This paper quantifies the influence of Al2O3 nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a Turbo-BII-HP boiling surface. Nanofluids are liquids that contain dispersed nano-size particles. A lubricant based nanofluid (nanolubricant) was made by suspending nominally, 10 nm diameter Al2O3 particles in a synthetic ester to roughly a 1.6 % volume fraction. The nanoparticles caused, on average, a 12 % degradation in the boiling heat transfer relative to that for R134a/polyolester mixtures without nanoparticles for the three lubricant mass fractions that were tested. The degradation was nearly constant for heat fluxes between 20 kW/m2 and 120 kW/m2. It was speculated that the boiling heat transfer degradation was primarily due to a combination of film boiling in the reentrant cavity rendering the nucleate boiling enhancement mechanism of the nanoparticles ineffective and a reduction in bubble frequency due to the increased surface wetting as caused by the nanoparticles.
Citation: Technical Note (NIST TN) - 1677
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST PubsReport Number:
additives, boiling, Al2O3, enhanced heat transfer, nanotechnology, refrigerants, refrigerant/lubricant mixtures, structured surface