Numerical and experimental study of absorption of H2O vapor in wavy falling film of LiBr aqueous solution in vertical tubes and in presence of non-absorbables

One of the main reasons for the discrepancies between theoretical predictions of absorption phenomena made by mathematical models when they are compared against experimental results under real conditions, are the presence of non-absorbable gases. It is well known that these non-absorbable gases inside the shell of the absorption chiller are produced mainly for two reasons: (i) air leakages (Oxygen-Nitrogen); (ii) gases produced by corrosion (Hydrogen). In order to evaluate the influence of the presence of non-absorbable gases, an experimental set-up which reproduces vapor absorption in a vertical falling film has been designed and built with a mass spectrometer analyzer. Parallelly, a mathematical model of falling film absorption of H2O by LiBr aqueous solution that considers the influence of non-absorbable gases has been implemented. The model is semi-empirical, based on Navier–Stokes equations together with energy and mass species simplified under the boundary layer hypotheses. Several experimental tests have been performed to determine the influence of the air concentration in the absorption performance. Moreover, a comparison of numerical results against experimental data has been performed under different working conditions with reasonable agreement.