Effect of Bulk Lubricant Concentration on the Excess Surface Density During R123 Pool Boiling
Mark A. Kedzierski
This paper investigates the effect that bulk lubricant concentration has on the non-adiabatic lubricant excess surface density on a roughened, horizontal flat pool-boiling surface. Both pool boiling heat transfer data and lubricant excess surface density data are given for pure R123 and three different mixtures of R123 and a naphthenic mineral oil. A spectrofluorometer waw used to measure the lubricant excess density that was established by the boiling of a R123/lubricant mixture on a test surface. The fluorescent technique was used to measure the effect of bulk lubricant concentration on the lubricant excess layer during refrigerant/lubricant mixture by the boiling process and accumulates on the surface in excess of the buolk concentration. The excess lubricant resides in a very thin layer on the surface and influences the boiling performance. Accordingly, the ability to measure the effect of bulk lubricant composition on the lubricant excess density and in turn the effect on the heat transfer would lead to a fundamental understanding of the mechanism by which lubricants can degrade or improve boiling performance. In support of this effort, heat transfer data are provided for pure R123 and three R123/lubricant mixtures at 277.6K. the heat transfer data shows that the lubricant excess causes an average enhancement of the heat flux of 9 % and 5 % for the 0.5 % and 1 % lubricant mass fractions, respectively,and an average degradation of 12 % in the heat flux for the 1.8 % lubricant mass fraction mixture.
Effect of Bulk Lubricant Concentration on the Excess Surface Density During R123 Pool Boiling, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD
(Accessed October 3, 2023)