ENTHALPY CALCULATION FOR A REFRIGERANT/OIL MIXTURE: CONSEQUENCES ON THE EVAPORATOR PERFORMANCE WORKING WITH R407C AND POE OIL

摘要

This work presents a method allowing the calculation of enthalpy of a refrigerant/oil mixture. To generalise this method, the considered refrigerant is also a mixture with a temperature glide (R407C). The suggested method requires the knowledge of the mixture liquid-vapour equilibrium properties (solubility curves) and the oil thermodynamic properties. In a first application of the model, the ln(P)-h-X' diagram for the refrigerant/oil mixture is plotted. Then, the ratios of the enthalpy changes through an evaporator, with and without taking into account the effect of oil are compared for several conditions (varying superheat, compression ratio). The results for the studied refrigerant/oil pair show that the calculated enthalpy change through the evaporator depends much on taking into account the effect of oil, since the relative decrease may reach 34% for a low superheat and a high oil mass-fraction. Lastly, the prediction of the quantity of the refrigerant dissolved in oil (and consequently that remains non-evaporated) at the outlet of an evaporator is performed for various superheats.