TM 5-685/NAVFAC MO-912
& SH U T
Figure 3-7. Diesel Engine Liquid Cooling System.
closed circuit through a radiator (engine-driven fan)
(2) The engine and its components are de-
or a water-cooled heat exchanger.
signed to withstand the mechanical and thermal
(b) Remote. Primary coolant in a closed cir-
stresses resulting from operating within certain pa-
rameters. The design also allows for the effects of
cuit is piped to a heat exchanger system not
temperature on the strength, resistance to fatigue
mounted with the engine. Pumps and controls may
and wear, the stresses induced by expansion and
also be remote. It is used for larger engines where
contraction, and allowance for wear and corrosion,
size and complexity of heat dissipation systems are
significant. It is also used to physically separate the
liquid processing from the electrical generation and
(a) Each component subject to heat is de-
signed to operate within stated temperature iimits.
Unsatisfactory operation, decreased life, damage or
c. System description and operation. Successful
failure will result if the engine operates outside of
operation of the engine depends upon the removal of
excess heat from lubricating oil, after cooler, and
these limits. Lubricants will lose their necessary
the engine components (cylinders, pistons, and
properties, clearances between parts will become
valves) to keep the engine temperature within the
too great or too little, and combustion of fuel will not
limits specified by the manufacturer. The kW rating
be proper. Fuel, air, exhaust and coolant passages
of the associated electric generator may require
may be fouled, melted, or chemically attacked, or
derating when any temperature at the operating
misalignment and excessive vibrations may result.
(b) Hot spots, cold spots, general overheating
engine exceeds the manufacturer's limits. Table 3-4
describes the various elements of the cooling sys-
and general overcooling can each cause problems.
Approximately one-third of the energy consumed by
an engine is removed by the cooling system.
(1) Overheating of the engine reduces the effec-
tiveness of engine lubricants, accelerates engine
(3) An engine used for auxiliary generator ser-
wear, and causes engine breakdown. Cooling pre-
vice will be one of proven capability and reliability
when operated within the limits specified by the
vents excessive stresses in or between engine parts
caused by unequal temperature within the engine.
manufacturer. A particular engine will require
stated rate of coolant flow at certain inlet and outlet
Also, cooling prevents loss of strength caused by
overheating of the engine's structural metal.
temperatures under various rates of fuel energy