Influence of the refrigerant on the performance of an hermetic piston compressor: theoretical analysis with a detailed mathematical compressor model in order to assist in the optimization of a R407C piston compressor to work with R290.

When a compressor designed to work with one refrigerant is required to work with another refrigerant of compatible pressure ratios. Some differences on the compressor performance which cannot be only explained on the basis of the different thermodynamic properties between refrigerants are to be expected. In order to optimize the compressor performance with different refrigerants, a design tuning of different compressor elements is usually required. In this contribution, a comparison of the behaviour of a piston compressor designed to work with R407C using R290 and R407C has been done. The comparison has been based on more than 100 experimental measurements at different evaporation temperatures, condensing temperatures and superheating levels. All these experimental measurements have been used to validate a detailed compressor model. The compressor model has been used to understand the different factors acting upon the compressor performance as a function of the external conditions and the differences derived from the refrigerant. Based on this, the model has suggested some modifications on the compressor design in order to adapt a R407C compressor to a R290 one.