Mass transfer

About: Mass transfer is a research topic. Over the lifetime, 27310 publications have been published within this topic receiving 577647 citations. The topic is also known as: mass transport.

Heat and mass transfer in packed beds

Abstract: Eddy mass diffusivities, effective thermal conductivities, and wall heat transfer coefficients were measured in an 8-in. tube packed with 1/2- and 3/4-in. glass spheres. Superficial mass velocities ranged from 110 to 1,640 Ib./(hr.) (sq. ft.), corresponding to modified Reynolds numbers of 100 to 2,000. Air was the main stream fluid in all cases. The modified Peclet group (DpV/E*td) was found to be constant at a value of about 12 in the region of fully developed turbulence. At lower Reynolds numbers this group varied with the flow rate. Effective thermal conductivities were correlated by an equation. Modified Peclet numbers for heat transfer were about 25% less than those for mass transfer. The wall heat transfer coefficient varied with the superficial mass velocity as hw = 0.090 (Go0.75). An explanation is suggested for the similarity in velocity dependence between these values and those for turbulent flow in an empty tube, based on channeling at the wall.

Mass transfer coefficients between gas and liquid phases in packed columns

Abstract: Bubbles which have been just generated from the porous plate are small and have an equal size, but sometime coalescence of these small bubbles occurs at a location slightly removed from the distributor, where the gas holdup is very large. Therefore, large and wide size distribution of bubbles are observed. This occurs easily in pure water and pure solvents. The surface active substances in water and solvents obstruct this coalescence of bubbles. In concentrated inorganic salt solutions, this obstruction is also recognized. For the extreme cases when no coalescence is observed and the coalescence occurs at the maximumrate, the correlations of the average bubble diameter and the conditions of bubble generation are obtained.

Multiple‐Rate Mass Transfer for Modeling Diffusion and Surface Reactions in Media with Pore‐Scale Heterogeneity

Abstract: Mass transfer between immobile and mobile zones is a consequence of simultaneous processes. We develop a “multirate” model that allows modeling of small-scale variation in rates and types of mass transfer by using a series of first-order equations to represent each of the mass transfer processes. The multirate model is incorporated into the advective-dispersive equation. First, we compare the multirate model to the standard first-order and diffusion models of mass transfer. The spherical, cylindrical, and layered diffusion models are all shown to be specific cases of the multirate model. Mixtures of diffusion from different geometries and first-order rate-limited mass transfer can be combined and represented exactly with the multirate model. Second, we develop solutions to the multirate equations under conditions of no flow, fast flow, and radial flow to a pumping well. Third, using the multirate model, it is possible to accurately predict rates of mass transfer in a bulk sample of the Borden sand containing a mixture of different grain sizes and diffusion rates. Fourth, we investigate the effects on aquifer remediation of having a heterogeneous mixture of types and rates of mass transfer. Under some circumstances, even in a relatively homogeneous aquifer such as at Borden, the mass transfer process is best modeled by a mixture of diffusion rates.