Experimental Study of Oil Mist Separation in Coalescing Filters Under Realistic Operating Conditions

Coalescence filters are used to separate oil droplets from gas streams, for example in compressed air treatment following oil-lubricated compressors. The oil droplets are separated onto the fibers of the filter medium, coalesce into larger liquid structures, and are transported through the medium via channels that form until they drain out at the rear of the filter. This process is influenced by a variety of parameters, including the flow velocity and the operating temperature.

In practice, coalescence filters are typically operated at temperatures of 75–80 °C, as found at the compressor outlet. At the same time, operation at reduced flow velocities offers significant potential for reducing energy consumption. However, most previous studies were conducted under laboratory conditions at room temperature and comparatively high flow velocities. Our own preliminary tests at elevated temperatures revealed altered filter behavior. Specifically, the pressure drop curve and oil distribution within the filter medium did not align with the predictions of existing models. These discrepancies suggest that temperature-induced changes in fluid properties, such as surface tension and capillary pressure, play a role that has not yet been sufficiently understood.

As part of this thesis, experimental investigations on full-scale filters will be conducted on an existing test bench. The goal is to clarify how coalescing filters behave at elevated temperatures and low flow velocities and to understand the mechanisms behind this behavior. To this end, the filter flow velocity and temperature will be systematically varied. The measured parameters will include differential pressure, drainage, local saturation of the filter layers, and fractional separation efficiency. Depending on your interests, there is the option to focus more on conceptual and design aspects, either as an alternative or in addition to the experimental work. Specifically, this involves the design and construction of an optical observation system to investigate the fluid structures within the filter medium during operation. The scope of the work will be adjusted depending on whether it is a bachelor’s or master’s thesis.

What I can offer you:

• Regular communication and guidance to ensure the successful completion of the thesis
• Support with problems and training in the experimental setup and measurement techniques
• Freedom to pursue your own ideas within the thesis
• Insight into a DFG-funded basic research project

Your responsibilities include:

• Developing and tracking a project plan for the thesis
• Conducting filtration experiments under variable operating conditions on an existing test bench and/or contributing to the design and expansion of the test facility
• Evaluating the experimental data and contextualizing the results within the current state of research

What you should bring to the table:

• Interest in the subject area and enjoyment of experimental and/or design work
• Ability to work independently and with a clear focus on goals
• Degree program: CIW/VT, BIW, MACH, or comparable

If you’re interested in the position, I’d love to receive an email with some information about yourself. I’d be happy to tell you more about the topic in a conversation and answer all your questions!

Contact information:

Britta Jaumann, M.Sc.
Email: britta.jaumann∂kit.edu
Phone: +49 721 608-42416

Straße am Forum 8
Bldg. 30.70, Room 107
76131 Karlsruhe