Trevor,
I am in complete agreement with almost all of what you said, however the
efficiency I was referring to was the overall radiator efficiency, comparing
the shrouded puller versus the pusher fan. I firmly believe that in a
stopped or slowly moving vehicle a shrouded puller (tractor) fan will do a
better job than a pusher.
We can debate whether having a fan hub in front of the radiator will provide
more of an obstruction to cooling than placing it behind the radiator, due
to turbulent vs. laminar flow through the slotted TR3A grill, but a fully
shrouded puller is going to outperform a pusher without the moving vehicle
air ram effect.
Jack Brooks
TS69032L
NJ car show: http://pages.hotbot.com/family/triumph
>At 11:57 PM +1100 3/2/99, Jack Brooks wrote:
>
>>Putting the fan in front of the radiator partially blocks the radiator,
>>inhibiting the flow of air and cooling. A "puller" fan is superior in
>>performance to a "pusher" in this respect.
>
>A pusher fan will block the air flowing into the radiator whereas a tractor
>(puller) fan will block the air coming out of the radiator. Is there
>likely to be any great difference in efficiency? A pusher fan will disrupt
>the flow of air through the radiator more than a tractor, but after it
>comes through the grill it is likely to be fairly turbulent already.
>
>In either case, electric fans normally windmill when travelling at any
>significant speed and present much less obstruction to airflow than their
>appearance would suggest.
>
>An argument can be made that a pusher fan increases the pressure, density,
>and heat transfer capacity of the air flowing through the radiator. A
>tractor fan does the opposite. But I am not sure that any of these issues
>count for much - space for the fan and simple convenient mounting points
>could be more important.
>
>>Since I am concerned about total
>>amps used for a given amount of cooling, it makes the most sense
>to install
>>the most efficient configuration, especially since I am getting rid of the
>>mechanical fan altogether and have lots of room for a fully shrouded fan.
>
>The electric fan will run when the car is stationary or moving slowly. In
>these circumstances the fan is creating the airflow not blocking it. It
>should not run very often and unless your electrical system is marginal it
>should cope. What the generator/alternator cannot supply will come out of
>the battery which will be replenished when the fan stops. Fans typically
>draw about the same current as the lighting system, so the fan should
>create no problems during the day. You could test it with the lights and
>fan operating together to see how the electrical system copes.
>
>Trevor Jordan
>74 TR6 CF29281U
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