Thermodynamics Basic Definitions and Relations

Thermodynamics, a science which deals with the heat and work relationship, Its concepts are almost all based on the experimental studies and depends on the properties of the substances. Three thermodynamics laws govern the whole principle of studying “what is thermodynamics?”. Thermodynamics course starts with an introduction of a system and its state of stability, any way thermodynamics confuses at a start and by practical experiences, this can be overtaken in time. While starting the course one should have to know some of the basics of heat, temperature and physical properties like specific heat, heat capacity, molar specific heat, etc,. With the following document thermodynamics, basics are explained that helps to understand and solve some of the example problems easily.

 Basic concepts in thermodynamics

To handle and solve the thermodynamics problems some of the basic definitions are to be known for easy calculations. All the properties of the system are related to one another and these relations can be used for solving and designing the thermodynamics systems like heat exchangers, pumps, turbines, etc. Some of the relations which help during equipment and process designing are internal and external energy change, enthalpy change, Gibbs free energy change, Helmholtz free energy change and Maxwell relations. Pressure and Temperature play the game of control of the properties which change the system of operation. If one property kept constant then other left out properties adjust for the optimum value, so a PVT relation is much to be considered for two-phase systems. Two of the most commonly used equation for solving the two-phase flow systems are Clapeyon equation and Clausis-Clapeyron Equation. In the same way, their is another equation which gives relation between the vapour pressure and the absolute temperature of the fluid system is Antoine Equation.

Thermodynamics have three important diagrams which are:

  1. T-S diagram (Temperature Vs Entropy)
  2. P-H diagram (Pressure Vs Enthalpy)
  3. H-S diagram (Enthalpy  Vs Entropy)

Thermodynamics relations and equations