/* bwrm15.c */
#include "bwrm.h"
#include <math.h>

#define MESSAGE (*m).b.tmp.errorcode



double
bwrmS2(/*
      calculate molar enthalpy 's'[J/kg-molK] of binary mixtures.
      The function 'bwrmSetSid1SI' must be already done for BWRM strucure
	  of each component,c1 and c2, respectively. */
  BWRM2 *m,
  char  mode, /* 'l' or 'L': BWRM structure,l for liquid phase is used.
                 'v' or 'V': BWRM structure,v for liquid phase is used.
                  else     : BWRM structure,b for bulk fluid   is used.  */
  double t,   /* [K] */
  double rho, /* [kg-mol/m3] */
  double y1   /* molar fraction of component 1 */
){
#define	P0 1.0
#define	MT (*cf).tmp
  double s1_id, s2_id, s_id;
  double y2;
  BWRM *cf;

  cf = &((*m).b);                                  /* bulk */
  if (mode == 'l' || mode == 'L') cf = &((*m).l);  /* liquid */
  if (mode == 'v' || mode == 'V') cf = &((*m).v);  /* vapor */
  
  RecalBWRM2(m, mode, t, rho, y1);
  y2 = 1.0 -y1;

  s1_id = (*m).c[1].s_id(t) + (*m).c[1].s_adj;
  s2_id = (*m).c[2].s_id(t) + (*m).c[2].s_adj;
  s_id = y1 * s1_id  +  y2 * s2_id;
  if (y1 > 0.0){
	s_id += Rgas * y1 * log( P0/(y1*(*cf).tmp.rhoRT) ) ;
  }
  if (y2 > 0.0){
	s_id += Rgas * y2 * log( P0/(y2*(*cf).tmp.rhoRT) ) ;
  }

  (*cf).s = s_id + bwrmdS(cf, t, rho);
  return( (*cf).s );
}