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Effect of CuO Nanoparticle Concentration on R134a/Lubricant Pool Boiling Heat Transfer.


pdf icon Effect of CuO Nanoparticle Concentration on R134a/Lubricant Pool Boiling Heat Transfer. (948 K)
Kedzierski, M. A.

MNHT2008-52116;

Micro/Nanoscale Heat Transfer International Conference. Proceedings. MNHT2008. January 6-9, 2008, Tainan, Taiwan, ASME, New York, NY, 1-8 pp, 2008.

Keywords:

heat transfer; lubricants; copper oxide; nanoparticles; tests; heat flux; uncertainity; experiments; volume fraction; temperature

Abstract:

This paper quantifies the influence of CuO nanoparticle concentration on the boiling performance of R134a/polyolester mixtures on a roughened, horizontal flat surface. Nanofluids are liquids that contain dispersed nano-size particles. Two lubricant based nanofluids (nanolubricants) were made with a synthetic ester and 30 nm diameter CuO particles stably suspended in the two mixtures to a 4% and a 2% volume fraction, respectively. As reported in a previous study for the 4% volume fraction nanolubricant, a 0.5% nanolubricant mass fraction with R134a resulted in a heat transfer enhancement relative to the heat transfer of pure R134a/polyolester (99.5/0.5) of between 50% and 275%. The same previous study had shown that increasing the mass fraction of the 4% volume fraction nanolubricant resulted in the smaller, but significant, boiling heat transfer enhancements. The present study shows that use of a nanolubricant with half the concentration of CuO nanoparticles (2% by volume) resulted in either no improvement or boiling heat transfer degradations with respect to the R134a/polyolester mixtures without nanoparticles. Consequently, significant refrigerant/lubricant boiling heat transfer enhancements are possible with nanoparticles; however, the nanoparticle concentration is an important determining factor. Further research with nanolubricants and refrigerants are required to establish a fundamental understanding of the mechanisms that control nanofluid heat transfer.