Fan Curves and Fan Laws
Fan Curves and Fan Laws
(OP)
Hello,
I have a question maybe you can help me with. We are upgrading an existing heating ventilating system. I have the original drawings that show the design CFM and SP. Is it possible to plot the fan curve using the affinity laws? I have used the CFM and SP relationship to plot a curve using the orignal design values as constants, varying the CFM from 100 to 10000 in 100 increments, and solving for the static pressure at the different CFM's. A plot of this looks more like a system curve than a fan curve. Am correct in assuming that this would be a system curve? I am assuming that the fan curve and the system curve intersect at the design cfm/sp.
I have a question maybe you can help me with. We are upgrading an existing heating ventilating system. I have the original drawings that show the design CFM and SP. Is it possible to plot the fan curve using the affinity laws? I have used the CFM and SP relationship to plot a curve using the orignal design values as constants, varying the CFM from 100 to 10000 in 100 increments, and solving for the static pressure at the different CFM's. A plot of this looks more like a system curve than a fan curve. Am correct in assuming that this would be a system curve? I am assuming that the fan curve and the system curve intersect at the design cfm/sp.





RE: Fan Curves and Fan Laws
The original fan would have been selected so that it's curve intersected the system curve at around the design flow rate (but with a margin "in hand" to be sure!). Thee fan could have been a constant flow type (vertical line) or constant head type (horizontal line) or (in the real world!) somewhere in between.
Only when you've selected a particular fan will you be able to superimpose the fan curve on your existing graph.
Regards,
Brian
RE: Fan Curves and Fan Laws