Heat exchangers are some of the most widely used energy-transfer devices, helping cool everything from car engines to power plants.

At the recent ARPA-e conference, organized by the U.S. Department of Energy, scientists from the University of Maryland showcased an advanced 3-D printer that, combined with a wire-laying head, cuts in half the time needed to manufacture heat exchangers.

David Hymas, a Ph.D. candidate at the University of Maryland, said that in most cases in a heat exchanger, the heat is transferred by forcing air over pipes or tubes with circulating water, which is often pumped from a nearby river or lake.

Reduce water use

“Currently power plants draw about 40 percent of all the freshwater supply in the United States,” Hymas said. Water consumption, he added, could be cut in half if lightweight air-cooled heat exchangers were created in 3-D printers.

“The water would flow in through one manifold entering these water tubes, right here, and then flow out through the other manifold. Air would blow across it, cooling these fins,” he said.

Printing a heat exchanger

At the school’s Advanced Heat Exchangers and Process Intensification Laboratory, Hymas showed off a heat exchanger manufactured in a lab-size 3-D printer that includes a wire-laying device. The first head in the machine builds up layers of polymer tubes, while another head lays copper or aluminum wire across them.

The printer used for testing the idea took almost 24 hours to create a shoebox-size heat exchanger, but research associate Farah Singer says the industrial-scale prototype machine proved to be much faster.

“It has 10 polymer heads and it is capable of printing, of laying at the same time, 45 fibers, 45 metal fibers, so we are talking about a full layer,” she said. “This machine is capable of printing in eight hours a 1 meter square heat exchanger. We are talking almost 20 kilowatts or 30 kilowatt heat exchanger.”

Reduction in weight and cost for 3-D-printed heat exchangers reaches 50 percent, depending on the application, which can range from power plants to air conditioning to cooling electronic devices.

“For the electronic cooling, for example, so far our experimental results have shown that we could have up to 52 percent reduction in cost while we have 26 percent increase in performance,” Singer said.

An added advantage is that 3-D printers allow creating very complex geometries, with the resolution between the cooling wires as low as 100 microns. The project was partially funded by the U.S. Department of Energy.
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