Heat exchangers are indispensable in numerous applications, including heating, cooling and industrial systems as well as in the aerospace industry. Despite their widespread use, their basic design has hardly changed in recent decades. A research team led by Bill King and Nenad Miljkovic from the University of Illinois is now using additive manufacturing to improve the efficiency and functionality of these components. Their work shows that 3D printing can be used to realize complex geometries that would not be feasible with conventional manufacturing methods.
The optimization of heat exchangers requires a balance between three key parameters: the degree of heat transfer, the amount of work required and the size of the component. Conventional manufacturing methods have so far ruled out many potentially more efficient designs because certain geometries could not be manufactured precisely enough.
“The design of heat exchangers, the mechanical geometry configuration of heat exchangers, has not changed in decades,” explains King, the project’s leader and a professor and Ralph A. Andersen Endowed Chair of mechanical science & engineering. “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.”
Additive manufacturing can now be used to implement almost any structure, including fluid-dynamically optimized channels that both minimize flow resistance and maximize heat transfer. This results in more compact, more efficient heat exchangers that are suitable for a wide range of applications.
As part of a project with the U.S. Navy, the team developed an additively manufactured two-phase heat exchanger that cools refrigerants in the phase transition from vapor to liquid. The novel design increases heat transfer by up to 50 percent compared to conventional designs with the same power consumption.
“Making better two-phase heat exchangers is critical for future energy-efficient systems,” said Nenad Miljkovic, the project’s co-leader and a Founder Professor of mechanical science & engineering. “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.”
In addition, the research team has developed simulation tools to virtually test tens of thousands of possible design configurations. This modeling makes it possible to identify the best geometries for specific applications and fully exploit the advantages of additive manufacturing. In the project, the scientists cooperated with the companies Creative Thermal Solutions Inc. and TauMat Inc. which specialize in energy efficiency technologies.
Work on additively manufactured heat exchangers will continue in order to investigate further design variants and further develop the modeling methods. The combination of 3D printing and optimized fluid mechanics could have a lasting impact on the production of energy-efficient heat exchangers and open up new fields of application.
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