Wilke and Hougan studied the mass-transfer characteristics of packed beds containing granular solids. In their experimental investigations, hot air was blown through a packed bed of porous celite pellets saturated with liquid water. The water evaporated under adiabatic conditions, and the rate of water transfer was determined by material balance using humidity measurements. From this data, they calculated the gas–film mass-transfer coefficient at a given flow rate. In one run, the following data were reported:

Estimate the gas–film mass-transfer coefficient by two appropriate correlations, one that includes the packed-bed void fraction, and a simpler correlation that does not account for the void fraction. Compare these estimates to the measured gas–film coefficient above.

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Gas-film coefficient, kg = 4.42 x 10³ kgmole/m² s atm Effective particle diameter, dp = 0.571 cm Packed-bed void fraction, e= = 0.75 Gas stream mass velocity, G = 0.816 kg/m² - s Temperature at particle surface, T = 311 K Total system pressure, P = 9.77 x 104 Pa