EDITORIAL pubs.acs.org/IECR
A Special Tribute to Honor Stuart Churchill on the Occasion of His 90th Birthday Throughout his career, spanning nearly 70 years, chemical engineers have celebrated the advances, writings, oral presentations, and commentary at technical meetings of Professor Stuart W. Churchill, Carl V. S. Patterson Professor Emeritus at the University of Pennsylvania. When editor Donald Paul announced this birthday Festschrift, I was honored, and humbled, by Stuart’s request that I write this Preface. The literature is a repository for Stuart’s numerous technical papers and books, written in close step with the progression of our profession, many achieved in collaboration with his 45 doctoral students and colleagues worldwide. Unique, among most of the leading researchers and educators in chemical engineering, are his published talks, editorials, and position papers, often focusing on advances, challenges to be overcome, and future directions for the chemical engineering profession. Stuart has been one of the most active participants in chemical and mechanical engineering conferences, engineering-wide meetings, organizational meetings of AIChE (as President in 1965), and r 2011 American Chemical Society
accreditation visits (for ECPD, before ABET), as well as a highly sought after seminar speaker, advisory board member, editorial board member, and consultant. Nearly all of Stuart’s writings were collected and scanned for a DVD by his daughter, Emily Sanders, on the occasion of his 85th birthday in 2005. Included were over 400 documents, with a comprehensive Oral History prepared by Joseph Marchese and Jeffrey Sturchio of the Center for the History of Chemistry in 1985 (currently the Chemical Heritage Foundation). To better appreciate the progression of chemical engineering through the second half of the 20th Century, Stuart’s Oral History is an excellent starting point. Special Issue: Churchill Issue Received: March 16, 2011 Accepted: March 16, 2011 Published: July 27, 2011 8803
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Industrial & Engineering Chemistry Research
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Figure 1. 90th Birthday dinner at the Gandy-Dancer Restaurant in Ann Arbor, MI on April 23, 2010. Stuart is with 11 of his doctoral students that attended the birthday dinner (from left to right, Warren Seider, Marty Gluckstein, Irv Miller, Jim Wilkes, David Hellums, Stuart, Mark Strenger, Humbert Chu, Christina Chan, John Chen, Lance Collins, and Vicki Booker).
Unfortunately, in this Preface, I’m unable to focus on even a subset of Stuart’s most significant contributions. Instead, after nearly 50 years with Stuart, 43 at the University of Pennsylvania, I chose to concentrate on the years following his required “retirement” from our standing faculty at age 70 in 1990. During this period, with professionals in their midfifties often encouraged to retire, his achievements were especially impressive. Many retirees remained active in consulting businesses, but unfortunately, their endeavors were often phased out. The loss of so many experienced, active minds, has, in my opinion, often impeded the solution of challenging problems, the development of new products, and overall industrial productivity. Fortunately for our profession, and especially for his close colleagues, Stuart’s career continues unabated to this day. His mobility has been reduced somewhat over the past 23 years, causing him to spend more time in his study at home, and in parallel, his collection of printed articles was downsized due to space limitations at Penn. However, personal computers and the Internet arrived just-in-time for him to access the literature from locations worldwide. Also, like colleagues everywhere, Stuart put aside written drafts in favor of composing communications (papers, e-mail, ...) using his PC keyboard.
’ BRIEF HISTORY Born and raised in Imlay City, Michigan, with his brothers, James, who became a federal judge in Detroit, and Robert, who practiced engineering and business, Stuart enrolled in a dualdegree program (to earn Bachelor’s Degrees in Mathematics and Chemical Engineering) at the University of Michigan in 1938. After graduation in 1942, he worked at the Shell Oil Company refinery in Wood River, IL for 4 years, before joining a colleague who started a small engineering venture, Frontier Chemical Company in Denver City, Texas, for 1 year. After 5 years in industry, he entered the chemical engineering doctoral program at Michigan in 1947, received his Ph.D. degree in 1952, became
Assistant Professor in 1952, Associate Professor in 1955, and Full Professor in 1957, a remarkably rapid rate of promotion. In 1962, he chaired the Department of Chemical and Metallurgical Engineering, served as AIChE President in 1965, and became the Carl V. S. Patterson Professor of Chemical Engineering at Penn in 1967. Until his required retirement in 1990, his focus was on research and teaching, devoid of administrative responsibilities. Throughout these years, he received many technical awards and was elected to the National Academy of Engineering (eventually receiving its Founders Award). When approached many times to consider positions such as Dean of Engineering, he declined, preferring to continue his concentration on research and teaching. Over the past 34 years, Stuart and his wife, Renate (aka Renee Usagi, her nom de plume as a classical guitarist), have lived in their home overlooking a small lake in Glen Mills, PA. Beginning in 1960, Renate became the associate editor of the journal International Chemical Engineering, published by the AIChE. She was promoted to editor in 1974, a position she retained for the next 22 years. In the 1950s, Stuart was at the forefront of the transition of engineering from a largely empirical discipline to one with a strong orientation toward applied mathematics. Initially, he and his students made landmark contributions to radiative heat transfer through an atmosphere containing particulates, a key input for models of climate change. Later, he developed sophisticated scaling concepts at a time when others had not progressed beyond rudimentary dimensional analysis. With J. David Hellums, he developed a generalized system of dedimensionalization that leads to the simplest possible description of mathematical models and identifies a similarity transformation, such as those of Blasius and Lev^eque, if one is possible. In the 1960s, 1970s, and 1980s, with many of his students, Stuart focused on experimental and theoretical research involving fluid flow and heat transfer, often involving natural convection (based upon research initiated with his student, William R. Martini, in the 1950s), and pioneered in the use of numerical 8804
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Industrial & Engineering Chemistry Research methods to solve the differential models. Gradually, they tackled an array of related problems including migration and freezing of water in soil, three-dimensional, unbounded viscous flow between convergent traveling surfaces, thermally stabilized combustion in refractory tubes, flow in helical coiled tubes, and double-spiral exchangers. With Prof. Hiroyuki Ozoe, a former student, and Paul K.-B. Chao, a doctoral student, he developed the use of streaklines as a tool for design and interpretation of complex patterns of flow. During these years, Stuart completed a project to unify the treatment of process calculations in terms of the rate concept, started nearly 2-decades earlier with Robert R. White. The result, which appeared in 1974, was the textbook, The Interpretation and Use of Rate Data: The Rate Concept (McGraw-Hill). This led Robert L. Kabel to comment in his laudatory paper (Chem. Eng. Commun., 1981, 9, 15): “The Churchill distinction between a process rate and a rate-of change clarifies an ambiguous situation replete with misunderstanding and loose usage.” Another key development at that time was the Churchill-Usagi equation for interpolating between two asymptotic or limiting solutions using just one empirical constant: yfxgn ¼ y0 fxgn þ y¥ fxgn This expression, because of its generality, minimal empiricism, and remarkable accuracy, is gradually replacing the historical correlations in terms of products of powers of dimensionless variables. This diversification of technical areas in transport-oriented research and teaching reflected the breadth of Stuart’s interests and his ability to guide research without directing it. In the words of his student, Dr. Martin E. Gluckstein, “He gave us enough rope to create a ladder with a noose and sufficient insight to prevent us from hanging ourselves.”
