Topic
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.
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TL;DR: The present work is aimed at the reviewing of the oxygen transfer rate (OTR) in bioprocesses to provide a better knowledge about the selection, design, scale-up and development of bioreactors.
1,203 citations
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TL;DR: In this paper, a dual-porosity model was developed for the purpose of studying variably saturated water flow and solute transport in structured soils or fractured rocks, where water in both pore systems is assumed to be mobile.
Abstract: A one-dimensional dual-porosity model has been developed for the purpose of studying variably saturated water flow and solute transport in structured soils or fractured rocks. The model involves two overlaying continua at the macroscopic level: a macropore or fracture pore system and a less permeable matrix pore system. Water in both pore systems is assumed to be mobile. Variably saturated water flow in the matrix as well as in the fracture pore system is described with the Richards' equation, and solute transport is described with the convection-dispersion equation. Transfer of water and solutes between the two pore regions is simulated by means of first-order rate equations. The mass transfer term for solute transport includes both convective and diffusive components. The formulation leads to two coupled systems of nonlinear partial differential equations which were solved numerically using the Galerkin finite element method. Simulation results demonstrate the complicated nature of solute leaching in structured, unsaturated porous media during transient water flow. Sensitivity studies show the importance of having accurate estimates of the hydraulic conductivity near the surface of soil aggregates or rock matrix blocks. The proposed model is capable of simulating preferential flow situations using parameters which can be related to physical and chemical properties of the medium.
1,109 citations
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TL;DR: In this paper, a water and heat management model was developed and used to investigate the effectiveness of various humidification designs for proton-exchange-membrane fuel cells and showed that at high current (> 1A/cm[sup 2], ohmic loss in the membrane accounts for a large fraction of the voltage loss in a cell and back diffusion of water from the cathode side of the membrane is insufficient to keep the membrane hydrated.
Abstract: Proper water and heat management are essential for obtaining high-power-density performance at high energy efficiency for proton-exchange-membrane fuel cells. A water and heat management model was developed and used to investigate the effectiveness of various humidification designs. The model accounts for water transport across the membrane by electro-osmosis and diffusion, heat transfer from the solid phase to the gas phase and latent heat associated with water evaporation and condensation in the flow channels. Results from the model showed that at high current (> 1A/cm[sup 2]) ohmic loss in the membrane accounts for a large fraction of the voltage loss in the cell and back diffusion of water from the cathode side of the membrane is insufficient to keep the membrane hydrated (i.e., conductive). Consequently, to minimize this ohmic loss the anode stream must be humidified, and when air is used instead of pure oxygen the cathode stream must also be humidified.
1,076 citations
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TL;DR: In this paper, the surface tension of aqueous solutions of methanol, ethanol, 1-propanol, and 2propanols was measured over the entire concentration range at temperatures of 20-50 C. The experimental values were correlated with temperature and with mole fraction.
Abstract: The surface tension of mixtures is a physical property of great importance for mass transfer processes such as distillation, extraction, or absorption. The surface tension of aqueous solutions of methanol, ethanol, 1-propanol, and 2-propanol was measured over the entire concentration range at temperatures of 20--50 C. The experimental values were correlated with temperature and with mole fraction. The maximum deviation was in both cases always less than 3%.
1,005 citations
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TL;DR: In this article, the published heat transfer data obtained from steady and nonsteady measurements are corrected for the axial fluid thermal dispersion coefficient values proposed by Wakao and Funazkri.
993 citations