<VV> Flow/Pressure/Cooling

[ScottyGrover at aol.com]

In the HVAC trade, this type of fan is known as a "Backward-inclined"  fan 
blade, and it is the most efficient fan used in the trade (bur it's not  
cheap.)
 For what it's worth, anything that closes up the clearances between  the 
fan and the "turkey roaster" so that air under pressure doesn't revert back  
through the fan, bypassing it--this air flow simply wastes energy.
 
Scotty from Hollyweird
 
.
 
 
In a message dated 5/23/2012 5:43:58 P.M. Pacific Daylight Time,  
mfrancis at wi.rr.com writes:

Perhaps  what IS important to remember, is that as the stock fan increases 
in 
RPM,  past a certain point, you are not experiencing the same percentage of 
flow  increase through the heads, so what you have is an increase in 
pressure  
inside the upper shroud.

This increase in pressure is what causes  the fan to consume more 
horsepower, 
as the turbulence along the tips  becomes a tight 'shear' point between the 
already pressurized side and the  incoming air movement through the vanes.

What might work better, and is  reflected in more recent fan designs, is a 
curved, swept-back tip around  the perimeter of the fan. This would allow 
the 
fan to 'slide' along the  shear point easier and as a result, might consume 
less horsepower than the  stock fan at the higher RPMs.

Mel Francis


----- Original  Message ----- 
From: "Joel McGregor" <joel at joelsplace.com>
To:  <virtualvairs at corvair.org>
Sent: Wednesday, May 23, 2012 7:09  PM
Subject: Re: <VV> Flow/Pressure/Cooling


> Does  someone have any references for this?  IF this is true I doubt we  
> would ever get to this point in our application.  I have a hard  time 
> believing that increasing the pressure could actually decrease  flow.  
I'm 
> not claiming that it is needed.  That's a  different debate.
> Joel McGregor
>  ________________________________________
> From:  virtualvairs-bounces at corvair.org 
[virtualvairs-bounces at corvair.org] 
>  On Behalf Of Smitty [vairologist at cox.net]
> Sent: Wednesday, May 23,  2012 6:59 PM
> To: virtualvairs at corvair.org
> Subject: <VV>  Costom Fans/ Thrown Belts
>
> Exactly right.  Both theory of  fluid dynamics and  experimental data show
> that at some point, an  increased differential in  pressure through a 
> nozzle
>  (cooling fins) has no increase in flow and can  actually lead to a  
> decrease
> in flow.
>  

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