It’s a win for both science and industry.
This week, the U.S. Department of Energy (DOE) awarded $1.5 million in funding to the joint Rice University and DexMat project, “High Thermal Conductivity Carbon Nanotube Fibers for Improved Heat Exchange.”
With an eye to decarbonizing the U.S. industrial sector, the project aims to produce low-CO2-footprint carbon nanotube (CNT) materials with superior properties–particularly in the realm of thermal conductivity–and at competitive costs.
The project could revolutionize a host of industrial applications, particularly heat exchange, spurring substantial energy efficiency gains throughout a cross-cutting array of industry.
Below, we explain the importance of heat exchangers, and Galvorn’s potential as a disruptive technology to the business-as-usual materials typically used in such industrial applications.
What are heat exchangers and why are they used?
Heat exchangers transfer heat from one medium or one process to another, typically by allowing fluid to flow past a solid surface with a high surface area. Take, for example, a heat exchanger used in a swimming pool. In this case, a boiler or solar heated water circuit is used to heat water which then warms the pool water.
Playing an integral role in a wide swath of industries, these devices can be found everywhere from HVAC and power generation, to the food and beverage industry and refrigeration, to pharmaceuticals and oil production.
And the emissions stemming from industrial heat processes within these sectors are far from small potatoes. According to Vox, "Heavy industry is responsible for around 22 percent of global CO2 emissions. Forty-two percent of that — about 10 percent of global emissions — comes from combustion to produce large amounts of high-temperature heat for industrial products like cement, steel, and petrochemicals. To put that in perspective, industrial heat’s 10 percent is greater than the CO2 emissions of all the world’s cars (6 percent) and planes (2 percent) combined.”
For this reason, and many others, heat exchangers are an important, cost-effective tool in our energy efficiency and wider decarbonization toolbox.
According to Fluid Handling Pro, heat exchangers enable energy efficiency by “facilitating the reuse of as much of the thermal energy generated or used during a process (such as heating, cooling, pasteurization, evaporation, etc.) as possible.” And this efficient heat transfer can both improve production facilities’ overall efficiency and reduce greenhouse gas (GHG) emissions in industries such as water treatment and chemical refining.
While heat exchangers aren’t exactly a new technology–they have been used by engineers for more than a century–they are getting better with age. New materials and design approaches are enabling even greater efficiency gains than ever before.
Zeroing in on the plate-fin heat exchanger
There are several types of heat exchangers out there; for this project, the DexMat-Rice University team will focus primarily on plate-fin heat exchangers.
Plate-fin heat exchangers use “plates and finned chambers to transfer heat between fluids, most commonly gases,” and are known to be both compact and lightweight. The plate fins themselves are generally made of highly conductive, lightweight materials, most commonly aluminum or copper.
However, it is time to move beyond the business-as-usual approach when it comes to the materials involved in the production of these devices.
Copper, for one, is growing scarce, and therefore, costly. And the mining and production of copper takes a heavy toll on both human and environmental health.
Aluminum, while a great thermal conductor, has been found to have lower strength and less resistance to cracking. And it, too, carries an imposing carbon footprint. In 2018, aluminum was responsible for 4% of global emissions. In fact, according to Carbon Chain, “Around 16 tonnes of CO2e are produced per tonne of aluminum. That means making a tonne of aluminum emits more carbon than burning 5 tonnes of oil.”
By swapping out copper and aluminum for high-performing, low-carbon materials, it is possible to achieve higher efficiency gains, at reduced emissions, enabling accelerated progress toward our global decarbonization and climate goals.
TL;DR? There is a need for a strong, light weight, high-performing, green material to take copper and aluminum’s place in the construction and operation of plate-fin heat exchangers.
The Galvorn opportunity
Galvorn, a high-performing carbon nanomaterial, offers an environmentally-friendly alternative to copper, aluminum, and other dirty incumbent materials in a host of applications– including heat exchangers–across a variety of industries.
This project will specifically target replacing the aluminum or copper fins used in heat exchangers with those made of Galvorn–and improving the thermal conductivity of Galvorn is the first step toward achieving this aim.
According to Geoff Wehmeyer, Assistant Professor of Mechanical Engineering, Rice University, “The high thermal conductivity and high specific surface area make Galvorn products appealing for heat exchange applications. The goal of this project is to further enhance the thermal conductivity of carbon nanotube fibers and demonstrate new textile-enabled CNT heat exchange geometries, with the goal of improved efficiency and lower emissions in the industrial sector."
Using Galvorn to produce the fins could offer many gains:
- Efficiency: Employing Galvorn, which could boast higher thermal conductivity than incumbent materials would enable higher efficiency of heat exchange. One of the goals of the work will be to further improve the thermal conductivity of Galvorn. While Galvorn already has achieved a thermal conductivity higher than that of aluminum, realizing a higher thermal conductivity than copper–routinely–has been challenging. The project team hopes to make some improvements that would allow Galvorn to reliably surpass the thermal conductivity of copper.
- Environmental: Galvorn can be produced in a manner that has lower GHG emissions than traditional high-thermal conductivity metals; and
- New shapes, sizes, and manufacturing methods: The unique mechanical properties of Galvorn (flexibility and strength) can enable new geometries and manufacturing methods for heat exchanger fins, such as those made of fabric, rather than traditional extruded metal rods or plates. Due to its fabric form, each filament of Galvorn itself has a high surface area on the micro- and nano-scale, which could enhance thermal contact with fluids even further.
A decarbonization multiplier effect
Why reinvent the wheel when you can simply improve it?
Thanks to the generous support from DOE, DexMat and Rice University researchers aim to do just that.
By working to improve Galvorn’s thermal conductivity, we can enable the development of the high-efficiency heat exchangers of tomorrow, simultaneously improving industry efficiency and decarbonization.