Introduction to Engineering Thermodynamics Thermodynamics System State and Property Thermodynamic Equilibrium Quasi-static Process

1. PREPARED BY: DHAVAL

2.  Introduction
 Thermodynamics System
 State and Property
 Thermodynamic Equilibrium
 Quasi-static Process

3.  What is THERMODYNAMICS?
 Thermodynamics is the science which deals with energy transfers and its effect on
the condition of a system.
 This study of science has led to the various laws of thermodynamics.
1. The zeroth law – concept of equality of temperature, thermal equilibrium.
2. The first law – law of conservation of energy, internal energy.
3. The second law – direction of flow of heat, concept of entropy.
4. The third law – absolute zero of entropy.

4.  A thermodynamic system is defined as a
fixed mass in a region of space under
consideration to analyse a problem.
 The system is identified by a boundary
drawn around the system where the
boundary can be classified as 1) rigid or
flexible and 2) real or imaginary.
 Everything external to the system is called
surroundings.
 Universe is the sum system and
surroundings.

5.  Classification of Thermodynamic Systems:
1. Closed system – no mass transfer, only energy transfer.
2. Open system – both mass and energy transfer across the boundary.
3. Isolated system – no mass or energy transfer takes place.

6.  State – the identification of the system by observable or measurable
characteristics is called the state of the system.
 Property – thermodynamic co-ordinates representing a system are called
properties of the system.
 Properties are classified as,
1. Intensive properties – independent of mass e.g. pressure, temperature,
viscosity, etc.
2. Extensive properties – depends on mass e.g. length, volume, all forms of energy,
entropy.

7.  A system is said to be in thermodynamic equilibrium which is incapable of any
change of its macroscopic properties and is in complete balance with its
surroundings.
 A system will be in thermodynamic equilibrium if it satisfies the condition of
mechanical, thermal and chemical equilibrium.
 Mechanical equilibrium – no unbalanced forces
 Thermal equilibrium – uniform temperature
 Chemical equilibrium – absence of any chemical reaction

8.  Quasi means almost slow or infinitely slow.
 A quasi-static process is defined as a process in which the properties of the system
depart infinitesimally or extremely small from the thermodynamic equilibrium
path.
 A quasi-static process is also called a reversible process.
 It is a succession of equilibrium states.