added example of computing critical-state properties

Cantera/python/examples/critProperties.py

@@ -0,0 +1,25 @@
+"""
+Print the critical state properties for the fluids for which Cantera has
+built-in liquid/vapor equations of state.
+"""
+
+from Cantera import *
+from Cantera.liquidvapor import *
+
+fluids = {'water':Water(),
+          'nitrogen':Nitrogen(),
+          'methane':Methane(),
+          'hydrogen':Hydrogen(),
+          'oxygen':Oxygen()}
+
+print 'Critical State Properties'
+print '%20s  %10s  %10s  %10s' % ('Fluid','Tc [K]', 'Pc [Pa]', 'Zc')
+for name in fluids.keys():
+    f = fluids[name]
+    tc = f.critTemperature()
+    pc = f.critPressure()
+    rc = f.critDensity()
+    mw = f.meanMolecularWeight()
+    zc = pc*mw/(rc*GasConstant*tc)
+    print '%20s   %10.4g   %10.4G  %10.4G' % (name, tc, pc, zc)
+