flyrotary@lancaironline.net Mailing List Archive

More details, Jeff?

From my reading on cooling systems, the only time I have read of an improvement in cooling using a restrictor plate is in the case where the water pump is cavitaing. The restrictor plate improving cooling in that case because it produces more back pressure around the impeller and eliminates/reduces the air bubble caused by cavitations. This permits the impeller to pump coolant rather than trying to pump air.

Otherwise, the old myth about restrictors/slow water cooling better is just that - a myth.

Now it may well be that a hose size larger than 0.75" dia is unnecessary for some installations and going above size that does not really increase flow rate or cooling, so not saying what you found to be in error, but just didn't want folks to think that restriction = better cooling.

The basic equation for heat removal ('Q') clearly shows that more mass flow ('M') equals more heat removal. Q = M*Dt/Cp - M being the mass flow of the coolant.

Here is a link to one of the better non-technical discussion of all aspects of cooling

http://www.stewartcomponents.com/Tech_Tips.htm

read Tech Tip #3 - Thermostats & Restrictors for a discussion about the restriction myth

FWIW

From: Jeff Whaley

Sent: Thursday, July 28, 2011 10:26 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Coolant Restrictor Plate

I saw Lynn’s coolant diagram with a restrictor plate in it … you guys with evaporator cores and 1” coolant hoses have a 1” restriction, this based on Mazda’s design of 1.5” inlet/outlet on the stock water pump and the stock design includes a thermostat. With all of that as a background (never had a thermostat), I decided to try a restrictor plate in my coolant system, using a 0.75” hole in a plate at the water pump outlet into my 1.5” radiator hoses. I can say that it doesn’t do any harm and may have actually provided about 5% improvement … more testing to follow.

Jeff Whaley

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