Account Of Mass Transfer Research Articles

Heat and Mass Transfer in Cesium Evaporation from Graphite Surface in Argon

The aim of the present work is mathematical modeling of the heat and mass transfer of 137Cs under the action of low-temperature equilibrium plasma flow on sections of graphite contaminated by radionuclides. The methods of investigation are calculation of the temperature and mass rate of evaporation of radiocesium by solving a system of quasi-homogeneous nonstationary heat conduction equations with boundary conditions of the first and third kind, which take account of mass transfer, by means of finite-difference elements using the ANSYS package.

Numerical simulation for volatile organic compound removal in rotating drum biofilter

Rotating drum biofilters (RDBs) could effectively remove volatile organic compounds (VOCs) from waste gas streams. A mathematical model was developed on the basis of mass transport and mass balance equations in an RDB, the two-film theory, and the Monod kinetics. This model took account of mass transfer and biodegradation of VOC in the gas-water-biofilm three-phase system in the biofilter, and could simulate variations of VOC removal efficiency with a changing specific surface area and porosity of the media due to the increasing of biofilm thickness in the biofilter. Toluene was used as a model VOC. This model was further simplified by introducing a coefficient of the gas velocity and neglecting the water phase due to the complexity of operating conditions. The equations for the biofilm phase, gas phase, and biofilm accumulation in this model were solved using colloction method, analytic method, and the Runge-Kutta method separately. A computer program was written down as MATLAB to solve this model. Results of numerical solutions showed that toluene removal efficiency in the RDB increased and reached the maximum values of 97% on day 4 after the startup, and then decreased the remained at 90% after 5 more days of operation. Toluene concentration was high at the outermost layer where more than 70% toluene was removed, and was low at the innermost layer where less than 10% toluene was removed. The dynamic removal efficiencies from this model correlated reasonably well with experimental results for toluene removal in a multi-layered RDB.

Dynamics of the Reaction of 2,4,6-tribromophenol and Benzyl Bromide by Phase Transfer Catalysis.

The dynamics of the alkylation of 2,4,6-tribromophenol in an alkaline solution of KOH/chlorobenzene solvent by phase transfer catalysis was simulated using the two-film theory, taking account of mass transfer and distribution of catalysts between the two phases as well as the intrinsic reaction kinetics in both the organic and aqueous phases. Independent experiments were designed to obtain the distribution coefficients and the overall mass transfer coefficients of the catalysts between the two phases. The organic-phase intrinsic reaction-rate constant was obtained by carrying out the half-organic phase reaction. Without adding benzyl bromide, a reaction was also conducted to obtain the aqueous-phase intrinsic reaction-rate constant. Comparing the results obtained from experiments, the aqueous-phase reaction rate is essentially instantaneous relative to the organic-phase reaction rate. The resistance of mass transfer of catalyst between two phases is negligible. The reaction rate in the organic phase is a rate-determining step for the two-phase reaction. The results obtained from the model’s prediction are closely consistent with the experimental data obtained from the phase-transfer catalytic reactions.

Diffusion and mass transfer in moderately concentrated disperse system with small peclet numbers

Nonsteady diffusion in a system with identical nonconducting spherical particles is considered, taking account of mass transfer with these particles.