What rules, energy or entropy?

[Studiot]

One thing you cannot describe a Carnot cycle engine as is a constant volume process. None of the four legs on an indicator diagram occur at constant volume. I do not know of a mechanism (if that is the right word) that is capable of extracting work with the working fluid at constant volume in a carnot engine.

There is a type of heat engine known as constant volume ( or Rochas) cycle engine that has two of the legs vertical (const vol)and two with the adiabatic gamma law expansion.

Another type with a (single) constant volume leg and a single adiabatic leg is the Lenoir gas engine.

However work is only only during the non constant volume parts of each cycle.

 

[Andrew Mason]

One thing you cannot describe a Carnot cycle engine as is a constant volume process. None of the four legs on an indicator diagram occur at constant volume. I do not know of a mechanism (if that is the right word) that is capable of extracting work with the working fluid at constant volume in a carnot engine.

There is a type of heat engine known as constant volume ( or Rochas) cycle engine that has two of the legs vertical (const vol)and two with the adiabatic gamma law expansion.

Another type with a (single) constant volume leg and a single adiabatic leg is the Lenoir gas engine.

However work is only only during the non constant volume parts of each cycle.

We are really going in circles now. Your concerns have nothing to do with whether an isolated system which is not internally in thermodynamic equilibrium will tend toward maximum entropy. I gave you a system that is not in thermodynamic equilibrium and showed you that it will end up in a final state of thermal equilibrium with zero entropy increase.

Why does the heat flow have to occur in a constant volume process? If heat flow occurs in a constant volume process, there will always be a net increase in entropy. It is only if heat flow occurs isothermally that there can be no increase in entropy. That is what occurs in a Carnot engine.

AM