Mass Transfer Coefficients for Packed Columns

Three methods of estimating binary mass transfer coefficients in packed columns are presented below. 

Many other correlations for packed columns have been presented in the literature they are reviewed by Ponter and Au-Yeung (1986). Mass transfer coefficients for two component systems in packed columns sometimes are reported as a correlation of the height of a transfer unit (see, e.g.. Fair, 1984). 

The methods of Onda et al. (1968) and of Bravo and Fair (1982) are illustrated in Example 12.3.1 mass transfer coefficients in structured packing are calculated in Example 12.3.2. 

Onda s Correlations for Randomly Packed Columns Onda et al. (1968) developed correlations of mass transfer coefficients for gas absorption, desorption, and vaporization in randomly packed columns. The vapor-phase mass transfer coefficient is obtained from 

The liquid-phase mass transfer coefficient is obtained from the following equation  

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With regards to handling data on industrial apparatus for gas-liquid mass transfer (such as packed columns, bubble columns, and stirred tanks), it is more practical to use volumetric mass transfer coefficients, such as KqU and K a, because the interfacial area a cannot be well defined and will vary with operating conditions. As noted in Section 6.7.2, the volumetric mass transfer coefficients for packed columns are defined with respect to the packed volume - that is, the sum of the volumes of gas, liquid, and packings. In contrast, volumetric mass transfer coefficients, which involve the specific gas-liquid interfacial area a (L L 5), for liquid-gas bubble systems (such as gassed stirred tanks and bubble columns) are defined with respect to the unit volume of gas-liquid mixture or of clear liquid volume, excluding the gas bubbles. In this book, we shall use a for the specific interfacial area with respect to the clear liquid volume, and a for the specific interfacial area with respect to the total volume of gas-liquid mixture. 

Mass transfer coefficients for packed columns sometimes are expressed as the height of a transfer unit (HTU). Thus, for the vapor and liquid phases, respectively,... 

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