Message-ID: <000e01c3b02c$3a272780$1702a8c0@WorkGroup>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2754099@logan.com>
Subject: Re: [FlyRotary] Radiator size
Date: Fri, 21 Nov 2003 07:37:29 -0500
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Hi Marc,

    Good to hear from you.  No doubt in my mind that many/most of your
comments are right on the mark.  While some of us are familar with K&Ws work
and understand at least the basic duct requirements as revealed in their
study, we are also forced to deal with the real world constraints in
packaging our cooling systems.  Different folks have different constraints.
I for one would find it very difficult to make my inlet duct the proper
length to benefit from the K&W study.   Also, I have never found any
heat/transfer data on the evaporator cores and I have looked - perhaps not
in the right places.  Since the cores are for airconditioners and not water
based coolant systems, I rather doubt we would find any useful data on
them - unless some well instrumented experments were run and data collected.
Several folks have run some flow test, but I don't recall any actually
runing temperature drops/vs airflow/vs coolant flow etc.

I agree that inadequate outlets will choke an otherwise adequate cooling
system.  My outlet is oversized.  My total inlet area of my orginal ducts
was 72 sq inches and my out let is 126 for an 1.75 ratio.  I have no cooling
problems , but undoubtedly incur more cooling drag than a smaller opening
would provide.

So good to hear from you - and hopefully you will add to our knowledge base
on such matters.

Best Regards

Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message -----
From: "Marc de Piolenc" <piolenc@mozcom.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, November 20, 2003 11:06 PM
Subject: [FlyRotary] Radiator size


> Dear Listmates,
>
> I've been a lurker on this list for some time, monitoring it for
> information on aircraft rotary engine installations. I've learned a good
> deal, but haven't had much to say. I'm chiming in now because the topic
> is one that I am studying intensively in order to write a book about it.
>
> I'm co-author of the first in a series of books about ducted propulsors,
> called (appropriately enough) Ducted Fan Design, Vol. 1. It presents a
> very simplified method of designing ducted fans and propellers in which
> the duct or shroud length is at least equal to the diameter of the
> rotor. Subsequent volumes will deal with short shrouds and other topics,
> but volume 2 is now reserved for cooling systems. This was originally
> supposed to be just a chapter or two in a book devoted primarily to
> propulsion, but as I did my research I discovered that, just as
> aerodynamicist Bruce Carmichael had said in his book on drag reduction,
> there is a huge gap between what cooling systems should cost in terms of
> drag and shaft power, and what they actually do consume. Even more
> surprising, even people who devote their whole lives to reducing drag,
> more often than not have only a vague empirical notion of how to achieve
> that with cooling systems. Hence in an airplane where external drag has
> been carefully optimized, a large increment in performance is often
> still available from improving cooling drag. Better still, the cooling
> effect can usually be improved as well.
>
> Good information was available in the past on this subject for those
> willing to dig for it. Some engine design texts could teach optimization
> of the coolant side of things, while a few aerodynamics texts - notably
> Kuechemann & Weber's _Aerodynamics of Propulsion_ - could teach radiator
> installations. All that is out of print. What is more, putting all the
> necessary guidance into modern language and in one consistent notation
> should make Volume 2 more accessible in every sense. So much for the
> commercial.
>
> There are a lot of questions on the list about the proper size for a
> radiator, but it is far more important to define the cooling duct's
> parameters first. The only mention of the duct in the latest digest of
> messages concerned the inlet, but the EXIT of the duct is far more
> important, because that and the pressure drop through the radiator
> control, in the final analysis, the mass flow through the radiator - and
> that is what produces the cooling effect. It is possible to spoil the
> effect of a good exit by poor inlet design - by making the inlet lip too
> sharp or cambering it the wrong way - but it really takes an effort! I
> doubt there is anybody on this list whose inlet is wrong.
>
> The proper duct parameters, in turn, depend on the pressure-drop and
> heat-transfer characteristics of the radiator core, as expressed in the
> modification of Miley's equation that I used in my article published in
> Contact! issue number 62. Two parameters are needed to express a
> particular core's presure drop characteristics, and another two for heat
> transfer. Each relation requires only two measurements to determine the
> two parameters, since the form of the relation is known. What's more,
> the pressure drop measurements can be carried out with no heat transfer
> taking place, as there are procedures for correcting for the occurrence
> of heat transfer in designing the duct. For heat transfer, obviously,
> entry and exit temperatures DO need to be taken for both the coolant and
> the air, simultaneously with the pressure drop and flow rate. Even so,
> these can be taken at the SAME two speeds previously calibrated for the
> pressure drop measurements. As a result, both the test rig and the test
> procedure can be simplified by comparison with NACA's early radiator
> installation test rigs, which may have inspired Rube Goldberg.
>
> The only problem is, I don't know anybody in the amateur-builder
> community who is doing this, and I don't know whether the cores that you
> folks are using come with the necessary information already provided by
> the manufacturer. It is, after all, much easier to pick two points off a
> plot than to derive them from tests... I would very much like to know,
> because aside from needing to give valid guidance in volume 2, I will
> soon be starting on a hovercraft project for a Catholic parish located
> upriver from town and needing reliable transportation for farm goods one
> way, building materials the other way. Although I'll be buying plans for
> a proven h/c design, I will still be on my own where radiator
> installation is concerned, as the hover crowd are at the pre-1921 stage
> of development where a bare radiator was thought to give the best
> cooling effect.
>
> If anybody out there has manufacturer's pressure drop and/or heat
> transfer data for a core or finished radiator that he could scan and
> send me, I would be most grateful. It doesn't matter what core - I just
> need to test my work so far against real hardware currently on the
> market.
>
> Regards to all,
> Marc de Piolenc
> Mass Flow
> http://www89.pair.com/techinfo/MassFlow/ductbook.htm
> --
> "The troops returning home are worried. 'We've lost the peace,' men tell
> you. 'We can't make it stick.' ... Friend and foe alike look you
> accusingly in the face and tell you how bitterly they are disappointed
> in you as an American. ... Never has American prestige in Europe been
> lower.... Instead of coming in with a bold plan of relief and
> reconstruction we came in full of evasions and apologies.... A great
> many Europeans feel that the cure has been worse than the disease. The
> taste of victory had gone sour in the mouth of every thoughtful American
> I met." --Life Magazine, January 7, 1946
>
>
>
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