Determining Overall Mass Transfer Coefficient for Gas Phase


Water is used to absorb the vapor of methanol at 300 K and 101.325 kPa. The concentration of methanol in both gas and liquid phases are very low, with the equilibrium relation following Henry’s Law. The known parameters are:

solubility of methanol in water = 1.995 kmol/(m3 .kPa)

local mass transfer coefficient for gas film kG = 1.55E-5 kmol/(m2.s.kPa)

local mass transfer coefficient for liquid film kL = 2.08E-5kmol/(m2.s.kmol/m3)

(1) Please determine the overall mass transfer coefficient for gas phase, KG,

(2) And determine the percentage of mass transfer resistance in gas film out of the overall resistance.

(3) At steady operation in certain section of the absorption column, the partial pressure of methanol is 5 kPa and the liquid composition is 2.11 kmol/m3. Please determine the methanol absorption rate NA, [kmol/(m2.h)] .


This question belongs to thermal engineering and discusses about mass transfer and absorptions.

Word count: 195


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