X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 10 [X] Return-Path: Received: from bay0-omc2-s19.bay0.hotmail.com ([65.54.246.155] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2022469 for flyrotary@lancaironline.net; Wed, 02 May 2007 20:09:53 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.54.246.155; envelope-from=lors01@msn.com Received: from hotmail.com ([65.54.250.88]) by bay0-omc2-s19.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.2668); Wed, 2 May 2007 17:08:57 -0700 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Wed, 2 May 2007 17:08:57 -0700 Message-ID: Received: from 4.171.129.207 by BAY115-DAV16.phx.gbl with DAV; Thu, 03 May 2007 00:08:53 +0000 X-Originating-IP: [4.171.129.207] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: oil coolers Date: Wed, 2 May 2007 20:08:49 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01BB_01C78CF5.B2630B20" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.50.0034.2000 Seal-Send-Time: Wed, 2 May 2007 20:08:49 -0400 X-OriginalArrivalTime: 03 May 2007 00:08:57.0412 (UTC) FILETIME=[3E681040:01C78D17] Return-Path: lors01@msn.com This is a multi-part message in MIME format. ------=_NextPart_000_01BB_01C78CF5.B2630B20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ernest Christley wrote:=20 Question from the peanut gallery. I don't plan to use a oil/water=20 exchanger, but aren't they counterproductive? The efficiency of the cooling relies on deltaT. The best situation is=20 having the hottest coolant interfacing with the air, and it has always=20 been my understanding that the oil exits the engine hotter than the=20 water. Will an oil/water exchanger reduce the overall efficiency of the = system by allowing the exit air, on average, to leave with less BTUs? Tracy Crook answered: Your questions get to the very heart of the issue and reveals more of = the complexity. I see you point about Delta T but since we are raising the coolant temp = (using the oil to water heat exchanger) this does increase the = efficiency of the radiator. The water temp is still not as high as the = oil was but there is a lot more surface area on the radiator than the = oil cooler and this makes up for the smaller delta T as compared to the = hot oil. With oil to air, we are only getting the high delta T on 30% = of the cooling system, with oil to water, we are increasing the = efficiency on 100% of the system. Lynn's point (below) about having to do 30% more cooling with the = radiator (with oil to water cooling) is true BUT, this is not the same = as saying that we need a 30% larger radiator. I don't know the exact = number but much of the 30% increase in heat dissipation comes from the = automatic efficiency increase from the higher delta T of the radiator. = This effect is very noticeable on the Renesis engine where the exhaust = ports in the side housings add about 8 - 10 degrees (at high throttle) = to the coolant temp above what the peripheral exhaust did. I did not = increase the radiator size to compensate for this because of the = efficiency boost from higher Delta T. The coolant temp after the = radiator was only about 1.5 degrees hotter than before, not a big deal. = What WAS hotter was the under cowl temps (air after the radiator) which = is the evidence that the air is indeed leaving with more BTUs. The problem for the Renesis is that the high end water temp is possibly = too high for oil to water coolers to be effective. There may be a work = around for this. The oil cooling water may have to be tapped off at the = heater port before it passes the exhaust ports. Tracy lehanover@aol.com wrote: > > > There is only air cooling. There is nothing else. If you can dump = the excess heat through the water radiator, > > then its a great idea, and works just fine. Oil temps above 160 = degrees cost power. The cooler the better. > > You will need 1/3 more water cooling than you started with to make = it work. You cannot fool Mother Nature.=20 > ------=_NextPart_000_01BB_01C78CF5.B2630B20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ernest Christley wrote: 

Question from the peanut=20 gallery.  I don't plan to use a oil/water
exchanger, but aren't = they=20 counterproductive?

 The efficiency of the cooling relies on=20 deltaT.  The best situation is
having the hottest coolant = interfacing=20 with the air, and it has always
been my understanding that the oil = exits the=20 engine hotter than the
water.  Will an oil/water exchanger = reduce the=20 overall efficiency of the
system by allowing the exit air, on = average, to=20 leave with less BTUs?
Tracy Crook answered:

Your questions get to the very heart of the issue and reveals = more of=20 the complexity.
 
I see you point about Delta T but since we are raising the coolant = temp=20 (using the oil to water heat exchanger) this does increase the = efficiency of the=20 radiator.   The water temp is still not as high as the oil was = but=20 there is a lot more surface area on the radiator than the oil cooler and = this=20 makes up for the smaller delta T as compared to the hot oil.   = With=20 oil to air, we are only getting the high delta T on 30% of the cooling = system,=20 with oil to water, we are increasing the efficiency on 100% of the = system.
 
Lynn's point (below)  about having to do 30% more cooling with = the=20 radiator (with oil to water cooling) is true BUT, this is not the same = as saying=20 that we need a 30% larger radiator.  I don't know the exact number = but much=20 of the 30% increase in heat dissipation comes from the automatic = efficiency=20 increase from the higher delta T of the radiator.  This effect = is very=20 noticeable on the Renesis engine where the exhaust ports in the side = housings=20 add about 8 - 10 degrees (at high throttle) to the coolant temp = above what=20 the peripheral exhaust did.  I did not increase the = radiator=20 size to compensate for this because of the efficiency boost from higher = Delta=20 T.  The coolant temp after the radiator was only about 1.5 degrees = hotter=20 than before, not a big deal.  What WAS hotter was the under cowl = temps (air=20 after the radiator) which is the evidence that the air is indeed leaving = with=20 more BTUs.
 
The problem for the Renesis is that the high end water temp=20 is possibly too high for oil to water coolers to be = effective.  There=20 may be a work around for this.  The oil cooling water may have to = be tapped=20 off at the heater port before it passes the exhaust ports.
 
Tracy
lehanover@aol.com=20 wrote:
>
>
> There is only air cooling. There is = nothing=20 else. If you can dump the excess heat through the water=20 radiator,
>
> then its a great idea, and works just fine. = Oil=20 temps above 160 degrees cost power. The cooler the = better.
>
> You=20 will need 1/3 more water cooling than you started with to make it = work. You=20 cannot fool Mother Nature. =
>
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