oil heat exchangers are also utilized. A liquid coolant
under pressure enters the water jackets absorbing heat
from the cylinders and other components described
above, and by the time it reaches the outlet has risen in
temperature. Water cooling systems are configured
such that the temperature differential between inlet and
outlet does not exceed 10 to 12F (-12 to -11°C). It is
not good practice, and may be destructive to the engine
to have a low intake temperature.
17-40. The coolant leaving the engine outlet enters a
radiator heat exchanger to exchange its heat to the
17-41. RADIATOR COOLING. See table 17-4.
Provide an entrance for fresh air at least as
large in area as the radiator itself. Do not
depend solely on apertures such as windows,
etc. Where possible, inlet shutters are utilized
to increase the inlet opening area by a factor of
one quarter to one half that of the radiator area.
temperatures, thermostatically controlled inlet
shutters should be considered.
Cool inlet air should not be required to find its
way to the engine room through stairwells,
corridors, etc., nor should it be required to travel
upward through a duct.
Table 17-4. Radiator and Crankcase Capacities
Radiator and ................................................
Crankcase oil ...............................................
17-42. A radiator is a closed system heat exchanger
consisting of finned tubes through which the engine
coolant passes. The heat exchanging air stream over
the fins is produced by a beltdriven, pusher-type fan (air
flow from rear of set towards the radiator). Cooling air is
drawn over the engine and pushed through the radiator
into a duct leading to the outlet vent, or unducted toward
the outlet vent. A radiator cannot itself absorb heat
(except for the very small amount to warm its own
metal) and is not to be regarded as a bottomless pit
capable of absorbing unlimited heat. The radiator
exposes the finned surface of its tubes to the passing air
stream to carry off engine heat.
17-43. A free supply of fresh air must be available and
recirculation of the air must be avoided. If the cooling
air is allowed to recirculate it would soon acquire enough
heat to raise the ambient temperature to approximately
the same temperature as the radiator, resulting in
engine overheating. A few basic rules should be
observed in locating a radiator cooled generating unit.
Provide an exit for heated air, preferably
ducted, allowing it to be carried completely
away. The exit opening should be larger than
the inlet opening to compensate for the
expansion of air due to heat. Bends in the
exhaust duct should be avoided where possible,
but if they are required, they should be
Cooling fan pressure generally should not be
However, if gravity drop louvers are utilized, the
louvers should be lightweight metal.
Where possible, position so that the direction of
fan output is directly toward the outlet.
Avoid ducting so the outlet constructed to the air
must make one or more right angle bends after
Where possible, position the engine so that