Miscibility analysis of low-GWP refrigerant R474A with Polyol Ester and Polyalkylene Glycol oils for mobile air-conditioning system.

The miscibility between refrigerant and lubricant plays a key role in ensuring reliable compressor lubrication, efficient heat transfer, and overall performance stability in automotive HVAC systems. Understanding the miscibility behavior of next-generation low-GWP refrigerants with various lubricants is essential for ensuring their successful application in modern automotive systems. R474A, developed by Daikin, is a low-GWP refrigerant specifically designed for mobile air-conditioning systems in battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs). This study experimentally investigates the miscibility of R474A with POE oils (Mobil EAL Arctic series and Ze-GLES RB) and a PAG oil (PS-D1), by varying the oil mass fraction from 0 % to 70 % over a temperature range of -10 ◦C to 60 ◦C. The experimental setup was developed in accordance with ASHRAE standards. Results are presented as saturation pressure vs. oil mass fraction graphs, miscibility charts, and phase separation diagrams. An inverse relationship was observed between the saturation vapor pressure and oil mass fraction for all three oils. R474A exhibited complete miscibility with both POE oils across the entire temperature and concentration range. In contrast, four distinct behaviors miscible, liquid phase separation, partially miscible, and immiscible were observed for R474A with PAG oil, particularly at higher oil mass fractions.