Numerical evaluation of ejector-assisted mechanical compression systems for refrigeration applications

A study of the conjugate effects of ejector performance characteristics, the activation pressure-temperature conditions at the generator and the interaction with the compressor on refrigeration systems was performed. Besides the conventional compression cycle which was used as a reference, three more configurations were selected for this study: a hybrid ejector-compressor booster and two cascade compressor-ejector cycles. The modelling methodology developed to handle such systems was based on the principles of thermodynamics and fluid dynamics and included two separate sub-cycles in constant interaction: a loop driven mechanically by a compressor, coupled with a thermally activated ejector loop. This cycle model was combined with a validated ejector model and manufacturer's compressor performance maps. A performance analysis and a parametric optimization were performed to select promising cycles. For given working conditions, substantial improvement in COP of the selected cycles over the conventional mechanical compression cycle was found.