Dynamic Modeling of Oil Transport in Vapor Compression Systems


In this paper, we propose a model describing the dynamics of refrigerant-oil mixture in vapor compression systems. This model uses the approach presented by Thome (1995) to calculate the thermodynamic properties of refrigerant- oil mixture. The governing equations for one-dimensional flow are modified with augmentation of oil mass balance. Partial derivatives of mixture density are carefully computed to ensure the consistence of the choice of state variables for all flow conditions. The existing models for heat exchanger and other components are refined accordingly. Numerical simulation for the start-up operation of an air-conditioning cycle is conducted to evaluate the efficacy of the proposed model. The results for the effect of oil on system performance are provided.