Thermal Chambers and Wind Tunnels at Corsair's Office

The Wind Tunnel: A Tool for System Designers

Completely runs the fan at a speed, measures the pressure at this location and then plots that point here. This point is not useful to system designers other than to just have some way of comparing the system. Um because this doesn't occur in real life if you have zero flow it's not doing any good for you at all. The wind tunnel begins by opening valves inside here and allowing some air to flow from first chamber into the second chamber and that reduces the static pressure and the flow increases.

So as that happens the next data point is here and then it opens up some more and here and here and here and it works its way all the way down until the pressure here equals atmospheric pressure and that is the zero resistance point or maximum flow which is the other spec that you see on the box. Which is also doesn't occur in reality because if you don't have any resistance there's nothing in the way of your fan right just in reality your system will be somewhere in between these points and you can plot a resistance curve for say like a radiator um and that curve will go up in this direction and where those two curves intersect is the actual pressure and flow that you will receive when you combine those elements in a system.

That's actually the really useful information. Each one of these lines is a different speed, this 100% 90% 80% and so on all the way down to 20%. The horizontal lines here are the fans RPM excuse me these are the fans RPM and so um this blue line corresponds with this orange kind of peach colored line this green line with this purple line Etc. It shows the RPMs over here and as you can see this fan is very stable regardless of the amount of resistance it receives it doesn't really fluctuate and speed very much and that so that's the report you get after using it mechanically uh let's I guess walk from this end to that end what's going on inside of the Wind Tunnel.

So let's back up just a smidge um here is the plate where we Mount the device to be tested a fan or a radiator I've even hooked up whole cases to this thing um and measured flow resistance in cases um this ring right here is attached to four pressure Taps. This is the static pressure sensor it measures this in relationship to atmospheric pressure outside of the room inside here there are several screens those are to diffuse the flow so that the air Flows at the same speed through the entire diameter of the Wind Tunnel that's necessary for the calculations because the math makes certain assumptions about the diameter of the wind tunnel and how fast the air is Flowing.

These two pressure Taps here are differential they're measured against each other this is the high side pressure this is the low side pressure um in this plate here in the middle there's a series of valves that start out about half an inch in diameter and go all the way up to several inches in diameter and it can open one or more valves depending on the type of test that it's doing. This chart here actually shows the smallest valve is 8 mm in diameter and the largest is 42 but in this 32 plus 42 and all and it tells you the CFM range for whatever combination of valves you have open at that time.

So when measuring the differential pressure across here and knowing the exact diameter of the valve it knows the parametric pressure and it knows the temperature and humidity of the air calculates the air density can then calculate the exact CFM flowing through the system um this chamber has a couple more screens in it to equalize the flow and then that tube goes out to a big fan right there that's the counter blower. Um this is necessary because the wind tunnel itself has significant airflow resistance and so it actually pulls a vacuum in this chamber in order to get the flow that it needs to achieve in the first chamber.

Um this chamber often operates below atmospheric pressure that's that's normal so in order to get to this chamber this point here to equal atmospheric pressure this chamber here has to be significantly below atmospheric pressure very cool then uh wrapping it all back to the end product. This is the the numbers that come up on the box at the end of the day come up in the new XC sheet comes from something like this I guess that's correct all the published specifications for all of our fat products come out of this machine um.

This machine costs about $75,000 and once a year I fly a guy out from Taiwan to come calibrate it um his calibration reports are nist trable and you can actually go up on the National Institute of Standards website and look it up um so I am very confident in the numbers and performance data that comes out of this machine.