Work Vehicle Entropy
Have you ever noticed that the more you’re required to speed up to get all your work done in a day, the more the cleanliness of your work vehicle suffers?
Some techs won’t clean their vans no matter how slow or busy the schedule gets, but for most of us, we prefer a clean and organized vehicle but in the really busy season it can slip a bit.
This is entropy at work
One way to think of entropy is the tendency for energy to be “wasted” or for energy to become more disorganized as it is changed from one form to another. In practical terms the higher the entropy the greater the waste in moving energy around and the lower the entropy the less energy is wasted or unusable.
When your van is clean you waste less energy trying to find what you need but that is easier to do when you aren’t “rushed”.
Don’t confuse entropy with enthalpy. Entropy is the measure of the “availability” of energy to do useful work, enthalpy is a measure of total heat content.
Another way to think of entropy is simply the tendency for everything to go from more organized to less organized over time.
When we talk about entropy in classroom settings when analyzing a pressure-enthalpy diagram of a refrigeration circuit like the one shown above. You will notice the red shape is nearly a rectangle other than the slanted line on the right that shows what happens when the refrigerant is compressed. Rather than going straight up and down it curves to the right to show that additional heat is added to the refrigerant (enthalpy) as it is compressed. This increase in enthalpy follows something called lines of constant entropy, in other words, as more energy is added to a system the faster the molecules move and the less organized they become.
As pressure and temperature increase, so (generally) does entropy, just like when it get’s hot and the dispatcher starts putting the pressure on you your van entropy also increases.
In a refrigeration circuit, the system will work more efficiently when we achieve the desired movement of BTUs with a minimal amount of entropy. Practically speaking this means using lower pressures and temperatures to move heat from one place to another when possible, but we still need to get the job done of moving heat from one place to another and in that process, entropy WILL occur.
We all know the guy who has the PERFECT van, the spotless tools and the clean uniform. His van stays that way because he hardly does anything and then he takes 20 minutes after every call wiping down and oiling his tools. He has very little entropy in his van because there is very little WORK being done.
Absolute zero is the temperature at which no molecular motion exists, in that state there is also no entropy. No heat, no work, no disorganization. More heat, more work, more disorganization (entropy).
So don’t use me as an excuse for a messy van, but if your boss hassles you too much on a busy day you can remind him. Heat and pressure result entropy and the back of that van… that’s entropy baby.
P.S. – For those of you engineering types I know that this article took some liberty with definitions. It’s an analogy, not a doctoral physics thesis.
Bryan Orr is a lifelong learner, proud technician and advocate for the HVAC/R Trade