Detailed dynamic refrigerant migration characteristics in room air-conditioner with R290

Abstract

Propane (R290) as flammable refrigerant posed additional fire and explosion risk in room air conditioner (RAC), refrigerant migration and redistribution have been recognized as essential factors for leakage characteristics and charge optimization researches. Hence, a detailed understanding of the dynamic behavior of RAC systems is beneficial to future charge analysis and model-based control design, and then a system-level finite-volume dynamic model was developed in this paper. For the purpose of realistic modelling, dynamic lubricant solubility and absorption rate, finite-volume model integrated with geometry configuration and fin equivalent simplification were adopted. On the other hand, transient solver and public domain software YSMP were derived from SINDA/FLUINT (S/F) platform to make models converge and reduce the CPU time. From the initial state assumptions given in this paper, simulated results like dynamic mass, temperature and pressure distribution were validated by experiments; and they had good conformity. It was found that refrigerant migration process before equilibrium could be divided into dramatic change phase and smooth change phase. Dramatic change phase was dominated by mass transfer, while smooth change phase was dominated by heat transfer. Finally, the sensitivity of conditions and geometries to each component charged fraction was studied. Under reasonable charged circumstances, greater displacement, less mass charged and larger volume ratio of condenser to evaporator will be beneficial for improving system stability during startup.