On the CFD Modeling Approach of Lubrication System for a Hermetic Reciprocating Compressor: Sliding Mesh vs Moving Reference Frame

The capacity of inverter compressors is adjusted with rotational speed thus a sufficient lubrication is required at low rotational speeds. This paper reports the performance of the Sliding Mesh (SM) and the Moving Reference Frame (MRF) methods in modeling lubrication system of a Compact-Type Inverter Compressor (CIC) used in household refrigerators. The two-phase flow inside the hermetic compressor is simulated using the Volume of Fluid Method (VoF) under transient, laminar and incompressible flow conditions. The simulations are carried out for eight crankshaft speeds, from 1200 RPM to 4000 RPM. The modeling performance of the SM and the MRF computations is evaluated by investigating the oil climbing time which is defined as the required time to reach oil to the uppermost of the crankshaft, and the oil mass flow rate released from the outlet of the crankshaft. The important finding is that the MRF method predicts higher oil mass flow rate below 3000 RPM, but above 3000 RPM, the SM method yields higher oil mass flow rate. The oil climbs the crankshaft faster in the SM model. The MRF model requires less computational time to achieve a solution.