CONTINUOUS_MODEL EvHumCtr ABSTRACT "adiabatic EVaporative HUMidifier with On/Off ConTRol. Purpose: Calculate the performance of an adiabatic evaporative humidifier with control. Limits: Assumes adiabatic process with water temp at the outlet air temperature and constant effective UA. Reference: Threlkeld, J.L. 1970. Thermal Environmental Engineering, 2nd Edition, Englewood Cliffs: Prentice-Hall,Inc. pp. 254-270. Clark, D.R. 1985. HVACSIM+ building systems and equipment simulation program: Reference Manual. NBSIR 84-2996, National Institute of Standards and Technology, Washingtion, D.C. ASHRAE HVAC 2 TOOLKIT Pages 4-102 - 4-106 Date: April 10, 1997 rev 1.0 June 25, 1998 rev 1.1 October 06, 1998 rev 1.2 Made by: Mika Vuolle Call: DRYBULB ENTHAL HUMRAT SATPRES UAHX WETBULB: Call SATTEMP History: Rev. 1.1 Presure is changed to make this useable in ICE library Contr is added to turn it on/off. TSetPoint is added and it is like in the other ICE secondary components. Rev. 1.2 RHMax is added " EQUATIONS /* Thermal related */ /* Calculate psychrometric properities of entering air */ hAirIn := ENTHAL (TAirIn,WAirIn); tWetBulbIn := WETBULB (TAirIn,WAirIn); /* Calculate the leaving air saturated humidity ratio */ PSat := SATPRES(tWetBulbIn); WAirSat := HUMRAT(pAir+1E5,PSat); /* Minimum reachable temperature */ NTU := UAEvap / mAir; Eff := 1 - EXP(-NTU); WAirOutMax := WAirIn + Eff * (WAirSat-WAirIn); TMin := DRYBULB(hAirIn,WAirOutMax); /* Limited abs humidity of leaving air stream */ /* for different cases */ WAirInLim := HUMRAT(pAir+1E5, RHMax/100*SatPres(TAirIn)); WAirCapLim := HUMRAT(pAir+1E5, RHMax/100*SatPres(TMin)); WSet := HumTH(TSet,HAirIn); WLim := HUMRAT(pAir+1E5, RHMax/100*SatPres(TLim)); WLim = HumTH(TLim,HAirIn); WAirOut = IF LINEARIZE(1) OR On < 0.5 THEN WAirIn ELSE_IF FullCap > 0.5 THEN WAirOutMax ELSE MIN(WSet,WLim) END_IF; /* Calculate the leaving air temperature assuming adiabatic process */ TAirOut = DRYBULB(hAirIn,WAirOut); /* Calculate sensible cooling capacity and make-up water flow */ QSen := MAir*(Cp_Air + Cp_Vap*WAirIn)*(TAirIn - TAirOut); MWater = MAir*(WAirOut-WAirIn); /* Pollution related */ /* Modes */ On := IF Event(G0,MIN((TAirIn - TSet),(WAirInLim - WAirIn))) < 0 OR Contr < 0.5 THEN 0 ELSE 1 END_IF; FullCap := IF Event(G1,MIN((TMin-TSet),(WAirCapLim - WAirOutMax))) > 0 THEN 1 ELSE 0 END_IF; LINKS UniAir AirFlowIn PAir, POS_IN mAir, TAirIn, XAir, WAirIn; UniAir AirFlowOut PAir, POS_OUT mAir, TAirOut, XAir, WAirOut; PMT WaterFlowIn PWat, POS_IN mWater, TWat; ControlLink Control Contr; T TempSetPoint TSet; /*leaving air dry bulb temperature setpoint*/ Z RHMaxLink RHMax; /*leaving air max relative humidity*/ VARIABLES MassFlow mAir IN 2.0 0 BIG "Dry air massflow rate" MassFlow mWater OUT .6E-2 0 BIG "Liquid massflow rate" Temp