Monday, May 12, 2025

Tapping a new toolbox, engineers buck tradition in new high-performing heat exchanger

University of Wisconsin-Madison

MADISON — By combining topology optimization and additive manufacturing, a team of University of Wisconsin–Madison engineers created a twisty high-temperature heat exchanger that outperformed a traditional straight channel design in heat transfer, power density and effectiveness.

And they used an innovative technique to 3D print — and test — the metal proof of concept.

High-temperature heat exchangers are essential components in many technologies for dissipating heat, with applications in aerospace, power generation, industrial processes and aviation.

“Traditionally, heat exchangers flow hot fluid and cold fluid through straight pipes, mainly because straight pipes are easy to manufacture,” says Xiaoping Qian, a professor of mechanical engineering at UW–Madison. “But straight pipes are not necessarily the best geometry for transferring heat between hot and cold fluids.”

Additive manufacturing enables researchers to create structures with complex geometries that can yield more efficient heat exchangers. Given this design freedom, Qian set out to discover a design for the hot and cold fluid channels inside a heat exchanger that would maximize heat transfer.

He harnessed his expertise in topology optimization, a computational design approach used to study the distribution of materials in a structure to achieve certain design goals. He also incorporated a patented technique, called projected undercut perimeter, that considers manufacturability constraints for the overall design.

With an optimized design in hand, Qian worked with colleague Dan Thoma, a professor of materials science and engineering at UW–Madison, who led the 3D printing of the heat exchanger using a metal additive manufacturing technique called laser powder bed fusion.

From the outside, the optimized heat exchanger looks identical to a traditional version with a straight channel design — but their internal core designs are strikingly different. The optimized design has intertwining hot and cold fluid channels with intricate geometries and complex surface features. These complex geometric features guide fluid flow in a twisting path that enhances the heat transfer.

Collaborator Mark Anderson, a professor of mechanical engineering at UW–Madison, conducted thermal-hydraulic tests on the optimized heat exchanger and a traditional heat exchanger to compare their performance. The optimized design was not only more effective in transferring heat but also achieved a 27% higher power density than the traditional heat exchanger. That higher power density enables a heat exchanger to be lighter and more compact — useful attributes for aerospace and aviation applications.

The team detailed its results in a paper published Feb. 19, 2025, in the International Journal of Heat and Mass Transfer.

While previous research has used topology optimization to study two-fluid heat exchanger designs, Qian says this work is the first to harness topology optimization and impose manufacturability constraints to ensure the design can be built and tested.

“Optimizing design on the computer is one thing, but to actually make and test it is a very different thing,” Qian says. “It’s exciting that our optimization method worked. We were able to actually manufacture our heat exchanger design. And, through experimental testing, we demonstrated the performance enhancement of our optimized design. The excellent work performed by the students, postdoctoral researchers and scientists in the three research groups made this advance possible.”

Sicheng Sun, a recent PhD graduate from Qian’s research group, is the first author on the International Journal of Heat and Mass Transfer paper. Additional co-authors include Tiago Augusto Moreira, Behzad Rankouhi, Xinyi Yu and Ian Jentz, all from UW–Madison.

The researchers patented their projected undercut perimeter technique through the Wisconsin Alumni Research Foundation.

This work was supported by ARPA-E grant DE-AR0001475 and National Science Foundation grant 1941206.

Journal

International Journal of Heat and Mass Transfer

DOI

10.1016/j.ijheatmasstransfer.2025.126809

Method of Research

Experimental study

Article Title

Topology optimization, additive manufacturing and thermohydraulic testing of high-temperature heat exchangers

Scientists hail new ‘industrially viable technology’ that can squeeze hydrogen from seawater

University of Sharjah

image:
Systematic illustration of the formation process of how the new device extracts hydrogen from seawater.
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Credit: Small (2025). DOI: https://doi.org/10.1002/smll.202501376

By Ifath Arwah, University of Sharjah

Researchers from the University of Sharjah claim to have developed a novel technology capable of producing clean hydrogen fuel directly from seawater, and at an industrial scale.

In a study published in the journal Small, the researchers report that they extracted hydrogen without the need to remove the mineral salts dissolved in seawater or add any chemicals.

According to the authors, the technology enables hydrogen extraction from seawater without relying on desalination plants, which require massive investments totaling hundreds of millions of dollars.

“We developed a novel, multi-layered electrode that can extract hydrogen directly from seawater efficiently and sustainably. Traditional methods face a host of problems, mainly corrosion and performance degradation caused by chloride ions in seawater,” said Dr. Tanveer Ul Haq, Assistant Professor in the Department of Chemistry, College of Sciences, University of Sharjah, and the study’s lead author.

