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Heat-conducting composite pipes save costs in seawater desalination

Seawater desalination plants require pipelines made of a special kind of steel or titanium – expensive material that is growing increasingly difficult to procure.

Heat-conducting polymer composites may soon replace titanium and high-alloy steel altogether. 

Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Germany are now developing an alternative to the titanium tubes: pipelines made of polymer composites.

The polymer composites are a plastic, and yet they conduct heat. Also, they can be produced in continuous lengths and are correspondingly more economical than their metal counterparts.

But what did researchers do to make a polymer heat-conducting?

“We introduced metal particles into the material – or more precisely, we add up to 50 percent copper microfibers by volume. This does not change the processing properties of the composite, and it can still be processed as any other polymer would,“ notes Arne Haberkorn, a scientist at IFAM.

The researchers have already developed the material itself; now they want to optimise its thermal conductivity.

To accomplish this, they are installing the piping in a pilot seawater-desalination plant where they are testing its thermal conductivity, checking to see how much of a microorganism-based coating forms on the pipes, and how heavily the material corrodes in its salty surroundings.

They then optimise the composite properties based on the results. The researchers have set the evaporation process to run at a temperature of 70 degrees Celsius – so there is hot gas heated to 70 degrees pumped through the pipelines.

This offers several advantages: fewer deposits congregate on the pipes, the material doesn‘t corrode as quickly, and the pressure differential between the inside and outside of the piping is not as dramatic.

The usage for the material are not confined to seawater desalination, either. “We developed the pipes for desalination plants because they place the highest demands on the material. Designed with these constraints in mind, it will be no problem using it in the food or pharmaceuticals industries,“ Haberkorn points out.

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