Analysis of ammonia vapor absorption into ammonia water mixtures: mass diffusion flux

Abstract

Ammonia absorption phenomenon is investigated experimentally by allowing superheated ammonia vapor to flow into a test cell to be absorbed into a stagnant pool of ammonia water mixtures of several ammonia mass fractions, Ci. Two main objectives are sought in this paper. The first one is to find out the dependency of the total mass absorption, which is estimated by two different methods; interface heat flux and vapor pressure drop, upon Ci. An equation is developed which allows calculating ammonia total mass absorption per unit area for the whole range of Ci. The second objective is to visualize the diffusion process in the liquid mixture. The visualized fringes show two layers with different speeds of fringes propagation. The layer with fast propagation represents pure thermal diffusion while the slow propagation layer is characterized by a superposition of mass and heat diffusions where heat effect is big at short time from starting the absorption and this effect decreases with the elapse of time. Mass diffusion flux is obtained by the developed equation and the visualized fringes and the predicted values from both methods are found to agree well. Mass diffusion flux shows a strong dependency on Ci in a way that it decreases dramatically with increasing Ci.