Pressure Control Via Vent and Inert Gas Valves

Preliminary signal flow diagram for column heat storage ctynamics 

Reduced signal flow diagram of preliminary diagram 

WjG = inert gas flow, Ibm/sec Wf = vent flow, Ibm/sec = column pressure, Ibf/ft  

From equation (17.6) we can see that open-loop pressure dynamics are essentially first order. Since in most cases the inert gas bleed and the vent flow are fiiirly small, the valve gains, SwjgIBBc and dwJdBc, tend to be small. Together with the first-order dynamics, this commonly leads to large controller gains (small proporticmal bands) and control valve saturation fcM fairly small disturbances. 

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