External Flow: Mass Transfer Chapter 7 Sections , 7.7, 7.8

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-to-Turbulent Flow: – Turbulent Flow: – Laminar Flow:

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? – Evaluate the surface vapor concentration at the surface temperature (assuming saturated conditions). Hence, with, the properties of the mixture may be approximated by those of species B.

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

Problem: Paper Drying (cont). SCHEMATIC:

Problem: Paper Drying (cont.)

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

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