Experimental study on heat transfer characteristics of R600a/POE/CuO nano-refrigerant flow condensation

• The effect of CuO nanoparticles on condensation of R600a/oil mixtures is investigated.
• A well empirical set-up has been established in order to measure the empirical data.
• Adding nanoparticles cause a maximum heat transfer enhancement up to 83%.

An experimental study is carried out on heat transfer characteristics of a nano-refrigerant flow during condensation inside a horizontal smooth tube. Experiments are conducted for three different working fluid types including: (i) pure refrigerant (R600a); (ii) refrigerant/lubricant (R600a/oil); and (iii) nano-refrigerant: refrigerant/lubricant/nanoparticles (R600a/oil/CuO). Polyolester oil (POE) is utilized as the lubricant in the two latter cases. In addition, nano-refrigerants (R600a/oil/CuO) are prepared by dispersing CuO nanoparticles with different mass fractions of 0.5%, 1% and 1.5% in the baseline mixture (R600a/oil). The implemented experiments covered a wide range of variables including: (i) mass fluxes from 154.8 to 265.4 kg/m2/s; (ii) vapor qualities between 10% and 80%; (iii) heat flux from 17 to 20 kW/m2; and (iv) condensation pressure from 5.1 to 6.2 bar. It is shown that significant heat transfer enhancement is achieved by adding nanoparticles to the baseline mixture and pure refrigerant. The maximum heat transfer augmentation was observed for nano-refrigerant with 1.5% mass fraction; 83% higher heat transfer rate compared to pure-refrigerant fluid flow at the same experimental conditions.