I have several of the Papst fans, and have great respect for their design and manufacture.
While sold as new, they are obviously pulled from some sort of equipment as there is dust inside once one removes the E clip on the hub and has a look inside, also some scratches on the fan body from whomever removed them from whatever they were in. They have huge dual NMB sealed ball bearings, similar to the size on skateboards/roller skates. Their accumulated hours upto that point are unknown, but likely a tiny fraction of how much longer the fan will run.
They draw about 0.56 amps at 12.8v and move a respectable amount of air at that voltage.
They are rated upto 30V.
Above 28v the amp draw starts rising exponentially and it does not get all that much faster. The 283 cfm rating is likely at 24v but I've seen it speed at 242cfm @ 24v too. There is a pretty big speed difference between 24 and 28 volts. Not really sure which spec to believe, but it does move a lot of air, especially for the current consumed and noise made.
CFM ratings are a bit misleading, as they measure the velocity of the air and multiply it times the diameter of the fan. where they measure that velocity can have huge differences in final number, and CFM readings are taken in a no restriction environment. When restricted, a high cfm fan might have aerodynamically stalled fan blades, making noise and little air flow.
I've not seen any static pressure rating of this fan.
Minimum possible rotational speed is ~7.33v, +/- 0.1v but it needs closer to 8v in order to start spinning on its own, this latter number depends on temperature. At minimum speed the fan is super quiet, more of a slight clicking, and one can follow an individual fan blade as it rotates with their eyes. Amp draw through a buck boost converter is right around the 0.1 amp range @7.33v. The 3 Papst fans I have, the minimum rotational speed varied slightly as did the noise made at minimum speed.
I now power mine from a 10 amp buck boost converter which has a current control potentiometer, and limit current to 2.42 amps which limits voltage to ~29v
The fan blades are well balanced with little improvement possible. The air output is fairly column like, not spreading far and wide like some computer fans with 4 hotspots of flow between the hub supports.
Resistance behind the fan blades does not greatly reduce flow and greatly increase noise, like it does with many fans.
Getting some sort of finger protection in front of or behind impeller can be an is$ue depending on application. They sell grilles for its unique hole spacing.
I had one failure of a Papst, but I was trying a new 5 amp buck boost converter which fried, then when i bypassed it the Papst released some magic smoke. Avoid 5 amp buck/boost converters, in my experience, I only found one good one, but unintentionally smoked it.
There are 5 or 6 wires inside the jacket, red and black are obvious. One of the others could be for PWM speed control. IDK.
I've not had good luck sending a PWM signal on the 4th wire with PWM speed control on a 4 wire PWM fan. Lots of fan failures in short periods of time.
If one wants to feed a PWM speed control signal on red and black power feed wires, make sure the PWM motor speed controller you buy says 21kHZ or higher, or the fan will whine annoyingly at reduced speeds, to anyone without well aged ears.
If one wants to get the full speed from the 24v Papst fan they need to be able to feed it upto 30 volts. I've run mine, unintentionally to about 33v for over a half hour. That was before I had a buck boost converter with current limiting potentiometer. The hub was warm, not hot.
One can turn the voltage pot upto 28v on such a device and use the current limiting pot to control fan speed too, but I find this is less efficient and harder to dial in a low speed.
I have a friend who is using a 28v boost converter then plans on using a PWM speed controller on its output. if he cant figure out which wire, if any is the PWM wire for speed control. I do not like this approach, but at 28v his papst was using about 0.15 less amps than mine through a buck boost converter at 28v output. Could be measurement error too, as we are 2k miles apart.
