External Flow: Mass Transfer

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# External Flow: Mass Transfer - PowerPoint PPT Presentation

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

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### External Flow:Mass Transfer

Chapter 7

Sections 7.2 - 7.5, 7.7, 7.8

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:

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?

Problem: Paper Drying

Problem 7.119 Use of radiant energy to dry slurry in a paper production process.

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.