Frederick W. Ahrens
Professor
| Address: | 43 Parkview Lane
Hortonville, WI 54944 |
| Phone: | 920.779.6268 |
| E-mail: | |
Education
- Ph.D., University of Wisconsin-Madison, 1971
- M.S., University of Idaho, 1965
- B.S., Case Institute of Technology, 1962
Research Areas and Descriptors
Background
The common thread in Dr. Ahrens' career has been research in the broad area of thermal/fluid sciences and systems. Previous employment includes the James River Corporation, University of Missouri, Argonne National Lab and Whirlpool Corporation. His early research dealt with nuclear reactor safety, residential refrigeration, air-conditioning and drying equipment, pulse combustion burners for heating, and compressed air energy storage power systems. The work resulted in development of significant expertise in computer-aided modeling, simulation and design optimization. In recent years, his academic and industrial research has focused on paper manufacturing process fundamentals and technologies, with extensive work in new forming technology, headbox design and control, enhanced pressing, non-compressive dewatering, and high-intensity drying. An underlying technical theme in much of Dr. Ahrens' research has been transport phenomena in porous media.
Research
Dr. Ahrens' current and recent research projects have a variety of emphases, such as describing fundamental transport mechanisms and phenomena, development of new/improved process technology, system analysis, design and optimization, and improving product performance via the altering the process. Motivated by the high capital cost of papermaking equipment and the energy intensiveness of paper drying, Dr. Ahrens, his co-workers and students are presently investigating ways to increase the productivity of high-speed paper machine dryer sections, and to reduce the high energy consumption of the through-air drying process. They are developing a new, high-intensity, pulse combustion-based impingement drying process (Pulsed Air Drying) that has the potential to enhance heat and mass transfer rates by a large factor, compared to steady flow impingement. They are also developing computer models of pressing and drying processes, for use in design and operational improvement. Much of the work is being done with paper industry participation and financial support. A recent DOE project involved evaluation/development of new microwave applicator technology for paper heating/drying. Another recent study investigated the impact of drying conditions on development of out-of-plane deformations (cockle) in paper. The research projects use laboratory and computer simulation techniques to study the fundamentals of water removal, as well as design and operational issues.
A primary goal of our future work in the drying area is to develop and experimentally verify a comprehensive model of Pulsed Air Drying (PAD) that can guide the development of a configuration that maximizes the drying rate enhancement. This will need to incorporate sub-models of the pulse combustor, the impingement zone and the moist paper. The development of PAD will also need to deal with system issues, including heat utilization, scale-up to multi-burner, multi-jet arrays, etc.
The current and planned drying and water removal research offers significant opportunities to graduate students seeking the challenge of fundamental problems involving the strong interaction of several physical/transport processes, coupled with the potential that the work will lead to important industrial applications.
Distinctions
- James River Corporation Awards
- Gold Key in Process Development (Forming Technology), 1991
- Neenah Technical Center Silver Key
- Best Scientific Discovery (Fluid Flow), 1990
- Process Development, 1991
- Process Commercialization, 1991
- Drying Technology Best Paper Award, 1986-1987
Selected Patents
- Method of Controlling Headbox Jet Velocity for Foamed Furnishes, U.S. Patent 6,355,142, March 12, 2002
- Papermaking Fabric, Process for Producing High Bulk Products and the Products Produced Thereby, U.S. Patent 5,853,547, with T. Gulya, G. Worry and W. Wright, December 29, 1998
- High Softness Embossed Tissue, U.S. Patent 5,409,572, with T. Kershaw, et al., April 25, 1995
- Multi-Layer Papers and Tissues, U. S. Patent 5,227,023, with J. R. Pounder and T. N. Kershaw, July 13, 1993
- Extraction Method and Apparatus, U.S. Patent 5,137,551, with J. Loughran and J. Benson, August 11, 1992
- Compressed Air Energy Storage System, U. S. Patent 4,281,256, with George T. Kartsounes, July 28, 1981
- Air Ejector Augmented Compressed Air Energy Storage System, U. S. Patent 4,237,692, with George T. Kartsounes, December 9, 1980
Representative Publications
- F. Ahrens and L. Wanamaker. 2003. Measurement of the Water Permeability and Capillary Pressure of Partially Saturated Paper Fiber Mats, using a Transient Flow Technique. Proceedings of Second Nordic Drying Conference, Copenhagen.
- F. Ahrens and C. Habeger. 2001. Use of New Applicator Design Ideas to Improve the Uniformity of Paper Drying via Microwave Energy. Drying Technology 19(10), 2531-2548.
- F. Ahrens. 1995. Effect of Shell Thermal Dynamics on Predictions of a Yankee Dryer Model. Proceedings of the ASME Heat Transfer Division, HTD-317-2, 427-435.
- F. Ahrens and A. strm. High-Intensity Drying of Paper. Drying Technology 4(2), 245-270.
- F. Ahrens. 1983. Heat Pump Modeling, Simulation and Design. Chapter in Heat Pump Fundamentals, J. Berghmans (ed.), Martinus Nijhoff, The Hague, 155-191.
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