=20 That's exactly what I HAD thought, until I was told that the air could pass through too fast and not pick up as much heat. This didn't make sense to me. Maybe I wasn't listening closely and missed the point altogether (wouldn't be the first time). =20 =20 What I DO know is that the air is flowing faster through the water radiator than the oil radiator. (I'm not sure I have the ASI's hooked up correctly, but they're both hooked up the same). I have a pitot behind each radiator hooked up to two separate ASI's. In slow cruise, say 125-130 kts, the water radiator ASI will read about 110knts and the oil ASI will read about 90 kts. The way it was behaving before I opened up the exit, it appeared that the air from the water radiator was trying to exit backwards through the oil inlet. I say this because of how high the oil temps were reading. I enlarged the cowl exit, and both the water and oil temps dropped significantly. =20 =20 The ASI's are referencing the static port for these readings; should they be referencing cowl or cabin pressure instead? Airspeeds readings seem awfully high to me. =20 =20 Mark (Going to the airport today to recalibrate temp sensors) =20 ------_=_NextPart_001_01C80387.EFEA1D68 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

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That's exactly what I HAD thought, until I = was told that=20 the air could pass through too fast and not pick up as much heat. =

Mark... this is what I was trying to = communicate. It could=20 be totally wrong so let's get more opinions. = Ed??

With respect to exit area size = only. =20

If the volume of air through the coolant = radiator was=20 moving faster than optimum the air delta T would be = lower than=20 it would be with slower air. Slower air at a higher delta T means less = air needs=20 to exit the cowl. What is optimum? Every install is unique so = it=20 needs to be viewed \ identified on each installation. Ed uses = a 30%=20 duct air speed as a reference point. If I understand this correctly the = diffuser=20 play a role in duct airspeed. If the air is not being diffused optimally = the=20 airspeed could be much higher than 30% through the part of the core. = Dennis H.=20 and I observed airspeeds through a test core at 50% + without a = diffuser.=20

Your inlets are 72sqin with 306sqin = core face for=20 water and 24.75 sqin with 102 sqin for oil. Both are=20 competing for the same exit area. IF = this is=20 an exit area problem only then enlarging it should improve both water = and oil=20 proportionally. Water should realize 2/3 of the = improvement and=20 oil 1/3. 306 sqin vs 102 sqin. Your improvements after = opening the=20 exit seem to track this very close. So increasing your exit area = further=20 should show more improvements in both oil and water to a point. But you = do not=20 need more water cooling improvements right?

Core 306 sqin at an airspeed of = 115mph.

40% or 46 mph =3D 8602 cfm 8602 cfm = at a 50 deg=20 air delta T =3D 7741 btu's \ min

30% or 34.5 =3D 6451=20 cfm 6451 cfm at a 80 deg air = delta T =3D=20 7741 btu's \ min

In this example 2151 cfm less air needs to flow = through the=20 water radiator to produce the same btu rejection. So what effect would = 2151 cfm=20 less air through the water radiator and exit area have on the oil = cooler's=20 ability to flow more air? Would it improve the oil cooler air flow by = 1/3 or 717=20 cfm? Not sure.

Can your radiator produce a 80 deg air delta T? = It may only=20 produce 60, 70 or??

Am I in left field here?

Bobby

(flow testing new radiator ducts prototype = today)

From: Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On Behalf Of Mark=20 Steitle
Sent: Sunday, September 30, 2007 4:28 AM
To: = Rotary=20 motors in aircraft
Subject: [FlyRotary] Another cooling=20 question

ED wrote:

<snip>

Mark, if you really had excess air flowing through your = radiators the=20 coolant would drop more than 4 Deg F. In fact, the more air flow = the more=20 coolant Delta T you would drop through the radiator.

<snip>

That's exactly what I HAD thought, until I was told that the air = could pass=20 through too fast and not pick up as much heat. This didn't make = sense to=20 me. Maybe I wasn't listening closely and missed the point = altogether=20 (wouldn't be the first time).

What I DO know is that the air is flowing faster through the water = radiator=20 than the oil radiator. (I'm not sure I have the ASI's hooked up = correctly,=20 but they're both hooked up the same). I have a pitot behind each = radiator=20 hooked up to two separate ASI's. In slow cruise, say 125-130 kts, = the=20 water radiator ASI will read about 110knts and the oil ASI will read = about 90=20 kts. The way it was behaving before I opened up the exit, it = appeared that=20 the air from the water radiator was trying to exit = backwards through=20 the oil inlet. I say this because of how high the oil temps were=20 reading. I enlarged the cowl exit, and both the water = and oil=20 temps dropped significantly.

The ASI's are referencing the static port for these readings; = should they=20 be referencing cowl or cabin pressure instead? Airspeeds readings = seem=20 awfully high to me.

Mark

(Going to the airport today to recalibrate temp sensors)

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