Question

7.9-1

7.9-1. Mass Transfer and Turbulence Models. Pure water at a velocity of 0.11 m/s is flowing at 261°C past a flat plate of solid benzoic acid where L = 0.40 m. Do as follows: (a) Assuming dilute solutions, calculate the mass-transfer coefficient k. Use physical-property data from Example 7.3-2. (b) Using the film model, calculate the equivalent film thickness. (c) Using the penetration model, calculate the time of penetration. (d) Calculate the mean surface renewal factor using the modified penetration model Ans. (b) Bj = 0.2031 mm; (d) s-3.019 × 10-2 s-1 REFERENCES )BIRD, R. B., STEWART, W. E., and LIGHTFOOT, E. N. Transport Phenomena. New York:

Answer 1

13 = 0.036 oD 415 0.40 m × 0.1 1 m/s × 1.2659 g/cms 1.26 mPa 0.036 ×0.40 m 7.97x10- cm2/s 1.26 mPa 1.2659 g/cm3 x7.97x10 cm/s k,-6.13x10-6 m/s Da, 1.245×10-9 m2/s = 0.2031mm 6.13x10-6 m/s 4D48-4×1.245×10-9THs = 42.18 s Trk,2 π( ) 6.13x10-6 m/s (6.13×10-6 m/s) 1.245x10-9m %= 3.019×10-2 s-1 2 m/s