No abstract

Microchannel technology as applied to chemical processing has resulted in impressive improvements in performance thresholds. Studies published for more than a decade show that enhanced performance in chemical reactors can be largely attributed to the reduction of transport distances. Chemical distillation is now emerging as a new area for the application of microchannel technology.A simplified method for simulating a microchannel distillation process has been developed and validated with experimental data. Both simulation and experiments show that the height of a theoretical transfer unit for the separation of hexane and cyclohexane in a microchannel distillation unit is reduced to centimetres. Vapour-side resistance was found to control mass transfer for the cases considered. The current simulation can serve as a tool for optimizing and refining the design of multiphase microchannel processes.

It is my annual hope that each year's Symposium will be the last. Not because I dislike the subject, or because I find Boulder inhospitable, but because I'd like to think that we can solve the problems of laser damage, and move on to new challenges.

The Twelfth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, September 30 –October 1,1980. The Symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific Research. Over 150 scientists attended the Symposium, including representatives of the United Kingdom, France, Japan, and West Germany. The Symposium was divided into sessions concerning Materials and Measurements, Mirrors and Surfaces, Thin Films, and finally Fundamental Mechanisms. As in previous years, the emphasis of the papers presented at the Symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high power systems. The wavelength range of prime interest was from 10.6 μm to the uv region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Alexander J. Glass of the Lawrence Livermore Laboratories, Arthur H. Guenther of the Air Force Weapons Laboratory, and Brian E. Newnam of the Los Alamos Scientific Laboratory were co-chairmen of the Symposium. The Thirteenth Annual Symposium is scheduled for November 17–18, 1981 at the National Bureau of Standards, Boulder, Colorado.