APPLIED THERMODYNAMICSEL 325 (3+0)

Recommended Books

Fifth Editions of:1. Basic Engineering Thermodynamics, By Rayner Joel2. Applied Thermodynamics, By T.D. Eastop

POINTS TO BE NOTED

Give respect have respect. Any kind of disturbance in the class is strictly prohibited. Cell phones must be in silent mode. No assignments or quizzes would be entertain AFTER DUE DATE. Class CR would collect the assignment and submit to me in my

office. The course outline and book list is available at my intranet link:

\\colonel\faculty share\TE\ahussain\Applied Thermodynamics Try to be punctual in the class, it may be possible that the door

would be locked after 10 minutes. NO COMPENSATION IN ATTENDANCE in any case Consulting Hours.

INTRODUCTION TO THERMODYNAMICS

Gross Domestic Product=GDP

Some application areas ofthermodynamics.

APPLICATION

What is Thermodynamic?

The name thermodynamics stems from theGreek words thermo(heat)anddynamics(power)

It is the study of heat related to matter inmotion.

Thermodynamics is the science of energyconversion involving heat and other formsof energy, most notably mechanical work.

This course : basic concepts + laws + fluidproperty + fundamental process +cycles +applications.

Without thermodynamics engines-petrolengines, gas turbines, steam turbines, etc-modern industrial society could not survive.

But there is the exploitation of natural finiteglobal resources, e.g. oil and coal.

Results in massive atmospheric pollution

As humankind insists, at present, on thecontinuance of industrial societies, a studyof engineering thermodynamics remainsessential.

WORKING SUBSTANCE: All thermodynamics system require

working substance.

In order that the various operationsrequired by each system can be carriedout.

Generally fluids are working substance.

Which are capable of deformation in thatthey can readily be expanded andcompressed.

It also takes part in energy transfer.

It can reject or receive heat energy orit can be the means by which work isdone.

Common examples of WorkingSubstance: Air and Steam.

PURE SUBSTANCE:

Substance with fixed chemical composition Can be single element: Such as, N2, H2, O2

Compound: Such as Water, H2O Mixture such as Air, Responsible for the receiving and removing

dynamic energy (working fluid) Example: Steam, water or a mixture of steam and water.

THERMODYNAMIC SYSTEM.

A thermodynamic system (a physical system) is aprecisely defined macroscopic region of theuniverse that is studied.

If the properties of a particular mass of asubstance, such as its pressure volume andtemperature, are analyzed, then the analysis issaid to be macroscopic.

In thermodynamics – “system is a closed region inspace or a body upon which experiments or studyis conducted”.

Changes in a system are associated with the transfer ofenergy

Surrounding: Every thingapart from system is called assurroundings

Universe: Both system andsurrounding together is calledas universe

Boundary: The invisible layerwhich separates system andsurrounding is called boundary

Control volume: Themaximum volume occupied bya system is called controlvolume

TYPE OF SYSTEMS

Closed System. Open System. Isolated System.

PROPERTIES In the macroscopic analysis of a substance any

characteristics of a substance is observed or measured iscalled a property of substance.

In thermodynamics, properties are the quantities used todetermine the state of a system.

Types of properties Internal or Thermostatic property- is dependent upon

the physical and chemical structure of the substance.E.g. Pressure, volume and temperature.

Intensive properties: These are independent of mass.Eg: pressure, temperature, time, etc.

Extensive properties: These are dependent on mass.Eg: mass, density, specific heat, etc.

State: In thermodynamics state is the term used to denote the

present conditions of the system.

If a property, or properties are changed then the state ischanged.

Properties are independent of any process which anysubstance may have passed through from one state toanother. Being dependent only upon end states.

At the particular state, a substance will have certainproperties which are the functions of that state.

PHASE CHANGE OF WATERPHASE CHANGE OF WATER

P = 100 kPa

T = 150 C

P = 100 kPa

T = 150 C

H2O:SuperVapor

H2O:SuperVapor

Qin

P = 100 kPa

T = 99.6 C

P = 100 kPa

T = 99.6 C

H2O:Sat. VaporH2O:Sat. Vapor

Qin

H2O:Sat. Liq.

Sat. VaporSat. Vapor

P = 100 kPa

T = 99.6 C

P = 100 kPa

T = 99.6 C

Qin

P = 100 kPa

T = 99.6 C

P = 100 kPa

T = 99.6 C

H2OSat. liquid

Qin

P = 100 kPa

T = 30 C

P = 100 kPa

T = 30 C

H2O:liquid

Qin

Water interacts with thermal energyWater interacts with thermal energy

Units Of P=pascal

FIGURE 2-11T-v diagram for theheating process ofwater at constantpressure.

Saturation Temperature, Tsat,at 1 atm pressure.

