In 2015, University of Wisconsin-Madison engineers received funding from the U.S. Department of Energy Advanced Research Projects Agency-Energy (ARPA-e) program to develop 3D-printed heat exchangers for power plants.
That grant allowed the researchers to design and manufacture proof-of-concept heat exchangers—and now, fueled by their initial success, they have received a $2.1 million extension to continue the project.
The team of mechanical engineers includes Assistant Professor Natalie Rudolph and Mead Witter Foundation Consolidated Papers Chair Tim Osswald, manufacturing leads; Professor Greg Nellis, heat exchanger design lead; and Professor Krishnan Suresh, design for manufacturing lead.
With the extension, the team is now focusing on 3D-printing heat exchangers for refrigerators rather than for power plants. At roughly a square foot with a thickness to be determined, the new exchangers are far larger than most case studies to date.
The shape of and material used to make a heat exchanger dictates its effectiveness. A good heat exchanger shape facilitates heat transfer, while its material conducts heat well. Metal heat exchangers, like most these days, conduct heat well but have shape constraints due to the limitations of conventional manufacturing processes.
“3D printing will find its place among manufacturing technologies. It’s only a matter of time.”
—Tim Osswald
Given these limitations, the UW-Madison engineers are using 3D printing to create heat exchangers that have finely detailed geometries with internal projections to increase turbulence and facilitate heat transfer. Such intricate shapes are impossible with traditional manufacturing.
For its work, the team employs a 3D-printing technique known as fused filament fabrication, in which polymer filaments are deposited in layers to “print” 3D products. And to increase the thermal conductivity of the heat exchangers, they use “highly filled” polymers, which they create by adding small copper particles to the polymer filament to impart heat-conducting properties. “Highly filled polymers open up a new world of possibilities,” says Rudolph.
The project extension brings aboard the industrial partners Teel Plastics of Baraboo, Wisconsin; Cosine Additive of Houston, Texas; and Greenheck Corporation of Wausau, Wisconsin; to implement the heat exchangers in industrial settings.
The partners are helping set competitive performance and cost targets for the project and provide insights on how to feasibly scale the production of 3D-printed heat exchangers. In return, they are learning about state-of-the-art additive manufacturing techniques used by UW-Madison researchers to help develop better products for their markets.
The impact of the project extends beyond heat exchangers. Because the 3D-printing industry is still relatively young, the project will help advance novel 3D-printing techniques.
In particular, the research will pave the way for emerging applications of highly filled polymers. For example, using these polymers would allow manufactures to print complex, heterogeneous products such as circuit boards in just one pass. And, down the road, manufacturers could print with polymer filaments made mostly of metal filler, then burn off all of the plastic while fusing the metal into a single piece—an inexpensive technique that allows them to create finely detailed solid-metal products.
“3D printing will find its place among manufacturing technologies,” says Osswald. “It’s only a matter of time.”