Convection-driven absorption of R-1234yf in lubricating oil
Experiments were carried out to determine rates of absorption of R-1234yf through the free surface of an initially stagnant layer of lubricant POE ISO VG 10 in a closed system. Rayleigh instability at the phase interface gives rise to natural mass convection-driven absorption. Mass transfer rates computed via a cooling-law relationship involving a time-dependent mass transfer coefficient and a refrigerant mass fraction driving force (assuming phase equilibrium at the interface) yielded good agreement with data for the system pressure decay as a function of time. Due to the lack of data on phase equilibrium of the R-1234yf/POE ISO VG 10 mixture, a PVT cell was designed and constructed to measure the solubility of the oil-refrigerant system. Tests carried out with R-134a/POE ISO VG 10 under the same conditions showed that R-1234yf offers lower absorption rates in the oil, which may result in higher values for the equalizing pressure in refrigeration systems.