SUBROUTINE TYPE75 (TIME,XIN,OUT,T,DTDT,PAR,INFO,ICNTRL,*)
C***********************************************************************
C*    Copyright ASHRAE.  Toolkit for HVAC System Energy Calculations
C*    UPDATED FOR THE TRNSYS-LIBARY BY RUEDIGER SCHWARZ AND NATE BLAIR
C*********************************************************************`**
C*    SUBROUTINE:             MIXOAIR
C*
C*    LANGUAGE:               FORTRAN 77
C*
C*    PURPOSE:                Calculate the leaving temperature,
C*                            humidity ratio and mass flow rate of two
C*                            mixed air streams by simple conservation.
C***********************************************************************
C*    INPUT VARIABLES  DESCRIPTION(UNITS)                     SAMPLE VALUES 
C*    XIN(1)   M1Ent Dry air mass flow rate of stream 1 (kg/s)     2.0000000
C*    XIN(2)   T1Ent Entering temperature of stream 1 (C)          1.6700000
C*    XIN(3)   W1Ent Entering humidity ratio of stream 1 (-)        .0017
C*    XIN(4)   M2Ent Dry air mass flow rate of stream 2 (kg/s)     1.65
C*    XIN(5)   T2Ent Entering temperature of stream 2 (C)         23.89
C*    XIN(6)   W2Ent Entering humidity ratio of stream 2 (-)        .0092
C*
C*    OUTPUT VARIABLES                                      
C*    OUT(1)    MLvg Dry air mass flow rate of mixed stream (kg/s) 3.65
C*    OUT(2)    TLvg Temperature of mixed stream (C)              11.7881
C*    OUT(3)    WLvg Humidity ratio of mixed stream (C)             .00509
C*    OUT(4) ErrStat Error flag (0=ok, 1=error) (-)                   (-)
C***********************************************************************
C     MAJOR RESTRICTION:      None
C
C     DEVELOPER:              Shauna Gabel, MS
C                             Michael J. Brandemuehl, PhD, PE
C                             University of Colorado at Boulder
C
C     DATE:                   January 1, 1992
C
C     INCLUDE FILES:          None
C     SUBROUTINES CALLED:     None
C
C     FUNCTIONS REQUIRED:     ENTHALPY
C							DRYBULB
C     REVISION HISTORY:       None
C
C     REFERENCE:              None
C***********************************************************************
C*    INTERNAL VARIABLES
C*    small         Small number used in place of zero
C***********************************************************************

      INTEGER ErrStat, IOPT, NI, NP, ND
      DIMENSION XIN(6),OUT(3), INFO(15)
      DOUBLE PRECISION XIN, OUT
	CHARACTER*3 YCHECK(6), OCHECK(3)

      DATA small/1.E-9/,CPAIR/1006.0/,CPVAP/1805.5/,HFG/2501000.0/
      DATA YCHECK/'MF2','TE1','DM1','MF2','TE1','DM1'/
	DATA OCHECK/'MF2','TE1','TE1'/

      M1Ent=XIN(1)
      T1Ent=XIN(2)
      W1Ent=XIN(3)
      M2Ent=XIN(4)
      T2Ent=XIN(5)
      W2Ent=XIN(6) 
      
      ErrStat = 0
	IOPT	= -1
	NI		= 6		!NUMBER OF CORRECT INPUTS
	NP		= 0		!NUMBER OF CORRECT PARAMTERS
	ND		= 0		!NUMBER OF CORRECT DERIVATIVES

	IF (INFO(7).EQ.-1) THEN
		CALL TYPECK(IOPT,INFO,NI,NP,ND)
C	 CHECKS TO SEE IF THE USER'S INFO MATCHES THE CORRECT NUMBER
		CALL RCHECK(INFO,YCHECK,OCHECK)
C	 CHECKS TO SEE IF THE INPUT AND OUTPUT UNITS MATCH
	ENDIF

C1*** Calculate the mass flow rate of the mixed stream.

      MLvg = M1Ent + M2Ent

C1*** If leaving flow is zero, set leaving conditions to those of
C1    stream 1 and RETURN.

