Thermally Advantaged Small Chassis (TASC) Design Guide

Section 2
E60781 11
Other Venting:
Besides the side vent, other vent locations are more difficult to specify as
configurations will vary and aesthetic opinions are diverse. While the side vent is
most critical, it is also important to ensure the total system is appropriately vented.
As the fans are specified as exhausting, vents will become inlets, drawing cool air in.
It is therefore beneficial to place venting near critical components, such as the hard
drive and power supply. In addition, the rear of the chassis should be well vented as
it generally has less aesthetic requirements as well as noise emission concerns.
Dust Considerations:
Depending on region, dust accumulation can pose a challenge as dust accumulates,
blocking fan inlets and degrading heat sink performance. For these concerns,
removable screens that may be cleaned by the user are the simplest option. While
there is associated air flow impedance by adding a screen, it is generally the best
option for dust prevention.
2.1.1.3 Chassis height
The distance between the CPU fan inlet and the side vent will impact thermal
performance. As the distance grows, recirculation within the chassis is worsened as
less cool air is drawn in from the exterior and directly into the heat sink. Distances
above 50mm are not recommended to maintain within T rise specification.
Figure 4. Recommendation of Chassis Height (Chassis Side View)
Note: distance between fan inlet and side vent should be less than 50mm unless custom air
guide is utilized.
2.1.1.4 General Component Layout
Component layout is specifically left open to the chassis manufacturer to maintain
flexibility and ability to provide differentiation. Besides height and vent size and
location recommendations, the final comment is to keep the zone between the vent
and the fan heat sink clear from obstruction. This includes, to the best ability,
allowing for cables to be routed around the fan heat sink, and not over the top of it.
By not obstructing the fan inlet, the fan is able to draw cool air into the fins, as well as
not impose added impedance to the fan.
Add in cards dissipating less than 20 Watts have been shown viable with the
recommended venting pattern and correct fan implementation. If a higher powered
50mm
HDD
ODD
IO