By Ivan Catton and Vijay K. Dhir

Dr. Novak Zuber passed away on Oct. 3, 2013. He was a true pioneer in the field of two-phase flow and heat transfer, beginning his illustrious engineering career with the development of a hydrodynamic theory for peak nucleate boiling and minimum film heat fluxes and his “Drift Flux” model.

Dr. Zuber was a Montenegrin born in the Moskva Hotel in Belgrade, Yugoslavia, on Dec. 4, 1922. Prior to his immigration to the United States, he was a member of the Balkan Air Force, an Allied air formation composed of units of the Royal Air Force (RAF) and South African Air force under the Mediterranean Allied Air Forces command. The unit was active from June 1944 until July 1945 under the command of RAF Air Vice Marshalls William Elliot and George Mills.

After the war, he attended the University of Rome in Italy from 1945 to 1947. From 1947 to 1949 he was a merchant seaman, working as a wiper in the engine room of a ship captained by a family friend.

His intense desire to pursue his scholastic dreams and the fact that he had an uncle in the Los Angeles area prompted him to jump ship during a stop in San Pedro, Calif. He found his way to the University of California at Los Angeles and was able to enroll in the school’s engineering program. In order to complete his education, he performed odd jobs such as washing dishes, washing cars, cleaning chicken coops and gardening. Basically, he worked jobs that didn’t require a green card.

Immigration finally caught up with him during graduate school. However, by that time, his work on high pressure boiling in support of the development of Rickover’s nuclear submarine had impressed the people at UCLA enough that they came to his rescue and he was able to complete his degree program, including a B.S., M.S., and Ph.D. His doctoral dissertation was a classical treatment of the hydrodynamic aspects of boiling heat transfer.

Dr. Zuber’s professional career began with a short period of time at Thompson Ramo-Woolridge (1958-1960) followed by his joining General Electric in Schenectady, N.Y., in 1960, where he began his research work in the General Engineering Laboratory and Research and Development Center.

It was at General Electric where he began his research on the two-phase fluid flow phenomenon and began the development of the now well-known and widely used “Drift Flux” model for describing average volumetric concentrations in two-phase flow systems. The significance of this model and its application in predicting the thermal-hydraulic behavior of nuclear power plants were major contributions to the field.

From 1967 to 1974 he was a professor of mechanical engineering at New York University and at the Georgia Institute of Technology, where he supervised seven theses for M.Sc. degrees and six doctoral dissertations, many of which were significant contributions to the two-phase flow and heat transfer literature. Specifically, the “Drift Flux” model has proven important in predicting the performance of two-phase flow systems in many applications other than nuclear power plants.

In 1974, Dr. Zuber began the second phase of his professional life by working with the U.S. Nuclear Regulatory Commission in the Office of Nuclear Regulatory Research. Until his retirement in 1991, he was responsible for reviewing and guiding the development of the NRC computer codes as tools for assessing safety of nuclear reactor systems. This began with his chairing the Advanced Code Review Group, a group composed of the leaders in the field, and culminated with him being responsible for developing and demonstrating the Code Scaling Applicability and Uncertainty methodology for Large Break Loss of Coolant Accidents (LBLOCA), a beginning of the deterministic approach to accident analysis.

He served as the U.S. representative on the international committee guiding the 2D/3D program, a major international program to resolve multidimensional effects during LBLOCAs. Just before his retirement in 1991, he was responsible for formulating a severe accident hierarchical scaling methodology that enabled resolution of what was thought to be a serious threat to public safety.

In his retirement, Dr. Zuber continued to make high level of professional contributions as a consultant to the U.S. NRC Advisory Committee on Reactor Safeguards and to the Jozef Stefan Institute in Slovenia.

Over the years Dr. Zuber made contributions to all aspects of two-phase flow and heat transfer, and many of his papers are landmark publications that opened the way for subsequent advancements.

Dr. Zuber’s contributions to the field of two-phase flow and heat transfer garnered several honors and awards. He was the first recipient of ASME Heat Transfer Division’s Memorial Award in 1961, the Technical Achievement Award from the Thermal Hydraulics Division of the American Nuclear Society in 1990, and meritorious service awards and a Special Achievement Certificate from the NRC for outstanding contributions. In 2005, at the 11th International Conference on Nuclear Reactor Thermal Hydraulics (NURETH-11), he was presented with a Medal of Honor for his lifetime achievements by  the Société Française de l’Energie Nucléaire. Dr. Zuber was a fellow of the ASME, published more than 50 technical papers and was a co-editor of several books.

Aside from his professional accomplishments, Dr. Zuber was a fascinating person with a keen mind and a strong sense of responsibility to the technical community. He was brutally honest and straightforward with scientists and engineers, and never lost sight of the need for practicality.
His many talks were laced with admonitions to young engineers that they had a responsibility to do the right thing. He had no patience for engineers that did not present their views in an honest and forthright manner. His concern for the education of young engineers led to the establishment of the Kerze-Cheyovich Research Fellowship at UCLA.

Many of his students and colleagues suffered his scorn when we came up short, and were better for it. Novak Zuber tracked in a “straight line,” and those who knew him well know what he meant when he used the phrase. At a small luncheon to celebrate his 90th birthday, he gave out copies of Stephen Hawking’s book, “The Dreams That Stuff Is Made Of.” He never gave up.