The researchers say that the wires and fabrics can deliver substantially more heating power per unit mass than conventional metal-alloy heaters when placed directly in flowing gases. The findings could point to a potential route for electrifying industrial heating.
Industrial facilities routinely heat gases for processes ranging from chemical production and drying to thermal treatment and manufacturing. Today, that heat is typically generated by burning fuels. While electric heating may sound like a simple replacement – passing current through a resistive element – heating moving gases can be difficult. Heaters must transfer energy rapidly and evenly into the gas stream without creating destructive hot spots, deforming or failing under extreme temperatures. Placing heating elements directly in the gas flow (a strategy known as immersion heating) improves efficiency, but significantly increases stress on the material.
An Assistant Professor of Mechanical Engineering at Rice University, Daniel J. Preston, says: “When you immerse a heater directly into a gas stream, you gain heat-transfer efficiency, but you also create a much harsher operating environment. Geometry, stability and performance all become tightly coupled.”
One of the most stubborn constraints is size. Thin heating elements exchange heat with gases effectively, but conventional metal alloys are difficult to fabricate and handle at very small diameters. CNTFs offer a striking alternative; they combine electrical resistivity suitable for Joule heating with exceptional strength-to-weight ratios and unusually high thermal conductivity compared with traditional heater materials.
A.J. Hartsook Professor of Chemical and Biomolecular Engineering at Rice University and Director of its Carbon Hub, Matteo Pasquali, says: “CNTFs behave very differently from metal wires. They are lightweight, flexible and remarkably strong, which allows us to consider heater geometries and fabrication techniques that would be impractical with conventional materials.”
Rather than adapting CNTFs to existing heaters, the team built devices made entirely from the fibres, including single filaments, parallel arrays and textile-like fabrics. Their key performance metric was specific power loading—the maximum heating power per unit mass a device can sustain before failure.
Across multiple configurations and operating conditions, CNTF heaters consistently achieved higher specific power loadings than comparable metal-alloy elements. The advantage was particularly pronounced in non-oxidizing environments, where carbon-based materials can withstand far higher temperatures without degrading. From a heat-transfer perspective, the fibbers' thermal properties proved especially important.
Assistant Professor of Mechanical Engineering at Rice University, Geoff Wehmeyer, says: “Their high thermal conductivity helps distribute heat and suppress localised hot spots, which are a common cause of heater failure. That heat spreading fundamentally changes how these devices behave under extreme conditions.”
The study highlights the fact that performance gains arise not only from material properties, but also from the new architectures those properties enable. CNTFs can be produced at extremely small diameters while remaining mechanically robust, enabling designs that are difficult to achieve using metal wires.
“Materials only become impactful when you can reliably build with them,” Pasquali says. “CNTFs provide unusual flexibility. For example, you can tie a knot in them and they do not break.”
A distinctive feature of the work is its reliance on textile-inspired manufacturing techniques. CNTF yarns can be woven, knitted and assembled into lightweight, high-surface area structures — geometries that are particularly well suited for immersion heating. An Assistant Professor of Mechanical Engineering at Rice University, Vanessa Sanchez, says: “Textile techniques give us extraordinary freedom in creating three-dimensional architectures. We can design heaters that are lightweight, porous and mechanically compliant while remaining electrically functional.”
Compared with rigid metal meshes, CNTF fabrics exhibit more uniform heating behaviour and reduced hot spot formation, benefits again linked to the fibres' ability to spread heat efficiently.
“This work required multiple layers of expertise,” Wehmeyer concludes. “Producing high-quality CNTFs is only the starting point. Understanding how they perform thermally and integrating them into functional devices is equally important.”