Heat Transport Augmentation in Rayleigh-Benard Cells Containing Two Pure Gases Mixtures

摘要

The trends observed in Figs. 1-3 may be condensed as follows: the heat transfer enhancement decreases as the exponent n increases, commencing with 103% for n = 1/4, passing through 56% for n = 1/3, and ending with 36% for n = 2/5. The optimal mass fractions w_(opt) in the binary gas mixtures are sensitive to the value of the exponent n also. In fact, w_(opt) increases constantly with n, starting from w = 0% for n = 1/4, passing through an intermediate value of w = 50% for n = 1/3, and culminating with a large value of w = 88% for n = 2/5. From a chemical standpoint, the molar masses of the pure components participating in the binary gas mixtures are 4 for He, 16 for CH_4, 28 for N_2, and 32 for O_2 (Ref. 3). From this it may be inferred that as the molar mass difference between the basic component He and the other components N_2, O_2, CO_2, and CH_4 increases, the relative heat transfer coefficient h_m/B tends to increase, too. In addition, the largest relative heat transfer coefficient h_(m,max)/B is shifted to the right part of the (h_m/B)-w diagram, moving toward the heavier component in the binary gas mixture, that is, N_2, O_2, CO_2, and CH_4.