Pressure/Flow Interaction between pump and Valve 1

[totalfit]

I am trying to model a pump(ID fan) and a valve(damper) in a furnace ID fan loop and am struggling to understand the interaction of pressure and flow under the following conditions. ID fan rated for 134000 ACFM @ 13" Damper is at the ID fan inlet.
If the ID fan starts with the damper fully closed, how do I calculate the pressure and resultant flows as the damper opens. We can assume the damper reacts in a Quick opening fashion.
Can anyone help me or does anyone what to make some money to help create the models.

 

[pmureiko]

A simple model would take into account the pressure drop across the valve, fan differential pressure, and pressure differential between the atmosphere and the furnace fire box. The pressure drop would be balanced by the differential available for flow. A more complex model is needed if there are significant friction losses in the air ducts or elevation changes.

Valve DP(function of flow) = Fan DP (function of flow)+ System DP

The pressure drop across the valve can be calculated from manufacturer equations and the valve flow characteristics (Cg and C1 for Fisher for example). I've curve fitted Cg versus % open with a polynomial. C1 is fairly constant.

For the fan you need a manufacturer capacity curve and also curve fit as a polynomial. Being a centrifugal fan you will get fairly constant discharge pressure if you are on the flat part of the curve, but can fall off quickly at high flow rates. I guess your probably near that portion of the curve and are better off with the actual curve.

 

[totalfit]

Thanks pmureiko, I wonder if you could explain in a little more detail, the following. Given the following data:
(System data in order of air flow)
Pri Fan running @ 37400ACFM & 4" @ 80 degF
Sec Fan running @ 37400ACFM & 10" @ 80 degF
PDrop across TOHeater = 3.1"
Pdrop across Multiclone = 3"
Various drops across dampers & Furnace = 5.2"
ID fan is capable of running @ 134250 & 13" & 630 degF
What would the pressure at the inlet of ID fan look like When ID fan not running and when IF fan running at full speed?
Can you guide me?