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.

Effects of biofilm structures on oxygen distribution and mass transport.

Abstract: Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. The oxygen distribution was strongly correlated with these strutures. The voids facilitated oxygen transport from the bulk liquid through the biofilm, supplying approximately 50% of the total oxygen consumed by the cells. The mass transport rate from the bulk liquid is influenced by the biofilm structure; the observed exchange surface of the biofilm is twice that calculated for a simple planar geometry. The oxygen diffusion occurred in the direction normal to the cluster surfaces, the horizontal and vertical components of the oxygen gradients were of equal importance. Consequently, for calculations of mass transfer rates a three-dimensional model is necessary. These findings imply that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood. (c) 1994 John Wiley & Sons, Inc.

Heat and mass transfer in capillary-porous bodies

Abstract: Publisher Summary Heat and mass transfer between capillary-porous bodies and surrounding incompressible liquid accompanied by a change of phase is not only of theoretical interest but also of great practical importance for some technological processes. Heat and mass transfer inside a porous body (internal heat and mass transfer) also has its unique character. Even now the mechanism of heat and mass transfer in evaporation processes is scantily investigated, and analytical investigations do not, therefore, lead to reliable results. This chapter presents an experimental study of heat and mass transfer in evaporation processes. To elucidate peculiarities of heat transfer with simultaneous mass transfer, a dry body (pure heat transfer) and a moist body (heat transfer in the presence of mass transfer) are investigated. Such a comparison makes it possible to establish relations for interconnected heat and mass transfer processes. In order to describe quantitative relations it is necessary to have a method of analysis which makes it possible to consider the interaction of the heat and mass transfer processes. One such method is the thermodynamics of irreversible processes. The experimental data presented well confirm the mathematical theory of thermodynamics of irreversible transfer processes.

Pressure solution in nature, theory and experiment

Abstract: Some of the features of water enhanced deformation of rocks by diffusive mass transfer (pressure solution) in nature which are pertinent to the rate controlling mechanism of the deformation are reviewed, and it is inferred that (a) the diffusion of matter in an aqueous intergranular film which can support shear stress is an essential part of the process, and (b) the diffusion is driven by stress induced chemical potential gradients, together with gradients due to local chemical reactions. The theoretical approach to the derivation of constitutive flow laws for creep by diffusive mass transfer is outlined, and a simplified flow law proposed. Crucial to the absolute rate of deformation predicted by the flow law is the estimation of the phenomenological coefficient which links diffusive flux to chemical potential gradient. It is argued that this should be several orders of magnitude less in thin, stressed aqueous films than for solutions of ions in large water volumes. Some simple experiments are described to address the question of (a) the existence of thin intergranular aqueous films which can support shear stress, and(b) the magnitude of the above phenomenological coefficient. The results obtained are consistent with the inferences made from the study of microstructures in naturally deformed rocks, and this is illustrated by means of extrapolation of theoreticallv derived relationships to conditions of natural rock deformation and sediment compaction by pressure solution.