CHAPTER - 1 Thermodynamic Review

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Power Plant Engineering Thermodynamic Review

1 Created by: Assistant Professor Dr. Mishaal AbdulAmeer AbdulKareem ... [email protected]

Chapter(1)ThermodynamicReviewSystem: Itisacollectionofmatterinsideanidentifiedboundary.Surroundings: Istheregionlocatedoutsidethesystemboundaries.Boundary: Istheinterfacebetweenthesystemanditssurroundings.ClosedSystem: A system with a real boundaries (fixed or moving), in

whichthereisNOtransferofmassacrossitsboundaries,(tank,pistonandcylinder).

OpenSystem: Asystemwithrealand/orimaginaryboundaries,inwhich

thereisatransferofmassacrossitsboundaries,(turbine,compressor,pipe,..)

Figure(1)

Boundary

SurroundingSystem

Figure(2)Closedsystem

Figure(3)Opensystem

Q

Tank System

Surrounding BoundaryPiston

System Pipe

Boundary

Surrounding

1 2

System

Boundary Turbine

1

2

Cylinder



IsolatedSystem: It is one in which neither mass nor energy cross theboundaries,butinwhichenergytransformationmaytakeplaceinsidetheboundaries.

WorkingFluid: It is the matter content within the boundaries of the

system,itcanbeliquid,vapororgas.Thestateoftheworkingfluid:Itisdefinedbyacertaincharacteristicscalled

properties, , , , , .Process:Itbeginsatonestateoftheworkingfluidandendsatanother.Cycle:Itisaseriesofprocessesthatbeginsandendsatthesamestate.The 1st Law of Thermodynamics: When a system undergoes athermodynamic cycle, then the net heat supplied to the system from itssurroundings is equal to the net work done by the system on itssurroundings.

Figure(4)Insulatedsystem Chemical

Reaction

Insulation

Vessel

System Thermodynamic

Cycle



TheMathematicalexpressionofthe1stLawforanopensystem:(1)PotentialEnergy KineticEnergy InternalEnergy FlowEnergy NetHeatAdded NetWork (Opensystem) (Closedsystem) SothatEquation(1)canbewrittenas: (2)

Energyenteringthesystem Energyleavingthesystem

12 12

12 12



Enthalpy Specificenthalpy , ;Specificheatatconstantpressureandvolumerespectively.ThesteadyflowenergyequationS.F.E.E.isgivenas;(3)Examplesofopensystem:

1 SteamGenerator: FromtheS.F.E.E.: 0 (Noshaftwork)

(4)

12 12

12 12

BSteam

Water

2

1

12 12

0



2 Turbine: FromtheS.F.E.E.: 0 (Insulation)

(5)

3 Pump:FromtheS.F.E.E.: 0 (Insulation) Butsince => (Volume)

2

1

~

Insulation 0

T

Pump1

2

Insulation 0

12 12

12 12

0

0



(6)4 Nozzle:FromtheS.F.E.E.: 0 (Insulation) 0 (Noshaftwork) 0

(7)

2 (Ideal gas)

2 (Incompressible fluid)

5 Throttling:FromtheS.F.E.E.: 0 (Insulation) 0 (Noshaftwork)

2

Insulation 0

1 2

12 12

00 0

12 12

0 0

1 2

Throttle valve

Insulation 0



(8)

TheMathematicalexpressionofthe1stLawforaclosedsystem:Because mass does not cross the boundaries of the closed system. Weneglectthe(P.E),(K.E)and(F.E)termsinequation(1); (9) (10)Examplesofclosedsystem:

1 Rigidtank:

Fromequation(9) 0 (Noshaftwork) (11)

2 PistonandinsulatedCylinder:Fromequation(9) 0 (Insulation)

(12)

Tank



TheEnthalpyEntropyDiagramforSteam(hs):Thischartisusefulonlyfortheenthalpychangeintheexpansionprocessinthesteamcycle.Example: Steamat(140bar,550Co)isexpandisentropicallyinaturbinetoapressureof(2bar).LocatetheexpansionlineontheEnthalpyEntropydiagramandfindthevaluesof(t2,x2).

h

s

1 0.9 0.8

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Createdby:AssistantProfessorDr.MishaalAbdulAmeerAbdulKareem [email protected]

PowerPlantEngineering TUTORIALSHEET1 ThermodynamicRevie

10

1 Steaminitiallyat(15bar,300Co)expandsreversiblyandadiabaticallyinasteamturbineto(40Co).Determinetheidealworkoutputoftheturbineperkgofsteamandfindthedrynessfractionattheturbineexit.[Ans.90kj/kg,0.825]

2 Asteamboiler initiallycontains(5m3)ofsteamand(5m3)ofwaterat(10bar).Steam istakenoutatconstantpressureuntil(4m3)ofwater is left.Evaluatetheheattransferredduringthisprocess.[Ans.5092.8kj]

3 Asteamturbinereceives(600kg/hr)ofsteamat(25bar,350Co).Atacertainstageoftheturbine,steamattherateof(150kg/hr)isextractedat(3bar,200Co).Theremainingsteamleavestheturbineat(0.2bar,0.92dry).Duringtheexpansionprocess,thereisheattransferfromtheturbinetothesurroundingsattherateof(10kj/s).Determinethepowerproducedbytheturbine.[Ans.78.125kW]

4 A(500ton/hr)steamat(65bar,400Co) leavestheboilertoenterasteamturbinefittedwiththrottlegovernor.Ata(50%)fullloadoftheturbine,asthegovernortakesaction,thepressureofsteamisreducedto(59bar)bythrottlingbeforeitisadmittedtotheturbine.Expansion in the turbine isadiabatic toapressureof (1.5bar). If the turbine isentropicefficiency is (80%). Calculate the power output from the turbine [Hint: full load = 500ton/hr].[Ans.41.277MW]

5 (9kg/s)ofsteam,initiallyat(40bar,300Co),expandsadiabaticallyinaturbineto(4bar).Determinethepowerproducediftheisentropicefficiencyoftheturbineis(78.5%).[Ans.3.15MW]

6 Steamisgeneratedat(60bar,400Co)issuppliedtoaturbineviaathrottlingvalvewhichreducesthepressureto(50bar).Expansionintheturbineisadiabatictoapressureof(2bar).Iftheisentropicefficiencyoftheturbinebeing(82%).Determinethetemperatureofsteaminterringtheturbineandcalculatetheworkoutputfromtheturbine.[Ans.t=392Co,W=547kj/kg]

CHAPTER-1 THERMODYNAMIC REVIEWTutorial sheet-1 Thermodynamic review

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CHAPTER - 1 Thermodynamic Review