Saturated Vapor

Saturation pressure,Psat,for 100°C

Saturated liquid

Fixed at a fixed pressure fora pure substance

SYSTEM WORK When work is done by a

thermodynamic system, it is ususllya gas that is doing the work. Thework done by a gas at constantpressure is:

For non-constant pressure, thework can be visualized as the areaunder the pressure-volume curvewhich represents the processtaking place. The more generalexpression for work done is:

Its unit is J (joules). Sign conversion

+ for work taken from a system- For heat given to a system

INTERNAL ENERGY (U OR E)

is the total of the kinetic energy due to the motion ofmolecules (translational, rotational, vibrational) and thepotential energy associated with the vibrational andelectric energy of atoms within molecules or crystals.

INTERNAL ENERGY

• Internal energy is defined as the energy associated withthe random, disordered motion of molecules.

Energy available within a system is called as internalenergy.

leaving the term heat to be used to describe that energytransfer process which results from a temperaturedifference.

Internal energy is a function of degree of randommotion, so it must be a property.

It is denoted by the symbol ‘U’.

Change in internal energy is denotedby the symbol ‘ U’.

Its unit is J (joules).

Internal Energy (U or E): (measured in joules)- Sum of randomtranslational(the energy dueto motion from one location toanother).,rotational(the energy due torotational motion),and vibrationalkinetic (the energy due tovibrational motion)energies

U: change in UU > 0 is a gain of internal

energyU < 0 is a loss of

internal energy----------------------------------Thermal Energy:same as internal energy

Vibrational kineticenergy in solids.The hotter theobject, the largerthe vibrationalkinetic energy

Motions of adiatomicmolecule in afluid

HEAT

HEAT

The transfer of energy as a result of atemperature difference is called heat.

“In TD heat is NOT an even a form ofenergy; heat is a mode of transfer ofenergy”.

“Heat is the transfer of energy by virtueof a temperature difference”.

“Heat is the name of a process, not thename of an entity” .

Hence it is not a property because heatenergy ceases to exist when the processfinishes.

It is given by symbol Q.

EQUILIBRIUM STATE

THERMAL EQUILIBRIUM

when two objects are placed incontact heat (energy) is transferredfrom one to the other until theyreach the same temperature (are inthermal equilibrium). When theobjects are at the same temperature.

THERMAL EQUILIBRIUMSystems (or objects) are said to be in thermal

equilibrium if there is no net flow of thermal energyfrom one to the other. A thermometer is in thermalequilibrium with the medium whose temperature itmeasures, for example.

If two objects are in thermal equilibrium, they are atthe same temperature.

Specific heat or specific heat capacity, c

Ti

TfT= Tf -Ti

QT

mc

Mass of object mSpecific heat (capacity) c Q mc T

heatQ

NO phase change during temperature change

Specific heat

Substance c (J.kg-1.K-1)

Aluminum 910

Copper 390

Ice 2100

Water 4190

Steam 2010

Air 1000

Soils / sand ~500

Process:

If a system experiences changes in state, then it iscalled as process

some special processes: isobaric process - constant pressure process isothermal process - constant temperature

process isochoric process - constant volume process isentropic process - constant entropy process

• Path series of states which a system passes through

during a process

STATE POSTULATE & CYCLES

• Cycles A process (or a series of connected processes) with identical

end states

WorkIf a system exists in which a force atthe boundary of the system is movedThrough a distance, then work is doneby or on the system. the force ceasesto beMoved, it ceases to do any work. workis therefore a transient quantity.It describes a process by which a forceis moved through a distance. work,beingA transient quantity, is therefore not aproperty.

Work is given the symbol W .If it isrequired to indicate a rate at whichwork isBeing done then a dot is placed overthe symbol W.

W=work done/unit time

Work and the Pressure-Volume Diagram

A Cylinder in which a fluid at pressure P is trapped using a piston of area A.The fluid here is the system.

Force on piston=pressure x area =PA ------------ eq (1)

Let this force PA be just sufficient to overcome some external load.Now let the piston move back a distance L along the cylinder while at theSame time the pressure of the fluid remains constant. This force on the pistonWill have remained constant.

Work done=force x distance ---------------- eq (2)Work done=PA x L

This equation could be rearranged to readWork done=P x AL

AL=Volume swept out by the piston, called the swept or stroke volume=(V2-V1)

Work done=P(V2-V1) ------------------------ eq. (3)

The graph appears as horizontal straight line ab whose height is at pressure Pandwhose length is from original volume V1 to final V2.

Area=P(V2-V1) --------------------------eq.(4)If the pressure is in newtons (N/m2) and the volume is in cubic meters(m3)then,By equation [3],the work done is given by the product of pressure and changein volume.

Units of work done=N/m2 xm3=Nm ---------------------eq. (5)

The unit, Nm (newton-meter) is the unit of work, the joule.1 Nm=1 J

Work and the Polytropic Process

Work and the hyperbolic Process

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