Heat and Mass Transfer in a Falling Film Absorber of Ammonia—Water Absorption Systems

Abstract

For ammonia-water generator-absorber heat exchanger (GAX) systems to work at high coefficient of performance, the heat and mass transfer components have to operate at optimum performance within a narrow range of conditions for the recovery of internal energy, in the present work, an analysis is performed to study the absorption process of an ammonia-water vapor mixture by an aqueous solution of ammonia in a falling film absorber. The combined heat and mass transfer processes involved arc analyzed through an integral formulation of the continuity, momentum, energy, and diffusion equations. The effects of vapor flow direction relative to the solution, cooling ability, ammonia concentration of solution and vapor, and interfacial momentum and heat transfer rate on absorption processes are investigated. The characteristics of the absorption process are found to be governed by the relative significance of the mass transfer resistance and the driving forces between the solution film and the vapor mixture.