VFD vs. damper controlled fan efficiency

[MeatWagon]

I am trying to evaluate the savings benefits of installing a VFD controlled fan. I can estimate the potential power usage of the VFD by applying the affinity laws because I have a good air flow demand profile for the system.

However, the current operation uses outlet dampers and/or inlet vanes to control the air flow. I am trying to figure out how to calculate the current power consumption as baseline usage. Is there an equation I can use to estimate fan power usage as a fuction of damper controlled flow? Is the power load profile different for inlet vane control than outlet damper control? I have the fan motor data but I do not have a fan performance curve. Is a fan curve necessary for my purposes?

 

[lilliput1]

No equation but there are performance charts available comparing all (3) systems. VIV bottoms out at about 45% turndown.

 

[MeatWagon]

Can anyone provide a source for these types of performance charts?

 

[lilliput1]

Do a google image search for "outlet damper variable inlet variable speed"

 

[walkes]

ABB used to provide software for comparing the different technologies on fan or pump systems.