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INTRODUCTION
Figure 2: Bottom-mounted radiator
Figure 3: Top-mounted radiator
4
1.2.2
Why two radiators
The optimum engine operating temperature is between
87° and 92° Celsius. The radiator reduces the temperature
of the cooling liquid by only 5°C to 12°C. The returning
"cold" coolant therefore has a minimum temperature of
approx. 75° Celsius.
The alternator should be kept as cool as possible. In
practice an alternator starts getting less efficient above 40°
Celsius. It is hardly possible to cool down the coolant of
the alternator below 40° by using a radiator. When a
vehicle is in the sun on a parking place the ambient
temperature itself could be 40° Celsius.
Because of the divergence in the working temperature of
engine and alternator it will be clear that it is not possible
to combine the cooling of the engine and alternator in one
radiator system.
Furthermore it will be clear that it is very difficult to cool an
alternator optimally with the aid of a radiator in conditions
with high ambient temperatures.
1.2.3
Why the alternator should be liquid-
cooled
For normal industrial use alternators are cooled by air.
This requires a flow of air through the alternator of many
m³ per minute. With the air, the noise comes out into the
open. Generators on vehicles can only made silent by full
enclosure in a sound shield canopy. The only opening in
the canopy is the inlet for combustion air. For that reason
the alternator is liquid-cooled. Although cooling the
alternator by circulating coolant through a radiator is not
ideal; it is much better than by air. Therefore air-cooled
alternators are rarely used in vehicles.
December 2016 / W-SQ6/8/12/16 for mobile applications / EN
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