The authors designed a specially engineered electrode which, in the words of Dr. Ul Haq, “overcomes these issues by creating a protective and reactive microenvironment that boosts performance while resisting damage.”

In a world where clean energy is no longer a luxury but a necessity, hydrogen stands out as one of the most promising solutions. Until now, scientists have primarily relied on pure water—a precious resource in many regions—to produce hydrogen.

This study addresses that challenge by introducing a new technology capable of generating hydrogen directly from seawater.

“In short, we’ve demonstrated that direct seawater electrolysis is not only possible but scalable, delivering industrial-level efficiency while protecting the electrode over long-term use,” Dr. Ul Haq added.

In their study, the researchers describe their device as a “microenvironment-engineered, multilayered electrode design for sustainable seawater electrolysis.” When in operation, the apparatus delivers “a geometric current density of 1 A cm⁻² in real seawater at an overpotential of 420 mV, with no hypochlorite formation and outstanding operational stability for 300 hours at room temperature.”

The electrode, the study notes, produces hydrogen at industrially relevant rates using untreated seawater. Nearly all the electrical input was converted into gas output, achieving a Faradaic efficiency of 98%.

“The advanced anode design achieves an industrially viable current density of 1.0 A cm⁻² at 1.65 V under standard conditions, marking a significant step toward scalable, desalination-free hydrogen production directly from seawater.”

Faradaic efficiency measures the effectiveness with which electrons participate in a given electrochemical reaction.

“We created an advanced electrode that works in real seawater without needing any pre-treatment or desalination,” said the study’s corresponding author, Yousef Haik, Professor of Mechanical and Nuclear Engineering at the University of Sharjah.

“Our system generates hydrogen at industrially relevant rates—1 ampere per square centimeter—with low energy input. This could revolutionize how we think about hydrogen production in coastal regions, especially in arid countries like the UAE, where freshwater is limited but sunlight and seawater are abundant.”

The technology’s strength lies in the electrode’s advanced, multilayered structure, which not only withstands harsh seawater conditions but thrives in them. The device forms “a protective metaborate film, preventing metal dissolution and non-conductive oxide formation”—an approach that eliminates the need for energy-intensive water purification.

“This bypasses costly desalination and complex water purification, making green hydrogen production cheaper and more accessible,” said co-author Mourad Smari, a research associate at Sharjah University’s Institute of Science and Engineering.

One of the most impressive features of the system is its longevity. “It runs for over 300 hours without performance loss, resisting corrosion that usually destroys similar systems,” said Dr. Ul Haq. The study explains that the carbonate layer “acts as an electrostatic shield,” protecting the electrode’s multiple layers from dissolution.

In performance tests, the electrode achieved a turnover frequency of 139.4 s⁻¹ at 1.6 V, which the authors consider one of the highest reported for similar systems.

“In summary, the multilayered electrode architecture developed in this study provides an effective solution for efficient direct seawater electrolysis,” the study concludes. “The ultrathin nanosheet morphology, with its high surface area, facilitates substantial catalyst exposure and activity, maximizing the surface sites available for direct seawater oxidation.”

Dr. Ul Haq emphasized the technology’s potential impact on clean and sustainable energy production.

“This technology can be applied in large-scale hydrogen plants that use seawater instead of precious freshwater. Imagine solar-powered hydrogen farms along the UAE coastline, using seawater and sunlight to produce clean fuel—with zero emissions and minimal resource strain.”

Asked to explain in simple terms how the multilayered design works, Dr. Ul Haq said, “The electrode’s layered design acts like a smart filter—allowing water in, blocking corrosion, and supercharging hydrogen production.” He added that the system’s performance is largely due to how it handles chloride ions in seawater.

The carbonate functionalization repels these ions and creates a local acidic microenvironment that accelerates the oxygen evolution reaction (OER), essential for hydrogen production. The paper notes that this mechanism “enhances OER kinetics and protects against chloride attack and precipitate formation.”

The technology has already attracted interest from “clean energy startups and regional innovation hubs,” Dr. Ul Haq noted. “Our innovation transforms seawater from a challenge into a solution… This is clean hydrogen made from the sea.”

The researchers are now looking forward to large-scale deployment of their technology. “We’re now moving from lab-scale to pilot-scale testing, looking to validate the technology under real-world outdoor conditions,” Dr. Ul Haq said. “Our next goal is to develop a modular hydrogen generator powered by solar energy, tailored for use in arid, coastal regions.”

Faradic efficiency: corrosion potential and corrosion current density recorded before and after 300 h electrolysis, chronopotentiometry of valance band spectrum, and Raman spectrum after 300 h continuous electrolysis in alkaline seawater.

Credit

Small (2025). DOI: https://doi.org/10.1002/smll.202501376