Mass transfer coefficient

About: Mass transfer coefficient is a research topic. Over the lifetime, 7827 publications have been published within this topic receiving 168354 citations.

Dissolved oxygen transfer at the sediment-water interface in a turbulent flow

Abstract: Laboratory experiments have been conducted in an effort to elucidate the details of the dissolved oxygen transfer mechanism at the sediment-water interface. Near-bed liquid turbulence and dissolved oxygen concentrations were measured for a range of Reynolds numbers from 2700 to 10,600 over a smooth bed. The results show that the shear stress velocity controls the dissolved oxygen diffusive layer thickness and therefore the local mass transfer coefficient at the sediment-water interface. From a dynamic point of view the results suggest the possibility that streamwise vortices control the interfacial dissolved oxygen transfer process. The research results will provide an opportunity to validate the existing conceptual models as well as enhance the development of new models that can improve our ability to predict dissolved oxygen and transport related parameters in lakes, reservoirs, coastal waters, and rivers.

Quantification of Density-Driven Natural Convection for Dissolution Mechanism in CO2 Sequestration

Abstract: Dissolution of CO2 into brine causes the density of the mixture to increase. The density gradient induces natural convection in the liquid phase, which is a favorable process of practical interest for CO2 storage. Correct estimation of the dissolution rate is important because the time scale for dissolution corresponds to the time scale over which free phase CO2 has a chance to leak out. However, for this estimation, the challenging simulation on the basis of convection–diffusion equation must be done. In this study, pseudo-diffusion coefficient is introduced which accounts for the rate of mass transferring by both convection and diffusion mechanisms. Experimental tests in fluid continuum and porous media were performed to measure the real rate of dissolution of CO2 into water during the time. The pseudo diffusion coefficient of CO2 into water was evaluated by the theory of pressure decay and this coefficient is used as a key parameter to quantify the natural convection and its effect on mass transfer of CO2. For each experiment, fraction of ultimate dissolution is calculated from measured pressure data and the results are compared with predicted values from analytical solution. Measured CO2 mass transfer rate from experiments are in reasonable agreement with values calculated from diffusion equation performed on the basis of pseudo-diffusion coefficient. It is suggested that solving diffusion equation with pseudo diffusion coefficient herein could be used as a simple and rapid tool to calculate the rate of mass transfer of CO2 in CCS projects.

Adsorption of Carbon Dioxide onto Activated Carbon and Nitrogen-Enriched Activated Carbon: Surface Changes, Equilibrium, and Modeling of Fixed-Bed Adsorption

Abstract: It has been reported that the CO2 adsorption capacity of the N-enriched activated carbon can increase or decrease. In this study a commercial activated carbon was functionalized with 3-chloropropylamine hydrochloride and its adsorption characteristics in a fixed-bed column were investigated. The N-enriched activated carbon presented lower BET surface area than the original activated carbon suggesting that the nitrogen incorporation partially blocks the access of N2 to the small pores. Although the surface basicity has increased it is not accomplished by an increase of the capacity of the adsorption of the N-enriched activated carbon. The breakthrough curves in a fixed bed column were obtained at different temperatures (301 K, 323 K, 373 K, and 423 K) and a total pressure of 1.01 bar using CO2 diluted in helium at two feed concentrations—10% and 20% (v/v). A model based on the Linear Driving Force (LDF) model for mass transfer was used to estimate the overall mass transfer coefficient and reproduced the br...