Download 14_Water Cooling System

WATER COOLING SYSTEM
LESSON FOURTEEN
1. HEAT SOURCES
 Burning of fuel
 Heat developed by compression of air
 Frictional heat
1. HEAT SOURCES
 Burning of fuel
 Heat developed by compression of air
 Frictional heat
2. HEAT DISTRIBUTION
 1/3 = converted into useful work ( transferred into mechanical energy /
BHP.
 1/3 = lost as exhaust gases
 1/3 = lost for cooling / absorbed by metallic walls of the combustion
chamber.
1. HEAT SOURCES
 Burning of fuel
 Heat developed by compression of air
 Frictional heat
2. HEAT DISTRIBUTION
 1/3 = converted into useful work ( transferred into mechanical energy /
BHP.
 1/3 = lost as exhaust gases
 1/3 = lost for cooling / absorbed by metallic walls of the combustion
chamber.
3. OVERHEATING
 Breakdown of L.O. film
 Loss in material strenght
 Excessive stresses due to unequal temperatures
 Faliure to maintain proper clearances between running parts.
4. COOLANTS
 Fresh water
 Luboil
4. COOLANTS
 Fresh water
 Luboil
5. COOLING WATER TEMPERATURE
5.1 The temperature should be kept as high as possible.
5.2 If to high, it will cause boiling of water and formation of scale
deposits ( incrustration )
5.3 If to low, it will lead to condensation of combustion gases on the
liner surfaces.
5.3.1 Product of condensation may:
 contain acids causing corrosion
 cause so called cold sludge in the L.O. increasing wear in all
moving parts
6. COOLING WATER TREATMENT & CONSEQUENCES
 If the cooling water is not properly treated, the closed cooling
systems may undergo fouling, formation of deposits ( preventing or
disturbing the heat transfer ). The deposit consists of loose sludge and
solid particles.
 Removal: mechanically ( first brushed or rinsed off with water ) or
chemically.
 Narrow spaces are chemically cleaned.
 Limestone deposits can be cleaned with acid solution.
6. COOLING WATER TREATMENT & CONSEQUENCES
 If the cooling water is not properly treated, the closed cooling
systems may undergo fouling, formation of deposits ( preventing or
disturbing the heat transfer ). The deposit consists of loose sludge and
solid particles.
 Removal: mechanically ( first brushed or rinsed off with water ) or
chemically.
 Narrow spaces are chemically cleaned.
 Limestone deposits can be cleaned with acid solution.
7. WATER COOLING SYSTEMS
 Large slow speed, two stroke engines have 2 separate closed
cooling circuits.
 A header or expansion tank allows venting of the system. The
header has connections from engine discharge & pump suction line.
 A heater is fitted with by pass to warm the engine when necessary.
 Cylinder jacket system
Water → lower end of the jacket → cylinder cover → exhaust valve cages
→ turbocharger → turbine cooling spaces → air separator → main
discharge.
 The piston cooling system
Water → piston cooling tank → piston water cooler → piston cooling
connections → return by gravity to supply tank