%0 Journal Article
%T Second Law Analysis of a Gas-Liquid Absorption Film
%A Nejib Hidouri
%A Imen Chermiti
%A Ammar Ben Brahim
%J Journal of Thermodynamics
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/909162
%X This paper reports an analytical study of the second law in the case of gas absorption into a laminar falling viscous incompressible liquid film. Velocity, temperature, and concentration profiles are determined and used for the entropy generation calculation. Irreversibilities due to heat transfer, fluid friction, and coupling effects between heat and mass transfer are derived. The obtained results show that entropy generation is mainly due to coupling effects between heat and mass transfer near the gas-liquid interface. Total irreversibility is minimum at the diffusion film thickness. On approaching the liquid film thickness, entropy generation is mainly due to viscous irreversibility. 1. Introduction Gas-liquid (and vapor-liquid) flows occur in a wide variety of situations such as: power generation, chemical processing, and energy production facilities. Some practical applications include condensers and reboilers, gas-liquid reactors (used in the production of pharmaceuticals and specialty chemicals), wetted wall absorbers, power systems, core cooling of nuclear power plant, and falling film reactors. In addition to normal gravity applications, gas-liquid (and vapor-liquid) flows also occur in many planned space operations such as: power cycles, active thermal control systems [1], propulsion devices, and storage and transfer of cryogenic fluids. Gas-liquid flows can be grouped into a number of different flow patterns. These flow patterns are based on the spatial and temporal distribution of the gas and liquid phases. Gravity is the major reason for such two-phase flows to exhibit a wide range of flow patterns with different characteristics. Gas-liquid absorption is one of the most important separation processes, the gas-liquid contactors in which absorption takes place are typically spray, trayed, or packed systems involving falling films. Falling film flow has found wide applications in modern equipments, because it is widely used in modern process industries such as vertical condensers, film evaporators, distillation columns, and packed and absorption towers. Various works are elaborated in order to study the coupled heat and mass transfer processes in gas or vapor absorption into a liquid film. The theoretical analysis of combined heat and mass transfer processes in the case of gas or vapor absorption into a laminar and/or turbulent liquid film as well as the temperature evolution and the concentration profiles in the film are developed [2¨C5]. Conlisk and Mao [6] considered the condensation of a two-component vapor mixture into a two-component
%U http://www.hindawi.com/journals/jther/2013/909162/