| 1 | #*------------------------------------------------------------------- |
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| 2 | * Model of a valve |
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| 3 | *-------------------------------------------------------------------- |
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| 4 | * |
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| 5 | * Streams: |
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| 6 | * * an inlet stream |
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| 7 | * * an outlet stream |
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| 8 | * |
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| 9 | * Assumptions: |
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| 10 | * * no flashing liquid in the valve |
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| 11 | * * the flow in the valve is adiabatic |
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| 12 | * * dynamics in the valve are neglected |
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| 13 | * * linear flow type |
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| 14 | * |
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| 15 | * Specify: |
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| 16 | * * the inlet stream |
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| 17 | * * one of: plug position (x), outlet temperature (Outlet.T) or |
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| 18 | * outlet pressure (Outlet.P) |
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| 19 | * or |
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| 20 | * * the inlet stream excluding its flow (Inlet.F) |
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| 21 | * * the outlet pressure (Outlet.P) OR outlet flow (Outlet.F) |
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| 22 | * * the plug position (x) |
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| 23 | * |
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| 24 | * |
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| 25 | *---------------------------------------------------------------------- |
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| 26 | * Author: Paula B. Staudt |
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| 27 | * $Id: valve.mso 37 2006-10-23 16:47:17Z paula $ |
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| 28 | *--------------------------------------------------------------------*# |
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| 29 | |
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| 30 | using "streams"; |
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| 31 | |
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| 32 | Model valve |
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| 33 | PARAMETERS |
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| 34 | ext PP as CalcObject; |
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| 35 | ext NComp as Integer; |
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| 36 | |
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| 37 | VARIABLES |
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| 38 | in Inlet as stream; |
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| 39 | out Outlet as stream_therm; |
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| 40 | x as fraction (Brief="Plug Position"); |
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| 41 | rho as dens_mass (Brief="Fluid Density", Default=1e3); |
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| 42 | v as vol_mol (Brief="Specific volume", Default=1e3); |
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| 43 | |
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| 44 | PARAMETERS |
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| 45 | rho_ref as dens_mass (Brief="Reference Density", Default=1e4); |
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| 46 | k as Real (Brief="Valve Constant", Unit="gal/min/psi^0.5"); |
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| 47 | |
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| 48 | EQUATIONS |
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| 49 | "Molar Balance" |
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| 50 | Inlet.F = Outlet.F; |
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| 51 | Inlet.z = Outlet.z; |
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| 52 | |
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| 53 | "Energy Balance" |
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| 54 | Inlet.h = Outlet.h; |
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| 55 | |
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| 56 | "Vapourisation Fraction" |
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| 57 | Outlet.v = Inlet.v; |
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| 58 | |
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| 59 | "Density" |
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| 60 | rho = Inlet.v*PP.VapourDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) + |
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| 61 | (1-Inlet.v)*PP.LiquidDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z); |
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| 62 | |
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| 63 | "Volume" |
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| 64 | v = Inlet.v*PP.VapourVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) + |
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| 65 | (1-Inlet.v)*PP.LiquidVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z); |
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| 66 | |
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| 67 | #if Inlet.P > Outlet.P then |
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| 68 | # "Flow" |
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| 69 | Outlet.F * v = k*x*sqrt((Inlet.P - Outlet.P)*rho_ref / rho ) ; |
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| 70 | #else |
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| 71 | # "Closed" |
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| 72 | # Outlet.F = 0 * "kmol/h"; |
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| 73 | #end |
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| 74 | end |
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