The Effect of Lubricant Concentration, Miscibility, and Viscosity on R134a Pool Boiling
Mark A. Kedzierski
This paper presents pool boiling heat transfer data for twelve different R134a/lubricant mixtures and pure R134a on a Turbo-BIITM-HP surface. Themixtures were designed to examine the effects of lubricant mass fraction, viscosity, and iscibility on the heat transfer performance of R134a. Themagnitude of the effect of each parameter on the heat transfer was quantified with a regression analysis. The mechanistic cause of each effect was given based on new theoretical speculation and/or that from the literature. The model illustrates that large improvements over pure R134a heat transfer can be obtained for R134a/lubricant mixtures with small lubricant mass fraction, high lubricant viscosity, and a large critical solution temperature (CST). The ratio of the heat flux of the R134a/lubricant mixture to that of the pure R134a for fixed wall superheatwas given as a function of pure R134a heat flux for all twelve mixtures. The lubricant that had the largest CST with R134a exhibited the greatestheat transfer: 100% 20% greater than that of pure R134a. By contrast, the heat transfer of the mixture with the lubricant that had the smallestviscosity and the smallest CST with R134a was 45% 9 % of that of pure R134a. High-speed films of the pure and mixture pool boiling were taken toobserve the effect of the lubricant on the nucleate boiling.
The Effect of Lubricant Concentration, Miscibility, and Viscosity on R134a Pool Boiling, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860804
(Accessed March 3, 2024)