      IF (ABS(MLvg) .LE. small) THEN
        WLvg = W1Ent
        TLvg = T1Ent

      ELSE

C1*** Leaving flow is not zero.  Proceed with calculations.
C1*** Calculate the humidity ratio of the mixed stream

        WLvg = (M1Ent*W1Ent+M2Ent*W2Ent)/MLvg

C1*** Calculate the mixed stream temperature from enthalpy and humidity

        h1Ent = ENTHALPY(CPAIR,CPVAP,HFG,T1Ent,W1Ent)
        h2Ent = ENTHALPY(CPAIR,CPVAP,HFG,T2Ent,W2Ent)
        hLvg = (M1Ent*h1Ent+M2Ent*h2Ent)/MLvg
        TLvg = DRYBULB(CPAIR,CPVAP,HFG,hLvg,WLvg)

      ENDIF
      
      OUT(1)=MLVG
      OUT(2)=TLVG
      OUT(3)=WLVG

      RETURN 1
      END

      REAL FUNCTION DRYBULB (CPAIR,CPVAP,HFG,H,W)
C***********************************************************************
C*    Copyright ASHRAE.  Toolkit for HVAC System Energy Calculations
C***********************************************************************
C*    FUNCTION:               DRYBULB
C*
C*    LANGUAGE:               FORTRAN 77
C*
C*    PURPOSE:                Calculate the dry bulb temperature of
C*                            moist air from enthalpy and humidity.
C***********************************************************************
C*    INPUT VARIABLES:
C*    H             Enthalpy                                      (J/kg)
C*    W             Humidity ratio                                   (-)
C*
C*    OUTPUT VARIABLES:
C*    Drybulb       Dry bulb temperature                             (C)
C*
C*    PROPERTIES:
C*    CpAir         Specific heat of air                        (J/kg C)
C*    CpVap         Specific heat of water vapor                (J/kg C)
C*    Hfg           Reference heat of vaporization of water       (J/kg)
C***********************************************************************
C     MAJOR RESTRICTIONS:     Uses perfect gas relationships
C                             Fit for enthalpy of saturated water vapor
C
C     DEVELOPER:              Shauna Gabel
C                             Michael J. Brandemuehl, PhD, PE
C                             University of Colorado at Boulder
C
C     DATE:                   January 1, 1992
C
C     INCLUDE FILES:          PROP.INC
C     SUBROUTINES CALLED:     None
C     FUNCTIONS CALLED:       None
C
C     REVISION HISTORY:       None
C
C     REFERENCE:              1989 ASHRAE Handbook - Fundamentals
C***********************************************************************

C*$INCLUDE: 'prop.inc'

C1*** Calculate the dry bulb temperature as a function of enthalpy and
C1*** humidity ratio.
C2*** hDryAir = Prop(CpAir)*TDB
C2*** hSatVap = Prop(Hfg) + Prop(CpVap)*TDB
C2*** Enthalpy = hDryAir + W*hSatVap

      Drybulb = (H-Hfg*W)/(CpAir+CpVap*W)

      RETURN
      END
      REAL FUNCTION ENTHALPY (CPAIR,CPVAP,HFG,TDB,W)
C***********************************************************************
C*    Copyright ASHRAE.  Toolkit for HVAC System Energy Calculations
C***********************************************************************
C*    FUNCTION:               ENTHALPY
C*
C*    LANGUAGE:               FORTRAN 77
C*
C*    PURPOSE:                Calculate the enthalpy of moist air.
C***********************************************************************
C*    INPUT VARIABLES:
C*    TDB           Dry bulb temperature                             (C)
C*    W             Humidity ratio                                   (-)
C*
C*    OUTPUT VARIABLES:
C*    Enthalpy      Enthalpy of moist air                         (J/kg)
C*
C*    PROPERTIES:
C*    CpAir         Specific heat of air                        (J/kg C)
C*    CpVap         Specific heat of water vapor                (J/kg C)
C*    Hfg           Reference heat of vaporization of water       (J/kg)
C***********************************************************************
C     MAJOR RESTRICTIONS      Uses perfect gas relationships
C                             Fit for enthalpy of saturated water vapor
C
C     DEVELOPER:              Shauna Gabel
C                             Michael J. Brandemuehl, PhD, PE
C                             University of Colorado at Boulder
C
C     DATE:                   January 1, 1992
C
C     INCLUDE FILES:          PROP.INC
C     SUBROUTINES CALLED:     None
C     FUNCTIONS CALLED:       None
C
C     REVISION HISTORY:       None
C
C     REFERENCE:              1989 ASHRAE Handbook - Fundamentals
C***********************************************************************


C1*** Calculate the enthalpy as a function of dry bulb temperature and
C1*** humidity ratio.

      hDryAir = CpAir*TDB
      hSatVap = Hfg + CpVap*TDB
      Enthalpy = hDryAir + W*hSatVap

      RETURN 
      END