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External Flow: Mass Transfer

External Flow: Mass Transfer

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External Flow: Mass Transfer

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  1. External Flow:Mass Transfer Chapter 7 Sections 7.2 - 7.5, 7.7, 7.8

  2. Mass Transfer Mass Transfer • Correlations for convection mass transfer coefficients associated with evaporation • or sublimation from liquid or solid surfaces in external flow may be inferred from • the corresponding heat transfer correlations for an isothermal surface by invoking • the heat-and-mass transfer analogy: • Example: Flat Plate in Parallel Flow • Laminar Flow: • Laminar-to-Turbulent Flow: • Turbulent Flow:

  3. Hence, with , the properties of the mixture may be approximated by those of species B. • Evaluate the surface vapor concentration at the surface temperature (assuming saturated conditions). Mass Transfer • Fluid Properties: • Assume a dilute, binary mixture of species A (the volatile species) and species B (the free stream fluid). • Evaluate the properties of species B at the reference temperature specified • for the correlation. If the correlation involves a property ratio, approximate the ratio as unity. How would you characterize the relative effectiveness of diffusion in gases, liquids and solids?

  4. Problem: Paper Drying Problem 7.119 Use of radiant energy to dry slurry in a paper production process.

  5. SCHEMATIC: Problem: Paper Drying (cont).

  6. Problem: Paper Drying (cont.)

  7. Problem: Paper Drying (cont.)

  8. Problem: Wet-and Dry-Bulb Thermometers Problem 7.128 Use of wet- and dry-bulb thermometers to determine temperature and relative humidity of air flow in a duct.

  9. Problem: Wet-and Dry-Bulb Thermometers (cont.)

  10. Problem: Wet-and Dry-Bulb Thermometers (cont.)

  11. Problem: Wet-and Dry-Bulb Thermometers (cont.)

  12. Problem: Wet-and Dry-Bulb Thermometers (cont.)