DAHLGREN, Va. – An invention with a surprising source of inspiration may offer the Navy enhanced and scalable capabilities to heat exchange applications.
Andrew Wagner and Steven Price, engineers at Naval Surface Center Dahlgren Division, are the recipients of a patent awarded by the U.S. Patent and Trademark Office for the capillary heat exchanger. The device allows for efficient transfer of heat between two sources of liquid or gas.
When asked about the development behind this invention, Wagner described an interesting source of inspiration. Working as a teenage lifeguard for an indoor pool at the YWCA in Windsor, N.Y., he would often get headaches due to the chlorine in the air. Although he could crack doors and windows to bring in some fresh air, patrons would often complain about the cooler temperature. “So, I started thinking of a way to exchange the indoor air with the outdoor air without losing the warmth,” said Wagner.
Another source of inspiration is a biological anecdote of a surprising nature heard by Wagner. The topic? How ducks avoid hypothermia while swimming in freezing temperatures. This is achieved via a mechanism known as countercurrent exchange, which is the principle mechanic in the invention.
As explained by Wagner: “Arterial blood traveling to the duck’s feet is cooled by passing an overlapping network of returning veins. By the time the blood reaches the feet, it is at the same temperature as the water. This prevents a loss of body heat. Likewise, the returning venous blood is warmed by arterial blood moving away from the body. By the time the blood circulates back towards the body it has been warmed, preventing hypothermia. I thought, why can’t this same principle be used with air?”
Move forward to the 2015 Print-a-thon held at Dahlgren, an event that showcases the Navy’s 3-D printing capabilities. Wagner hears a presentation that describes the advantages of 3-D printing: “Unlike the methods of ‘mold,’ pouring materials into molds to shape them; ‘fold,’ bending materials to the desired shape; and ‘hole,’ carving materials to the desired shape; 3-D printers are well suited to intricate interior designs such as honeycombs.” This triggers a recall to his indoor pool conundrum and the countercurrent exchange mechanism. “On the morning the designs were due, I took a piece of graph paper and sketched out the layers needed to divide a main duct or pipe into dozens of capillaries,” said Wagner.
Wagner was then assisted by Steven Price, whose expertise helped transpose Wagner’s idea into a reality. Describing the collaboration between the two, Wagner said “Steve helped get it out of my head and into a 3-D modeling tool, including making the layers seamlessly meet and finally get a small model of the device printed.” Before long, Wagner and Price began work on their application for the patent, which was awarded in August 2019.
Although originally designed to exchange air, the capillary heat exchanger can be used for both liquids and gasses. Furthermore, it can be scaled to have an increased number of capillary channels, or have longer channels. These alterations allow the heat exchanger to respectively handle larger volumes or recapture more energy.
Potential applications for the capillary heat exchanger include the venting of air on naval vessels. The device could be used to exchange stale air from inside a ship with outside air without losing the cooling in warmer climates, or the heat in cooler climates. The invention can also be used as a heat exchanger to cool engines or other equipment that faces extreme temperatures. Speaking on this potential use, Wagner remarked that “just last year, a group working on putting lasers on aircraft came to us to consider using this scalable solution to help cool their laser within the weight requirements.”
As for future enhancements to the invention, Wagner envisions that as 3-D printing technology improves, the conductivity of the metals within the capillaries can be varied. “This will help limit the amount of heat that travels down the capillaries rather than through the membranes, increasing the efficiency of the heat transfer,” said Wagner.
Andrew Wagner expresses gratitude for his patent co-author Steven Price, the base patent lawyers and the team that made the 2015 3-D Print-a-thon possible. Wagner is grateful for the unconditional support of his wife, Tamie, and God who in his words “put all these people, events, and thoughts in my path.”
Steven Price thanks his patent co-author Andrew Wagner for his novel idea and willingness to participate in the 3-D Print-a-thon. Furthermore, he is thankful for the support of Dennis McLaughlin who is a former NSWCDD technical director, and members of the command’s additive manufacturing team: Ricky Moore, Al Waineo, Josh Eubanks, and Kahle Sullivan. “They are an amazing team that have worked hard to leverage metal additive manufacturing to create technology that supports the warfighter in novel and impactful ways,” said Price. Lastly, he thanks his wife Kayla for her constant love and support.