That’s right! Let’s talk… thermo.
As in… Thermodynamics.
I know, I know. This is precisely nobody’s favorite subject. But hear me out on this, as someone who, probably just like you, hated Thermodynamics with the white-hot intensity of a thousand suns. Could be in my case that Thermo was one of only 2 “C’s” I was awarded as in my post-first-semester (which was a train-wreck) undergraduate career – that I was awarded said “C” after I was utterly (redacted)-over on the final exam for that class, which probably cost me graduating “with honors”, which I missed by precisely 0.003 grade-points…
Not that I’m bitter about any of that.
That is, until I had to teach it.
And then I learned something that utterly changed the way I thought about this particular branch of engineering/science/whatever. It’s this…
Thermodynamics. Describes. Literally. Everything.
No, I’m totally serious. As a heart-attack.
So why don’t we just get started in the hope that in this series of posts, which will be sprinkled-in over the next couple of months, I’ll be able to convince you of the true marvel that is Thermo.
So, what is this marvel, anyway?
Simply put: Thermodynamics is the science that treats of the movement (dynamics) of energy.
That’s it. Nope, it’s really not more complicated than that. All the rest is detail.
But it’s precisely the details that everyone gets hung up on.
Which is precisely why I’m going to try to keep this at the big picture level, at least for a while. Because, you see – literally everything is… energy. Literally. Everything.
So if you understand the movement of energy, you understand… everything. (OK, that’s perhaps an obscure, Gen-X reference, but I really love that line in a show I otherwise could have done without.)
Now that all sounds a little “woo-woo” and stuff, and I understand because I was right there with you for a decade or more. But I fully expect you’ll be right here with me now by the end of our discussions.
We mathematically defined several forms of energy in the previous post (link here, if you want a refresher). What we didn’t do is define energy conceptually. Energy can be thought of as the ability to cause changes. As such, Thermodynamics is the study of the storage, transfer, and transformation of that which causes change… energy.
Energy can be quantified into several different categories…
- Internal Energy (usually associated with temperature)
- Kinetic Energy (the energy of motion)
- Potential Energy (the energy of distance)
- Chemical Energy (the energy of composition)
Something important to know about energy, as it relates to “Systems” (which we’ll define presently), is that energy can be transferred across a system boundary in the form of Heat or Work. Further, energy can be transformed from one form to another (for example, the conversion of Potential into Kinetic Energy or Work into Heat). The study of this transformation is usually called Energy Conversion, or E-Con.
By a “system” we’re referring to a general Thermodynamic System. Now, we can make this really complicated, or we can simply state that a System, as we’re going to talk about it here, is a measurable, identifiable quantity of stuff (highly technical term, I know), with (important point here) identifiable boundaries. When we talk about Thermodynamics, we are always talking about Systems and Surroundings. The boundary constrains the System, and it’s across these boundaries that energy is transferred from the Surroundings to the System (or vice-versa) in the form of Heat or Work.
Systems are described as either being open, isolated, or closed. Closed Systems transmit energy across boundaries, but not material. Whereas open systems can have energy and/or matter flow across system boundaries. In contrast, isolated systems are insulated from the surroundings and cannot transfer energy or matter across system boundaries.
A brief history lesson
Let’s take a step back and get a quick overview of how Thermodynamics came about in the first place. With the development of the first steam engines in the 18th-century, contemporary engineers and physicists needed to develop the science of these creations, to better understand and optimize their operation. The fundamental laws of Thermodynamics were developed in the 1850’s, and relate to the quality (first law) and quantity (second) of Energy.
Classical Thermodynamics, the science developed over the 17th and 18th centuries, was developed first-and-foremost for the purpose in designing and analyzing large-scale systems. It is therefore concerned with the energy of a System as a whole. And the particular system these researchers were concerned about, were steam engines. As such, over the years developed a comprehensive set to tables describing the various properties of the most critical substance on our planet – water, and in particular, the gaseous form thereof – steam.
And so came to be the fabled… steam tables.
We’ll be talking a great deal about steam tables as we go along.
Just for the sake of completion, the branch of thermodynamics that is principally concerned with energies at the molecular level is known as Statistical Thermodynamics.
As stated previously, literally everything is energy. Thus, though there is little surprise that Thermodynamics is broadly applied in the power and energy industries, there is little in science, engineering, and for all intents and purposes life, that cannot be explained from a thermodynamic perspective.
For example, A.A. Griffith developed the modern theory of fracture mechanics by employing the first law of Thermodynamics to balance the strain energy (potential energy) associate with the asymptotic field around a crack tip against the energy required to create a unit amount of free surface (surface energy, also a form of potential energy). Griffith’s theory greatly demystified many long-used but poorly understood manufacturing processes. The aircraft industry, in particular, was able to make a quantum leap in the safety and robustness of their products by smartly applying Griffith’s theory.
Well, I’m noticing my typing is getting sloppy though I’m barely into 4-pages of my lecture notes (a mere 116 or so to go!). So I believe I’ll leave it at that for now. Stay tuned for our next talk about this fascinating and important subject, where we’ll dive a little deeper into systems, introduce the concept of control volumes, and begin a multi-post discussion regarding properties and states of systems.
Strap in lasses and lads, it gets all the more fun from here!