X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 10 [X] Return-Path: Received: from ispmxmta05-srv.windstream.net ([166.102.165.166] verified) by logan.com (CommuniGate Pro SMTP 5.1.4) with ESMTP id 1733325 for flyrotary@lancaironline.net; Wed, 03 Jan 2007 12:50:10 -0500 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.166; envelope-from=montyr2157@alltel.net Received: from ispmxaamta08-gx.windstream.net ([162.40.142.190]) by ispmxmta05-srv.windstream.net with ESMTP id <20070103174918.TQOD10623.ispmxmta05-srv.windstream.net@ispmxaamta08-gx.windstream.net> for ; Wed, 3 Jan 2007 11:49:18 -0600 Received: from Thorstwin ([162.40.142.190]) by ispmxaamta08-gx.windstream.net with SMTP id <20070103174917.YFGB4808.ispmxaamta08-gx.windstream.net@Thorstwin> for ; Wed, 3 Jan 2007 11:49:17 -0600 Message-ID: <002b01c72f5f$8de76820$01fea8c0@Thorstwin> From: "M Roberts" To: "Rotary motors in aircraft" Subject: EM2 Data Logger pix Date: Wed, 3 Jan 2007 11:49:45 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0028_01C72F2D.432B8D70" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0028_01C72F2D.432B8D70 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: M Roberts=20 To: flyrotary-report@lancaironline.net=20 Sent: Wednesday, January 03, 2007 10:55 AM Subject: Re: EM2 Data Logger pix Monty, I don't understand what you are saying/implying about the "large = diameter rad hoses" ("The reason for cars requiring large diameter rad = hoses is now less muddy in my muddy fuddled brain."). I'm planning to = run autosized rad hose and split into two parallel smaller hoses into = two evap cores, with everything (inside area of fittings) sized to be = equal to the auto hose inside area. I'm definitely NOT going to run the = smaller hoses and fittings used by most folks so far. Just goes against = my sense of "basics". David Carter David, I am simply saying that in my opinion it is not necessary to use the = large auto sized hoses in our application. They are an automotive driven = requirement. The biggest resistance in the system is the cooler or the = engine block. The hoses are not the driver, unless you go to some = ridiculously small size. Take a look at an F1 car sometime, they use = small hoses. The reason for the large hoses in a street car is to cool a = heat soaked engine at a stop light when the water pump is barely turning = over and there is no flow or head pressure from the pump.=20 Think of a full throttle blast onto the freeway with an already hot = motor. Then you get stopped in traffic. The flow from the pump goes to = nil. The head pressure from the pump goes to nil. The heat flux from = that full throttle blast is just making its way to the coolant. At this = point you need all the help you can get. You need a big hose! This does not happen in an airplane unless you abort a takeoff run.=20 Do whatever you think is best, that is why this is called experimental = aviation. ;-). It certainly won't hurt anything to use larger hoses. It = is just a little extra weight. It gives you a little more coolant volume = and more thermal mass. I just don't think that it is necessary to do so. = This data does not show that there is anything "wrong". The steady state = data shows that the cooling effectiveness is VERY good. The air exiting = the radiator is close to the exit temp of the engine coolant after the = radiator. In fact it is within about 10 deg or so!! That means the = cooler is VERY effective. The airplane is not swallowing a huge amount = of drag producing air to cool the engine.=20 If you use a great big thin radiator with a small air delta T you have = to swallow a lot more air which equals drag. It also shows that there is quite a bit of thermal mass in the system. = That gives you a margin of safety. Nothing is instant. The argument that = you need some huge radiator always neglects this fact. If you use the = old NACA criteria for a fully laden air cooled bomber taking off in = North Africa, you will wind up with a huge radiator. Air cooled engines = are not the same as liquid cooled engines and we are not flying bombers = in North Africa. There is a lot more thermal inertia in our system than = an air cooled engine. Tracy had a climb duration of almost a minute. It = was another 20 sec or so after he chopped the throttle and the rpm, = coolant flow, and TAS went DOWN until the temps peaked. If you can't get = over your obstacle and level off a little and up the speed in one min, = you need to stop trying to fly over Mt McKinley at Vx. It takes time for the heat flux to make its way through the metal to the = coolant. Then to the radiator, and finally to the air. When the rpm, = coolant flow, airspeed are all changing, you cannot make comparisons = between the various temps. It is not a valid comparison. Too many = interactions and thermal resistances to deal with. There is also no way to know what is going on with any kind of boiling. = To do that you need a thermocouple on the surface of the metal in the = coolant passage. Information that we don't have. If you saw a jump in = the water pressure NOT related to rpm change you could surmise the = existence of some type of boiling. But to be sure you need a TC on the = wall of the coolant passage. Monty ------=_NextPart_000_0028_01C72F2D.432B8D70 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----=20
From: M = Roberts=20
Sent: Wednesday, January 03, 2007 10:55 AM
Subject: Re: EM2 Data Logger pix

