Experimental investigation of condensation heat transfer of R600a/POE/CuO nano-refrigerant in flattened tubes

• Published in: International communications in heat and mass transfer 2017-11, Vol.88, p.236-244
• Main Authors: Ghorbani, Babak, Akhavan-Behabadi, M.A., Ebrahimi, Sasan, Vijayaraghavan, Krishna
• Format: Article
• Language: English
• Subjects: Condensation heat transfer; CuO nanoparticles; Flat tube; Mass flux; R-600a; Vapor quality
• ISSN: 0735-1933; 1879-0178
• DOI: 10.1016/j.icheatmasstransfer.2017.09.011

In this study, the effect of addition of copper oxide nanoparticles on condensing heat transfer coefficient of R600a refrigerant flowing in a flat tube condenser has been investigated experimentally. The test setup consists of a pump, condenser test, second condenser, evaporator, heaters, and flow meter. The validation of the study was done by comparing the obtained condensation heat transfer coefficients with different empirical correlations in the literature. Different fluids including pure R600a, R600a-oil with Polyester oil (POE) mass percentage of 1%, and three R600a-oil-nanoparticle mixtures with mass percentages of 0.5%, 1%, and 1.5% were studied experimentally. It was shown that adding nanoparticles will result in 4.1%, 8.11%, and 13.7% average increase in condensing heat transfer coefficient with respect to the R600a-oil mixture. The greatest amount of increase was reported for the weight fraction of 1.5%, where it was observed that the condensing heat transfer coefficient for the mixture passing through the flattened tube is averagely 109.3% higher than its corresponding value for the pure refrigerant flowing in the round tube with the same mass flux. It was also found that an increase in mass flux resulted in an increase the heat transfer coefficient at all vapor qualities.