Positive Air Pressure Cooling: This is a type of cooling setup where you have more air (CFM) moving into your case than being pumped out. This creates heat pockets where the hot air can’t get out and just serves to heat your case up. Unless you are using a special cooling system, don’t use this.
Negative Air Pressure Cooling: This is the most common cooling setup. This is when more air (CFM) is pumped out of you case than pumped in. This creates a vacuum effect where hot air is sucked out and the inside temp stays pretty stable. A guide
http://www.xoxide.com/computer-cooling.html
Technically both setups will have more CFM exiting than entering due to the increase in density from the temperature rise. Just use the push/pull analogy. As a side note, not everything from other sites, such as xoxide.com, is necessarily correct.
SECTION 2
Maybe mention that the CFM is linearly proportional to the speed and proportional to the diameter cubed. Noise proportional to ~ speed^5.5 and diameter^7.5.
Also, half this section is a direct quote from another site on the in depth difference of bearing types. Is this really necessary?
SECTION 3
Express thermal conductivity as W/m-K (W/mK is read as watt per millikelvin).
The reason that filling in the gaps helps – the thermal conductivity of air is 0.025 W/m-K. If there is a 1 micron (1E-6 m) average gap between the CPU heat spreader and the heat sink base, there is a resulting contact resistance of 0.063 K/W. Put in perspective, a decent heat sink has an overall thermal resistance of about 0.2 K/W (lower resistance = better cooling)
Aerodynamics: It sounds kind of weird but this is a huge factor in heatsink performance. Good heatsinks are designed so that air can move quickly through it, leaving no empty spaces. A single tiny heat pocket can completely ruin an otherwise decent heatsink. This factor also depends on the fan CFM. A heatsink with great aerodynamics will only benefit from a fan that can blow enough air to utilize this factor.
Aerodynamics is independent of CFM. The convection coefficient, on the other hand, is directly related to the CFM (or, more accurately, the velocity).
Thermal Transfer: This is the most obvious one since heatsinks are in existence to transfer heat. Surface area is needed to dissipate a lot of heat but thicker fins allow for more heat transfer. A happy medium needs to be found between surface area and mass. Most heatsinks have a thick base to transfer heat from the CPU and then move the heat to very thin fins on the top.
Technically you need to optimize the fin efficiency which is dependent on the length, cross sectional area, and convection coefficient. The convection coefficient is going to depend on the fin spacing – in too closely spaced fins the thermal boundary layers meet and cooling ceases.
SECTION 4
Heatspreaders. These are little metal plates that are attached to RAM cards and they try to dissipate the heat from the chips. These aren’t as effective as many manufacturers advertise.
Heat spreader is a term for, well, anything that spreads heat – an example being the piece of metal that is on all recent CPUs – and not exclusively for the RAM heat spreaders.
) or there are some errors ... regardless, a good start and points definitely noted.