An area where 1U chassis are unique is internal volume. How much can you stuff inside, AND, can you properly cool it under all the conditions in which it will be deployed? The issue of watt density vs. thermal dissipation in a 1U chassis begins with reduced ratio of internal air volume. Now, if you’re only dissipating a few watts then conduction or convection may be adequate. But, when power goes up, things get more interesting. There’s more airflow back pressure, air is more turbulent and luck would have it, air doesn’t flow where you need it most. Actually, luck doesn’t have anything to do with it. Can you get enough air in and back out again (fast enough to cool adequately), etc? If airflow isn’t uniform under pressure (negative or positive) then what makes air flow the way it does . . . relatively unpredictably. Getting air to flow how you might think it should flow is like herding chickens.
We’ve had great success and have developed numerous cost effective techniques and strategies. Some of these strategies go beyond just the enclosure, fans and holes in the chassis. It often begins at the board level. While we don’t design PC boards, if we are involved early enough in the product design process we can provide valuable input into component placement that can yield significantly improved thermal dissipation.
In this example, even though all the air intake was in the front 25% of the enclosure and there was a spread of 4 high-volume fans, the majority of the air would go around the heat sinks, not through them. We suggested separating the hottest components from each other. We also employed zoning and compression airflow techniques resulting in successful cooling of this 375 watt 1U chassis.
