Heat Exchangers Get a Polymer Makeover

A team of researchers at Rice University, led by Daniel J. Preston, assistant professor of mechanical engineering, has developed and tested a low-cost, easy-to-deploy, high-performance heat exchanger made with thin sheets of polymer.  

Metal heat exchangers have provided reliable thermal management across a variety of industries, but their limitations are becoming increasingly difficult to overlook. Material and manufacturing costs for traditional units are steep. In addition, metal is susceptible to chemical corrosion and fouling, which is the accumulation of unwanted materials such as rust, algae, and more.  

These challenges play out against a backdrop where the need for effective and low-cost thermal management solutions is increasing. The proliferation of data centers — nearly 3,000 new data centers were being planned or constructed across the country in late 2025, adding to the 4,000 operational ones, according to the American Edge project — is driving demand for effective thermal management.  

The polymer alternative checked all the requirements. “We were able to achieve performance comparable to metal-based alternatives while leveraging some advantages inherent to polymers such as corrosion and fouling resistance in addition to substantially lower cost,” said Richard Fontenot, doctoral candidate in mechanical engineering, and lead author of a related study published in Advanced Science. (These polymer heat exchangers achieved a heat transfer capacity per cost up to 4x higher than state-of-the-art equivalents). 

The flexible polymer heat exchangers can be flat-packed and subsequently deployed to 60-times their original volume for use, a characteristic that will be especially useful in space applications.   
 

The role of analytical modeling 

Validation to consider a non-metal source to manufacture heat exchangers came from nature. Certain species of sharks and tuna have bundles of blood vessels called rete mirabile, which act as heat exchangers to regulate body temperature. It’s proof that effective heat exchange can occur even between components that have low thermal conductivity.  

But why choose polymers, specifically thermoplastics, from all available candidate materials? First, early literature on polymer-based heat exchangers has shown promise, but designs have stalled because they have not delivered desired advantages. But their light weight and low costs show a lot of promise. And because thermoplastics are transparent, it’s easier to detect fouling and blockage and clean the unit, Fontenot pointed out.  

Discover the Benefits of ASME Membership

Convinced of thermoplastics’ potential in heat exchangers, the Rice team started with analytical modeling to further explore them as candidates.  

Thermal heat exchangers must be manufactured with a low heat resistance to heat transfer so they can let the heat pass through its walls. While the focus on the material used to make the exchanger is warranted, the thermal resistance of the circulating fluid also matters. “What most people don’t realize is that there’s also a thermal resistance associated with heat transfer within the fluid streams themselves,” Preston said.  

The finding, the result of analytical modeling, is radical because it means that the material used to construct the heat exchanger is not as big a factor in its performance as we once thought (or at least not that big a deal).  
 

Additional lab testing 

But geometry does play a role. Because thermal resistance increases with thickness, the walls of the heat exchanger must be very thin. The team tested various thicknesses and found a 22 percent drop in performance when doubling the thickness. “On the other hand, even if one were to make the sheet infinitely thin, the performance only increases by an additional 25 percent, so we’re already getting pretty close to the best possible performance that we can get,” Preston said.  

To fabricate a trial specimen, Fontenot used a sheet lamination technique to hermetically seal ultrathin polymer sheets, each of which is approximately 50 µm.  

While polymers are good candidates, the team had to overcome a fabrication challenge: Thin and flexible polymer sheets can buckle when there’s a lot of liquid sloshing around. To prevent such instabilities from blocking flow, channels should not overlap exactly. Fontenot offset the polymer sheets by at least 20 percent while still delivering a good area for heat exchange. (The area of overlap needs to be optimized because it’s one of the key factors influencing the performance of the heat exchanger, Preston pointed out.)  

The researchers tested two materials, nylon and polyethylene, in a high concentration of hydrochloric acid to simulate conditions of a hostile environment for the device like those encountered in chemical processing or desalination plants. The nylon unit failed within a mere 10 seconds while the polyethylene heat exchanger remained operational for over a month without any material degradation. Aluminum also failed within a few minutes, further validating the conclusion that not all metals make good candidates for thermal heat exchangers in difficult operating environments. 

Most of the experiments were conducted at 60 ℃, and the team successfully tested the heat exchanger at this temperature for an extended period of time of over a week. “Given that the material is thermoplastic, there would be some temperature where you would have compromised performance, and that temperature may be lower than metal counterparts, but we found that the other benefits certainly outweigh the potential cap on temperature,” Preston said.  

Poornima Apte is a technology writer based in Walpole, Mass.