Enhancement of vapor absorption in LiBr falling film on the sinusoidal wall of cooling water channel: A fully-coupled approach.

This study investigates the enhancement of water vapor absorption in falling films of LiBr aqueous solution by focusing on the coupled effects of wall geometry and thermal boundary conditions. A cooling channel with water flow is introduced adjacent to the falling film, simulating heat transfer conditions more representative of practical absorption systems. A two-dimensional computational model employing a fully coupled interface tracking method is used to simulate the flow dynamics and interfacial transport phenomena. A novel fully coupled interfacial heat and mass transfer (FCIHMT) method is proposed, incorporating implicit coupling of interface temperature, pressure, and mass fraction fields with interior nodes. The impact of sinusoidal wall geometry, characterized by wave number and height, is compared with that of a flat wall under various cooling water temperatures and flow rates. The results demonstrate that sinusoidal walls significantly enhance absorption performance, achieving improvements between 40% and 250% compared to flat walls. This enhancement is primarily attributed to the increased cooling contact area, intensified thermal gradients, and induced secondary flow structures, which improve local heat and mass transfer efficiency. Detailed analyses of velocity fields, temperature distributions, and LiBr mass fraction profiles reveal complex flow dynamics, including recirculation zones and interfacial oscillations. The findings highlight the potential of sinusoidal wall configurations for enhancing absorption efficiency in industrial applications such as refrigeration and air conditioning systems.