Message-Id: <200311261819.MAA19508@mail.datarecall.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: dcarter@datarecall.net
Subject: Re: [FlyRotary] Re: radiator size
Date: Wed, 26 Nov 2003 18:19:56 GMT

Ed,

I hereby award you the "gracious, kindly, coherent, helpful, non-
confrontational response" award - on behalf of the FlyRotary list
   (but with no authority to do so other than my own desire to say "thank you" 
for such even-tempered, helpful, 'go the extra mile', and 'above and beyond 
the call of duty' participation in this valuable e-mail forum.)

David Carter

> > >
> > > At 03:27 PM 11/19/2003 -0600, you (Jim Sower) wrote:
> > > >Isn't the conventional wisdom 3 cuin/hp?  Al Wick's Subaru is about 2.5
> > > >but his
> > > >Soob doesn't have the cooling requirements of a rotary and I believe he
> > has a
> > > >really nice (efficient - good recovery) plenum.  I would think 3
> minimum
> > > >unless
> > > >you have really good ducting and plenum.
> > > >Just a theory ... Jim S.
> > >
> > > Hi, Jim....sorry for the delay in responding.  Regarding Al Wick's
> > radiator installation, he broke all the rules.  He just put the darned
> > radiator in front of the NACA inlet scoop, and has NO exit plenum. After
> the
> > air passes thru the radiator, it just slowly finds it's way out the rear
> of
> > the cowling. Odd thing is that he can do extended full power climbs
> without
> > overheating. Go figure ! I should be so lucky.  Paul Conner
> >
> > >
> 
> Since Al Wick is reportedly cruising at 200 mph on 5 gph producing around
> 55HP, he may be able to climb out on less power as well. It  all depends on
> what his fuel burn rate is on his extended climbout.  If you produce power
> compariable to a rotary, then you will need cooling capacity to accommodate
> it.  So depending on a particular configuration, you might get great cooling
> simply because you are not producing much power - not necessarily a
> desireable outcome.  Clearly if your cooling requirements are less, the
> design features of your cooling system may stray further from "good"
> practices without serious adverse effect.  On the other hand, if your
> installation configuration (power/airspeed) place heavy demands on your
> cooling system, then failure to following "best" practices could lead to
> cooling problems.
> 
> 
> Given that you are producing X amount of power, its going to take Y amount
> of cooling period!.  The upper external limiting factor for cooling is going
> to be bounded by the mass flow through your radiators.  Regardless of
> whether you are using large thin radiator or small thick ones, if you do not
> have the minimum air mass flow through them adequate to carry away the waste
> heat - you will eventually over heat.
> 
> >From experience it appears that 4 cubic inches per HP produced is a good
> ball part figure for sizing your radiators for a rotary.  So 160 HP x4 = 640
> cubic inches which happens to be two 9x10x3.6 evaporator cores (not counting
> side tanks).  We know that size radiator has the capacity to cool a 160 HP
> (possibly more depending on airspeed) provided you get the mass flow through
> it.  Now getting the mass flow through it is not necessarily a trival
> problem - especially for you pusher folks.
> 
> But,  if getting the required air mass flow through a 640 in^3 radiator is
> problematic for an installation, it is doubtful (in my mind)  that going to
> a larger radiator is going to buy you much.  If your configuration
> constrains airflow to the point it is  inadequate for removing heat from
> your 640 in^3 radiator then I don't see how going to a larger radiator will
> buy you anything as you won't have the mass flow to support it either.
> 
> So, I would suggest caution about assuming that what appears to work for
> someone else is also going to work for you - unless you have a near
> identical configuration producing near identical power
> 
> FWIW
> 
> Ed Anderson.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
> 


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