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Date: Tue, 13 Nov 2007 17:31:27 -0800 (PST)
From: Ron Springer <ron2369@sbcglobal.net>
Subject: Re: Thick vs Thin was : Diffuser Configuration Comparison
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-2470566@logan.com>
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Message-ID: <992741.95552.qm@web81314.mail.mud.yahoo.com>

Ed,

Step 3 was just an assumption, but you are right. The
largest source of total pressure loss in the system is
the radiator, and if you change that you will
definitely change the mass flow rate through the
system. The total pressure loss will be more for the
smaller frontal area and thicker radiator, so the mass
flow rate should be less for that case. How much less
cannot be stated because it depends on all of the
geometric details from the inlet to the exit of the
duct.

Also, I just noticed that the friction and heat
transfer scaling that I mentioned in the last email is
at the top, right of page 9-3 in Hoerner. Thought I
would mention that since you quoted him.

Ron


--- Ed Anderson <eanderson@carolina.rr.com> wrote:

> Hi Ron,
> 
> I understand your succinct and clearly spelled out
> process, but I guess 
> where I depart is at step 3.
> 
>  My point is if you change the core,  you have
> changed both the mass flow 
> and deltaT.  You would not put a core 1/2 the
> frontal area of the original 
> thin core without changing at least the diffuser
> cross section area not to 
> mention the area after the core.  So even if you
> left the inlet the same 
> size,  I am confident there is no way you would get
> the same mass flow as 
> before, perhaps more, perhaps less, but not the same
> because by changing the 
> core we have changed the parameters of the system
> and the flow through it.
> 
> I content that by selecting the characteristics of
> the thick radiator you 
> can influence both the flow and the delta T.
> 
> But, I will readily admit that being confident does
> not necessarily equate 
> to being correct - just confidently wrong {:>)
> 
> Ed