Analysis of Ammonia Vapor Absorption into Ammonia Water Mixtures--Rate of Absorption Reaction

Ammonia vapor absorption has been investigated experimentally by allowing superheated ammonia vapor to flow into a test cell to be absorbed into stagnant pool of ammonia water mixtures of different ammonia initial mass fraction Ci. Mass absorption rate has been estimated by two ways where the first one is the Ibrahim and Klein actual state equation, and the second one is the interface heat flux that has been estimated by inverse heat conduction solution. Absorption reaction rates for the different cases of Ci have been obtained through the change of ammonia vapor composition during absorption. The reaction rates show a great affinity between ammonia and water to react chemically. They also show strong dependency upon Ci in that the reaction rate decreases dramatically with increasing Ci. Absorption process has been visualized by Mach-Zehnder interferometer and the obtained fringes have been analyzed to get the concentration distribution together with that obtained by theoretical solution in which ammonia concentration at the interface changes with time. The obtained optical images allowed us to distinguish between two layers with different speeds of fringes propagation. The layer with slow propagation of fringes reflects pure mass diffusion with negligible heat effect especially after long time from starting the absorption, while the layer with fast propagation of fringes reflects a thermal controlled diffusion.