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Re: [Amps] LK 500 ZA heat

To: jeremy-ca <>
Subject: Re: [Amps] LK 500 ZA heat
From: Tim Long <>
Date: Mon, 13 Aug 2007 22:08:43 -0400
List-post: <>
Carl OM,
Tom is spot on.  This is a real answer just like Toms.
OK so you insist on the heat exchanger analogy with your automobile and 
electric fan.  The reason that an electric fan is not sitting out in 
front of your radiator is because at 30+ mph the electric fan and its 
motor would get in the way and restrict air flow.  The fan is not 
running at this speed and the air flow through the radiator due to 
vehicle motion far surpasses what a fan could produce.   At low speeds 
and idle, the fan comes on and sucks air through the radiator.  A little 
is better than none.  Vehicles boil over during traffic jams don't 
they?  The ideal situation would be to move the fan in front of the 
radiator to run at idle and to remove the fan altogether at normal 
travel speeds.
So an enclosed pressurized box of electronics is more efficiently cooled 
with a fan on the air intake.  Cooling is more efficient  if the air 
flow is turbulent versus laminar.  It is easier to direct turbulent air  
at tube pins and plate caps when these tube parts are close to the 
intake fan that is directing cool air at them.  OK, so you notice that a 
fan in your computer is in the power supply and in the exhaust path.  It 
is there because it is the cheapest place, not because it works best.  
The fan on your CPU blows onto the CPU and the fan on your video card 
blows onto the video chip.
BTW, the reason your fan is electric is because most engines are 
transverse mounted in front wheel drive vehicles and because it is cheaper.
73, Tim, W2UI

jeremy-ca wrote:
> Tom, you are so predictable. When you cant come up with a real answer you 
> resort to personal attacks.
> I dont know when the last time you lifted the hood in a car but horsepower 
> robbing engine driven fans have been out of favor for around 25 years. The 
> choice of all manufacturers is an electric pulling fan. This also holds for 
> 500-800 hp and higher street rods with big V8's stuffed in very restrictive 
> spaces. The Internet is full of studies of the comparisons between push and 
> pull cooling.
> The air flow analogy is valid no matter the platform.
> Carl
> KM1H
> ----- Original Message ----- 
> From: "Tom Rauch" <>
> To: "jeremy-ca" <>; "dave arruzza" <>; 
> <>
> Sent: Monday, August 13, 2007 3:28 PM
> Subject: Re: [Amps] LK 500 ZA heat
>>>> If you pressurize the inlet of a fan or blower, it greatly
>>>> increases outlet pressure. If you draw on the outlet it
>>>> hardly changes airflow. The inlet fan largely sets the
>>>> volume of air. The same is true for restrictions. If you
>>>> restrict an inlet, there is a huge air volume change. If you
>>> Tell that to the millions of car owners with electric fans that pull the 
>>> air thru the restrictive radiator. Tests have long proven that trying to 
>>> push the air thru the radiator is a bad idea.
>> Carl,
>> It's just silly to drag in unrelated arguments against something that is a 
>> clearly known fact, especially something so easy to prove with minimal 
>> research or experimentation.
>> Cars suck air through the radiator because that's where the drive system 
>> is. They aren't about to extend a shaft through the middle of the 
>> radiator, so they burn up some extra horsepower with a less efficienct air 
>> system. Also the movement of the car through the air is what does 90% of 
>> the air movement, the only real thing the fan does is cool the system when 
>> the vehicle is stopped or at slow speed. That's also when BTU's generated 
>> by the engine is less, since the fuel volume being burned is lowest.
>> Analogies to a 200 horsepower engine in a system that is not pressure or 
>> noise critical and can't put the fan in the optimum place is a tremendious 
>> waste of time.
>>> Placing a small fan in exhaust mode has also saved many sweep tube rigs 
>>> from premature tube failure. Ask anyone who used Drake C Line in contests 
>>> for example.
>> Anything is better than nothing Carl. He was talking about adding a fan to 
>> a system that already has a fan, not a convection system like the Drake. 
>> This was just another lame meaningless analogy.
>> It is an undisputable fact air movers act like I outlined, and something 
>> everyone designing or modifying a cooling system should know. Even someone 
>> working on a car.
>> 73 Tom
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