Robert L. Pigford

Diffusion in a ternary gas system with application to gas separation

Abstract Measurements are reported of the separation effected by diffusion of a gaseous mixture of hydrogen and nitrogen through two organic vapours for the cases of (a) stagnant vapour and (b) countercurrent flow of the vapour relative to the hydrogen and nitrogen. Comparison of the data with classical diffusion theory is facilitated by the use of simple geometry in the diffusion zone, and by careful control of the experimental boundary conditions. In general, the data agree well with theory based on a one-dimensional diffusion model, for both stagnant and flowing vapour. The role of countercurrent vapour flow in effecting large enrichments is particularly emphasized. For example, the measured separation factor for a hydrogen-nitrogen mixture was increased about thirty-fold when the mass flow of vapour was raised from zero to about three times the rate of feed flow. The theoretical analysis is extended to determination of performance characteristics for a practical diffusion stage separating isotopes of low natural abundance of the light component.

Analytical solution for cycling zone adsorption

Abstract An analytical solution is presented for calculating the performance of a cycling zone adsorption device. The solution includes the effects of film mass-transfer resistance between phases and square-wave temperature cycling in the standing wave mode of operation. The results are in excellent agreement with those obtained by direct numerical integration of the governing partial differential equations. The analytical solution is presented in the form of a convergent series, which is convenient to use.

Gas absorption with chemical reaction on a sieve tray

Abstract The rate of adsorption of carbon dioxide into four different sodium carbonate—bicarbonate buffer solutions and a sodium hydroxide solution has been experimentally determined for a six-inch diameter sieve tray. An analysis of these results using the penetration theory yields unexpectedly high values of interfacial area and contact time. Similar results had previously been obtained for packed columns [7]. It is proposed that this discrepancy is owing to the fact that the entire froth is not well mixed. This leads to some of the interfacial liquid becoming saturated with gas and thus ineffective for absorption. An analysis has shown that the fraction of ineffective area may be as much as 40 per cent of the total.

Allan Philip Colburn—the years in education

ALLAN COLBURN’S early professional career has been outlined by his good friend and co-worker, Thomas Chilton, in a companion paper in this publication. The two men collaborated directly in a number of important pieces of work which contributed magnificently to the new field of chemical engineering, in its adolescent stages in the United States at the time. Theirs was a unique opportunity to apply scientific tools to the many new and intriguing problems of chemical manufacture afforded by the growth of an important chemical company. Through them, and a few others with similar insight, chemical engineering became known to practicing engineers and to students alike as a professional field unique .among the engineering branches in its opportunities to use the basic sciences, including chemistry, and mathematics for a wide spectrum of problems characteristic of the chemical and petroleum industries. Thus, it was with a well-known reputation for original work having practical significance that Allan Colburn came to the University of Delaware in 1938 to head a fledgling department in what was then a small and unimpressive college. Some have said that he made the change so that he would be free to follow a less physically demanding schedule. Those who knew his work in these early days remember his almost boundless energy and his devotion to his new responsibilities, not only in his own department but in many other affairs at his institution. Allan Colburn’s father had been a school teacher; it appeared to Allan’s friends that he, too, had found his place in the world. Even his plan to take a nap after lunch each day for the sake of his recovery from illness was soon discarded in favor of the many new interests which he found on the campus. Naturally, there was much work that was incomplete at the time of the transition from industry to teaching. The important papers [IO, 121 on the transfer-unit concept and its use in treating experimental data as well as engineering design were yet to appear, but the thoughts behind them quite clearly came from the industrial years. A new interest in thermodynamic properties of solutions, frequently pointed out by Colburn as the key problem for the whole field of distillation, had led to a series of studies of vaporliquid compositions in collaboration with H. C. Carlson of the Du Pont Company. Today their paper [6] is one of the most widely quoted works in the field, for it set the stage for a long series of papers by chemical engineers throughout the world, a series which is far from completion. Professor Colburn’s interest in heat-transfer problems appeared again soon in his university work. Shortly after taking up his new duties he became involved as a consultant in several important investigations supporting the war effort. One of these involved the need to provide better air cooling of finned cylinders for aircraft engines. The problem was to obtain nearly uniform cooling around the circumference of the cylinder, the air flow being confined to narrow passages between the fins. The similarity to and differences from heat transfer in exchangers with parallel passages were pointed out in a publication with Lemmon and Nottage [37] in 1945, A related paper, published by the National Advisory Committee for Aeronautics [23] was concerned with the influence of vapor bubble formation on a hot surface, above the boiling point of a liquid which flows over the surface to cool it. The vapor bubbles cannot grow except in the very thin layer of superheated liquid at the surface itself, yet their appearance in this layer, which accounts for the major resistance to heat conduction, can greatly increase the cooling rate -a problem of obvious importance for the design of liquid-cooled engine cylinders. At about the same time the first of a series of