Refrigerant desorption and foaming in mixtures of HFC-134a and HFO-1234yf and a polyol ester lubricating oil

This paper presents a study of refrigerant desorption leading to foam formation in refrigerant-oil mixtures undergoing controlled depressurization. An experimental apparatus was designed and constructed to allow measurements of the depressurization rate, foam height and refrigerant gas mass flux resulting from expansion and desorption from a saturated liquid mixture. Quantitative data and high-speed video analyses were used to identify the main physical mechanisms in the foaming process, namely, bubble cavitation and growth, foam growth and foam decay. The experimental results for the maximum foam height, foam lifetime and liquid supersaturation during desorption were explored as a function of the overall initial refrigerant mass fraction and system temperature. A mathematical model based on integral mass balances was proposed and compared with the experimental data with deviations smaller than 20%.