­Obituary Prof. Dr.-Ing. habil. Achim Dittmann

April 7, 1941 - May 1, 2026

In the early hours of May 1, the first really mild spring night of 2026, Prof. Achim Dittmann - an ardent thermodynamicist, aesthete and world traveler, indeed cosmopolitan - fell asleep forever.

Having grown up in Leipzig, his passion for aerospace engineering drew him to Dresden. But because training in this field was discontinued in 1961, his path led him - what a stroke of luck from today's perspective - to study thermal engineering. With his pronounced urge to get to the bottom of things, it was only logical that an intensive research phase at the Institute for Thermodynamics and Energy Economics at TUD Dresden University of Technology followed immediately after in 1967. After successfully completing his doctorate in 1973 and gaining important teaching experience, Achim Dittmann's career path actually took him just a few hundred meters further along Zeunerstraße in 1976. The new tasks as group and department head of the Institute for Energy Supply proved to be challenging, as he had to develop efficient, resource-saving high-temperature heat pumps with a solvent intermediate circuit based on an ammonia-water mixture and test them in practice in a very short space of time. This was a great success, as was his habilitation in 1982.

In the phase leading up to his appointment as full Professor of Technical Thermodynamics in 1983, I met Achim Dittmann in person for the first time at the Thermodynamics Colloquium in Altenberg. What a thematic arc of suspense! Prof. Elsner's lecture on negative absolute temperatures on the one hand and Prof. Dittmann's presentation on the latest generation of heat pumps on the other.
His intensive time as full Chair of Thermodynamics until 2006 was characterized by a similar arc of tension between in-depth research into thermal and energetic state variables of important fluids in the one- and two-phase region and their application to increase the quality of energy management processes on the one hand and, on the other, teaching that was clear, yet challenging and encouraging for students and doctoral candidates. He was always committed to people and the cause and never allowed himself to be bent.

In all these years, Prof. Dittmann has always shown great personal commitment to the interests of students, doctoral candidates and colleagues. By acquiring interesting projects and writing countless doctoral and appointment reports, he has steered the academic careers of his protégés in the right direction, also promoting career entry through his extensive network of contacts and always attaching particular importance to the human aspect. You will sorely miss Achim Dittmann as an excellent professional mentor and good friend.

Since even in the early 2000s it was hardly possible to seamlessly fill important core professorships at TU Dresden, Prof. Dittmann also held the Chair of Energy Systems Engineering and Heat Economy of his companion Joachim Zschernig on an acting basis until the beginning of 2009. Since 1993, Achim Dittmann and Joachim Zschernig have continuously pursued the idea of the Center for Energy Technology - a link between theory and practice as well as traditional fossil and renewable energies that is so important for engineering education and research, which was able to start operations in 2011.

For him, even in retirement, redefining tradition did not just mean advancing combined heat and power generation as the "driving force" of energy supply - as he always called it. He also remained involved in many other energy technology issues. The district heating industry appreciated his detailed advice and his critical view of many a new development. We will miss his brief but focused appearances at the Dresden District Heating Colloquia.

Together with his friend and research partner Dr. Claudius Nestke, for example, he sounded out the admissibility of temporary operating states of district heating networks in two-phase areas. Anyone who was able to follow the last year of Prof. Achim Dittmann's life was amazed and respectful to see how he drew strength from writing the publication on critical mass flow density in memory of Claudius Nestke and how the joint discussions on the topic visibly gave him strength.

On April 7, 2026, I was able to sit next to a life-affirming Achim Dittmann on his 85th birthday and toast the new year with him. For us companions from near and far, these and similar images bring to a close the arc of our shared journey through exciting stages of life, combined with gratitude for what we have learned, the challenging discussions and joyful memories of wonderful times. As an outstanding scientist and teacher, he follows such important thermodynamicists as Richard Mollier, Leopold Carl Friedrich Merkel and Hans Faltin in the Tolkewitz urn grove.

With deepest sympathy and thanks to Karin Rühling also on behalf of Jens Meinert, Clemens Felsmann, Christiane Thomas, Thomas Sander and many relatives of the Institute of Power Engineering

The funeral service will take place on Wednesday, June 3, 2026 at 12 noon in the celebration hall of the Tolkewitz Urnenhain.