Getting rid of the heat
- In nature, there are three methods heat transfer: radiation,
convection,
and conduction. Without getting too scientific, radiation refers to transfer
of heat in form of "waves" which can travel through any medium, including
vacuum. The heat we receive from the sun is a form heat transfer by radiation.
Convection refers to transfer of heat due to the movement of substances, such
as hot air rising to the top of the room. Conduction is direct transfer of
energy from molecules of a hotter object to a colder one. Conduction works on
the principle that the molecules of a hot object transfer their energy to the
"less energetic" molecules of the colder object when they are in direct
contact in order to maintain equilibrium. Air cooling of the CPU uses
principles of conduction and convection to dispel excessive heat and keep the unit cool.
The
heatsink must be in direct contact with the CPU core at all times, which is
why thermal compounds are used to fill any possible gaps that there may be
even if it is not visible by the naked eye. By means of
conduction, the heat from the core is directly transferred to the heat sink.
As long as the heatsink has a lower temperature than the processor core, heat
will travel through them and core will be kept cool. Should heatsink become
the same temperature as the processor core then the cooling will stop being
effective. So now the next problem to address is how to keep
the temperature down. The main solution would be to keep the heatsink cool by transferring
it's heat to the surrounding air. For maximum contact with air, increasing the
surface area of the heatsink would be essential. Even so, air is a poor
conductor which means that it does not readily transfer heat. Convection comes
to play here; by using a fan to force air flow on to the heatsink, the air
molecules will take away heat energy from the molecules of the heatsink when
they come in contact, and carry it away as the fan pushes them out and takes
in colder air from the surroundings. In this manner the temperature of the
heatsink is kept down and in turn the processor remains cool.
