Researchers improve heat exchanger performance with 3D printing

According to the University of Illinois Urbana-Champaign, new work from Bill King, Nenad Miljkovic, and their colleagues is innovating the design of heat exchangers – using 3D printing to dramatically improve functionality. The published work can be found here.

These devices, whose purpose is to transfer heat between fluids, are ubiquitous across many commonplace applications: they appear in HVAC systems, refrigerators, cars, ships, aircraft, wastewater treatment facilities, cell phones, data centers, and petroleum refining operations, among many other settings.

“The design of heat exchangers, the mechanical geometry configuration of heat exchangers, has not changed in decades,” said King, a Professor at the university and Ralph A. Andersen Endowed Chair of Mechanical Science and Engineering, and project lead. “The heat exchangers that we have today look almost exactly like the heat exchangers that we had 30 years ago. And the reason that there’s been so little innovation in heat exchangers has been that they are fundamentally limited by the manufacturing process.”

Precise design of the three-dimensional shapes within these devices can optimize trade-offs among three key factors: the rate of heat transfer, the amount of work that must be applied to achieve the transfer, and the size of the heat exchanger. However, traditional manufacturing methods have meant that many desirable shapes were unachievable in practice.

“If you could have any shape at all, it might not be the shapes represented by existing heat exchanger technologies,” said King. “[With AM] we can make many, many shapes – almost an infinite number of shapes that are not possible with today’s manufacturing technologies. And so we can make shapes that allow for complicated 3D geometries. We can link large passages for fluid flow that promote easy fluid motion, with small passages that promote high heat transfer. So we can make things that have three-dimensional shapes that allow fluids to be mixed and routed in unconventional ways.”

In a project with the US Navy, the team successfully designed, produced, and tested a 3D printed two-phase heat exchanger – meaning that the refrigerant comes in as a vapor and then cools down and leaves as a liquid – transferring its heat to cooling water that also flows through the heat exchanger. The device has complicated 3D geometries that significantly improve heat transfer – geometries that would not have been manufacturable with conventional manufacturing. By one measure, their heat exchanger outperforms traditional designs by 30% to 50% for the same amount of power.

“Making better two-phase heat exchangers is critical for future energy-efficient systems,” said Nenad Miljkovic, a Founder Professor of Mechanical Science and Engineering, and the project’s co-leader. “With additive manufacturing, we increase the volumetric and gravimetric power density of the heat exchanger, resulting in lower mass and higher compactness. This results in a higher level of performance, and also enables the integration of high-power devices in mobile applications like cars, ships, and aircraft, which classically could not be achieved with state-of-the-art heat exchanger technology.”

As part of the research, the team developed modeling and simulation tools that allowed them to virtually test tens of thousands of possible configurations with different sizes, shapes, and ways that flows would move back and forth within the heat exchanger. Those tools allowed them to explore and optimize within the huge design space enabled by AM.

The Illinois team collaborated with two companies on this project, Creative Thermal Solutions Inc. and TauMat Inc., both of which work on energy efficiency technologies.

The team is now continuing its work in this area, building out modeling capabilities further so that they can explore even more designs.