introduntion to thermo dynamics

7/29/2019 Introduntion to Thermo Dynamics

1/15

Introduction to Thermodynamics

System

-collection of matter(which has mass andoccupies space) within prescribed andidentifiable boundaries

open system-transfer of mass across boundaries

-exchange of heat and matter across boundaries

Closed system-exchange of energy but not matter


2/15

Heat

-form of energy transferred from one body to

other body due to temperature difference-Heat may flow across the boundary

-unit is J ,BTU. Calorie

- Denoted by Q , -Q(body releases)

- Q surrounding -Q body releases heat to

surroundings

- +Q body absorbs heat


3/15

Internal energy (U)

- The total energy contained by the

thermodynamic systemElements

-K.E (motion of system particles)

-P.E (static energy of atoms)

-Internal energy can be changed by heating

Or doing work on system


4/15

1st Law of Thermodynamics

- Energy can neither be created nor be

destroyed but it can change from one form toanother form.

- Change in internal energy=total heat added

and work done- +W work done on system andW work doneby the system

Temperature

- Degree of hotness or coldness

Pressure

-force applied per unit area of surface.


5/15

Enthalpy (H)

- Amount of energy in a system capable of

doing mechanical work

Entropy (S)

-Amount of energy in a system no longer

available for doing mechanical work.


6/15

Adiabatic Process

Occurring without loss of heat or gain

- Q=0 (heat added to system)

- 1st Law of thermodynamics

-

- Work done by the internal energy.

- Adiabatic compression

- gain in internal energy (+U)- Adiabatic expansion

- Loss of internal energy (-U)


7/15

gain in internal energy (+U) Loss of internal energy (-U)


8/15

Latent Heat

-Heat absorbed or radiated during a change of

phase at a constant temperature andpressure.


9/15

CARNOT CYCLE AND CARNOT ENGINE

2

nd

law- Indicates that in any complete cycle the gross

heat supplied plus the net work input must be

greater than zero.


10/15

-So thus for any cycle there is net work o/p ,

heat must be always rejected.

- For any cycle in which heat is supplied at lowtemperature and rejected at high

temperature.

- So there will be positive work input.- Applicable to any system involving heat

transfer.


11/15

CARNOT CYCLE AND CARNOT ENGINE

Nicholas Leonard Sadi Carnot, an engineer in

French army originated use of cycle (Carnot) inthermodynamic analysis in 1824 and these

concepts provided basics upon which second

law of thermodynamics was stated by Clausiusand others.

Carnot cycle is a reversible thermodynamic

cycle comprising of four reversible processes.


12/15

Thermodynamic processes constituting Carnot

cycle are:

(i)Reversible isothermal(a process or changetaking place at constant temperature) heat

addition process, (12, Qadd)

(ii)Reversible adiabatic expansion process (2

3, Wexpn +ve)

(iii)Reversible isothermal heat release process

(3

4, Qrejected) (iv)Reversible adiabatic compression process

(41, Wcomprve)


13/15


14/15

Gas turbine plant: Carnot heat engine


15/15

introduntion to thermo dynamics

Documents