Effect of IF-WS₂ Nanolubricant on R134a Boiling on a Reentrant Cavity Surface

This report quantifies the influence of inorganic fullerene-like tungsten disulfide (IF-WS₂) nanoparticles on the pool-boiling performance of R134a/polyolester mixtures on a commercial (Turbo-ESP) boiling surface. Tungsten disulfide nanoparticles, of roughly 150 nm, were used at a 15% mass fraction in a base polyolester lubricant to produce the test nanolubricant. The nanolubricant was mixed with R134a at a 1% mass fraction. The study showed that the nanolubricant caused an average 37% degradation in the boiling heat flux as compared to R134a/neat-lubricant boiling on a reentrant cavity surface at the same superheat. Similarly, boiling with R134a/neat-lubricant caused, on average, a 27% degradation in the boiling heat flux as compared to pure R134a boiling and the same superheat. An analysis was presented which showed that the nanoparticles were too large and too dense to promote a boiling enhancement. In addition, the fullerene-like structure and the large size encouraged nanoparticle settling, which presumably filled cavities of the boiling surface leading to additional boiling degradations.