CONTINUOUS_MODEL CeSfBeam ABSTRACT "Active cooling OR heating ceiling beam. Stifab-Farex models BRTa and BSAc. !! Handled as purely convective unit, with TQ interface to zone. The beam model includes an idealized supply terminal w damper, modelled separately by CeSupt.nmf. CeSfBeam handles either cooling or heating, with just one liquid circuit. CeSfBeam models only the heat transfer supplied by the liquid, the load from the ventilation air is modeled in CeSupt.nmf. One parameter 'ColdOrHot' specifies sign of heat flux. No condensation is assumed in cooling case. Model can combine output from one or more ceiling units, with individual parameters for geometry and heat transmission properties. These have been weighed together in a preprocessing stage. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Water flow If massflow control signal 'LiqContr' is positive, ideal internal massflow control is enabled. Requested massflow is maintained by adjusting pressure drop 'DpLiq' down to 'dp0Liq'. When DpLiq is below dp0Liq, linear (laminar) flow is assumed and requested massflow is no longer maintained. MLiq = MliqMin * DpLiq/dp0Liq. Flow control can also be turned off by giving a negative control signal (less than -0.5), in which case MLiq = MLiqMax * DpLiq/dp0Liq. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Heat exchange with air Due to the large secondary air flow from the zone, the heat exchange is assumed to be determined by zone air temperature, rather than supply air temperature. Heat resistance between liquid and air is divided into two fractions (we assume that convection to air dominates over radiation to zone surfaces): rTot = rFin + rAir. The corresponding temperature differences are related: TLiq - TSurf rFin ---------------- = ---- TSurf - TZoneAir rAir Date: 2000-09-27 Made by: Axel Bring History: 010103 ABg ExpLoc Safeguard: ExpLoc against dtLiqAir = 0 TLiqOut against loss of Jac el when ExpLoc outside range Rev 1.0 Coefficients in P = k dT^n are varying as a function of supply air flow. " EQUATIONS /***************** Begin of Liq section ***********************/ /* water massflow */ DpLiq := PLiqIn - PLiqOut; MLiq = IF DpLiqOk > 0.5 OR (DpLiq > dp0Liq AND LiqContr > -0.5) THEN MLiqMax*LiqContr + MLiqMin*(1 - LiqContr) ELSE_IF LiqContr > -0.5 THEN MLiqMin * DpLiq/dp0Liq ELSE MLiqMax * DpLiq/dp0Liq END_IF; /* liquid to surface heat balance */ TLiq := TSurf + (TSurf - TZoneAir) * kF_ALiq; dTLiqAir := ColdOrHot * (TLiq - TZoneAir); ExpLoc:= ColdOrHot * (TLiqOut-TLiqIn)/IF abs(dtliqair) > 0.0001 THEN dtliqair ELSE sign(0.0001,dtliqair) END_IF; /* TLiqOut = TZoneAir - (TZoneAir-TLiqIn) * IF MLiq > 0 THEN IF ExpLoc > -0.01 THEN EXP(-0.01) ELSE_IF ExpLoc < -5 THEN EXP(-5) ELSE EXP(ExpLoc) END_IF ELSE 0.0001 END_IF; */ TLiqOut = TZoneAir - (TZoneAir-TLiqIn) * IF MLiq > 0 THEN IF ExpLoc > -0.01 THEN EXP(-0.01+(ExpLoc+0.01)*1e-6) ELSE_IF ExpLoc < -5 THEN EXP(-5+(ExpLoc+5)*1e-6) ELSE EXP(ExpLoc) END_IF ELSE 0.0001 END_IF; /* interpolate in table to get kAct, nAct for current air flow MAir */ CALL LookUp2 (THREE,nPoint, TabLiq, MAir*AirFract, kAct, nAct); /* total absorbed heat */ QLiq := IF dTLiqAir < 1 THEN length * kact * dTLiqAir ELSE length * kact * dTLiqAir**nact END_IF; /* water heat balance */ 0 = ColdOrHot * QLiq + MLiq * cp_liq * (TLiqOut-TLiqIn); /****************** End of Liq section ************************/ /* heat balance w zone */ 0 = ColdOrHot * QLiq + QZone; /* saturated modes */ DpLiqOk := IF Event(GLiq, DpLiq - dp0Liq) > 0 AND LiqContr > -0.5 THEN 1 ELSE 0 END_IF; LINKS TQ Zone TZoneAir, POS_IN QZone; UniAir AirIn PAir, POS_IN MAir, TAir, X, Hum; UniAir AirOut PAir, POS_OUT MAir, TAir, X, Hum; PMT LiqIn PLiqIn, POS_IN MLiq, TLiqIn; PMT LiqOut PLiqOut, POS_OUT MLiq, TLiqOut; ControlLink Control LiqContr; VARIABLES /* air stream */ Pressure PAir IN 1375 -BIG BIG "Air pressure in/out" MassFlow MAir IN 0.024 0 BIG "Air massflow" Temp Tair IN 26 ABS_ZERO BIG "Supply air temperature" fraction_y X IN 594 0 BIG "Pollutant fraction" HumRatio Hum IN 0.006 SMALL BIG "Moisture fraction" /* liquid flow */ Pressure PLiqIn IN 600 0 BIG "Pressure at water inlet" Pressure PLiqOut IN 0 0 BIG "Pressure at water outlet" Pressure DpLiq LOC 600 0 BIG "Panel and valve total pressure drop" MassFlow MLiq OUT 0.005 0 BIG "Liq massflow" Temp TLiqIn IN 15 ABS_ZERO BIG "Liq supply temperature" Temp TLiqOut OUT 15.5 ABS_ZERO BIG "Liq return temperature" Temp TLiq LOC 16 ABS_ZERO BIG "Average liquid temperature" Control LiqContr IN 0.5 -BIG 1 "Controller input 1 -> mmax, 0 -> mmin, -1 turns off control action" GENERIC GLiq A_S 1 " " GENERIC DpLiqOk A_S 1 "Mode memory, = 0 for linear behavior, = 1 for controlled" /* zone contact */ Temp TZoneAir IN 17 ABS_ZERO BIG "Zone air temperature" HeatFlux QZone OUT 30 -BIG BIG "Heat from zone" /* device behaviour*/ Temp Tsurf OUT 17 ABS_ZERO BIG "Average surface temperature" Temp dTLiqAir LOC 10 ABS_ZERO BIG "Liq-to-Air temp difference" HeatFlux QLiq LOC 90 0 BIG "Total heat from liquid" GENERIC ExpLoc LOC -0.03 -BIG BIG "Value inside function call EXP(), itroduced as a safe guard" Factor kact LOC 10 SMALL BIG "Factor from eq P = k dT^n" Factor nact LOC 1.2 SMALL BIG "Exponent from eq P = k dT^n" MODEL_PARAMETERS INT nPoint SMP 3 1 BIGINT "number of points" INT THREE CMP 3 3 3 "3" PARAMETERS Factor ColdOrHot S_P -1 -1 1 "1 for heating, -1 for cooling" Factor AirFract S_P 1 0 1 "Device's part of air flow" Length length S_P 1 SMALL BIG "Total panel length" Factor kFinLiq S_P .2 0 0.5 "Fin resistance / Total ditto" Pressure dp0Liq S_P 10 SMALL BIG "Pressure drop under which waterflow is nolonger maintained" MassFlow mLiqMax S_P 0.01 SMALL BIG "Water massflow at Contr = 1 and Dp > dp0" MassFlow mLiqMin S_P 1.E-4 SMALL BIG "Water massflow at Contr = 0 and Dp > dp0" HeatCapM cp_liq S_P 4187 SMALL BIG "Liquid specific heat" Factor kF_ALiq C_P .25 0 1.0 "Fin resistance / Air ditto" /* content of matrix 'Table': MassFlow mFlow[nPoint] S_P 0.024 SMALL BIG "Massflow points in polygon " Factor k[nPoint] S_P 10 SMALL BIG "Factor from equation P = k dT^n" Factor n[nPoint] S_P 1.2 SMALL BIG "Factor from equation P = k dT^n" Values at zero air flow are fetched from kEgen,nEgen in database */ Factor TabLiq[nPoint,THREE] S_P 1 0 BIG "Coeffs from equation P = k dT^n" PARAMETER_PROCESSING Three := 3; kF_ALiq := kFinLiq / (1 - kFinLiq); END_MODEL