Heat Exchange
On engineering for community resilience.
It’s a hot one, folks. This past Monday, I successfully moved to Western Massachusetts in advance of my new job at UMass Amherst! I wanted to explore the area more, but a) I had a lot of unpacking to do and b) the temperatures have been in the Fahrenheit 90s so…no. I’ll be in my air-conditioned home assembling my IKEA furniture and organizing my record collection, thank you very much.
[Image description: my record collection in my new living room, its 500+ entries nearly bursting out of this IKEA KALLAX.]
But I’m a chemical engineer, right? Shouldn’t I be able to do something about this heat, besides mindlessly blasting the AC? Can I use my vast knowledge of fluid mechanics and material properties to, perhaps, help cool off my community?
Let’s review the fundamentals (no don’t go there’s a point to this I promise). At some point, every chemical engineering student learns about heat exchangers. The premise is simple: one cold fluid passes over a hot fluid (without being mixed) and the two “exchange” energy, cold becoming hot and hot becoming cold. Remember that “fluid” here can mean a liquid or a gas. The most important design variable is the surface area of heat transfer; the more that these fluids are in contact with one another, the more effective the heat transfer. This is fairly intuitive; elephant’s ears are super big so that its blood vessels, carrying warm blood, can have as much cool wind pass over them as possible, preventing the giant animal from overheating (see image below).
In industry, one of the most popular versions of this is the “shell-and-tube” exchanger, where to facilitate heat transfer, one fluid (e.g. something hot) is passed through a series of tubes while the other fluid (e.g. something cold) is run over the tubes, maximizing the surface area of heat transfer. Everything else is just fancy math: the size of the exchanger, the number of tubes that the fluid gets passed through, the thickness and heat transfer coefficient of the tube material, and dozens more variables are all fine-tuned by people with degrees like mine so that the “cold stream outlet temperature” gets as close to the “hot stream inlet temperature” as possible, and vice-versa. And voilà, cooling!
[Image description: Science imitates nature. Left: A shell-and-tube heat exchanger schematic (top) and heat exchanger IRL (bottom). Right: A diagram of thermoregulation in nature (top) and an elephant ear (bottom).
So why am I telling you this? Well, the more I think about how engineers can best serve their communities as both scholars and activists, the more I think about heat exchangers and the more I think about clay. Terra cotta is a material with the unique property of being able to absorb liquid water and cool the environment around it via evaporative cooling. Translation: air gets colder when it passes over wet clay. This simple premise has been used for housing in hot climates for thousands of years, but recently, artists and engineers have been collaborating to add a modern twist.
Meet the CoolAnt Beehive, a terra cotta-based heat exchanger designed for Deki Electronics in Noida, NCR, India. India is prone to heat waves, and working in an electronics factory makes that heat even worse. The Beehive is a practical, functional, and artistic design that’s not unlike a shell-and-tube heat exchanger, except that they only require a light, continuous flow of water across the clay pipes. The device is able to cool the air coming into the factory floor by six degrees Celsius, from 42 °C to 36 °C (107.6 °F to 96.8 °F). This is a great achievement for a low-tech solution, especially considering that winds above your body temperature (an average of 37 °C/98.6 °F) are incredibly dangerous. (Side note: don’t run a fan to cool off when it’s above 95 °F; it’ll only heat you up more!)
[Image description: The terra cotta heat exchanger designed for a factory in India. As long as the clay tubes are wet, the air passing through them gets cooled by 6 °C. Photos courtesy of Ant Studio.]
Part of why I’m obsessed with this concept is how punk it is. Imagine this: there’s a building in your area (perhaps a school or community center) that gets incredibly hot in the summer, but the people who own the space can’t afford a new HVAC system. So, you and your community gets together to build them their own Beehive for use when the weather gets especially hot. All you’d need is clay, a metal frame, and for everyone in the neighborhood to make a few tubes. You could make a fun day out of it, host a potluck, get the kids involved, and teach everyone about how air conditioning works, leaving the water flow part to the techies. In a matter of hours, you would not only have a brand-new cooling system, but one that’s beautiful to look at, one where everybody in the community can say “I made that tube up there on the top right! I contributed to this big science project, and now it’s helping people!”
Essentially, this is my dream scenario…
[Image description: the romantic clay-molding scene from Ghost, where Demi Moore is labeled “my community”, Patrick Swayze is labeled “my STEM background”, and the clay is labeled “sustainable climate solutions”.]
…or, for this particular project…
[Image description: ditto, except Patrick Swayze is labeled “me” and the clay is literally clay.]
This is what I mean when I talk about “engineering for community resilience”. Climate change is here, and as the temperatures get hotter, we need sustainable cooling solutions that are designed by and for the communities that they serve. If engineers can work with their communities to create imaginative and artistic solutions to problems, we can weather any heat wave, storm, or winter that the world throws at us. As an engineer, this is my responsibility!
How about you? Are you an engineer who’s applying your academic know-how in your community? If not, what are some problems in your community that you could use an engineer to help solve? Let me know in the comments or DM me on social media with your ideas!
Currently Reading
Most of my time this week was spent unpacking boxes, but I did pencil in some time for analog doomscrolling (this is what I call paper news). The same day I moved into my new place, a copy of the area’s local newspaper showed up in mailbox (without me ever requesting one). Jokes aside, it has been extremely useful in telling me what’s going on around these parts. Apparently just a town over in Amherst, teachers are striking for better working conditions. Also, the town now has a non-police affiliated, BIPOC-led community task force to respond to non-violent emergency calls and “to be a general resource for people experiencing homelessness, mental health issues, substance abuse, youth and more”. Based!! These are amazing stories and I never would have heard about them without the local news covering them! The paper also included an op-ed summarizing all the candidates up for local election in November, as well as a ranking of the top 10 ice cream places in the county; both are critical information that I was clueless on until now. READ YOUR LOCAL PAPER!!
Watch History
F.D Signifier makes fantastic video essays about the Black male experience. His latest on the sexual objectification of Black men is wonderful, and even includes the perspectives of Black trans men and Black sex workers. Go watch this (and, honestly, all of his videos)!
A smaller channel, Them Fatales, just put out a video on the racism still present in mainstream Italian culture. It’s worth the watch, and even makes connections to homophobia, transphobia, and fatphobia.
Bops, Vibes, & Jams
Lucy Dacus covered Cher’s “Believe” and it’s honestly beautiful.
Quick Actions
Talk to your neighbors if you haven’t recently! Ask how they’re managing in the heat, if they need someone to check in on their animals while they’re at work, or just generally how they’re doing. It’s always worth being on good terms with the people you live around! (Yes, I am bullying you into reading your local paper and talking to your neighbors. I am 80 years old.)
And now, your weekly Koko.
That’s all for now! See you next week with more sweet, sweet content.
In solidarity,
-Anna