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1. SATHEESAN M.P.
LECTURER IN MECHANICAL ENGINEERING
S.N.P.T.C. KANHANGAD
SEMESTER-4
MECHANICAL ENGINEERING
Subject-AUTOMOBILE ENGINEERING
UNIT-1 COOLING SYSTEM

2. COOLING SYSTEM
1.Air cooling.
2.Water cooling.
I.Thermosyphon water cooling system.
II.Forced circulation cooling system.

3. AIR COOLING

6. MERTIS OF AIR COOLING
1.Cylinder and cylinder heads are less complicated.
2.Reduced engine weight as there is no water jackets.
3.Cheaper to manufacture.
4.Reduced overall size as there is no radiators.
5.Engine warm-ups more quickly.
6.Quick starting up of engine.
7.Risk of coolant frost damage to water jackets are
not there.

7. DEMERTIS OF AIR COOLING
1.Greater mechanical noise due to fan.
2.Not suitable for multi cylinder engines.
3.Not suitable for agriculture and construction
application as the space between cooling
fans are likely to be blocked with vegetable
matters like grass, weeds, mud etc.

9. Water cooling.

11. Thermosyphoncooling system

12. Thermosyphoncooling system

13. FORCED CIRCULATION COOLING SYSTEM

20. working of thermostat

23. Compare air and water cooling systems.

25. WORKING WATER COOLING SYSTEMS
Aliquidcoolingsystemworksbypassingliquidcontinuallythroughthepassagesin
theengineblock.Poweredbythewaterpump,thecoolantispushedthroughthe
engineblock.Asthesolutionstravelsthroughthesepassages,itabsorbsheatfrom
theengine.
Afterleavingtheengine,thisheatedliquidtravelstotheradiatorwhereitiscooled
bytheairstreamenteringthegrilleofthecar.Theliquidwillcoolonitstravels
throughtheradiator,returningonceagaintotheenginetopickupmoreofthe
engine’sheatandcarryingitaway
Thereisathermostatbetweentheengineandtheradiator.Thethermostat
regulateswhathappenstotheliquid,dependingonthetemperature.Iftheliquid’s
temperaturefallsbelowacertainlevel,thesolutionbypassestheradiatorand
insteadisdivertedbacktotheengineblock.
Thecoolantwillcontinuetocirculateuntilitreachesacertaintemperatureand
opensthevalveonthethermostat,allowingittoonceagaintravelthroughthe
radiatortobecooled.
Becauseoftheextremeheatoftheengine,itseemslikeitwouldbeeasyforthe
coolanttoreachaboilingpoint.However,thesystemispressurizedtopreventan
occurrencelikethis.Whenthesystemispressurized,itmakesitmuchmoredifficult
forthecoolanttoreachapointofboiling.

26. working of Air cooling system
•Intheaircoolingsystem,theheatisdissipateddirectlytotheair
afterbeingconductedthroughthecylinderwalls.Aircooling
systemshavefinsandflangesontheoutersurfacesofthecylinders.
Theheadsservetoincreasetheareaexposedtothecoolingair,and
soraisetherateofcooling.Thebasicprincipleinvolvedinthis
methodistohaveacurrentofairflowingcontinuouslyoverthe
heatedsurfaceoftheenginefromwheretheheatistoberemoved.
Theamountofheatdissipatedbasedonthefollowingfactors.
•Thesurfaceareaofmetalintocontactwithair.
•Therateofairflow.
•Atemperaturedifferencebetweentheheatedsurfaceandtheair.
•Theconductivityofthemetal.
•Forcompleteuseofair-cooling,thesurfaceareaofthemetalwhich
comesincontactwithairisimprovedbyprovidingfinsoverthe
cylinderbarrels.Morethesurfaceareainacontactwithair,more
theheatisdissipated.Highertherateofairflow,highertheheatis
dissipated