Heat Engines

 

Thermodynamics, Cengel

Work can easily be converted to heat directly and completely, but converting heat to work requires the use of some special devices. These devices are called heat engines. Heat engines differ considerably from one to another, but all can be characterized by the following:

1. They receive heat from a high temperature source (solar energy, oil furnace, nuclear reactor, etc)

2.  They convert part of this heat to work (usually in the form of a rotating shaft)

3.  They reject the remaining waste heat to a low temperature sink (the atmosphere, rivers, etc)

4.  They operate in a cycle.

Heat engines and other cyclic devices usually involve a fluid to and from which heat is transferred while undergoing a cycle.

The term heat engine is often used in a broader sense to include work -producing devices that don't operate in thermodynamic cycles.