rived values can be used in the absence of experimental data. The equations are as follows:

where:

= mass flowrate of liquid (kg/sec • m2) = mass flowrate of gas (kg/sec • m2) = diffusion coefficient (m2/sec)

ScL = Schmidt number, (pL/pLDL)

ap gas-phase mass-transfer coefficient (kmol/N • s) liquid-phase mass-transfer coefficient (m/s) density of liquid (kg/m3) viscosity of liquid (N • s/m2) effective packing diameter (the diameter of a sphere with equal surface area) = dry outside surface area of packing

In this model, a is assumed to equal aw, the wetted area of the packing, and is calculated by the following equation:

where H is the Henry's law constant and PT is the total pressure. The accuracy of estimating column height depends mostly on the Kya correlation chosen for the calculation. In mass-transfer operations, Ky can be broken down to the mass-transfer coefficient in the gas phase ky and in the liquid phase kx. This two-resistance theory is widely accepted (McCabe 1993) and leads to the following relationships:

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