Ultrasonic cleaning

Tech center seeks partner for the next phase

A Florida-based non-profit technology development company wants to take ultrasonic garment cleaning to the next level by building a prototype ultrasonic cleaning machine.

The Fraunhofer Technology Center in Hialeah, Florida, believes an ultrasonic clothes washing process offers several benefits, ranging from reduced energy and water consumption in laundry, time and money savings for households, less discharge of waste cleaning solvents.

Thomas L. Hoffmann, manager of technology development for Fraunhofer, said the prototype model of a continuous flow washing system would be the outgrowth of past research and experimention with ultrasonic cleaning of textiles. He cited an ultrasonic cleaning system demonstrated in Spain as an example of the technology in action.

In that system, fabric from a roll is passed through the ultrasonic cleaning system. The concept, Hoffmann believes, can be adapted to a continuous flow system in which garments would be cleaned ultrasonically.

Getting from the current state of the art -- cleaning a bolt of unstructured fabric to cleaning individual garments -- is the development phase that Fraunhofer is working on. To that end, Fraunhofer is seeking partners to invest in the process. The technology center believes the next phase of the development process -- building a prototype machine -- could be completed in two years at a cost of $2 million.

Hoffmann said Fraunhofer would like to find a partner within the laundry and drycleaning industry, one that would eventually be in a position to manufacture and sell the equipment. The technology center is primarily involved in developing and manufacturing support services for small and mid-size companies in the fields of textiles, automatic products manufacturing, biomedical products, medial instruments, tool and die and others. Fraunhofer concentrates on contract project work carried out on a confidential basis with proprietary rights protected for the customer.

Fraunhofer USA is a subsidiary of Fraunhofer Gesellschaft, a German company engaged in applied research in advanced technologies. The USA subsidiary also works with government and academic institutions to assist economic growth and development through new technologies.

Saving energy, reducing pollution
Fraunhofer believes that ultrasonic garment cleaning should interest both the U.S. Environmental Protection Agency and the U.S. Department of Energy since it provides dual benefits of reduced pollution and reduced energy consumption. The approach it envisions is based in part on Department of Energy research that found ultrasonically cleaned fabrics show acceptable soil removal and sufficient potential to warrant further development.

Home laundry accounts for about 22 percent of domestic water use in the United States, according to Fraunhofer. That totals 174 million cubic feet of water annual at a cost of about $5 billion. The energy used to heat water and run clothes dryers costs another $15 billion.

If universally adopted, an ultrasonic washing process could cut these costs in half, Fraunhofer believes. Even if only 10 percent of U.S. families used this approach, annual saving in water and energy would be $1 billion. Since those calculations are for the U.S. alone, worldwide adoption of the technology would lead to even greater savings and pollution reduction.

Thomas also said that the system could benefit the cleaning and laundry industry, not only by resolving environmental issues that the industries face now but also by providing an opportunity for professional cleaners to capture more of the home laundry market, especially if the system were used in combination with the "Smart Box" pick up and delivery set up envisioned by Kansas City cleaner David Porter.

Porter has conducted extensive investigations into both ultrasonic cleaning and the "smart box" service and surveys of his customer base indicate that consumers would be favorable to a scheme that would relieve them of much of the workload of processing laundry at home. Porter worked with the DOE's Kansas City office in tests of ultrasonic applications for fabric cleaning.

As Fraunhofer describes the ultrasonic washing process, mechanical forces induced by high intensity sound in a fluid media dissolve and displace adherent contaminants very efficiently. This occurs because strong sound waves propagate well through water, which is nearly incompressible. During such propagation, negative acoustic pressure causes the fluid to fracture generating so-called "cavitation bubbles."

These water vapor-filled bubbles grow first during the negative acoustic pressure cycle and then collapse rapidly when the pressure of the sound wave is reversed. This collapse accompanies a violent implosion of the bubble, generating fluid jets and shock waves which propagate into the fluid. The micro-agitation occurring in the vicinity of the cavitation bubble effectively displaces soil particles, which are bound to the fabric by ionic or cohesive forces. This agitation takes place not only at the textile surface, but also deep within the structure of the fabric. Compared to conventional methods, ultrasonic washing is faster, uses less energy, requires only small volumes of liquid, cleans more thoroughly, and may be more gentle.

Hoffmann can be reached at Fraunhofer's Technology Development Center by phone, 305-863-9096; fax 305-863-9097 or email, tlh@FTeCH.org. More information is also available on the FTech web site: http://www.FTech.org.

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