CFD Study of Phase Separators in A/C Automotive Systems

In the refrigerant circuit of an automotive air-conditioning system, oil is needed to lubricate the moving parts of the compressor. However, it is desired to limit the presence of oil within the compressor, avoiding its flow to the areas of heat exchangers (like evaporator and condenser), in order to improve the efficiency of the heat transfer process. The oil separation is done immediately downstream of the compressor in a device using either impinging or centrifugal effects on the refrigerant carrier gas flow. The oil phase is assumed to exist as a secondary phase in the form of droplets. The main requirement for a good design of an oil separator device is to achieve the maximum liquid separation with the smallest pressure drop for the gas flow. The numerical simulations were performed using Eulerian Multiphase model and Mixture model of FLUENT6 on fully unstructured tetrahedral meshes of various design iterations of the separator. Resulting CFD flow fields were used to compare separation efficiency and pressure drop of different designs and flow regimes.