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From: "William" <wschertz@ispwest.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-484752@logan.com>
Subject: Re: [FlyRotary] Re: oil cooler duct suggestion
Date: Sun, 24 Oct 2004 16:41:15 -0500
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Ed,
A third part of the equation is that the evaporator core may not function
very well as an 'oil' cooler, because it lacks the turbulence generators in
the oil flow passages. If the air temperature rise is low (20F you
speculated) I would look at the oil side of the equation.

Bill Schertz
KIS Cruiser # 4045
----- Original Message ----- 
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, October 24, 2004 9:03 AM
Subject: [FlyRotary] Re: oil cooler duct suggestion


> All good points, Bernie
>
>   My impression is that Rusty 1st objective is he would like for the oil
> temps to be lower.  Assuming that the GM core, Rusty is using for an oil
> cooler provides adequate air/metal contact area, then it would appear to
me
> that the problem at this time is getting more cooling effectiveness from
the
> airflow.  If you have adequate mass flow through the core, you will cool.
> However, if you have not adequately slowed the air down (diffusion) then
> your cooling drag could be higher than necessary.  But, it would appear to
> me at this point that cooling is the crucial aspect rather than minimizing
> cooling drag.  Tight 90 deg turns right before the core does not promote
> more flow through the core (in my opinion).
>
> According to K&W (if I understood the math), the more parallel  the flow
is
> to the core surface at entry to the core the greater the pressure loss is
> and the less cooling effectiveness.  They mention that in these cases the
> use of guide vans to direct the airflow more directly into the core
passages
> can result in cooling effectiveness approaching the straight-in duct. They
> also point out that staggering the core layers of the heat exchanger can
> also help (not feasible in this case).
>
> There appears to be two situations possible:
>
> 1.  There is adequate air mass flow to cool - but the system is not
> transferring the heat to the air with the best efficiency.  In this case,
> better diffusion offers improvement.
>
> 2.  There is not have adequate air mass flow to cool - in this case, it
does
> not matter how effective you diffuser is, your system will not cool
> adequately.
>
> So either situation could apply in Rusty's case.
>
>  If the delta T of the cooling air across the core  is in the vicinity of
> 40-50F then I would estimate that he has adequate diffusion but perhaps
not
> adequate air mass flow to cool.  In other words, the system  is
transferring
> the coolant heat to the air with high efficiency - but, simply not enough
> air to carry away adequate heat.
>
>  If the Delta T is closer to 20F then he may have sufficient air mass flow
> but inadequate diffusion (does not slow the air down enough for maximum
heat
> transfer)
>
> Even with the best diffuser  a system will not adequately cool if there is
> inadequate mass flow through the core.  So my focus would be 1st focused
on
> increasing the mass flow. Just my opinion, of course.
>
> Ed Anderson
>
>
>  >
> > Rusty and Ed,
> >
> > Ed, maybe you know more about his configuration than what I can glean
from
> his schetches. I think we need to know whether he is trying to almost
> totally diffuse the air like mine (hopefully :>) ) to minimize the turning
> pressure loss and allow the flow to accelerate thru the cooler or whether
he
> is trying to do the Lamar type min height and volume flow path.
> >
> > Rusty, what is the x-cross maximum area perpendicular to the cooler
> compared to the inlet area?
> >
> > Boy the weather looks like it should be good on Wed for your flight down
> Ed. Rusty, really sorry you aren't going to make it next weekend, I really
> want to meet the guy behind all these emails.
> >
> > Bernie
> >
> > >>  Homepage:  http://www.flyrotary.com/
> > >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
> >
>
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html