SURFACE TENSION OF THE MIXTURES OF R134A AND PAG OILAT LOW OIL-CONCENTRATIONS

摘要

In the vapor-compression refrigerating system a refrigerant circulates with a small amount of lubricating oilrnfrom the compressor. The surface tension is one of the most important properties that govern the heatrntransfer in boiling and condensation processes. This paper reports the effect of PAG oil on the surfacerntension of refrigerant, R134a. The surface tension was measured with the ring method. Measurements werernconducted for a temperature of 278.15 K and relatively low oil-concentrations up to 32 mass% while the testrnfluid was always kept at saturated state. The overall uncertainty in surface tension was estimated to be lessrnthan ±5%. The present results demonstrate that the oil mixing once decreases the surface tension of thernmixtures by about 10% to that of R134a at low oil-concentrations up to 16% and then increases it to that ofrnPAG oil.