Each refrigerant has different properties even same temperature saturation. But sometimes when we use other refrigerant, there is refrigerant has unique properties, may properties change when pressure constant but temperature different. That refrigerant is zeotropic. Generally refrigerant consists of 3 kind refrigerant. The first is pure refrigerant, the second is zeotropic and the last is azeotropic. Pure refrigerant usually consists of at least one fluid, for example R-22, R-134a, and so on. But pure refrigerant has related tightly with other fluid. Different with zeotropic refrigerant. That refrigerant is mixture refrigerant that has composition among liquid and vapor depends on temperature even pressure constant. In contrast, azeotropic may have same content with zeotropic but different composition. azeotropic has unique effect, liquid and vapor strictly change without different composition on pressure constant and a point of temperature.
Figure above that alternative refrigerant from Bitzer introduce us about pure refrigerant.
Figure above about zeotropic refrigerant and azeotropic in small picture on composition and temperature with pressure constant.
Actually the kinds of refrigerant effect on their thermodynamic properties and heat transfer. When refrigerant mixture is zeotropic, on pressure constant, value temperature is called gliding temperature. In general saturation temperature is temperature when fluid change of phase, but in here, temperature also changed when phase changed too in along of heat exchanger.
Mol n-butane = 0.6
Mol n-heptane = 0.4
How many vapor produce from 1 mol as input, if mol butane result 0.8
1 mol consists
0.33 x mol in liquid + 0.8 x (1-mol inliquid) = 1 mol x 0.6
0.33x + 0.8 – 0.8x = 0.6
0.2 = 0.47 x
x = 0.425 ==> Mol in liquid
Mol in vapor = 1-0.425 = 0.575