Thermodynamics and the Industrial Revolution

The study of thermodynamics really took off at the end of the Industrial Revolution. Kind of like parachute pants and mullets in the 1980s, only more useful.

Need a fun refresher on the Industrial Revolution? Check out this video.

Before heat engines became an important part of how we manufacture things (and how people make big bucks), studying the laws of thermodynamics was sort of a nerdy-scientist-sitting-in-his-laboratory kind of thing to do. "Let's think about heat, temperature, and energy until our heads start spinning, just to better understand how the universe works," thought the scientists of yore. That's a noble undertaking, but clearly not for everyone.

Then came the Industrial Revolution. Suddenly, we humans no longer made everything by hand. Machines, such as the steam engine, did a lot of the work for us. We could then manufacture ten, twenty, fifty times as much in a day as we could before. Underlying all of this productivity and oodles and oodles of profit was what? Everyone's favorite engine, Thomas the Tank Engine. Well, no. The other favorite engine, the heat engine.

The importance of the heat engine to the Industrial Revolution gave all of the thermodynamic brain gymnasts a tangible (and again, can we say profitable?) purpose: to make better and better heat engines.

Heat engines work by turning heat into mechanical work. Heat is input into the engine, by, for example, heating steam, and that input of heat is turned into work, such as the steam rising and turning a turbine or a wheel. The problem for industrialists was the huge inefficiencies of the early heat engines. Very little of the input heat turned into mechanical work.

Also, input heat doesn't grow on trees. Well, we can use trees as fuel, but we still have to spend time and money growing and cutting down those trees. Or time and money mining coal, to burn and heat the steam that turns the wheel. The more input heat that turns into work, the less money it costs the industrialist to run his factory.

The French scientist, Sadi Carnot, realized the importance of improving heat engines. His 1824 discovery, that the most efficient heat engine is one that's reversible, was driven by his desire to keep up with British engineers and his belief that had the French possessed more efficient heat engines, the Napoleonic Wars could have ended quite differently. Finding a more efficient way to turn heat into work meant military and economic superiority—and if there's one thing industrialists love, it's military and economic superiority.

From there, the study of thermodynamics took off, and for a long time it was an engineering science focused mainly on continually improving heat engines. Just so you know, the maximum theoretical efficiency of a Carnot Engine is 63%, but in the real world 40% is pretty dang awesome. Think about that the next time you're stuck in traffic.