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Effect of Lubricant on R410A Horizontal Flow Boiling.


pdf icon Effect of Lubricant on R410A Horizontal Flow Boiling. (304 K)
Sawant, N. N.; Kedzierski, M. A.; Brown, J. S.

NISTIR 7456; 37 p. September 2007.

Keywords:

flow boiling; lubricants; heat transfer; refrigerants; degradation; fluorescence

Abstract:

This paper experimentally determines the effect of lubricant on R410A horizontal flow boiling. A baseline was established by measuring the convective boiling heat transfer performance of pure R41 OA. In addition, the heat transfer performance of an R410A/lubricant (99.6/0.4) mixture was measured and compared to that of the lubricant free refrigerant. The measured convective boiling Nusselt numbers for the lubricant-free R410A and R41OA/lubricant mixture were compared to an existing correlation. The correlation was shown to predict 71% and 83% of the lubricant-free R410A and the R41OA/lubricant Nusselt numbers to within - 20%, respectively. The mean degradation in the heat transfer performance with the addition of lubricant was approximately 6.7%. A measurement technique for observing the fluorescence of the lubricant in the annular flow was developed. Further improvements in the technique are necessary before it can be used to visualize the distribution oflubricarit within the flow.