As I shared earlier (here), a significant challenge confronting me in writing my second book is that I have many unanswered questions regarding thermodynamics’ micro-to-macro connections. I have begun the process of answering these questions by listing them all here and then creating individual pages for each with the intent to share my ongoing progress in answering them or at least presenting where I’m at and hoping you, the reader, could help me in answering them. Since I committed to sharing progress at certain intervals, here’s where I’m at with three questions. Please check out my thinking and see where you can help. Thank you in advance.
Adiabatic compression. Why doesn’t the speed of the piston matter?
I believe that the answer to this question is that while an increase in speed of the inward moving piston results in an increase in the speed of the rebounding atoms, it also decreases the amount of time required to arrive at a fixed final volume. So the molecules gain more energy but spend less time gaining that energy such that the total energy gained (due to the work of the piston) is the same, regardless of piston speed. I share an obscure technical paper that supports this thinking.
I hypothesize that the J-T effect is due solely to the attractive forces between molecules; the repulsion forces play no role. The critical issue is then the speed of the moving molecules. Faster speeds, caused either by higher temperatures for fixed composition or lower molecular weight for fixed temperature (think hydrogen), decrease the significance of the attractive forces as manifested by a decrease in cooling effects, and beyond a certain point only the delta (PV) term remains. This term seems to be negative, for reasons I don’t fully understand, and so with increasing speeds and thus decreasing attraction/cooling effects, heating results.
Does combustion destroy exergy?
Despite what the literature says, my calculations suggest it doesn’t. Please check out my calculations to see if they are valid.
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