TAirIn IN 25 ABS_ZERO BIG "Inlet temp of air" Temp TAirOut OUT 17.5 ABS_ZERO BIG "Outlet temp of air" Temp TWat IN 10 ABS_ZERO BIG "Inlet temp of water" Temp TSet IN 16 ABS_ZERO BIG "Set temperature" Temp TMin LOC 16 ABS_ZERO BIG "Minimum temperature" Temp TLim OUT 16 ABS_ZERO BIG "RH limited temperature" HumRatio WAirIn IN 0.007 SMALL BIG "Moisture content of inlet air" HumRatio WAirOut OUT 0.10 SMALL BIG "Moisture content of outlet air" HumRatio WAirOutMax LOC 0.10 SMALL BIG "Max moisture content of outlet air" HumRatio WAirInLim LOC 0.10 SMALL BIG "Limited moisture content of inlet air" HumRatio WSet LOC 0.10 SMALL BIG "Moisture content of out air at set temp" HumRatio WAirCapLim LOC 0.10 SMALL BIG "Moisture content of air at full cap" HumRatio WLim LOC 0.10 SMALL BIG "RH limited moisture content" HumRatio WAirSat LOC 0.11 SMALL BIG "Leaving air saturated humidity ratio" Pressure PSat LOC 1595 SMALL BIG "Saturate pressure" Enthalpy hAirIn LOC 42973 -BIG BIG "Entering air enthalpy" Temp tWetBulbIn LOC 15.32 ABS_ZERO BIG "Entering air wet bulb temp" Factor NTU LOC 1.448 SMALL BIG "Number of transfer units" Factor Eff LOC 0.7651 SMALL 1 "Heat transfer effectiveness" Factor RHMax IN 99 SMALL 99 "Maximum rel hum at leaving air stream [%]" HeatFlux qSen LOC 15499 -BIG BIG "Sensible heat transfer coefficient" Control Contr IN 0 0 1 "Control input 0 = Off 1 = On " Generic On A_S 0 0 1 "Humidifier On / Off " Generic G0 A_S 1 -BIG BIG "G0 memory" Generic FullCap A_S 0 0 1 "Humidifier FullCap / Normal " Generic G1 A_S 1 -BIG BIG "G1 memory" /* Pressure related */ Pressure PAir IN 1325 SMALL BIG "In air pressure" Pressure PWat IN 1 SMALL BIG "Water pressure" /* Pollution related */ Fraction_y XAir IN 594 0 BIG "Pollutant fraction" PARAMETERS /*Thermal related */ /* Rated condition */ MassFlow MEvapRat S_P 1.8 SMALL BIG "Dry air mass flow rate at rating " Temp TEvapRat S_P 26.7 ABS_ZERO BIG "Entering air dry bulb temp at rating" HumRatio wEvapRat S_P .11E-1 SMALL 1 "Entering air humidity at rating" Factor EffEvapRat S_P .8 SMALL 1 "Humidity effectiveness at rating" /* Calculated rated condition parameters */ Temp TWetRat C_P 19.2 ABS_ZERO BIG "Entering air wet bulb temp at rating" HumRatio wSatRat C_P .014 SMALL 1 "Leaving air saturated humidity ratio at rating" HeatFlux qRat C_P .045 -BIG BIG "Humidity transfer at rating" MassFlow UAEvap C_P 2.89 SMALL BIG "Overall transfer coefficient" Factor ErrStat C_P 0 0 1 "Error status indicator" PARAMETER_PROCESSING /* Thermal related */ tWetRat := WETBULB(TEvapRat,WEvapRat); wSatRat := HUMRAT(P_atm_0,SATPRES(tWetRat)); qRat := MEvapRat*EffEvapRat*(wSatRat-WEvapRat); UAEvap:= UAHX(MEvapRat,WEvapRat,BIG,wSatRat,qRat,1,ErrStat); IF ErrStat > 0.5 THEN CALL NMF_ERROR ("UA calculation failed") END_IF; END_MODEL