2. Temperature-slip refrigerant diagrams

For example, in refrigeration applications, the composition of a refrigerant mixture remains invariant in the vapour and liquid phases (if we neglect the influence of lubricating oil). In the liquid-vapor equilibrium zone, this is no longer strictly true, but we can almost always dispense with precise calculations of the exact composition of the gas and liquid phases at the expansion valve outlet and in the evaporator. By analogy with pure substances, we generalize the notion of vapour titre by that of average titre, equal to the mass of the vapour phase, all constituents taken together, referred to the total mass of the liquid and vapour phases. A much simpler fixed-composition mixture model can then be used. An equation numerically adjusted to the experimental values of a given mixture is thus both much more precise and easier to calculate than the general formulation we have just seen....