refrigerant-oil mixtures, compressor start up, desorption, foaming
This paper deals with the experimental assessment of refrigerant desorption leading to foam formation in R-134a/POE oil mixtures undergoing controlled depressurization. An experimental apparatus was designed and constructed to allow measurements of pressure drop rate, foam height and refrigerant gas mass flux resulting from decompression and desorption from a saturated liquid mixture. High-speed video recording of the phenomenon enabled the identification of three main periods during the depressurization/foaming process, namely, depressurization without cavitation, vapor flashing and rapid foam growth, and foam layer 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 physical properties of the liquid phase.