The Optimum Column Number for the Best Performance of Thermal Diffusion in the Frazier Scheme with the Total Sum of Column Height Fixed

The effect of column number N, as well as the column height h of thermal diffusion columns, on the degree of separation in the Frazier scheme with the total sum of the column height L (=Nh) fixed, has been investigated. The equations, which may be employed to predict the optimum column number N* for the maximum separation Δ _N,max, have been derived. Considerable performance in separation is obtainable if the column number, as well as the column height, in a Frazier scheme with the total sum of the column height fixed is properly assigned for a certain flow-rate operation.     

The Improvement of Thermal Diffusion Performance in the Modified Frazier Scheme by Increasing the Column Heights at a Constant Ratio

The effects of column number and the variation of column heights on thermal diffusion along the modified Frazier scheme, has been investigated with the total sum of column heights fixed. The equations, which may be employed to predict the optimal number of columns and the optimal column-height ratio for the maximum separation, have been derived. Considerable improvement in performance is obtainable if the column-height ratio and/or column number in a modified Frazier scheme with the total sum of column heights fixed are properly assigned for a certain flow-rate operation, instead of using the conventional Frazier scheme of uniform column height with the same total sum of column heights.     

Enrichment of Heavy Water by Thermal Diffusion in the Frazier Schemes with Column Heights Varied at a Constant Increment for Improved Performance

The improvement of heavy water enrichment by thermal diffusion in the Frazier scheme with column heights varied at a constant increment and with the total sum of column heights fixed, has been investigated. The equations, which may be employed to predict the optimal column number and the optimal column-height increment for maximum separation, have been derived. Considerable improvement in heavy water enrichment is obtainable if the column number and column-height increment in a modified Frazier scheme with the total sum of column heights fixed, are property assigned under certain flow-rate operation, instead of using the conventional scheme of uniform column height.     

The optimum plate aspect ratio for the best performance in a flat-plate thermal diffusion column of the frazier scheme

The effects of plate aspect ratio on the degree of separation, production rate and plate surface area in a flat-plate thermal diffusion column of the Frazier scheme, have been investigated. Theoretical considerations show that when the thermal diffusion columns of the Frazier scheme are constructed with the best plate aspect ratio, maximum separation, maximum production rate or minimum plate surface area can be obtained. The optimum plate aspect ratio for maximum separation is obtained with given production rate and plate surface area, while that for maximum production rate is determined with the degree of separation and plate surface area fixed, and that for minimum plate surface area is estimated with known degree of separation and production rate. It is interesting that the optimum plate aspect ratio for maximum separation is exactly the same as that for minimum plate surface area. The maximum separation and maximum production rate are achieved without changing any total expenditure, while the design with minimum plate surface area results in minimizing the total expense.     

Recovery of deuterium from water-isotopes mixture in flat-plate thermal-diffusion columns of the Frazier scheme with optimum plate-spacing

The effect of plate-spacing on the degree of recovery and production rate for the recovery of deuterium from water-isotopes mixture in flat-plate thermal-diffusion columns of the Frazier scheme with fixed operation expense has been investigated. The equations for estimating optimum plate-spacing for maximum recovery and maximum production rate have been developed. Considerable improvement in performance is obtainable when thermal-diffusion columns with optimum plate-spacing are employed for operation.     

Thermal diffusion in inclined flat-plate columns of the frazier scheme

The separation theory of thermal diffusion in inclined flat-plate columns of the Frazier scheme has been developed and investigated. The equations for the best angle of inclination and maximum separation have been derived. Considerable improvement in separation is obtained when thermal diffusion columns are operated at the best angle of inclination.     

Reduction of metal ions in dilute solutions using a GBC-reactor Part II: Theoretical model for the hydrogen oxidation in a gas diffusion electrode at relatively low current densities

The GBC-reactor is based on the combination of a gas diffusion anode and a porous cathode. A theoretical model for gas diffusion electrode, valid at relatively low current densities, is derived. This is based on the pseudohomogeneous film model including an approximation of the Volmer–Tafel mechanism for the hydrogen oxidation kinetics. Results show a severe mass transfer limitation of the hydrogen oxidation reaction inside the active layer of the gas diffusion electrode, even at low current densities. Empirical formulae are given to estimate whether leakage of dissolved hydrogen gas into the bulk electrolyte occurs at specific process conditions. A simplified version of the model, the reactive plane approximation, is presented.     

Dispersed plug flow model for steady-state laminar flow in a tube with a first order sink at the wall

Steady state, laminar flow transport in a tube with a first order sink at the wall involves two dimensions—radial and axial. In this paper, a novel iterative technique has been proposed for reducing such a two-dimensional model to an equivalent one-dimensional dispersed plug flow model. The latter yields an analytical expression for the equivalent axial dispersion and a simple, closed form, but approximate, analytical solution of the original two-dimensional problem. The operating range in which this analytical solution is useful has been investigated for a system with mass transfer at the wall.