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CHAPTER-2

BASICS OF THERMODYNAMICS

Thermodynamics can be defined as the science which deals with the relation between

heat, work and properties of the system.

Use of Thermodynamics:

Designing work producing machine Heat engine, Steam engine, Gas turbine

Designing work Absorbing machine Refrigerator, Air compressor

No work transfer systems -boiler, condenser and furnace.

Where no work is transferred, the Thermodynamic problem involves the use of heat to

produce the change in state or the transfer of mass with a chemical reaction, as in the

combustion of a fuel.

2.1 LAW OF ENERGY CONSERVATION

Energy can neither be created nor be destroyed if mass is conserved.It is defined as the

internal energy remains unchanged if the system is completely isolated.

If Q=0; W = 0 then U =0

2.2 BASIC CONCEPTS

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System

Boundary

Surrounding

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2.2.1 System:

It can be defined as a definite quantity of matter, which is bounded by a closed surface.

a. Closed system:

It is a system in which energy alone is transferred and not mass.

b. Open system:

It is a system in which both energy and mass transfer takes place.

2.2.2 Surroundings:

Anything other than a system are called surroundings

2.2.3 Property:

The parameter which gives the quality or condition of the system is known as property.

Properties are classified as intensive and extensive properties

a. Intensive property:

Property which does not depend upon mass of the system is Intensive

property E.g. Pressure, Temperature, Thermal conductivity etc.

b. Extensive Properties

Property which depends upon mass of the system is Extensive Properties.

E.g. volume, mass, energy etc.

2.3 THERMODYNAMIC LAWS

2.3.1 Zeroth Law of thermodynamics:

If two bodies are in thermal equilibrium and a third body is in thermal equilibrium with

any one of the first two bodies, then it can be inferred that all the three bodies are

in thermal equilibrium.

2.3.2 First Law of Thermodynamics:

If any system is carried through a cycle then the summation of the work delivered to the

surroundings is proportional to the summation of the heat taken from the surroundings.

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2.3.3 Second Law of Thermodynamics:

First Law gives only energy balance. It does not mention anything about the direction of

energy transfer Thermal equipments can be identified only when the direction of energy

transfer is known.Second Law gives both energy balance and direction of energy transfer.

2.3.4 Boyles Law

If temperature remain constant, than volume is inversely proportional to temperature.

2.3.5 Charles Law

If pressures remain constant then volume is directly proportional to temperature.

2.4 THERMODYNAMIC PROCESS

2.4.1 Reversible process

A Reversible Processes for a system is defined as a process which once having taken

place, can be reversed and leaves no change in either the system or the surrounding.

Quasi static process is a reversible process. All natural or spontaneous processes are

reversible process.

2.4.2 Irreversible process

Any process which is not reversible is irreversible. All real and actual process is

irreversible processes.

2.4.3 Cyclic process

A process which repeated again and again called as cyclic process like Rankine cycle

2.5 THERMODYNAMIC CYCLES

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2.5.1 GAS POWER CYCLE

2.5.2 VAPOUR POWER CYCLE (RANKINE CYCLE)

2.5.3 COMBINE CYCLE

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BOILER

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