Elements of Mechanical Engineering for BE

IC Engines, Gears

1. Elements of Mechanical Engineering
By
Dr Manjunatha Babu N S
Associate Professor & Head
Mechanical Engineering

2. Module 1
Introduction to Mechanical Engineering

3. Module 1
Role of Mechanical Engineering in Industries and Society:

4. Module 1
Emerging Trends and Technologies in Mechanical Engineering in different Sectors:

5. Module 1
Steam & Its Properties

6. Module 1
Steam & Its Properties, Formation of Steam
1)Itcancarrylargequantitiesofheat
2)Itisproducedfromwaterwhichis
cheapandreadilyavailable
3)Itcanbeusedforheatingpurposes
afteritsdutyasworkingagentis
completed.
4)Itcanbeusedpurelyasaheating
mediuminfoodprocessingIndustries
becauseofafast,easilycontrollable
andhygienicmethodofheating.

7. Module 1
Steam & Its Properties, Formation of Steam

8. Module 1
Steam & Its Properties, Formation of Steam
enthalpy
athermodynamicquantityequivalenttothetotalheatcontentofasystem.Itis
equaltotheinternalenergyofthesystemplustheproductofpressureand
volume.
athermodynamicquantityrepresentingtheunavailabilityofasystem'sthermal
energyforconversionintomechanicalwork,ofteninterpretedasthedegreeof
disorderorrandomnessinthesystem.
entropy
Types:Wetsteam,Drysteam,Superheatedsteam
WetSteam:WhensteamcontainswaterparticlesthenitisknownasWetsteam
DrySteam:Whenwetsteamisfurtherheatedthenallwaterparticlesgetconvertedintovapourandresulted
steamiscalleddrysteam.
SuperheatedSteam:Whendrysaturatedsteamisheatedtohighertemperaturesthensteamobtainedisin
superheatedstate.ThissteamismostlyusedinPowergeneration.

9. Module 1
Steam & Its Properties, Formation of Steam
Enthalpy of Steam:
theamountofenergythatresultswhenitiscreatedfromaliquid,typicallyatits
boilingtemperatureinthetransitionfromliquidtogas.
Specificenthalpyofun-saturatedwater(hw):
Itissimplytheamountofheatrequiredtoraisethetemperatureofonekgofwaterfrom
0℃toitsactualtemperaturewhichisbelowitssaturationtemperature.Itcanbe
calculatedbymultiplyingactualtemperatureofunsaturatedwaterwithitsspecificheatwhich
isconsideredequalto4.187kJ/kg/K.Itisdenotedash
w.
Specificenthalpy of saturated water (h
f):
Itisthequantityofheatrequiredtoraisethetemperatureofonekgofwaterat0
0
Cto
itsboilingpointorsaturationtemperaturecorrespondingtothepressureapplied.Itis
denotedash
f.Itcanbecalculatedbymultiplyingthespecificheatofwatertothetotalrisein
temperature.ThespecificheatCp
wofwatermaybeapproximatelytakenasconstanti.e.,
4.187kJ/kgK,butinactualitslightlyincreaseswithincreaseinsaturationtemperatureor
pressure.

10. Module 1
Steam & Its Properties, Formation of Steam
Latentheatofsteam(h
fg)
LatentheatofsteamataparticularpressuremaybedefinedasthequantityofheatinkJ
requiredtoconvertonekgofwateratitsboilingpoint(saturatedwater)intodry
saturatedsteamatthesamepressure.ItisusuallydenotedbyLorh
fg.Itdecreaseswith
increaseinpressureorsaturationtemperature.
Wetanddrysteam
Wetsteamisthatsteaminwhichthewholeofwaterhasnotvaporizedbuttheun-
vapourizedwaterispresentintheformofmist/fogsuspendedincompletelyvaporized
waterorsteam.Duetothismistthewetsteamisvisible.
Howeverthedrysteami.e.,inwhichthevaporizationiscompleteisinvisibleorcolorless.
Anysteamwhichiscompletelydryandpresentatsaturationtemperatureiscalleddrysaturated
steam.

