For those wanting to look into it in more detail, the "Do not operate region" is where a couple of undesirable conditions known as "surge" and "stall" occur. In surge, you typically have a more or less unrestricted inlet, and a large volume of air downstream that can allow pressure to build up without escaping. In stall, you have a flow restriction greater than the maximum static pressure the fan can achieve. Because the fan can't generate enough pressure to get the air moving freely, the flow rate gets stuck in the stall trough. It's not really visible with the fan selected for the video example, but other fan curves can have rather dramatic valleys in them towards the left side of the curve. Hunting is not an inherent behavior of the fan, it's found when the fan is controlled with a feedback loop (a PID in some form or another), most commonly controlled off of static pressure. If you try to operate in a region of the curve where one static pressure can indicate two different flow rates, you end up in a situation where the controls endlessly ramp the fan speed back and forth, or endlessly move a damper, because it can't settle in to a single operating point.
If we have a fan just as a propeller, without any electric motor, how can I size and select a driver for it( considering the BHP)? Should I divide the BHP in the fan curve by the efficiency of the electric motor?
Here, it is generally mentioned how to choose fans theoretically and how to read fan curves. These curves and values will change for each model fan, but the logic will remain the same.
Presenter is easy to understand and follow. Overall a great video! Greetings from the UK
Wow, it was a very good explanation. Thanks a lot, now I understand the fan curves.
For those wanting to look into it in more detail, the "Do not operate region" is where a couple of undesirable conditions known as "surge" and "stall" occur.
In surge, you typically have a more or less unrestricted inlet, and a large volume of air downstream that can allow pressure to build up without escaping.
In stall, you have a flow restriction greater than the maximum static pressure the fan can achieve. Because the fan can't generate enough pressure to get the air moving freely, the flow rate gets stuck in the stall trough. It's not really visible with the fan selected for the video example, but other fan curves can have rather dramatic valleys in them towards the left side of the curve.
Hunting is not an inherent behavior of the fan, it's found when the fan is controlled with a feedback loop (a PID in some form or another), most commonly controlled off of static pressure. If you try to operate in a region of the curve where one static pressure can indicate two different flow rates, you end up in a situation where the controls endlessly ramp the fan speed back and forth, or endlessly move a damper, because it can't settle in to a single operating point.
what you say is indeed more accurate, hunting is pid loop and is different from stall region
Thank you for this video, really appreciate this👌🏾
This was incredibly helpful, thank you!
If we have a fan just as a propeller, without any electric motor, how can I size and select a driver for it( considering the BHP)? Should I divide the BHP in the fan curve by the efficiency of the electric motor?
Thanks for sharing
Is this chart just for your fans, or any fan in any system.
Here, it is generally mentioned how to choose fans theoretically and how to read fan curves. These curves and values will change for each model fan, but the logic will remain the same.
Good ❤
you lost me on hertz