Effect of nanoparticle size on nucleate pool boiling heat transfer of refrigerant/oil mixture with nanoparticles

Effect of nanoparticle size on nucleate pool boiling heat transfer of refrigerant/oil mixture with nanoparticles was investigated experimentally. For the preparation of the test fluid, refrigerant R113, ester oil VG68, and Cu nanoparticles with three different average diameters of 20, 50 and 80 nm were used. Experimental conditions include a saturation pressure of 101.3 kPa, heat fluxes from 10 to 80 kW m^?2, nanoparticle concentrations in the nanoparticles/oil suspension from 0 to 30 wt%, and nanoparticles/oil suspension concentrations from 0 to 5 wt%. The experimental results indicate that the nucleate pool boiling heat transfer coefficient of R113/oil mixture with Cu nanoparticles is enhanced by a maximum of 23.8% with the decrease of nanoparticle size from 80 to 20 nm under the present experimental conditions, and the enhancement increases with the decrease of nanoparticles/oil suspension concentration or the increase of nanoparticles concentrations in the nanoparticles/oil suspension. A general nucleate pool boiling heat transfer coefficient correlation for refrigerant/oil mixture with nanoparticles is proposed, and it agrees with 93% of the existing experimental data of refrigerant/oil mixture with nanoparticles within a deviation of ±20%.