Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Sun, 12 Oct 2003 15:55:52 -0400 Message-ID: X-Original-Return-Path: Received: from ms-smtp-03.southeast.rr.com ([24.93.67.84] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2633687 for flyrotary@lancaironline.net; Sun, 12 Oct 2003 10:21:22 -0400 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03.southeast.rr.com (8.12.10/8.12.2) with SMTP id h9CEIxW0027497 for ; Sun, 12 Oct 2003 10:19:00 -0400 (EDT) X-Original-Message-ID: <001601c390cb$dcad1f80$1702a8c0@WorkGroup> From: "Ed Anderson" X-Original-To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: solo's & Delta T... no more emergencies X-Original-Date: Sun, 12 Oct 2003 10:19:34 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0013_01C390AA.55724CA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0013_01C390AA.55724CA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: [FlyRotary] Re: solo's & Delta T... no more emergencies Todd, It might not be too surprising about the oil temp varying as it = does. The key as you mentioned is the power load. Here's my thinking. = Since the oil is the primary cooling medium for the rotors where the = power is produced, it would seem to me that a rise in temperature (due = to a power increase) would first be localized to and noticed in the oil = - before some of the increased heat perhaps diffused over to the = coolant system. Thus a surge in oil temperature as the power increases = may well result in a larger temperature drop until it reaches thermal = equilibrium again.=20 If the cooling part of my spreadsheet is anywhere close to reality, = it shows that the Mazda oil cooler is actually not rejecting sufficient = heat at certain power settings and airspeeds. Indeed, of the evaporator = cores and oil cooler, it appears the cores support getting rid of some = of the heat the oil cooler apparently does not reject under certain = operating conditions. This again implies (at least to me) that you = might see a surge in oil temps before the increased heat from the oil = diffuses over into the coolant system and stabilizes temps.. Someplace I read that when a cooling system is operating at its = greatest Delta T, it is not only operating at its most efficient it is = also operating on the verge of cooling failure {:>). In that by = definition, the greatest Delta T means the temperature difference has = stabilized and only the mass flow now has any affect on heat removed. = If Temperature of incoming medium continues to increase pass this point = and results in no further delta T difference, that means the additional = heat is not being completely rejected. Only alternative in that case to = get rid of the additional heat is to increase mass flow. Ok, that has exposed my ignorance about heat transfer - Bill? anybody = else have a theory? Ed Anderson I don't have a OAT sensor on my plane but the ground temp was 9C. = I took it up to 13000, where it should have been ~ -17C. Oddly enough I = seem to have a constant 20C delta T on the coolant but the oil delta T = will vary between 5 and 20 degrees depending on power load. =20 SNIP . This indicates (to me) possible localized boiling in the block for a = few seconds until the flow increases again, reducing the pressure. For = this reason I've taken to switching the pump to bypass the controller = while practicing touch & goes. ------=_NextPart_000_0013_01C390AA.55724CA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
 Subject: [FlyRotary] Re: solo's & Delta = T... no=20 more emergencies
 Todd,
 
    It might not be too = surprising=20 about the oil temp varying as it does.  The key as you mentioned = is the=20 power load.  Here's my thinking.  Since the oil is the = primary=20 cooling medium for the rotors where the power is produced, it would = seem to me=20 that a rise in temperature (due to a power increase) would first be = localized=20 to and  noticed in the oil -  before some of the=20 increased heat perhaps diffused over to the coolant = system. =20 Thus a surge in oil temperature as the power increases may well result = in a=20 larger temperature drop until it reaches thermal equilibrium=20 again. 
 
 If the=20 cooling part of my spreadsheet is anywhere close to reality, it shows = that the=20 Mazda oil cooler is actually not rejecting sufficient heat at certain = power=20 settings and airspeeds.  Indeed, of the evaporator cores and oil = cooler,=20 it appears the cores support getting rid of some of the heat the oil = cooler=20 apparently does not reject under certain operating = conditions.  This=20 again implies (at least to me)  that you might see a surge in oil = temps=20 before the increased heat from the oil diffuses over into the coolant = system=20 and stabilizes temps..
 
Someplace I read=20 that when a cooling system is operating at its greatest Delta T, it is = not=20 only operating at its most efficient it is also operating on the verge = of=20 cooling failure {:>).  In that by definition, the greatest = Delta T=20 means the temperature difference has stabilized and only the mass flow = now has=20 any affect on heat removed.  If Temperature of incoming medium = continues=20 to increase pass this point and  results in no further delta = T=20 difference, that means the additional heat is not being completely=20 rejected.  Only alternative in that case to get rid of the = additional=20 heat is to increase mass flow.
 
Ok, = that has=20 exposed my ignorance about heat transfer - Bill? anybody else have a=20 theory?
 
Ed=20 Anderson
 
 
    I don't have a OAT sensor on my plane but = the ground=20 temp was 9C. I took it up to 13000, where it should have been ~ -17C. = Oddly=20 enough I seem to have a constant 20C delta T on the coolant but the = oil delta=20 T will vary between 5 and 20 degrees depending on power load. =20
 
SNIP
 
. This=20 indicates (to me) possible localized boiling in the block for a few = seconds=20 until the flow increases again, reducing the pressure. For this reason = I've=20 taken to switching the pump to bypass the controller while practicing = touch=20 & goes.
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