Heat Engine

A heat engine is a machine that converts heat into mechanical energy, which may subsequently be used to perform tasks. It does this by decreasing an active substance’s temperature from a higher temperature. Thermal energy is generated by a heat source, which increases the temperature of the working material. The functional material causes work inside the engine’s functioning body while heat is transferred to a cooler sink until it cools to a low temperature.

Some of the heat energy is converted into work using the properties of the agonist. The active substance can be any system with a heat capacity other than zero but is most commonly a gas or liquid. During this process, some of the heat is lost to the environment and is not converted into work. Some of the energy cannot be used due to friction and drag.

Types of Heat Engine

The principle that determines the functioning of heat engines has been classified. Even though all of the tenets stem from Thermodynamics, each form of heat engine uses a distinct approach to convert heat energy to mechanical work. The following are some examples of several types of thermodynamic heat engines: 

1. Internal Combustion Engine: An internal combustion engine (ICE / IC engine) is a thermal engine that uses an oxidizer to burn fuel in a combustion chamber that is part of a working fluid (usual air) flow circuit. All components of an internal combustion engine are directly affected by the expansion of the hot and high-pressure gas produced by combustion. Force is usually directed at the piston, turbine blade, rotor or nozzle. By converting chemical energy into valuable kinetic energy, this force pushes, moves and propels everything the engine is bound to. It replaced the external combustion engine in situations where engine size or capacity was important. 

2. Stirling Engine: A Stirling engine is a heat engine that converts heat energy into mechanical work by periodically contracting and expanding air or another gas (hydraulic) at various temperatures. For example, a Stirling engine is a closed-loop regenerative heat engine with a constant gaseous working medium.

Components of a Heat Engine

The heat engine consists of three main components:

 Source: A heat source with an unlimited heat capacity should be maintained at a continuous high temperature. The amount of heat absorbed or added does not affect its temperature.

 Working material: This should be a material that collects or rejects heat to the sink. This is the active component.

Sink: A limited thermal capacity sink must be present and it must be maintained at a fixed high temperature such that no heat is taken or supplied and the temperature somehow doesn’t vary.

P-V Diagrams

PV diagrams (Pressure-Volume) are a common visualisation technique used to examine heat engines. Because gas is commonly used as an active ingredient in machines, the ideal gas law connects the PV diagram to temperature, allowing the three fundamental variables for gas to be tracked throughout the engine cycle. Furthermore, because labour is only done whenever the volume of a gas varies, the diagram depicts the work performed.

Because the energy of an ideal gas is proportional to temperature, the PV diagram, together with the temperatures determined using the perfect gas law, determines the changes in internal energy of the gas, allowing the first law of thermodynamics to be used to calculate the amount of heat added. In conclusion, the PV diagram serves as a foundation for analysing any heat engine that employs a gas as a functional ingredient.

Ideal Heat Engine

It is not easy to design a heat engine whose main function is to absorb heat from a high-temperature environment and convert it into work. It is impossible to create a heat engine that does not release heat to the environment. Alternatively, creating a heat engine with an efficiency of 1.00 or 100 cannot be achieved.

Conclusion

A heat engine works by using energy given in the heat and then exhausting the heat that cannot be used for work. The analysis of the interactions of heat and work is known as thermodynamics. The functioning of a heat engine is constrained by the first and second laws of thermodynamics. The first law applies energy conservation to the system, while the second restricts the machine’s maximum efficiency and defines the path of energy flow.