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Monday, 23 September 2019
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Raw materials & technologies, Technologies

Triple protection for heat-exchangers

Thursday, 4 May 2017

When processing milk and juice, the food industry is using heat exchangers throughout the process. To have no risk to the consumers, they have to be free from microbes. A novel nano-coating combines three advantages.

New nano-coatings have anti-adhesive, anti-corrosive and antimicrobial effects. Source: Ollmann/INM

New nano-coatings have anti-adhesive, anti-corrosive and antimicrobial effects. Source: Ollmann/INM

Especially in the numerous grooves and recesses of the heat exchanger, persistent biofilms can remain stuck. As a result, heat exchangers must be cleaned at regular intervals using aggressive chemicals. These increase the sensitivity for corrosion, especially if mild steel is used as heat exchanger material.

Fight against undesired biofilms

Now the INM – Leibniz Institute for New Materials is introducing new nano-coatings that reduce the effort required for cleaning heat exchangers as well as their corrosion. In these new coatings, the research scientists combine antiadhesive, anticorrosive and, on demand, also antimicrobial properties. The developers achieve the anti-adhesive characteristics by introducing hydrophobic compounds that are similar to common Teflon. These inhibit the formation of any undesired biofilm and allow residues to be transported out more easily before they clog up the channels of the heat exchangers.

Structures act as diffusion barrier

At the same time the researcher use structures that act as diffusion barrier in their coatings. These inhibit the sensitivity for corrosion prevoked from corrosive substances or aggressive cleaning agents. To prevent microbes, bacteria or fungus from adhering to surfaces, the scientists additionally use colloidal copper in the coating. Due to the oxygen or water that is present in many processes, copper ions are released from the copper colloids. These migrate to the surface and, as a result of their antimicrobial effect, they prevent microbes from proliferation and growth.

Keeping the paint chemically stable

"In addition, we can keep the paint chemically stable. Otherwise it would not withstand the aggressive chemicals that are required for cleaning,” explained Carsten Becker-Willinger, Head of "Nanomers" at INM. Adding that the paint could also be adapted for special mechanical loads, he explained that this was important for paint used in heat exchangers, too. Due to mechanical vibrations, the individual plates of the heat exchangers could be subjected to a certain amount of abrasion at points of contact.

Interesting for air conditioning

Principally, the paint developed could also be used in other contexts, Becker-Willinger said, including the large sector of air conditioning with heat exchangers. Furthermore, the paint could be used for equipment in water purification plants, for example. It can be applied using standard methods such as spraying or immersion and subsequent hardening. It can be used on stainless steel, steel, titanium or aluminum. By selectively adapting individual constituents, the developers are able to respond to the particular, special requirements of interested users.

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