11. Module 1
Steam & Its Properties, Formation of Steam
Drynessfraction
Thistermreferstoqualityofwetsteam.Itisdefinedastheratiooftheweightofdrysteam
actuallypresentstotheweightoftotalwetsteamwhichcontainsit.Itisdenotedbyx.
WhereW
d
=Weightofdrysteamin1kgofwetsteam,
W=Weightofwaterinsuspensionin1kgofwetsteam
Drynessfractioniszeroforsaturatedwaterandonefordrysaturatedsteam
Wetnessfraction
It is the ratio of the weight of water/ moisture in suspension in a wet steam sample to the
total weight of wet steam. It is calculated by subtracting x from 1
Specificenthalpy of wet steam (h
ws)
Itmaybedefinedasthequantityofheatrequiredtoconvert1kgofwaterat0
0
Cinto
wetsteamofagivenqualityandatconstantpressure.Itmaybedenotedbyh
ws.Itisequal
tothesumofspecificenthalpyofsaturatedwaterandlatentheatofdryfractionofsteam.So
h
ws=h
f+x.

12. Module 1
Steam & Its Properties, Formation of Steam
Specificenthalpy of dry saturated steam (h
g)
Itmaybedefinedasthequantityofheatrequiredtoconvert1kgofwaterat0
0
Cintodry
saturatedsteamatgivenconstantpressure.Itmaybedenotedbyh
g.Itisequaltothesumof
specificenthalpyofsaturatedwaterandlatentheatcorrespondingtogivensaturationpressure
andtemperature.Thush
g=h
f+h
fg
Specificenthalpy of superheated steam (h
sup)
Itisdefinedasthequantityofheatrequiredtoconvert1kgofwaterat0
0
Cintothe
superheatedsteamatgiventemperatureandpressure.Itmaybedenotedash
supandis
equaltothesumofspecificenthalpyofdrysaturatedsteamandproductofspecificheatof
superheatedsteam(C
s)todegreeofsuperheat.h
sup=h
g+C
s(t
sup-t
s)
,
Where,h
gandt
sarethespecificenthalpyofdrysteamandsaturationtemperatureat
correspondingpressureandC
S&t
sup
arespecificheatofsuperheatedsteamand
temperatureofsuperheatedsteamatthesamepressure.

13. Module 1
Steam & Its Properties, Formation of Steam
SpecificVolume of Water/Steam
The volume of a unit mass of water/steam is known as its specific volume
Specificvolumeofsaturatedwater(v
f)
Itisdefinedasvolumeof1kgofwateratsaturationtemperaturecorrespondingtothegivenpressure.Itis
denotedbyv
f.Itcanbecalculatedexperimentally.Itslightlyincreaseswithincreaseinsaturationtemperatureand
hencethepressure.Thereciprocalofsp-volumeisequaltodensity.
Specificvolumeofdrysaturatedsteam(v
g)
Itisdefinedasvolumeof1kgofdrysaturatedsteamcorrespondingtothegivenpressure.Itisdenotedby
v
gandcanbecalculatedexperimentally.Asdrysaturatedsteamisagas,itsspecificvolumedecreaseswith
increaseinpressureorthesaturationtemperature.
Specificvolume of wet steam of quantity x
Itisthevolumeof1kgofwetsteamandisdenotedasv
ws=x.v
g+(1-x)v
f
Atlowpressurethevalueofv
fisverysmallascomparedtov
g;sotheterm(1-x)v
fmaybeneglected.Then
volumeof1kgofwetsteam=x.v
g

14. Module 1
Steam & Its Properties, Formation of Steam
Specificvolume of Superheated Steam (v
sup
)
Itisthevolumeof1kgofsuperheatedsteamandcanbedeterminedbyassumingthatthe
steambehavesasaperfectgasi.e.,obeysthegaslaws.Itisdenotedbyv
sup
LetP=pressureunderwhichsteamissuperheated.
t
sup=temperatureofsuperheatedsteam
v
g=Specificvolumeofdrysaturatedsteam
t
s=saturationtemperatureatpressureP.
Since,P=constant,so

