<VV>Mo Fan

[JVHRoberts at aol.com]

No. 
The power requirement of any centrifugal blower at any given speed is  
determined by air flow. Let it run wide open, and power consumption maxes out.  
Choke the flow, no matter which end you choke, and the power requirement goes  
DOWN. Heating of the air on a Corvair blower has more to do with how much it's  
beating up the air, since the pressure ratios are SO low, adiabatic heating is 
a  secondary effect. 
 
 
In a message dated 7/14/2005 2:36:48 P.M. Eastern Standard Time,  pp2 at 6007.us 
writes:

>Sorry Padgett, but this is just not correct. When you block the  output
>cooling air, the fan has much less work to do and the required  horsepower 
>goes DOWN,
>not up.

Guys: the fan loss (hp  required) has nothing to do with the amount of air 
moved but rather the  power required to turn the fan. The power required to 
turn the fan at  maximum air movement (unblocked inlet and outlet) is 
actually a middle  value. Block the inlet and the fan is turning in a 
partial vacuum of its  own creation and the power required for a constant 
rpm goes down (in the  tank vacuum example or a turbosupercharger, the rpm 
will increase). Block  the outlet and the air density in the plenum goes up, 
increasing the drag  on the impeller. This increases the power required to 
turn the fan and the  temperature of the air in the plenum goes up slightly.

Now if you want  to get heat quickly and increase the heater air flow in 
cold weather, this  makes sense since the change in drag is not a whole lot 
for the engine  driven cooling fan in a Corvair but in a turbo, particularly 
one making a  lot of boost, it is a serious issue.

Padgett