Analytical solution for combined heat and mass transfer in laminar falling film absorption with uniform film velocity – Isothermal and adiabatic wall

• Introduction of a more versatile analytical solving procedure using the Laplace transform.
• Analytical solution to the combined heat and mass transfer for the isothermal and adiabatic wall.
• Evaluation of the influence of the thermal wall boundary condition on the absorbed mass flux.
• Discussion of the influence of the Lewis number on the absorbed mass flux.

In the present study the Laplace transform is applied to the partial differential equations obtained from the differential energy and absorbate balances for the combined heat and mass transfer problem in laminar falling films with uniform film velocity.By means of the inverse Laplace transform an analytical solution is provided for the isothermal as well as for the adiabatic wall boundary condition. Temperature and mass fraction profiles across the film as well as the evolution of the absorbed mass flux as a function of the flow length are presented for the adiabatic wall condition as well as for the isothermal wall with different wall temperatures. Furthermore, the influence of the Lewis number on the absorbed mass flux is discussed.In addition, the present method allows to apply other wall boundary conditions than the isothermal or the adiabatic wall boundary, which will be addressed in a subsequent study.