15. Module 1
Steam & Its Properties, Formation of Steam
Specificentropy of saturated water (s
f)
ThespecificentropyofsaturatedwaterataparticularpressurePandsaturationtemperatureT
sisgiven
asthechangeinentropyduringconversionofonekgofwaterat0
0
Cintosaturatedwateratthat
pressure.Thewateratfreezingpoint0
0
Cor273Kisconsideredasdatumwhere,absoluteentropyistakenas
zero.IfC
Wisspecificheatofwaterthenthechangeinentropyof1kgwaterduringtemperaturechangefrom
273KtoTKisgivenas
Changein specific entropy during evaporation, (s
fg
)
During evaporation heat added =h
fg= Latent heat of water
Specificentropy of dry saturated steam (s
g
)
Itistheentropyofonekgofdrysaturatedsteamandisgivenasthesumofentropyof1kgofsaturated
waterandentropychangeduringevaporation.Itisdenotedbys
g.
Thuss
g=s
f+s
fg
Specificentropy of wet steam
Specificentropyofwetsteamisequaltosumofspecificentropyofsaturatedwaterandchangeinspecific
entropyduringevaporationofdryfractionofsteam.Itisdenotedbys
ws s
ws=s
f+x.

16. Module 1
Steam & Its Properties, Formation of Steam
ApplicationofSteaminSugarIndustry:
Steamboilersareveryimportantintheprocessingoperationsofcrystallizationand
dryinginsugarmills.
Stages of Sugar extraction from Sugarcane:
1. Washing
2. Extraction
3. Purifying juice
4. Crystallization
5. Centrifugation
6. Drying

17. Module 1
Steam & Its Properties, Formation of Steam
Stages of Sugar extraction from Sugarcane:
1.Washing & 2. Extraction
Oncethecanehasbeengraded,itiswashedtoremoveanyimpuritiesahead
ofbeingprocessed.Thecleaningofthecanecanbedonewetordry.Dry
cleaningisthepreferredmethodasitismoreenvironmentallyfriendly.
3. Purifying juice
Thesugarcanejuiceisthensentforclarification.Thejuiceistreatedfor
precipitateeliminationviacoagulationandsedimentation.Thejuicegoes
throughaboilingprocess,wheremoistureisboiledoff.Duringtheboiling
evaporationprocessaround75%ofthewaterisremoved,resultingina
syrupconcentrate.
4. Crystallization
The syrup is placed in large vessels where it is rotated slowly, allowing it to
cool evenly. Seeding is then carried out, where small seed crystals are added
to the syrup to catalysethe crystallisationprocess. The molasses separates
from the crystals, and the liquid is ready for the next stage.

18. Module 1
Steam & Its Properties, Formation of Steam
5. Centrifugation & 6. Drying
Tocompletetheprocess,centrifugingthentakesplace.Duringthisprocessthecrystallised
syrupisseparatedfromthesugaranddriedbybeingputintocentrifuges.This
producesrawsugarbyseparatingthesugarcrystalsfromthesurroundingmolasses.

19. Module 1
Steam & Its Properties, Formation of Steam
Applications of Steam in dairy industry
Steamisquitecommonlyusedforheating
andsterilizingdairyequipment,bothonthe
farmandinthedairymanufacturingplant.
Itisusedinthesmallself-containedoilor
electricsterilizersandinlargecontinuous
canwashers.
Boilersinthedairyindustriesmainly
performtheprocessesofmilkpasteurization
andUltraHeatTemperature(UHT)

20. Module 1
Steam & Its Properties, Formation of Steam
Application of Steam in Paper Industry
Steamispivotalinthepaperindustryforthe
processofdryingthepaper,energy
requirement,andthecookingofwoodchipsin
thedigester.
UniformHeating
SteamCarriesAmpleHeat
PrecisioninSteamTemperature

