What properties are necessary for Enclosability, and what are its characteristics?

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Is the property of Enclosability necessary and Sufficient for a 100% efficient engine? Yes.

Necessary Conditions

  1. The conversion to work must be loss-less. It must produce only Work and Heat, total equaling the given amount of Fuel Heat. Strict Reversibility meets this requirement, so is sufficient, but not necessary in general. (All conversions of energy are "loss-less" in some sense. Here, we mean the end energy product is not converted to a useless form of energy, light, sound, changes in solid or liquid materials, chemical, etc.)
  2. Because a volume once expanded may not revert to its original state, unless something external also changes, the minimum number of constrained volumes is 2.
  3. No Fuel Heat is diffused outside the Heat Engine.
  4. Either
    • In Steady State, the Pressure Envelope will maintain the same average temperature.
    • Or, A Pressure Envelope is not needed for operation. The Engine can run in a vacuum.
  5. All Fuel Heat is converted to work, or retained.

Unnecessary Conditions

  1. Transient behavior is ignorable.
  2. Cyclic changes to Pressure Envelope are ignorable, provided they do not trend. (Pressure, Temperature., Volume)
  3. Heat Engine may or may not intake and exhaust its working vapor, provided the exhaust contains no Fuel Heat.
  4. Chemical changes (combustion of Oxygen), are ignorable, as not directly related to Heat Engine, but to its source of heat. "Heat" is the fuel of the heat engine. How heat is provided is unrelated to Heat Engine efficiency.

Properties of an Enclosable Heat Engine

Simply stated, one can place an Enclosable Heat Engine in a confined space, a room, and run it indefinitely without increasing the heat of the room air. The engine gets heat from a heat source other than the enclosure, and produces work, exported from the enclosure.

An Enclosable engine may retain fuel heat, but it must be stable or cyclic.

Since no Heat leaves the Enclosable Engine, and only Work is exported, Conservation of Energy requires the added (fuel) Heat be equal to the exported Work.

In the steady state, the incoming Heat energy must exactly equal the outgoing Work energy,
so the engine is 100% fuel efficient.

Satisfying this property of loss-less conversion is sufficient to satisfy 100% efficient
operation. It is not necessary the heat to work transformation be reversible,
although with Vapor Engines, the conversion is reversible in the strict sense.

Real materials will not be ideal, so will limit actual efficiency to less than 100%. An Enclosable
Engine design will still approach 100% efficiency, with 90+% efficiency easily obtainable.

By way of analogy, Electricity takes the path of least resistance. Bare wires on the ground could lead to the erroneous conclusion that "Electricity is inherently inefficient" as power is lost due to grounding or shorts.
Insulated wires have neither perfect (infinite resistance) insulation nor perfect (zero resistance) conductors. However, Electricity passed through insulated wires can approach 100% efficiency at delivering electrical energy where needed.

Because of the necessary condition of no heat diffusion outside of the engine, it is likely a necessary characteristic of Enclosable Heat Engines to have Thermal Insulation, and Recycle Heat