Monty,

I = don't understand=20 what you are saying/implying about the "large diameter rad hoses" ("The = reason=20 for cars requiring large diameter rad hoses is now less muddy in my = muddy=20 fuddled brain."). I'm planning to run autosized rad hose and split into = two=20 parallel smaller hoses into two evap cores, with everything (inside area = of=20 fittings) sized to be equal to the auto hose inside area. I'm definitely = NOT=20 going to run the smaller hoses and fittings used by most folks so far. = Just goes=20 against my sense of "basics".

David Carter
 
 
David,
 
I am simply saying that in my opinion it is not = necessary to=20 use the large auto sized hoses in our application. They are an = automotive driven=20 requirement. The biggest resistance in the system is the cooler or = the=20 engine block. The hoses are not the driver, unless you go to some = ridiculously=20 small size. Take a look at an F1 car sometime, they use small hoses. The = reason=20 for the large hoses in a street car is to cool a heat soaked engine at a = stop=20 light when the water pump is barely turning over and there is no flow or = head=20 pressure from the pump.
 
Think of a full throttle blast onto the freeway with an already = hot=20 motor. Then you get stopped in traffic. The flow from the pump goes to = nil. The=20 head pressure from the pump goes to nil. The heat flux from that full = throttle=20 blast is just making its way to the coolant. At this point you need all = the help=20 you can get. You need a big hose!
 
This does not happen in an airplane unless you abort a takeoff = run.=20
 
Do whatever you think is best, that is why this is called = experimental=20 aviation. ;-). It certainly won't hurt anything to use larger hoses. It = is just=20 a little extra weight. It gives you a little more coolant volume and = more=20 thermal mass. I just don't think that it is necessary to do so.=20
 
This data does not show that there is = anything=20 "wrong". The steady state data shows that the cooling effectiveness = is VERY=20 good. The air exiting the radiator is close to the exit temp of = the engine=20 coolant after the radiator. In fact it is within about 10 deg or = so!! That=20 means the cooler is VERY effective. The airplane is not swallowing = a huge=20 amount of drag producing air to cool the engine.
 
If you use a great big thin radiator = with a small=20 air delta T you have to swallow a lot more air which equals = drag.
 
It also shows that there is quite a bit = of thermal=20 mass in the system. That gives you a margin of safety. Nothing is = instant. The=20 argument that you need some huge radiator always neglects this fact. If = you use=20 the old NACA criteria for a fully laden air cooled bomber taking off in = North=20 Africa, you will wind up with a huge radiator. Air cooled engines are = not the=20 same as liquid cooled engines and we are not flying bombers in North = Africa.=20 There is a lot more thermal inertia in our system than an air cooled = engine.=20 Tracy had a climb duration of almost a minute. It was another 20 sec or = so after=20 he chopped the throttle and the rpm, coolant flow, and TAS went = DOWN until=20 the temps peaked. If you can't get over your obstacle and level off a = little and=20 up the speed in one min, you need to stop trying to fly over Mt McKinley = at=20 Vx.
 
It takes time for the heat flux to make = its way=20 through the metal to the coolant. Then to the radiator, and finally to = the air.=20 When the rpm, coolant flow, airspeed are all changing, you cannot make=20 comparisons between the various temps. It is not a valid comparison. Too = many=20 interactions and thermal resistances to deal with.
 
There is also no way to know what is = going on with=20 any kind of boiling. To do that you need a thermocouple on the surface = of the=20 metal in the coolant passage. Information that we don't have. If you saw = a jump=20 in the water pressure NOT related to rpm change you could surmise = the=20 existence of some type of boiling. But to be sure you need a TC on the = wall of=20 the coolant passage.
 
 
Monty
 
 

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