I am unable to agree that the usage of an electrical fan will save
power.
After all, the energy for the fan has to come directly from the
engine if it is a directly driven fan and from the battery in case of
an electrical fan. The battery in turn is charged through the
alternator, which draws power from the engine shaft.
The energy used will be marginally higher with the electrical system
because of the efficiency losses in 2 conversions - mechanical to
electrical at the alternator and electrical to mechanical at the fan
motor.
The advantage really is that the fan will run only when
necessary, if a thermal switch is used.
This can also be achieved through the electromechanical clutch that is
used on Peugeots.
Of course, the clutch consumes power, and the difference in power
consumed will depend on whether the losses in 2 conversions is
greater than, equal to, or less than the consumption of the clutch.
Another efficient method used is the thermostatic clutch used on many
Japanese vehicles, which uses a kind of fluid coupling on the fan
shaft with a thermally controlled mechanism This fan freewheels when
the temperature of the flowing air is low, and will engage
when it gets warmer. This neither consumes power for engaging /
disengaging, nor incurs the losses of a double conversion system.
jb
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J.Balamurugan Phone: +91 (431) 552281
Computer Support Group FAX: +91 (431) 552133
Regional Engineering College jb@rect.ernet.in
Tiruchirapalli 620015
INDIA
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