21. Module 1
Steam & Its Properties, Formation of Steam
Application of Steam in Food Processing Industry
Thefoodindustryneedsheatateverystageofthe
process.Directheatorheatinthefromofsteamis
anessentialfactoroffoodprocessingindustry.
steamisusedforcooking,drying,andwarming,andfor
generalutilize-cleaning.
Steamisalsousedtoeliminatemicrobiologicalriskin
food.
Steamusedbyfoodprocessorscommonlyfallsintotwo
broadcategories.Thefirstistheso-called“culinary,”
“sanitary”or“clean”steam.
Thesecondcategoryofsteamusedbyfoodprocessorsis
oftenreferredtoas“utilitysteam”

22. Module 1
Energy
Energy Resources
Energy
FormsofEnergy
All forms of energy are inter-convertible by appropriate processes.
Energyexistsintheearthorcomesfromtheouterspace.Theenergyexistingintheearthis
calledcapitalenergyandthatwhichcomesfromtheouterspaceiscalledcelestialorincome
energy.
Renewable&Non-renewable

23. Module 1
Steam & Its Properties, Formation of Steam
Renewable Energy Resources
directsolarenergy,
windenergy,
tidalenergy,
hydelenergy,
oceanthermalenergy,
bioenergy,
geothermalenergy,
peat,fuelwood,
fuelcells,
solidwastes,hydrogenenergy
Non -Renewable Energy Resources
Fossilfuels
(coal,petroleumandpetroleumproducts)
Nuclearfuelsandheattraps

24. Module 1
Hydel Energy
Apowerplantthatutilizesthepotentialenergy
ofwaterforthegenerationofelectricalenergy
isknownasahydroelectricpowerplant.
Inahydropowerplant,awaterheadiscreated
bybuildingadamacrossariverorlake.
Thewaterturbinechangesthekineticenergyof
thefallingwaterintomechanicalenergyatthe
turbineshaft.

25. Module 1
Thermal Power Plant
It is the power plant which is used to generate electricity by the use of
steam turbine.
In the steam power plant, the pulverized coal is fed into the boiler and
it is burnt in the furnace. The water present in the boiler drum changes
to high pressure steam.
From the boiler the high-pressure steam passed to the superheater
where it is again heated up to its dryness.
This superheated steam strikes the turbine blades with high speed and
the turbine starts rotating at high speed.
The generator converts the mechanical energy of the turbine into
electrical energy.
After striking on the turbine the steam leaves the turbine and enters into
the condenser. The steam gets condensed with the help of cold water
from the cooling tower. The condensed water with the feed water enters
into the economizer.

26. Module 1
Nuclear Power Plant
Ageneratingstationinwhichnuclearenergyis
convertedintoelectricalenergyisknownasnuclear
powerstation.
Themechanicalorrotatingenergydevelopedbythe
turbineistransferredtothegeneratorwhichinturn
generatestheelectricalenergy.

27. Module 1
Solar Energy
Solarenergyistheenergy
obtainedbycapturingheatand
lightfromtheSun.Energyfrom
theSunisreferredtoassolar
energy.
itdoesnotemitgreenhousegases.
a)SolarPhotovoltaicConversion
b)SolarThermalConversion

28. Module 1
Tidal Energy
Tideisaperiodicriseandfallofthewaterlevel
oftheseawhicharecarriedbytheactionofthe
sunandmoononthewateroftheearth.
Thehighestlevelofthetidalwaterisknownas
thehightide.Thelowerlevelofthewateris
knownaslowtide.Theleveldifferencebetween
thehightideandthelowtideisknownastidal
range.
Twotidalcyclesoccurduringalunarof24
hours&50minutes.

29. Module 1
Wind Energy
Windenergyisdefinedasthekineticenergy
associatedwiththemomentoflargemassofair
overtheearthsurface.
Thecirculationofairiscausedbytheuneven
heatingandcoolingoftheearthsurface.