Effect of Lubricant on R410A Horizontal Flow Boiling.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899