heat-sink. The heat-sink dissipates heat by a steady-state heat-conduction to the air. However, this heat-transfer only occurs as a result of the difference of temperature between the heat sink and the air. Thus, both the energy source box, and the cabinet require obviously a suited ventilation.

“the bark of one dog was repeated thousand times along a forty years' dark”

Since the first prototypes until the 80386 /486 desktop generation, the processor and the bus chip-set worked with low MHz clock frequencies, and all the electric energy loss in the form of heat was dissipated only adding the proper heat sink arrangement. The vendor contract, and the installation guide of all these old machines recommended care with the air quality of the installation place, mainly because the old magnetic media drives were easily damaged by smoke and dust. Under these ideal clean surrounding care conditions, obviously, it is possible to maintain the same prototype ventilation paradigms. So, the use of the energy-source fan taking air inside the PC cabinet remains in place of the correct solution to ventilate and to cool all these old PC generations (i. e.) the problem created by this fail was simply transferred to the consumer, and only solved by more surrounding air requests in the contract clauses.

“and remains until the present”

The same error was widely repeated without questioning. So, until the present days this lamentable cooling mistake, that is present in all electric machines, remains untouched in place of the correct engineer solution.

Newer computer electronic circuits works with GHz clock frequencies. This fact increases the electric energy loss in the form of heat in all parts of the machine, and so, a great amount of more heat needs to be conducted to the internal cabinet air. The new processors and their chip-sets need much more cooling, with great efficiency both, in the heat-transfer solutions and ventilation.

(in the end of old electronic age, cold transistors and leads took place of hot valves and lamps ... now we can cook eggs again in electronic devices ... there is something putrid in this realm... one may ask oneself: are there some association between Intell and intellectvs? )

THE PROCESSOR COOLING

To cool actual processors, the electronic engineers must install a big fan-heat-sink unit, which is placed efficiently in contact with the metallic processor top surface by using thermal grease, and finally secure them all onto a suitable socket base. In the desktop models the form and size of the cpu-fan-heat sink unit may also vary, although the motherboard vendors suggest the use of high quality fan with 4800 rpm at least.

Applying only this solution has been the practice to take the cooling air inside cabinet by the fan and discharge it into the heat sink When there is, between the heat sink and the local air, a great difference of temperature this arrangement can resist, but if the surrounding air temperature increases, this apparatus fails, and the machine can burn if no external ventilators are provided to push the air directly to the machine with the cabinet all open.

THE INTERNAL AIR IS GUILTY

To take the cool air directly outside the CPU to the processor heat sink, other circular region with small holes is aligned with a tube until the square CPU_fan_heat sink As this circle-square tube-fan connection is imperfect, it is evident that part of the used-air flow is pulled through those four circle-square open spaces to low pressure regions inside the tube, which are created by the same fan, and circulates again across the heat sink with great loss of cooling efficiency, and the internal air is heated, and the above mentioned trouble returns ...

THE COOLING COMEDY CLIMAX

Very pressed to occult their difficulty to solve this critical and ridiculous mistake of heat-transfer, the electronic engineers did not think so far, they applied again their linear solution, and simply installed small fans in several devices, (we already can see fans in HD, video controllers …), and to complete the show of “fluid mechanics”,they distributed several fans pushing air out of the cabinet, through an amount of small holes made in a circular region with the same diameter of the fan.

In the climax of this amount of accumulated mistakes, beyond the oldest energy-source fan taking air inside the cabinet, now we can see that there is one of these big fans at each end, fighting against the other fans, and the result has very low heat-transfer efficiency.

THE ANNOUNCED DEATH

Outside of laboratory conditions the air quality is out of control. Under home conditions the air is unappropriated to cool personal computer machines using the above dark age solution. So, as we already know, the CPU box is not well ventilated, the internal air circulation will overheat near components and other devices inside the CPU and it can burn.

On the other hand, as we already know, it has been found preferable, therefore, to install ventilating ducts, taking cool air from outside the CPU. Therefore, if this same CPU box is well ventilated, then Machines thus ventilated accumulate dirt quickly and the general thermal efficiency loss occurs still more quick, because the blades of all fans are damaged by dusty layer and lost efficiency, and because dust penetrates in the fan rotor and stops it, then its circuit burns and the short circuit produce more heat, and finally the energy-source circuit burns and the machine collapses.

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