Flow-Boiling of R-134a/POE/CuO Nanofluids in a Horizontal Tube

摘要

The influence of CuO nanoparticles on the flow-boiling of R-134a/polyolester mixtures in a horizontal tube is quantified. A lubricant-based nanofluid is prepared with a synthetic ester and 30-nm diameter CuO particles stably suspended in the mixture to a 4% volume fraction. For a 0.5% nanolubricant mass fraction in a mixture with R-134a, the nanoparticles have no apparent effect on the two-phase boiling heat transfer coefficient. However, for a nanolubricant mass fraction of 1%, an enhancement between 42% and 82% in the heat transfer coefficient is manifest, over that of the same refrigerant-oil mixture without nanoparticles. A further increase in the nanolubricant mass fraction to 2% results in a still larger improvement in heat transfer coefficient of between 50% and 101%. In addition to heat transfer enhancement, it is found that the presence of nanoparticles has an insignificant effect on the system pressure drop (within the experimental uncertainty) when compared to baseline data.