Dr. Willem Elenbaas

This write-up is about Dr. Willem Elenbaas, now deceased, a former employee of the Philips Company in Eindhoven, The Netherlands. At the time Dr. Elenbaas was awarded the 1973 IES Gold Medal an article on the subject appeared in Lighting Design & Application¹. The article is repeated here:

"The Illuminating Engineering Society's Gold Medal is awarded for 'the purpose of giving recognition to meritorious achievement which has conspicuously furthered the profession, art, or knowledge of illuminating engineering.' On April 10, 1973, the Medal Awards Committee met and selected Dr. Willem Elenbaas as the 1973 recipient. Only one Medalist (and sometimes none) is selected annually, and anyone in the world is a potential candidate for the honor.

"Dr. Elenbaas, the 28th Medalist selected by the Society is currently retired from N. V. Philips in Eindhoven, Netherlands, where he had served as director for development of the lighting division since 1958.

"Dr. Elenbaas, through his numerous papers and books, and his leadership in technological development, has possibly made the greatest contribution to the field of gas discharge lamps that can be attributed to a single individual. He has spent a lifetime concerned with the development of lighting sources. His reputation was established early in his career. Scarcely an engineering paper in America or Europe in the field of mercury lamps or iodide-mercury lamps is presented without a reference to his book, 'The High Pressure Mercury Vapor Discharge," first published in 1951. He is indeed regarded as the 'father' of the modern mercury lamp, and his research in the early development of that lamp led to the first comprehensive technical description of the mercury arc discharge. He is undoubtedly the leading authority on the high pressure mercury discharge.

"Dr. Elenbaas was the first to derive the formula that allows us to calculate the exact amount of mercury needed to give a specified arc voltage over a wide range of tube diameters and lengths. The importance of this formula was immediately evident to workers in the field, and it made the design of new sizes easy and practical for all. This derivation was one of the cornerstones in the development of the mercury lamp industry, and in itself is the foundation for the iodide-mercury lamps.

"His series of papers, published in 'Physica' from 1934 through 1938, are a classic presentation in their own right, and these established his reputation as a physicist of first rank. Not only is the practical formula mentioned previously derived from these papers, but a rather complete description of the arc is also given in detail. He presents the elementary theory of the discharge, derives and characterizes the temperature distribution of the arc, explains the internal convection, the gradient, the spectrum, and many other features of the arc in a logical and lucid manner.

"The tremendous output of work during his career is evident from the list of over 60 publications of which he is the sole author. He also holds 50 patents, and for 19 of these he is the sole inventor - a record that is difficult to equal.

"Dr. Elenbaas began his career with Philips in 1929 in the Physical Laboratory, Light Divison, and in 1949 he was appointed manager. Then, in 1953, he became the assistant director of the Light Group, and in 1958, he was appointed director, the position he held until his retirement in 1968.

"Dr. Elenbaas is a pioneer in the research and development of gas discharge lamps in general, and of high pressure mercury lamps in particular. In Europe he is regarded as the father of the high pressure mercury vapor lamp as it is known today."

An obituary of Dr. Willem Elenbaas (Apr 27, 1906 - Feb 7, 1989) follows, which was kindly provided by the Philips Company Archives, Eindhoven, The Netherlands²:

"Willem Elenbaas was born in Gapinge, in the province of Zeeland, on April 27th 1906. He attended the 'HBS' (secondary school) in the provincial capital of Middelburg. After taking his finals he went to Utrecht to study physics. On January 20th 1930 he took his doctor's degree with a thesis entitled: 'Intensity Measurements in the Helium Spectrum'.

"He has no fewer than 85 publications to his name. His first publications (from 1929) dealt mainly with the subject of his doctor's thesis, the helium spectrum, but as early as 1930 he wrote his first article about magnetism, his research subject in the Philips Research Laboratory. Seven publications on this theme written by him saw the light in the period until 1933.

"In 1932 Elenbaas published the first of a long series of articles on the subject which established his fame in the lighting world: the high pressure mercury discharge lamp, which today is still one of the most important street lighting lamps. He joined the Philips Lighting Division in 1942.

"Elenbaas also had much to contribute in the field of low pressure mercury discharge lamps, i.e. fluorecent lamps. Thus he wrote three chapters of a book on fluorescent lighting under the editorship of Professor Zwikker, his predecessor as Head of the Philips Lighting Development Department. The name Elenbaas is connected to five books, of which he was either the editor or (co-) author.

"Elenbaas is frequently cited in the literature, especially in connection with the Elenbaas-Heller equation, which describes the temperature distribution in high pressure gas discharges. One of his articles, dating from 1935, and an article written by the research scientist Heller - who died in a concentration camp - induced R. Rompe and P. Schulz in 1939 to name the equation after these two authors.

"Elenbaas's name is also linked to an article on yet another subject, heat transfer. In 1942 he wrote 'Heat Dissipation of Parallel Plates by Free Convection'.

"In 1986 Professor Landis, Professor of Mechanical Engineering in the University of Wisconsin in Milwaukee proposed that a dimensionless quantity composed of the Grashof and Prandtl numbers be called the 'Elenbaas number', more than 40 years after Dr. Elenbaas's original publication!

"Dr. Elenbaas retired from Philips in 1968. At that occasion the Dr. Elenbaas Award was created, an award which has since been given to several outstanding research scientists in the field of lighting.

"Elenbaas himself was awarded the Gold Medal of the Illuminating Engineering Society of the USA in 1973.

"Eindhoven, 16th December 1987
"H. Nienhuis"

In the obituary given above mention was made of the work Dr. Elenbaas published on the subject of heat transfer by free convection. This writer utilized the results of that work frequently in his own work dealing with free convection from incandescent lamp filaments. The work of Elenbaas established the functional dependence of the Langmuir film diameter on gas pressure, viscosity and temperature.

The writer is most grateful for the obituary of Dr. Elenbaas that was kindly supplied by the Philips Company Archive in Eindhoven, The Netherlands. The photograph of Dr. Elenbaas was saved from reference No. 1.