Diffusional Layer Transfer and and Management, large mass-transfer rat - PDF document

Diffusional Layer Transfer and and Management, large mass-transfer rates, heat and diffusional mass as exerted friction, (corresponding, effectively, injection). In corrections for this influ- approximate theories layer model, Without mass from fluid 9 and Integrating this twice with Eq. 13 model correction has been This thermal correction factor factor. It original result and has been engineering ap- actual heat transfer (or Stanton number the zero heat transfer (or discussion above, it has however pointed out this result In case ferred. In the section such With application boundary conditions: the temperature film is wall is this section film is solved alternative correction factor rived which accounts for both the dimen- sionless mass actual mass-transferring next to transfer takes shown in to the fraction attains the and boundary result being described Eqs. 10 boundary conditions transferred heat through simply given as reference transfer on heat transfer. mass is distinguished. Namely, situation where and the case whereby the entire film; this dimensionless mass In order the entire extra conditions required. These Stagnant film. dYIY=y dYIY=y’ Eqs. 17 3 and and substitu- and 16 to the wall follows from Eqs. 21 as: correction factor In Figure drawn against 0.25, 0.5, 0.75 figure reveals correction factor, which is 14. Both correction factors reduce vanishingly small mass- transfer rates. zero, that effective mass-trans- zero. This recommended for time for 14 coincide, along external surfaces, where flow in the other then represents turbulent, free and/or forced convec- (or Stanton) Sherwood num- Thermal correction correction factor correction factor still prevailing numbers and hence Momentum Transfer model correction factor for wall mass exerted friction. Brouwers recapitulated their friction factor with as frictional dimensionless mass frictional correction on the mass transfer the entire Fanning friction factor. actual fric- factor (or from multiplying friction factor In the previous section, momentum equation equation presented previous section as correction factor: lines in Figure Summarizing, Eq. 29 recommended for cal correction factor 32 reckons actually effective. Fog Formation this section alternative correction investigate fog formation mixture for In case reveals that heat transfer to the model (curve gradient near alternative analysis should gas mixtures practical case tangency condition discussed below. al. (1950) introduced the tangency condition binary mixtures cooled channels. a subsequent article this condition tangency condition based on heat and diffusional mass-transfer component at a stagnant improved tangency con- (1991), fog in mixtures water vapor could be excellently explained. experiments were originally Johnstone et with mixtures nitrogen and n-butyl alcohol could not be explained satisfactorily. Fog observed experimen- but could explained theoretically the tan- water vapor, that for experiments concerning laminar a tube 19 and 34, it follows for said these experiments ternative thermal correction factor n-butyl alcohol Brouwers, 1991) should be de- Brouwers (1991) higher and observed fog probably explained. n-butyl alco- hol, fog namely observed while the theoretical measured interface temperature, denoted has been recomputed values unchanged. Indeed the 0.1”C only. still below observed fog nitrogen and n-butyl alcohol be explained yet. can be attributed to: nitrogen and n-butyl al- does not from unity forced convective flow in the entrance a tube does not and related not large enough This can be to the relatively small difference between vapor vapor bulk mole a better reduced and stressed again, nitrogen and water vapor and hence analysis and conclusions (1991) with mixtures remains film model provides correction factors for the wall mass (such as transfer and exerted friction been demonstrated that the tional correction not account mass-transferring layer correction factors not generally an improved correction factors rate and These correction factors represented simple analytical expressions reveal substantial influence actual diffusional film thickness transport phenomena. applied in tangency condition. This condition predict fog experimental results al. (1950) cannot be explained with nor alternative thermal correction the pre- possible with is less unity and/or molar specific . . . integration constants, diffusion coefficient, velocity in the direction film thickness, m correction factor dimensionless film thickness condition for fog Literature Cited gleichen Feld bei “Film Models Transport Phenomena Fog Formation, Exchangers and Improved Tangency Condition for Brouwers, H. and A. Chesters, “Film Models for Fog Formation: the Classical Film Model,” Hougen, “Design Cooler Condensers 197 (1937). Shenvood, “Diffusion D. Kelley, 2298 (1950). and Momentum Transfer for over a Flat Plate NACA Techn. uber die