ADDED   mttroot/mtt/lib/comp/simple/ES_eqn.m
Index: mttroot/mtt/lib/comp/simple/ES_eqn.m
==================================================================
--- /dev/null
+++ mttroot/mtt/lib/comp/simple/ES_eqn.m
@@ -0,0 +1,63 @@
+function  structure = ES_eqn(name,bond_number,bonds,direction,cr,args, ...
+    structure,eqnfile);
+% ES_eqn - equations for ES component
+% 
+%     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+%     %%%%% Model Transformation Tools %%%%%
+%     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 
+% Matlab function  ES_eqn
+% ES_eqn(name,bond_number,bonds,direction,cr,args, ...
+%    structure,eqnfile);
+
+
+
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% Version control history
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% $Id$
+% %% $Log$
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+% Copyright (c) P.J. Gawthrop, 1997.
+
+
+if nargin<6
+  eqnfile = 'stdout';
+end;
+
+% Check that there are exactly two bonds.
+ports = 2;
+if check_bonds(bonds,ports,'ES')==0
+  return
+end
+
+
+% There are 2 ports; extract the information
+e_bond = bonds(1,:);
+s_bond = bonds(2,:);
+
+% The efforts are the same
+if e_bond(1)==1 %effort imposed on the enthalpy bond 
+  fprintf(eqnfile,'%s := %s + t_0;\n' , ...
+    varname(name,bond_number(2), 1), ...
+    varname(name,bond_number(1), 1) );
+else %effort imposed on the entropy bond 
+  fprintf(eqnfile,'%s := %s - t_0;\n' , ...
+    varname(name,bond_number(1), 1), ...
+    varname(name,bond_number(2), 1) );
+end;
+
+% The flows need to be converted
+if e_bond(2)==-1 %flow imposed on the enthalpy bond 
+  fprintf(eqnfile,'%s := %s/(%s + t_0);\n' , ...
+    varname(name,bond_number(2), -1), ...
+    varname(name,bond_number(1), -1), ...
+    varname(name,bond_number(2), 1) );
+else % flow imposed on the entropy bond 
+    fprintf(eqnfile,'%s := %s*(%s - t_0);\n' , ...
+    varname(name,bond_number(1), -1), ...
+    varname(name,bond_number(2), -1), ...
+    varname(name,bond_number(2), 1) );
+end;