Leonard A. Wenzel gave 52 years of service to Lehigh, including 21 as chairman of the department of chemical engineering. He was respected by his peers as a caring administrator who led a period of dramatic growth in the chemical engineering department and gave invaluable encouragement to young professors launching their research careers.

Career at Lehigh

Wenzel joined the faculty in 1951, the year Lehigh's chemical engineering department was established, and served as department chairman from 1962 to 1983. During that time, the department faculty grew from five to 18 professors.

But it was Wenzel's love of teaching and his trust in professors that colleagues most remember him for.

William E. Schiesser '55, the R.L. McCann Professor of engineering and mathematics, was Wenzel's student and colleague.

"Dr. Wenzel was an excellent teacher," said Schiesser, who took several classes from Wenzel as an undergraduate. "Everybody wanted to be in his classes. He made everything very clear and he wrote his solutions in great detail on the blackboard."

Wenzel gave freely of his time to students and professors alike, Schiesser said.

"Dr. Wenzel had an interest in anybody who came by his office. His door was always open. We had the same number of students then as we do now, but far fewer professors. But Dr. Wenzel never gave the impression that he was rushed for time."

In 1968, Wenzel approved the purchase of a $2.1-million CDC 6400 computer, one of the largest and most powerful instruments of its kind. He allowed Schiesser to spend half his time in the university computer center, then located in Packard Laboratory, to learn how to use the machine.

"Buying the 6400 was an incredible undertaking," said Schiesser. "It gave us as much computing power as any other university in the country. It enabled us to combine scientific computing and engineering.

"I don't know how many other chairmen would have been willing to let me spend so much time with that computer," said Schiesser. "Dr. Wenzel's decision had a tremendous influence on how my career developed. It determined my entire future."

Leslie Sperling, professor emeritus of chemical engineering and author of 14 books, said Wenzel gave unqualified support to his desire to write.

"In the 1970s," said Sperling, "John Manson [professor of chemistry] and I became interested in writing a book on polymer blends. I didn't know anything about book writing or whether Len Wenzel would consider this as part of my duties. But I wanted to become better known in my field.

"Len told me, 'A book is worth 50 publications.' And he was right. We published Polymer Blends and Composites in 1976. Before that, I was getting about one out of 10 of my research proposals funded. Afterwards, that went up to nine out of 10. I'm pretty sure the book had a lot to do with that.

"I have had the pleasure of having good bosses in my life," said Sperling. "I put Len Wenzel at the top. He was a wonderful man who went way out of his way, not only for me but for many of us."

William L. Luyben, professor of chemical engineering, collaborated with Wenzel in teaching introductory chemical engineering and in writing the textbook Chemical Process Analysis: Mass and Energy Balances.

"The outstanding characteristic of Len Wenzel was his genuine and sincere concern and interest in the students," said Luyben.

"He was also a very good department chairman. His philosophy was to hire good people and let them alone. There was no micro-managing. He trusted people."


Wenzel earned his bachelor's degree in chemical engineering from Pennsylvania State University, and his M.S. and Ph.D. from the University of Michigan. Before joining the Lehigh faculty, he worked as a research engineer for several industrial companies. He also served with the U.S. Navy from 1944 to 1946.

Wenzel's research interests spanned thermodynamics, cryogenics, and mixed-gas adsorption. He taught the chemical engineering department's course in thermodynamics from 1951 until last year.

Besides Chemical Process Analysis, Wenzel co-wrote the text Principles of Unit Operations with Lehigh professors Alan Foust, Curtis Clump, Louis Maus and Bryce Andersen. The text has been translated into several languages and is considered a classic. He also co-wrote Introduction to Chemical Engineering with Andersen.

In 1969-70, Wenzel served as expert and project coordinator for a UNESCO project aimed at developing a graduate program in chemical engineering at the Universidad Industrial de Santander in Bucaramanga, Colombia. He also served as a UNESCO consultant in Colombia and Venezuela.

From 1978 to 1979, Wenzel served as chairman of the Lehigh University Forum. In 1982, he was elected a Fellow of the American Institute of Chemical Engineers in 1982. His Lehigh honors include the Hillman Award for service and the Stabler Award for teaching. Wenzel died in 2003 at his home in Bethlehem, after a long illness. He was 80 years old.

Sunday, January 21, 1923
Date of Death: 
Sunday, November 23, 2003
Notable Achievement: 
Esteemed faculty member of Lehigh's ChE dept