Using mixtures of the zeotropic refrigerant mixture R-22/R-142b, a series of experiments was performed to determine the sectional and average heat transfer coefficients. Experiments were also conducted to compare three different heat transfer enhancement methods to that of smooth tubes. They were microfins, twisted tapes, and high fins. Measurements at different mass fluxes were obtained at six refrigerant mass fractions from 100 percent R-22 up to a 50 percent/50 percent mixture of R-22/R-142b. All condensation measurements were conducted at an isobaric inlet pressure of 2.43 MPa. This pressure corresponds to a saturation temperature of 60°C for R-22. The measurements were taken in 9.53 mm outer diameter smooth tubes and microfin tubes with lengths of 1603 mm. The heat transfer coefficients were determined with the Log Mean Temperature Difference equations. It was found that microfins were more suitable as an enhancement method than twisted tubes or high fins. Also, that the heat transfer coefficients and pressure drops decrease as the mass fraction of R-142b increases.
R-22 and Zeotropic R-22/R-142b Mixture Condensation in Microfin, High-Fin, and Twisted Tape Insert Tubes
Contributed by the Heat Transfer Division for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received by the Heat Transfer Division August 21, 2000; revision received April 5, 2002. Associate Editor: T. Y. Chu.
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Smit, F. J., and Meyer, J. P. (September 11, 2002). "R-22 and Zeotropic R-22/R-142b Mixture Condensation in Microfin, High-Fin, and Twisted Tape Insert Tubes ." ASME. J. Heat Transfer. October 2002; 124(5): 912–921. https://doi.org/10.1115/1.1484394
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