applied thermodynamics(lecture 1)
TRANSCRIPT
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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