INTRODUCTION OF THERMODYNAMICS | FULL NOTES OF THERMODYNAMICS | FOR GATE AND ESE AND ALL COMPPPETETIVE EXAMINATION

 INTRODUCTION :-

THERMODYNAMICS IS THE science of energy transfer and its effect on the physical properties of substances. 

THERMODYNAMICS SYSTEM :-

A thermodynamics system is defined as a quantity of  matter or a region in space upon which attention is concentrated in the analysis of a problem . 

everything external to the system is called the surrounding or the enviroment . the system is seperated from the surrounding by the system boundary . 

THERE ARE THREE CLASSES OF SYSTEM :-

1) closed system 

2) open system 

3) isolated system 

1) CLOSED SYSTEM ;-

A system of a fixed mass . There is no mass transfer across the system boundary . there may be energy transfer into or out of the system . 

2) open system :-

the open system is the one  in which matter cross the boundary of the system . there may be energy transfer also . most  of the engineering device are generally open systems. 

3)isolated system :-

• a system is which there is no intraction between the system and the surrounding . there is no mass and energy transfer across the system boundary .
• any operation in which one or more of the properties of a system change of state is called a change of state.
• the succession of state passed through during a change of state is called the path ,
• A thermodynamic cycle is defined as a series of state changes such that the final state is indentical with the initial state .

 

PROPERTIES MAY BE OF TWO TYPES:-

INTENSIVE PROPERTIES :- it is a properties are independent of the mass of the system . PRESSURE , TEMPERATURE.

EXTENSIVE PROPERTIES :- Dependent to mass . VOLUME , ENERGY , The value of mass is increased the value of the extensive properties also increases .

Extensive properties per unit mass are called intensive properties. ex:- specific volume , specific volume , density etc.

HOMGENOUS AND HETROGENOUS SYSTEM ;-

A system considering of a single phase is called a  homogenous system. while, a system considering of more than one phase is known as a hetrogenous system.

THERMODYNAMICS EQUILIBRIUM:-

A system is said to exist in a state of thermodynamics equilibrium when no change in any macroscopic property is registered , if the system is isolated from its surrounding .

A SYSTEM WILL BE IN A STATE OF THERMODYNAMICS EQUILIBRIUM IF THE CONDITIONS FOR THE FOLLOWING THREE TYPE OF EQULIBRIUM ARE SATISFIED:-

• MECHNICAL EQUILIBRIUM
• CHEMICAL EQUILIBRIUM 
• THERMAL EQUILIBRIUM

When the  condition for any one of the three type of equilibrium are not satisfied a system is said to be in non-equilibrium state.

QUASI -STATIC PROCESS 

Infinite slowness is the characteristics feature of a quasi static process.

PURE SUBSTANACE:-

A pure substance is defined as one that is homogenous and invariables in chemical composition throughout its mass . The relative propertition of the chemical elements constituting the substance are also constant.

CONCEPT OF CONTINUUM:-

FORCE:-

The force acting on a body  is defined as newton second law of motion . The unit of force is the newton (N). A force of one newton produces an accleration of 1 m/s2 when applied to a mass 1KG .

1 N = 1KG M /SECOND SQURE

The value of g at sea level is 9.8m/s2.

PRESSURE:-

pressure is the external normal compressive force exerted by a system against unit area of the boundary surface. delta Fn is the component of force normal to delA.

Unit of pressure is pascal  . which is the force of one newtons acting on a area of 1metre square .

GAUGE PRESSURE ;-

the pressure relative to the atmosphere is called gauge pressure :

ABSOLUTE PRESSURE>ATMOSPHERIC PRESSURE:-

P gauge = P abs - P atm 

WHEN P abs < P atm:-

P vac = P atm - P abs                                       the unit oF 1mm of HG PRESSURE IS CALLED TORR.