A Numerical Model of Marangoni Convection in a Static Absorber in the presence f Surfactant Additives

The Marangoni effect is exploited in a variety of thermochemical applications, including absorption heat pumps to enhance heat and mass transfer rates. Certain absorption machines have benefited from rate enhancing additives for many years, yet the absorber is still a relatively large and expensive component in such systems. A better quantitative understanding of the mechanisms causing increased transfer rates may lead to improved designs and can aid the search for effective additives for machines using LiBr-H2O and other working pairs. A numerical model has been developed for the absorption of vapor into a static horizontal liquid film containing small concentrations of a surfactant additive. The two-dimensional finite difference model accounts for the occurrence of Marangoni convection. An effective additive enhances the absorption rate by causing intense surface mixing. Studies have been performed to determine the degree of enhancement achievable with additives relative to diffusion-controlled transfer. The influence of absorbate and additive Marangoni numbers, as well as additive diffusivity is considered