three statements of the second law establish the theoretical performance for systems undergoing cycles while interacting with thermal reservoirs

power cycle efficiency

refrigeration cycle

heat pump cycle

Key Terms and Concepts

• Clausius statement - states that it is impossible for any system to operate in such a way that the sole result would be an energy transfer by heat from a cooler to a hotter body

• thermal reservoir - a special kind of system that always remains at a constant temperature even though energy is added or removed by heat transfer

• Kelvin-Planck statement - states that it is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

• entropy statement - it is impossible for any system to operate in a way that entropy is destroyed

• irreversible process - when the system and all parts of its surroundings cannot be exactly restored to their respective initial states after the process has occurred

• reversible - if both the system and surroundings can be retured to their initial states

• irreversibilities

  • heat transfer through a finite temperature difference

  • unrestrained expansion of a gas or liquid to a lower pressure

  • spontaneous chemical reaction

  • spontaneous mixing of matter at different compositions or states

  • friction-sliding friction as well as friction in the flow of fluids

  • electric current flow through a resistance

  • magnetization or polarization with hysteresis

  • inelastic deformation