In search of the optimal airflow

Fan In search of the optimal airflow

2024-07-16 Source: HS Coburg | Translated by AI 4 min Reading Time

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Taiwan Machine Tool & Accessory Builders' Association (TMBA)

Large industrial ventilation systems work so well that they are barely noticeable in everyday life, but they have one drawback: energy consumption. Especially since the eco-design directive for industrial fans is set to be tightened next year. New solutions are needed.

PhD student Manuel Fritsche has developed a new method for simulating and designing air flows in fans.(Image: Natalie Schalk / Coburg University.) — PhD student Manuel Fritsche has developed a new method for simulating and designing air flows in fans.
(Image: Natalie Schalk / Coburg University.)

In the highway tunnel or the shopping center, you can't just quickly open a window—the fact that there is no thick air here is thanks to modern technology.

Nevertheless, there is a need for action in the fan sector. The reason is an EU regulation: No. 327/2011 as part of the ErP Directive 2009/125/EC prescribes ever stricter requirements for the energy efficiency of these machines. "The minimum efficiency is systematically increased by the legislator over time," says Manuel Fritsche. "This poses a serious technical challenge for fan manufacturers." Manuel Fritsche developed a solution for this in his doctoral thesis at Coburg University and FAU Erlangen-Nuremberg (Germany).

Flows are complex processes.

He sits at a computer in the Coburg University's fluid mechanics lab; the two large screens in front of him display a blend of pink, yellow, and green. "Numerical flow simulations," he explains. To display them, calculations are made on how various factors affect air flow at the fan.

"Flows are complex processes: They involve turbulence, three-dimensionality, non-stationarity." The interaction determines how airflows flow. For example, if turbulence occurs on the fan blade, the energy is not well converted; the efficiency is poor. Ideally, the air simply flows along the blade of the fan. "Engineers have thought about what the optimal flow control is before," Fritsche reports. "They then created several prototypes and tested which one works best." For about 20 years, these tests have been shifting more and more into computer simulations, and instead of building a few prototypes as before, the 34-year-old has conducted thousands of simulations for his doctoral thesis.

Where previously known procedures fail

In front of the wind tunnel in the Coburg University's fluid mechanics lab, University President Prof. Dr. Stefan Gast, Manuel Fritsche and Prof. Dr. Phillip Epple (from right) discuss how the new method improves the energy efficiency of ventilation systems.
(Image:Natalie Schalk / Coburg University.)

For the well-known design methods, a cylindrical hub shape and aerodynamically profiled blades are assumed, for which empirical profile data is required. However, low-pressure axial fans are usually made in industrial practice from uniformly thick sheet metal with three-dimensionally bent blades for cost and manufacturing reasons. For this, Fritsche has developed a "simulation-driven design and optimization strategy for the application case of an axial fan with guide apparatus."

For the above-average performance of this doctoral thesis, he was awarded "Magna Cum Laude". The cooperative promotion at the Faculty of Mechanical Engineering and Automotive Technology of Coburg University of Applied Sciences was supervised by Prof. Dr. Philipp Epple, head of the Laboratory for Fluid Mechanics, and Prof. Dr. Antonio Delgado from the Chair of Fluid Mechanics at Friedrich-Alexander University Erlangen-Nuremberg.

Prof. Dr. Philipp Epple from Coburg University, doctoral student Manuel Fritsche with 3D-printed prototypes of the developed fan impellers, and Prof. Dr. Antonio Delgado from Friedrich-Alexander University Erlangen-Nuremberg (from left).
(Image:Christian Voll.)

Epple is very pleased with the completed doctoral procedure of his research associate. Fritsche has been connected with the university for a long time. He lives in Ebensfeld in the Lichtenfels district, has already completed his diploma and master's studies at the Faculty of Mechanical Engineering and Automotive Technology of Coburg University of Applied Sciences and remains at the faculty as a postdoc after his doctorate. His Coburg doctoral supervisor Epple thanks the dean Prof. Dr. Alexander Rost for supporting this doctoral procedure. "I would also like to express my special thanks to the university management," says Epple. "In particular, our president Prof. Dr. Stefan Gast and our vice president for research, Prof. Dr. Martin Synold, have created the necessary framework conditions and continuously support research and doctoral projects."

Science and industry: a successful transfer project

President Gast himself comes from the Faculty of Mechanical Engineering and Automotive Technology, has experienced Fritsche's work up close for some time and is very pleased that the research results from this doctoral thesis are being transferred into industrial practice. The dissertation is part of a cooperation project between Coburg University and a fan manufacturer, which is funded by the Central Innovation Program for Small and Medium-Sized Enterprises (ZIM) of the Federal Ministry of Economics.

Fritsche's new design and optimization procedure was validated with the help of prototypes from the industrial partner. "As a hand sample, the Institute for Prototype and Model Technology of Coburg University also created fans for me using 3D printing technology," adds the doctoral student.

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Design axial fans with optimal operating behavior

Based on his research, axial fans can now be designed with significant efficiency increases and optimized operating behavior. This contributes to meeting the future stricter EU guideline. Wherever large ventilation systems are used, such as in car parks or shopping centers, the developed method can improve the energy efficiency of fans - and this hits the real crux of the sometimes cumbersome EU regulations: It is a contribution to climate protection.