’ LAST TWO DECADES New topics included thermally stabilized combustion as a means of devolatilizing coal with Christina Chan and Visiting Professor Norio Arai, and natural convection in Czochralski crystallization with Vicki Booker. As his last doctoral students completed their work and he no longer had access to a laboratory, he improvised by working primarily at his desk with a PC, by working with undergraduates, and by collaborating with colleagues. In the early 1990s, beginning with Christina Chan as an informal postdoc, Stuart virtually “reinvented” fully developed turbulent flow and convection in channels by expressing the time-averaged equations of conservation in terms of the local fractional contribution of the turbulent fluctuations to the shear stress and heat flux density rather than in terms of heuristic quantities such as the eddy diffusivity and the mixing length. One unexpected consequence was the discovery that the turbulent Prandtl number can be expressed wholly in terms of these two fractions and thereby that it has direct physical significance. He utilized the results of the contemporary development of direct numerical simulation to devise generalized predictive expressions for these quantities. With his grandson, Stefan Zajic, then an undergraduate at Penn, he devised theoretically based predictive equations for turbulent convection in channels in the form of analogies that are substantially more accurate both functionally and numerically than the classical ones. The experimental work to supplement his theoretical calculations as well as some of the calculations were carried out by
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collaborators including his colleague, Professor Noam Lior, his former doctoral student, Professor Hiroyuki Ozoe in Japan, his former visitor, Professor Arai, also in Japan, and Dr. Bo Yu, a doctoral student of Ozoe in China. In the mid-2000s, Stuart increasingly focused on fluid flow and heat transfer in tubular chemical reactors. In several papers, he drew attention to the inadequacy of the classical assumption of “plug flow”, that is, perfect radial mixing. The major textbooks on chemical reactor engineering teach students to make this idealization in order to simplify tubular reactor models, thereby unwittingly excluding the use of heat transfer to control the temperature and leading to predictions of reactor length far less than those that can be achieved in fully developed flow. This realization led us to add a section to our design textbook (Seider, Seader, Lewin, and Widagdo, Wiley, 2009), with the assistance of my student, Charles G. Slominski, on the use of computational fluid dynamics to estimate conversions properly in tubular reactors. We show that secondary flows in spiral tubes increase conversions, which are increased further using lemniscate tubes, approaching the assumption of perfect mixing. At Stuart’s suggestion, we translated this book section into a research contribution titled “Helical and Lemniscate Tubular Reactors”, which is coauthored with him in this Festschrift. On the basis of my doctoral work, in 1971, Stuart and I coauthored a paper entitled “Confined Jet Mixing in the Entrance of a Tubular Reactor”. Since then, the focus of my research and teaching has been on process and product design rather than transport phenomena. Almost 40 years later, our design research comes full-cycle to account for fluid mechanics in reactors. Throughout these years, I’ve benefited from Stuart’s engineering science interactions and his call for more rigorous transport calculations in obtaining reliable designs. Also, after 40 years, it is a privilege to write once again with Stuart. As stated by our coauthor, Professor J. D. Seader, “his wording is as close to poetry as is possible for technical writing.” Viewed differently, Stuart’s breadth extends far beyond that of most engineering science researchers. His enthusiasm for design research and teaching has increasingly suggested interactions for us in recent years. Also, for the last 30 years, even in retirement, Stuart continues to enthusiastically advise one of our senior design groups. He understands the importance of teaching students how to translate engineering science principles into process and product designs that satisfy consumer needs and to seek designs that optimize profitability in the face of uncertainty. Finally, we were happy to return to Ann Arbor on April 23, 2010 to participate in a joyous celebration of the installation of Professor Sharon Glotzer into the Stuart W. Churchill Collegiate Chair authorized by the Regents of the University of Michigan and to celebrate Stuart’s 90th Birthday. In Figure 1, Stuart is shown with 11 of his former doctoral students, from Michigan and Penn, at the dinner celebration. Warren D. Seider Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104-6393 e-mail:
[email protected] 8805
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