Diesel engine.
Diesel cycle

Endothermic engine



Thermodynamics is the part of physics that deals with the relationship between heat and work. It studies the effects of the variation of pressure, temperature and volume of a physical system (we understand by physical system a liquid, a material, a set of bodies, etc.), at a macroscopic level, that is to say, that can be observed.

The term thermodynamics comes from the stem therm, which means heat and dynamics that refers to movement. The movement of heat in a body.

Matter is composed of different particles that move in a disordered way (what is called entropy). Thermodynamics studies this disordered movement.

Thermodynamics is of great importance because it describes a large number of physical phenomena, including the operation of thermal engines.

Study of thermodynamics

The main elements that we have to study thermodynamics are:

  • The laws of thermodynamics. These laws of thermodynamics define the way in which energy can be exchanged between physical systems in the form of heat or work. There are 4 laws of thermodynamics that are listed beginning with the zero law of thermodynamics.
  • Entropy. Entropy defines the disorder in which the internal particles that make up matter move. Entropy is a quantity that can be defined for any system.

In thermodynamics, the interactions between different systems are studied and classified. This study leads to define concepts such as thermodynamic system and its contour. A thermodynamic system is characterized by its properties, related to each other by the state equations. These can be combined to express the internal energy and thermodynamic potentials, useful for determining the equilibrium conditions between systems and spontaneous processes.

With these tools, thermodynamics describes how systems respond to changes in their environment.

Historical evolution of thermodynamics

In the beginning, technological developments, such as the so-called steam engines or thermometers, were carried out empirically. But it was not until the nineteenth century when scientists like Carnot and Joule formalized their results and determined the theoretical causes of their functioning.

Initially, thermodynamics was studied to increase the efficiency of the first steam engines.

Applications of thermodynamics

Thermodynamics can be applied to a wide variety of science and engineering topics, such as motors, phase transitions, chemical reactions, transport phenomena, and even black holes.

The study of thermodynamics is of great importance in thermal engines. The diesel cycle, the Otto cycle or the steam engine or the Stirling engine have a close relationship with thermodynamics and its laws because there is an exchange of heat in all of them.

The results of thermodynamics are essential for other fields of physics and chemistry, chemical engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, and materials science to name a few.

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Last review: August 30, 2017