Engineering Thermodynamics



The name thermodynamics stems from the Greek words Therme (heat) and Dynamics (power). Thermodynamics is the branch of science which deals with energy and energy interactions and its effects on system and surrounding.

Applications of Thermodyanics

Major applications of thermodynamics are in

  1. Human heart’s pumping system
  2. Aircraft, Aeroplane &Aerospace,
  3. Steam Boiler, Steam Turbine, Power Plant,
  4. Fluid Mechanics & Fluid machines,
  5. Modes of heat transfer-Conduction, Convection & Radiation
  6. Refrigeration system &Air-conditioning
  7. Home appliances,
  8. Automobile or Internal combustion engine,

Basic Terms used in Thermodynamics

1. Thermodynamic System-It is a fixed mass or region in space where our study is focused.

2. Surrounding Everything except the system becomes surrounding.

3. Boundary It is a real/imaginary surface that separates the system from its surrounding. Boundary can be fixed /movable.

Figure- Boundary, System, Surrounding in thermodynamics.

Also read: Internal Combustion EngineSteam BoilersPUMP

Types of Thermodynamics System

a)  Closed system

b)  Open system

c)  Isolated system

a) Closed System

It is also known as a control mass. It consists of a fixed amount of mass and no mass can cross its boundary. But energy interaction can take place between system and surrounding. Example:- I.C. Engine without valve, Putting a lid on a cooker makes a closed system etc.

b) Open System

It is also known as control volume. It usually enclosed a device that involves mass flow such as a compressor, turbine or nozzle. Both mass and energy can cross the boundary of a control volume. Example: Turbine, Nozzle, Compressor etc.

c) Isolated System

It is a special case, where energy and mass are not allowed to cross the boundary, that system is called an isolated system

Example:- Universe.

Some fundamental terms used in Thermodynamics

1. Property

Any characteristics of a system is called a property.

1.1 Properties of system

Property is any characteristic of the system. Like for an example:- Pressure (P), Temperature (T), Volume (V), mass (m), velocity, viscosity, Thermal conductivity (k), thermal expansion coefficient (alpha) and electric resistivity etc.

Properties are considered to be of two types first is intensive/intrinsic property and second is extensive/extrinsic property.

1.1.1 Intensive/Intrinsic properties

Those properties which are independent of mass of system, known as Intensive properties.

Example: Temperature, Pressure & Density.

1.1.2 Extensive/Extrinsic Properties

Properties which are dependent on the mass of a system, known as Extensive properties.

Example:-  Enthalpy, Entropy, Energy, Volume etc.


Extensive properties per unit mass are called specific properties and these properties are known as Intensive properties.

Specific Volume, v = V/m

Specific Energy, e=E/m

All specific properties are intensive properties.

Important points with respect to properties:-

  1. Properties are point functions.
  2. Properties are independent of past history
  3. Properties are exact differentials.

2. State

Consider a system not undergoing any change. At this point, all properties can be measured or calculated throughout the entire system, which gives us a set of properties that completely describes the condition or the state of the system. If property changes state changes.

3. Equilibrium

A thermodynamic system is said to be under equilibrium if it satisfies the following equilibrium conditions: –

a) Thermal Equilibrium

If the temperature is same throughout the system.

b) Mechanical Equilibrium

A system is in the mechanical equation if there is no change in pressure at any point of the system with time.

c) Phase Equilibrium

When the mass of each phase reaches an equilibrium level.

d) Chemical Equilibrium

A system is in chemical equilibrium if it’s chemical composition does not change with time.

4. Process

   Any change that a system property undergoes from one equilibrium to another is called a process & the series passes during a process is called the path of the process. To describe a process completely, one should specify the initial and final states of the process as well as the path it follows, and the interaction with the surrounding.

5. Cycle

   A system is said to have undergone as cycle if it returns to its initial state at the end of the process, That is for a cycle the initial and final states are identical.

Basic of Thermodynamics [Complete Notes]

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