This paper investigates the effect that oil concentration had on the boiling performance of an R123/paraffinic mineral oil mixture on a roughened, horizontal flat surface. For all compositions, the lubricant caused a heat transfer degradation relative to the heat transfer of pure R123 of between 2 % and 70 % for the range of measured heat fluxes. The heat transfer degradation was shown to increase with lubricant mass fraction. The minimum heat transfer degradation for each mixture ranged between 2 % and 12 % and occurred at approximately 20 kW/m2. For a given composition, the heat transfer degradation increased as the heat flux increases from roughly 20 kW/m2 to 90 kW/m2. In addition, the effect of two trial additives on the pool boiling heat transfer of an R123/paraffinic mineral oil mixture were examined in order to test the validity of a theory for choosing oil additives to enhance boiling performance. The verification tests were inconclusive. More research with lubricants and additives with greater differences in surface tensions is required to develop a more rigorous and quantifiable theory for designing additives that improve boiling heat transfer.
Citation: NIST Interagency/Internal Report (NISTIR) - 7336
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
additives, boiling, enhanced heat transfer, paraffinic mineral oil, refrigerant/lubricant mixtures, refrigerants