CONTINUOUS_MODEL AirShunt


ABSTRACT  "Recirculating AirShunt w on/off control.

           This shunt model is link-compatible with ICE secondary models
           HxSimCtr and MixBxCtr, except that it lacks a setpoint interface.

           The model has on off control:
             on    maximum fresh air
             off   min(0.001 * MSup, MExh)

           Model takes account of possible condensation in the mixing process.


              MFresh   --->   --->  MSup        ----
              TSupIn        ^       TSupOut   |
                            |                 |
                          MReturn             | Zone
                          TExh                |
                            |                 |
              MExhOut  <---   <---  MExh        ----
              TExh                  TExh

Date:      Dec, 2000

By:        Axel Bring
           
Call:      Enthal   from Psychro1.nmf
           HumRat   from Psychro2.nmf
           SatPres  from Psychro3.nmf

Revisions
"


EQUATIONS

/* Air mass balances */
  MFresh = IF FreshOn > 0.5 THEN
             min(MSup,MExh)
           ELSE
             min(0.01*MSup,MExh);
           END_IF;
  MReturn := MSup - MFresh;

  MExh = MReturn + MExhOut;

/* Moisture balance */
  WSupMix := (MFresh * WSupIn + MReturn * WExh) / MSup;
  WSupMax := HumRat(PSup + 1E5, SatPres(TSupOut));
  WSupOut = MIN(WSupMix, WSupMax);

/* Energy balance */
  HSupIn  := Enthal(TSupIn,WSupIn);
  HExh    := Enthal(TExh,WExh);
  HSupOut := Enthal(TSupOut,WSupOut);
  MSup * HSupOut = MFresh * HSupIn + MReturn * HExh;

/* Fraction balance */
  MSup * XSupOut = MFresh * XSupIn + MReturn * XExh;


LINKS

/* type      name           variables ....  */

   UniAir    SupIn         PSup, POS_IN  MFresh, TSupIn,  XSupIn,  WSupIn; 
   UniAir    SupOut        PSup, POS_OUT MSup,   TSupOut, XSupOut, WSupOut;

   UniAir    ExhIn         PExh, POS_IN  MExh,    TExh, XExh, WExh; 
   UniAir    ExhOut        PExh, POS_OUT MExhOut, TExh, XExh, WExh;

   Z         FreshCtr      FreshOn;



VARIABLES

/* type      name         role   def          min      max   description*/

   Pressure   PSup        IN    1325         -BIG      BIG   "Pressure of entering and leaving
                                                              supply air"
   Pressure   PExh        IN    1325         -BIG      BIG   "Pressure of entering and leaving
                                                              exhaust air"

   MassFlow   MSup        IN       3.2          0      BIG   "Supply air massflow rate"
   MassFlow   MFresh      OUT      3.2          0      BIG   "Fresh air massflow rate"

   MassFlow   MExhOut     OUT      3.2          0      BIG   "Leaving exhaust massflow rate"
   MassFlow   MExh        IN       3.2          0      BIG   "Incoming exhaust massflow rate"
   MassFlow   MReturn     LOC      3.2          0      BIG   "Return massflow rate"

   Enthalpy   HSupIn      LOC  10000         -BIG      BIG   "Incoming supply enthalpy"
   Enthalpy   HSupOut     LOC  10000         -BIG      BIG   "Leaving supply enthalpy"
   Enthalpy   HExh        LOC  30000         -BIG      BIG   "Incoming exhaust enthalpy"

   Temp       TSupIn      IN      10     ABS_ZERO      BIG   "Entering supply temp."
   Temp       TSupOut     OUT     15     ABS_ZERO      BIG   "Leaving supply temp."
   Temp       TExh        IN      25     ABS_ZERO      BIG   "Entering exhaust temp."

   HumRatio   WSupIn      IN       0.01     SMALL        1   "Humidity ratio of entering supply"
   HumRatio   WSupOut     OUT      0.01     SMALL        1   "Humidity ratio of leaving supply"
   HumRatio   WSupMax     LOC      0.01     SMALL        1   "Max humidity ratio of leaving supply"
   HumRatio   WSupMix     LOC      0.01     SMALL        1   "Humidity ratio of mixed air"

   HumRatio   WExh        IN       0.01     SMALL        1   "Humidity ratio of entering exhaust"

   Fraction_y XSupIn      IN     594            0      BIG   "Pollutant fraction fresh air"
   Fraction_y XSupOut     OUT    594            0      BIG   "Pollutant fraction supply air"
   Fraction_y XExh        IN     594            0      BIG   "Pollutant fraction exhaust air"

   Factor     FreshOn     IN       1            0      BIG   "Fresh air On / Off"


END_MODEL