Wilhelm, Richard Herman

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(b. New York City, 10 January 1909; d Center Harbor, New Hampshire, 6 August 1968)

chemical engineering.

Richard Wilhelm was the son of Ernst Richard Wilhelm, a cabinetmaker originally from Germany, and Ida Emma Krebs Wilhelm. He attended New York City schools for all of his early education. He received the B.S. degree from Columbia University in 1931 and a degree in chemical engineering in 1932. In 1934, while he was completing doctoral work at Columbia, he was hired as an instructor in the chemical engineering department at Princeton, where he remained until his death. In 1935 he received the Ph.D. from Columbia, and in 1937 he married Rachel Marjorie Hixson. They had three children: David, Joan, and Karen. Wilhelm rose through the academic ranks at Princeton to the position of professor of chemical engineering in 1946 and chairman of the department in 1954. During World War II he was involved in several programs of the National Defense Research Committee, first as a consultant for the Chemical Warfare Panel and later as codirector of a research project carried out at Princeton for the Office of Rubber Director. His association with that committee continued until 1953.

Although primarily an academician, Wilhelm served as an engineering consultant on reactor design for several chemical manufacturers. He was an active member of many professional and scientific societies and was a recipient of the William H. Walker Award in 1951, the Professional Progress Award in 1952, the Warren K. Lewis Award in 1951, (all of the American Institute of Chemical Engineers), and the Industrial and Engineering Chemistry Award of the American Chemical Society. He was also a fellow of the American Academy of Arts and Sciences.

In 1964 Wilhelm’s wife died. Two years later he married Sarah Kollock Strayer, the widow of Princeton economics professor Paul J. Strayer.

Wilhelm’s contribution to the field of chemical engineering was strongest as a theoretician in chemical reactor design and as an educator and mentor of chemical engineers. In the early years of the chemical industry, as in many other areas of applied science, the design of large-scale manufacturing technology was mainly an empirical process. The 1930’s was a period of rapid expansion in the chemical industry, particularly in petroleum refining; accompanying this sudden growth was an increased interest in the theoretical and mathematical modeling of chemical reactor systems. The ability to create such models was facilitated by a growing body of knowledge about fluid mechanics and heat and mass transfer. Wilhelm’s theoretical work lay in the realm of fluid transport through chemical reactor systems, specifically in maintaining a stable set of reactor conditions in spite of the continued flow of reactants and products through a high-temperature environment.

Wilhelm’s earliest papers, published in 1939, dealt with fluid flow and viscometry. In the 1940’s and 1950’s his work centered on the modeling of particle flow through packed and fluidized catalytic beds. For packed–bed reactors he was able to develop a mathematical model for dispersion processes that proved useful in predicting regions of abnormally high temperature. To deal with fluidized beds, in which the reactants flow through a loosely packed catalyst, producing a boiling effect, Wilhelm studied heat and mass transfer phenomena in systems of turbulent flow; he was the originator of much of the standard terminology in this field. However, he was hampered by the fact that the whole area of turbulent flow, because of the complexity of the fluid dynamics involved, was beyond the reach of simple mathematical modeling at that time. It was not until the last years of his life, when his attention had turned elsewhere, that the sufficiently sophisticated computer technology was developed that could have simplified his task.

In the mid 1960’s Wilhelm’s activity centered on a method of separating liquid mixtures that he had originated and named parametric pumping; upon it his remaining research was concentrated. This method consisted of pumping a solution through a column of fixed solid adsorbent while varying two of the system’s parameters, such as temperature and direction of flow, synchronously. Wilhelm was able to provide a mathematical description for this process. He felt that the process might have explanatory power outside the realm of engineering and suggested that parametric pumping might prove to be a model for active transport of ions through cell membranes, where pH would replace temperature as a variable parameter. In the years following his death, parametric pumping theory has not proved to have either the industrial applications or the explanatory power that Wilhelm hoped for.

Equal in importance to his contribution to the theory of reactor engineering was Wilhelm’s role as an educator of chemical engineers. As chairman of Princeton’s chemical engineering department for fourteen years, he brought that department to national prominence. (In 1966 the American Council on Education cited Princeton’s chemical engineering graduate program as the second most attractive in the nation) Wilhelm’s doctoral students rose to prominence in university engineering department as well as in the chemical industry. His educational philosophy held that the primary function of the university is to teach, and the undergraduate student should be its primary focus. He was exceptionally active in academic life and unceasingly concerned with the articulation of engineering and other disciplines, especially the life sciences.

Wilhelm had intended to resign the chair of chemical engineering in 1969 in order to give more time to research, especially to the application of parametric pumping theory. In April 1968 he was elected to the National Academy of Engineering, and in June, Princeton made him Henry Putnam university professor, an endowed chair recognizing scholarship of extraordinary ability. On 6 August of that year, while vacationing with his family at the seashore, Wilhelm died of a heart attack. In his memory the American Institute of Chemical Engineers established the R. H. Wilhelm Award in chemical reactor engineering in 1973. Princeton instituted the Wilhelm Lectureships in 1974.


I. Original Works. A complete bibliography of Wilhelm’s published papers (forty-eight in all) is in Rutherford Aris, “R.H. Wilhelm’s Influence on the Development of Chemical Reaction Engineering”, in Chemical Engineering Education, 17 (Winter 1983), 10–15, 38–41. His doctoral dissertation is “Vapor Phase Nitration of Benzene” (Columbia University, 1935). Key papers on his research include “Fluidization of Solid Particles”, in Chemical Engineering Progress, 44 (1948), 201–218, with Mooson Kwauk, an early paper on fluidized beds; “Progress Towards the A Priori Design of Chemical Reactors”, in Pure and Applied Chemistry, 5 (1962), 403–420, in which he discusses the difficulty of modeling industrial reactor systems, and his successes in doing so for packed-bed reactors” “Parametric Pumping: A Model for Active Transport”, in Katherine Brehme Warren, ed., Intracellular Transport (New York, 1966), 199–220; and “Parametric Pumping: A Dynamic Principle for Separating Fluid Mixtures”, in Industrial and Engineering Chemistry Fundamentals, 7 (1968), 337–349, with Alan W. Rice, Roger W. Rolke, and Norman H. Sweed.

II. Secondary Literature. Aris’s article, cited above, is a good summary of Wilhelm’s contributions to chemical reactor theory. An assessment of his success as an educator is in “Dick Wilhelm of Princeton” in Chemical Engineering Education, 2 (1968), 60–61. An autobiographical sketch of his contributions to chemical engineering theory is in McGraw-Hill Modern Men of Science, II (New York, 1968), 600. His colleague at Princeton, R. K. Toner, summarized his career in the Wilhelm memorial issue of Industrial and Engineering Chemistry Fundamentals, 8 (1969), 178–179.

Margaret Jackson Clarke