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Cooling System

This document discusses engine cooling systems. It explains that cooling systems work to prevent overheating by removing excess heat from the engine. They also regulate the engine's temperature to maintain optimum operating efficiency and prevent corrosion. The consequences of an engine running too hot or too cold are then outlined. Finally, the document describes different types of cooling systems, including air cooling, open-jacket liquid cooling, thermosiphon cooling, and modern pressurized liquid cooling systems that use pumps, radiators, fans, thermostats, and coolant to regulate the engine's temperature.

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Abera Zewdu
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270 views11 pages

Cooling System

This document discusses engine cooling systems. It explains that cooling systems work to prevent overheating by removing excess heat from the engine. They also regulate the engine's temperature to maintain optimum operating efficiency and prevent corrosion. The consequences of an engine running too hot or too cold are then outlined. Finally, the document describes different types of cooling systems, including air cooling, open-jacket liquid cooling, thermosiphon cooling, and modern pressurized liquid cooling systems that use pumps, radiators, fans, thermostats, and coolant to regulate the engine's temperature.

Uploaded by

Abera Zewdu
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Cooling Systems

Prevent Overheating:
Excess Heat generated in engine Peak temperatures exceed melting point of metal Cooling removes excess heat

Regulate Temperature
Regulate Temperature Allow engine to warm up in cool weather Cold engine less efficient Cold engine allow corrosive compounds to form Maintain engine in optimum range.

Consequence of engine running to hot:


Pre-ignition Detonation Knock
All result in very high pressure rise and possible damage to engine

Heat Fatigue of components


Burnt Pistons Burnt Valves

Failure of lubrication system


Oil breakdown Oil film at cylinder destroyed at 200C
Scoring of piston & sleeves

Warping & fracture of components

Consequence of engine running to cold:


Unnecessary Wear Poor Fuel Economy
Incomplete Combustion Lower coolant Temperature
More energy transferred out of cylinder Energy from is wasted & not available for work (Power)

Promotes corrosive conditions in engine


Water of combustion reacts with sulfur oxides in exhaust
Forms acids

Allows water & sludge to accumulate in crankcase Over time, fuel diluting the oil will accumulate
Normally lighter volatile fuel will evaporate as temp. rises

Cooling Systems
AIR COOLING SYSTEMS
Use air to dissipate heat directly. Transfer of heat to air more difficult.
Require fins and baffles to increase surface area Fans used in large engines to blow air around engine

Used in small engines and some large engines More Difficult to control temperature Most vehicles are water-cooled

LIQUID COOLING SYSTEMS


Liquid cools engine, air cools the liquid Engine heat absorbed by liquid Liquid travels to radiator
Airflow through radiator cools liquid

Cooling Systems
OPEN-JACKET SYSTEM
No pump Water open to air, not pressurized Evaporation cools water Convection draws cool water in bottom Hot water rise through engine to outlet

THERMOSIPHON
No pump Close cooling system Cool water enters bottom of engine
Water heats up, small vapor bubbles, density decreases Less dense hot water rises Colder water entering bottom forces hot water in radiator

Fan pulls air through radiator

Cooling Systems
MODERN COOLING SYSTEM Similar to thermo siphon but pump added for positive circulation. Thermo siphon is still present in modern systems but not major factor.
Radiator
Heat exchanger to air Coolant reservoir Forces air through radiator Fan requires energy
Belt driven, direct to engine (Continuous Energy use) Stationary, slow vehicles under constant load Belt driven, thermostatically controlled clutch Many larger engines Electric Motor, thermostatically controlled clutch High speed vehicles, normally no fan needed Many cars, fan only runs when car stationary

Fan

Water pump
Centrifugal pump circulates water through engine & radiator Draws cool water from bottom of radiator, into engine Temperature controlled valve (more later) Antifreeze
Prevents freezing in winter Helps prevent overheating in summer Anti-corrosion

Thermostat

Coolant

RADIATOR
Cellular type core Tubular, Tube and Fin type

Radiators

Pressurization
Increase boiling pinot temperature 1oC for each 4 kPa increase in pressure Prevent coolant loss under normal temperatures Pressure relief into overflow chamber at high temp & pressure Vacuum valve when liquid cools, allow air into radiator
Suck in liquid from overflow chamber

Operation of Pressure control Radiator Cap


Check cap for excessive pressure and vacuum

WARNING: OPEN CAP ON HOT ENGINE OPEN SLOWLY, CARFULLY WITH LARGE THICK CLOTH

FANS
Suction Type
Smaller, high speed vehicles Slow moving, dirty environment Improve airflow

Blower Type Shrouds

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