Question

What does a heat engine consist of?

Answer 1

A typical heat engine has the following elements:

A working substance: It is called the system. It can be an ideal gas for an ideal heat engine (to be discussed later). For a practical heat engine, the working substance can be a mixture of fuel vapour and air in a gasoline (petrol) or diesel engine, or steam in a steam engine. It is the working substance that absorbs heat and does work.

Hot and cold reservoir: The working substance interacts with the reservoirs. The hot reservoir is the source of heat. It is at a relatively high temperature and is capable of providing a large amount of heat at a constant higher temperature, T_H. It is also called as the source. The cold reservoir absorbs a large amount of heat from the working substance at a constant lower temperature, T_C. It is also called as the sink.

Cylinder: Generally, the working substance is enclosed in a cylinder with a moving, frictionless, and massless piston. The working substance does some work by displacing the piston in the cylinder. This displacement is transferred to the environment using some arrangement such as a crank shaft which transfers mechanical energy to the wheels of a vehicle.