THERMODYNAMICS | DEFINITION, SCOPE, APPLICATIONS | THERMODYNAMIC SYSTEM

THERMODYNAMICS:

Thermodynamics is the science that deals with the conversion of heat into mechanical energy. It is based upon observations of common experience, which have been formulated into thermodynamic laws.

SCOPE OF THERMODYNAMICS IN THERMAL ENGINEERING:

Thermal engineering is a very important associate branch of mechanical, chemical, metallurgical,
aerospace, marine, automobile, environmental, textile engineering, energy technology, process engineering of pharmaceutical, refinery, fertilizer, organic and inorganic chemical plants. Wherever there is combustion, heating or cooling, exchange of heat for carrying out chemical reactions, conversion of heat into work for producing mechanical or electrical power; propulsion of rockets, railway engines, ships, etc., application of thermal engineering is required. Thermodynamics is the basic science of thermal engineering.

APPLICATIONS OF THERMODYNAMICS IN THE FIELD OF ENERGY TECHNOLOGY:

  1. Central thermal power plants, captive power plants based on coal.
  2. Nuclear power plants.
  3. Gas turbine power plants.
  4. Engines for automobiles, ships, airways, spacecrafts.
  5. Direct energy conversion devices: Fuel cells, thermoionic, thermoelectric engines.
  6. Air conditioning, heating, cooling, ventilation plants.
  7. Domestic, commercial and industrial lighting.
  8. Agricultural, transport and industrial machines.

All the above engines and power consuming plants are designed using laws of thermodynamics.


THERMODYNAMIC SYSTEM | CLOSED SYSTEM, OPEN SYSTEM AND ISOLATED SYSTEM:

Thermodynamic System:
In thermodynamics the system is defined as the quantity of matter or region in space upon which the attention is concentrated for the sake of analysis. These systems are also referred to as thermodynamics system.
It is bounded by an arbitrary surface called boundary. The boundary may be real or imaginary, may be at rest or in motion and may change its size or shape. Everything out side the arbitrary selected boundaries of the system is called surrounding or environment.

TYPES OF SYSTEM:
The analysis of thermodynamic processes includes the study of the transfer of mass and energy across the boundaries of the system. On the basis the system may be classified mainly into three parts.

  1. Open system
  2. Closed System
  3. Isolated system
  • Open System:

The system which can exchange both the mass and energy (Heat and work) with its surrounding. The mass within the system may not be constant. The nature of the processes occurring in such system is flow type.

  • Closed System:

The system which can exchange energy with their surrounding but not the mass. The quantity of matter thus remains fixed. And the system is described as control mass system.
The physical nature and chemical composition of the mass of the system may change.
Water may evaporate into steam or steam may condense into water. A chemical reaction may occur between two or more components of the closed system.

  • Isolated System:

In an Isolated system, neither energy nor masses are allowed to cross the boundary. The system has fixed mass and energy. No such system physically exists. Universe is the only example, which is perfectly isolated system.

In an Isolated system, neither energy nor masses are allowed to cross the boundary. The system has fixed mass and energy. No such system physically exists. Universe is the only example, which is perfectly isolated system.

OTHER SPECIAL SYSTEM:

  • Adiabatic System:

A system with adiabatic walls can only exchange work and not heat with the surrounding. All adiabatic systems are thermally insulated from their surroundings. Example is Thermos flask containing a liquid.

  • Homogeneous System:

A system, which consists of a single phase, is termed as homogeneous system. For example, Mi×ture of air and water vapour, water plus nitric acid and octane plus heptanes.

  • Hetrogeneous System:

A system, which consists of two or more phase, is termed as heterogeneous system. For example, Water plus steam, Ice plus water and water plus oil.

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