UY1: Concept of heat engines and heat pumps

A heat engine is a device that converts heat into mechanical energy.

Conceptualising the heat engine: The heat engine must carry a working substance (usually a gas) through a cyclic process in which the system passes through a series of states.

During the cycle: 

  • the working substance absorbs heat (Qh) from a hot reservoir
  • converts part of that heat into mechanical energy (i.e., work output by the engine Wout)
  • then expels the rest of the heat (Qc) to a cold reservoir to return to the initial state, and the cycle repeats.

All these cycles comprise of the following basic gas processes:

  • isothermal
  • adiabatic
  • isochoric
  • isobaric

Next: Isothermal Process

Previous: More about internal energy

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