Oil Presence Effect on Thermodynamic Performance of the Evaporator Working with R290

Abstract

Propane (R290) as a natural refrigerant has attracted much interest in the refrigeration and air conditioning fields. To increase the solubility-database for R290 in oils and better understand the oil presence effect on evaporator performance, solubilities of R290 in two polyol ester oils (RL 32H and RL 68H) were measured from 253.15 to 343.15 K. The nonrandom two-liquid model was used to correlate the measured data. R290 is more soluble in RL 68H than in RL 32H. New pressure− enthalpy−vapor quality diagrams were plotted for pure R290 and R290/oil blends at different circulating oil mass fractions. A demarcation point was found along the isotherms of the R290 and R290/oil blend, that is mainly dependent on the solubility and circulating oil mass fraction. The lower is the demarcation point, the greater is the contribution of the sensible heat, which is unfavorable to the heat transfer. The enthalpy changes through an evaporator with and without the presence of oil were analyzed, indicating that the enthalpy change ratio increases as the superheat rises and the mass fraction of the circulating oil decreases.