Ho-Ming Yeh

A Study of the Graetz Problems in Concentric-Tube Continuous-Contact Countercurrent Separation Processes with Recycles at Both Ends

Abstract A mathematical model for the concentric-tube square-off continuous-contact countercurrent separation process with recycles at both ends is developed to predict the concentrations of product. An analytical solution is obtained by means of the orthogonal expansion method. It has been found that only the positive eigenvalues for the enriching section and the negative eigenvalues for the stripping section are required during the calculation of the concentrations of product. Numerical results are presented for the separation of a benzene-n-heptane mixture in a concentric-tube thermal diffusion column.

The Effect of Curvature on the Transport Coefficients of Thermal Diffusion in Concentric-Tube Columns

Abstract The effect of curvature on the transport coefficients of thermal diffusion in concentric-tube columns has been investigated and the results were obtained graphically. It has been found that the results for the nearly plane case obtained by Yeh and Ward still can be used for the extreme cylindrical case, with the transport coefficients multiplied by the modifying factors presented.

Experimental Studies on the Separation of Deuterium Oxide in Continuous Thermal Diffusion Column for Low Concentration Range

Abstract Separation equations for the enrichment of heavy water in a continuous-flow thermal diffusion column have been derived for low-concentration operations. Experimentals on two feed concentrations of the H2O-HDO-D2O system have also been conducted, and the results quantitatively confirm the predictions of theory.

The Enrichment of Heavy Water in a Continuous-Type Inclined Thermal Diffusion Column

Equations of the best angle of inclination and the maximum separation for the enrichment of heavy water in a continuous-type inclined thermal diffusion column have been derived. Considerable improvement in separation was obtained by employing the inclined column instead of using the Clusius-Dickel. 19 references, 4 figures, 3 tables.

Improvement in Separation of Concentric-Tube Thermal Diffusion Columns with Viscous Heat Generation under Consideration of the Curvature Effect

Abstract The separation efficiency of concentric-tube thermal diffusion columns with viscous heat generation has been investigated under consideration of the curvature effect. The results were obtained graphically and were compared with those obtained by Yeh and Cheng in which they neglected the curvature effect. Considerable improvement in separation was obtained by employing a rotary column instead of a stationary one.

The Simplified Equation of Separation for the Enrichment of Heavy Water in a Batch-Type Thermal Diffusion Column

Abstract A simple but precise equation of separation for the enrichment of heavy water in a batch-type thermal diffusion column has been derived with the consideration of a pseudobinary mixture. The experiment has also been conducted for various initial concentrations of D2O and the results are in agreement with the prediction of the theory.

Separation Efficiency of Rotary Thermal Diffusion Columns with the Inner Tube Cooled and the Outer Tube Heated

Abstract Adjusting the temperature gradient to the opposite direction in rotary thermal diffusion columns results in improving the separation efficiency. In the case of small σ, even this modified rotary column gives better separation than the original rotary one developed in previous work.

Comparison of Various Methods of Calculating a Separation Factor in Thermal Diffusion

Abstract An improved equation of separation applicable to the whole range of concentration in flat-plate thermal diffusion columns has been derived by the least squares method. Separations calculated from this equation are more accurate than those from the generalized equation obtained by Yeh and Chu, particularly for low flow-rate operations and equifraction solution.

The Improvement of Separation in Zone Refining Processes with Zone Length Varied along the Ingot

Abstract Adjusting the zone length properly and continuously along the ingot during zone melting substantially increases the separation efficiency by controlling the solute concentration in the liquid zone. Considerable improvement in separation was obtained by employing the process with a partially optimized zone length versus distance.

Experimental Studies on the Degree of Separation in Thermal Diffusion Columns

Abstract Data were obtained in a flat-plate continuous-flow thermogravitational column to check the theories developed by Furry et al., and Yeh and Chu. Separations of benzene-n-heptane mixtures were measured, with flow rate, feed concentration, and temperature difference being varied in the experiments. Yeh and Chus work are in excellent agreement with the experimental data, while the agreement of Furry et al.s work with the experimental results is fair for equi-fraction solution and poor for high and low values of feed concentration.