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Sustainable and clean

Professor Natalie Germann simulates superheated steam dishwasher

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Portrait of a women in front of a grey background, the woman is Prof Natalie Germann. © Aliona Kardash​/​TU Dort­mund
Natalie Germann is professor for fluid mechanics at the Department of Biochemical and Chemical Engineering of TU Dort­mund Uni­ver­sity.

Will dishwashers in fu­ture no longer clean our dishes with water and detergents, but instead just with superheated steam? This is the question that Professor Natalie Germann, professor for fluid mechanics at the Department of Biochemical and Chemical Engineering of TU Dort­mund Uni­ver­sity, is exploring. To this end, she has simulated a superheated steam dishwasher. The results sound highly promising: clean dishes, all bacteria killed off, fast cycle, low water and energy consumption. Professor Germann will present her findings to an in­ter­na­tio­nal audience of experts at Americal Physical Society Conference of the Division of Fluid Dynamics (APS DFD) in Phoenix, USA, at the end of No­vem­ber.

The simulation shows, among others, how the superheated steam rises out of the nozzles at the bottom of the dishwasher and condenses on the sides.

Professional steam cleaners are already used on a large scale, for instance in hotels, to clean floors, windows or furniture efficiently and disinfect them in the same step. In fu­ture, this technology could also replace conventional dishwashers, which use vast quantities of tabs and salt, are unable to kill off some types of harmful bacteria despite temperatures of up to 70 °C, have long cycles and consume a lot of water. “Steam at a temperature of 180 °C cleans surfaces more thoroughly, quickly and thus more efficiently,” explains Professor Germann. “In addition, it can also kill off heat-resistant bacteria within a few seconds. This is im­por­tant above all for professional use in hospitals and restaurants.”

She is working on the development of an in­no­va­ti­ve type of superheated steam dishwasher together with two industrial partners: Medeco Cleantec and Herion Engineering from Bavaria, Germany.

By means of a simulation, Professor Natalie Germann from TU Dort­mund Uni­ver­sity and Dr. Laila Abu-Farah from the Technical Uni­ver­sity of Munich (TUM) have studied the potential of superheated steam. Firstly, it was a matter of understanding the physical processes: How powerful is the steam’s effect in the dishwasher? How far does it reach? How does it cool down, and how does it condense? Which bacteria are killed off? “Such a simulation is very complex and challenging,” says Professor Germann. As a basis for first of all simulating the turbulent flow of steam inside the appliance, the researchers used the freely available OpenFOAM software. This was combined with another software to simulate temperature and the accompanying condensation. The researchers also added a bacteria model to simulate the inactivation of bacteria on the surface of the dishes.

The superheated steam kills off the bacteria on the plate in 14 seconds.
The simulation shows the flow of steam (arrows) and the temperature in the superheated steam dishwasher. It is hotter near the sides and on the surface of the plate (red) than in the empty space (blue).

“The finished simulation shows the complex dynamics between flow, temperature, and bacterial inactivation in a simplified dishwasher geometry and confirms that the superheated steam does indeed clean reliably and in a short time,” says Professor Germann, summarizing the results. The findings will contribute, for example, to selecting the right arrangement of nozzles in a superheated steam dishwasher. The researchers plan to publish their results in the form of a manuscript in the in­ter­na­tio­nal journal Physics of Fluids. In a next step, the aim is to couple the simulation with experiments to determine, among others, whether cleaning agents are still necessary at all in superheated steam dishwashers.

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Location & approach

The campus of TU Dort­mund Uni­ver­sity is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is “Dort­mund-Eichlinghofen” (closer to South Cam­pus), and from B 1 / A 40 “Dort­mund-Dorstfeld” (closer to North Cam­pus). Signs for the uni­ver­si­ty are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

To get from North Cam­pus to South Cam­pus by car, there is the connection via Vo­gel­pothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at North Cam­pus and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

TU Dort­mund Uni­ver­sity has its own train station (“Dort­mund Uni­ver­si­tät”). From there, suburban trains (S-Bahn) leave for Dort­mund main station (“Dort­mund Hauptbahnhof”) and Düsseldorf main station via the “Düsseldorf Airport Train Station” (take S-Bahn number 1, which leaves every 15 or 30 minutes). The uni­ver­si­ty is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duis­burg.

You can also take the bus or subway train from Dort­mund city to the uni­ver­si­ty: From Dort­mund main station, you can take any train bound for the Station “Stadtgarten”, usually lines U41, U45, U 47 and U49. At “Stadtgarten” you switch trains and get on line U42 towards “Hombruch”. Look out for the Station “An der Palmweide”. From the bus stop just across the road, busses bound for TU Dort­mund Uni­ver­sity leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop “Dort­mund Kampstraße”. From there, take U43 or U44 to the stop “Dort­mund Wittener Straße”. Switch to bus line 447 and get off at “Dort­mund Uni­ver­si­tät S”.

The AirportExpress is a fast and convenient means of transport from Dort­mund Airport (DTM) to Dort­mund Central Station, taking you there in little more than 20 minutes. From Dort­mund Central Station, you can continue to the uni­ver­si­ty campus by interurban railway (S-Bahn). A larger range of in­ter­na­tio­nal flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the uni­ver­si­ty station.

The H-Bahn is one of the hallmarks of TU Dort­mund Uni­ver­sity. There are two stations on North Cam­pus. One (“Dort­mund Uni­ver­si­tät S”) is directly located at the suburban train stop, which connects the uni­ver­si­ty directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the “Technologiepark” and (via South Cam­pus) Eichlinghofen. The other station is located at the dining hall at North Cam­pus and offers a direct connection to South Cam­pus every five minutes.

The facilities of TU Dort­mund Uni­ver­sity are spread over two campuses, the larger Cam­pus North and the smaller Cam­pus South. Additionally, some areas of the uni­ver­si­ty are located in the adjacent “Technologiepark”.

Site Map of TU Dort­mund Uni­ver­sity (Second Page in English).