Sender: <marv@lancaironline.net> (Marvin Kaye)
To: flyrotary
Date: Tue, 25 Mar 2003 04:10:03 -0500
Message-ID: <redirect-2085611@logan.com>
From: keltro@att.net
Subject: Re: [FlyRotary] Re: Thick or Thin?

			
			
			
			

> > Hi All,
> >
> >    Would someone please help me better understand the physics involved
> with this?
> >
> >    It appears to me that, especially given the airspeeds we're talking
> about, as long as there is significant temperature differential between the
> air and the tube/fin at the trailing end of the air path, the radiator is
> working.
> > Isn't it the case that our biggest concerns with thick cores are (1)
> saturation of the airstream, (2) weight per transferred BTU, (3) drag?
> >
> >    So, for a given transfer rate, one might expect a thick core radiatior
> to be heavier than a thin one, but offer less drag.  If the load due to
> additional weight is less than the drag of the lighter thin core, aren't we
> ahead?
> >
> > Dale
> 
> Your observations are correct Dale, but in reality the weigh factor is
> insignificant.  Of course  there is a limiting factor on how far we can go
> with thick rads.  At some point there is not enough dynamic pressure to push
> enough air through a very thick rad to carry away the required BTUs, even if
> the air is heated to the theoretical limit equal to (almost) the coolant
> temperature.  An airplane flying at 200 MPH has a lot of dynamic pressure
> potential so the limit is relatively high (compared to passenger cars).
> 
> It is worth noting that the dynamic pressure at only 120 mph is enough to
> support the weight of your body.  120 MPH is the terminal velocity of a sky
> diver in free fall.
> 
> Tracy Crook
> 
      Well put Tracy! I agree as I have practical experience in free-fall.

        Kelly Troyer