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R134a/Al2O3 Nanolubricant Mixture Pool Boiling on a Rectangular Finned Surface

Published

Author(s)

Mark A. Kedzierski

Abstract

This paper quantifies the influence of Al2O3 nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a rectangular finned boiling surface. Nanolubricants with 10 nm diameter Al2O3 nanoparticles of various volume fractions (1AlO, 2AlO, and 3AlO) in the base polyolester lubricant were mixed with R134a at two different mass fractions (0.5 % and 1 %). The study showed that nanolubricants can significantly improve R134a boiling on a rectangular finned surface. For example, the R134a/1Al0 (99/1), R134a/3Al0 (99/1), and the R134a/2Al0 (99/1) mixtures exhibited average enhancement of approximately 18 %, 102 % and 113 %, respectively. The nanoparticles had practically no effect on the heat transfer relative to that for R134a/polyolester mixtures without nanoparticles for R134a boiling with the 1AlO nanolubricant at a 0.5 % mass fraction with the refrigerant. This confirms, what was shown in a previous publication for a smooth surface, that for a particular system, a critical level of nanoparticles must be exceeded before an enhancement can be achieved. The present study suggests that passively enhanced surfaces are likely to require more nanoparticle loading than a smooth surface to achieve similar heat transfer. This is based on the finding that the boiling heat transfer enhancement was shown to be a strong function of the absolute nanoparticle surface density that resides on the heat transfer surface and not the nanoparticle concentration in the nanolubricant as previously believed. The enhancement was shown to increase for three different boiling surfaces (from three different studies) as more nanoparticles accumulate on the boiling surface. Accordingly, a previously developed model for predicting refrigerant/nanolubricant boiling on a smooth surface was corrected so as to be dependent on the nanoparticle surface density rather that the nanoparticle concentration. In addition, the model was modified in order to predict the refrigerant/nano
Citation
Journal of Heat Transfer-Transactions of the ASME

Keywords

additives, aluminum oxide, boiling, enhanced heat transfer, nanolubricant, nanotechnology, refrigerants, refrigerant/lubricant mixtures, structured surface

Citation

Kedzierski, M. (2012), R134a/Al<sub>2</sub>O<sub>3</sub> Nanolubricant Mixture Pool Boiling on a Rectangular Finned Surface, Journal of Heat Transfer-Transactions of the ASME (Accessed April 20, 2024)
Created October 31, 2012, Updated February 19, 2017