Mailing List Message #3482
From: William <>
Subject: Re: [FlyRotary] Electric Water Pumps and Heat Rejection
Date: Fri, 3 Oct 2003 20:43:03 -0500
To: Rotary motors in aircraft <>
Last year I made measurements on the Mazda Water pump installed on the
block, pumping the water through the block. I have a 225K PDF file
describing the tests. if someone wants a personal copy, email me and I will
send it out.

Key points: I drove the pump at 2500 to 5500 rpm, by varying pulley size. I
drove the pump with a 1.5 horsepower saw motor, and had no difficulty using
only one belt. However, when I tried an 8 inch drive pulley supplied by Paul
Lamar to go higher in pump rpm, the motor would blow my circuit-breaker.  So
the power goes up dramatically as the rpm goes up, but at reasonable rpm,
the power is within the capability of the 1.5horse motor.
Bill Schertz
----- Original Message -----
From: "Ed Anderson" <>
To: "Rotary motors in aircraft" <>
Sent: Thursday, October 02, 2003 3:11 PM
Subject: [FlyRotary] Electric Water Pumps and Heat Rejection

> > In a message dated 10/1/2003 11:53:22 PM Eastern Daylight Time,
> > writes:
> >
> > > I was away for a few months late last year and the first half of
> > >  this year.  What's the status of Leon's EWP these days?
> > >  Inquiring minds need to know ... Jim S.
> > >
> > At the national championship races at Mid Ohio I saw a "C" sports racer
> with
> > a 12A and a remote electric pump. It must have been working, and at the
> > highest possible stress levels. A race (For them) is about 35 minutes
> above 8,000
> > RPM.
> >
> > Lynn E. Hanover
> >
> I agree Lynn, I think some of the views on electric water pumps are based
> some faulty analysis.
> While I do not desire an Electric Water Pump, I know that some of you do
> various reasons.  There is certainly a lot of opinions regarding them of
> that there is no doubt.  One analysis was conducted that supposedly
> that an Electric water pump would not be suitable for aircraft use and
> probably be of benefit only to very short duration evens, such as drag
> racers.  That analysis was based on the fact that the Mazda water pump
> supposedly consumed 13-16 HP at 6000 rpm.  The analysis then continued to
> show that a 16 HP 12 volt water pump would consume somewhere around 400
> and be impossibly large (about the size or bigger than the 13B)  - clearly
> proving that electric water pumps were totally unfeasible for aircraft
> Well, the only problem I found with the Analysis is the assumption that
> 13-16 HP consumed by the mechanical water pump was all required to provide
> the necessary coolant flow rate.  I strongly suspect that a lot (if not
> most) of that power was consumed pumping against unnecessary head pressure
> (at that rpm), turbulence, and other non-cooling losses.  If 16 HP is
> required then clearly an EWP is hopeless, but at least one person has had
> least one flight and had no serious cooling problems although I believe
> pump failed shortly thereafter (apparently nothing to do with its use).  I
> have also noted that on the other list, flow tests have been conducted
> a new water pump housing and a Mazda pump caltrage.  The flow figures are
> impressive - over 20 GPM (can't remember the exact figure) which looks
> good for engine use.  What I found VERY interesting is that the test rig
> motor driving the pump is a 2-3HP electric motor... a long ways from 16
> HP{:>).
> Sometimes, you just have to try it to see.  Don't get me wrong, I am all
> using any mathamatical tools and engineering logic to assess the potential
> of any component.  But, I have seen too many times when the "experts" have
> been wrong.  Its generally not the theory that they base their
> pronouncements on (or even in some cases experience), its the overly broad
> conclusions they draw or the failure to understand the real-world factors
> and the role they play.
> I continue to have excellent cooling from two evaporator cores whose
> thickeness supposedly relgate them to the "hopeless" category for cooling.
> In realiity, when I did the BTU heat rejection calculations for my
> crusing at 170 MPH TAS burning 7.5 GPH, I found the radiator (evaporator)
> cores have a cooling capacity reserve of 58% above that being used at that
> power setting. This is taking in to account that their extra thickenss
> adversley effect the thermal gradient (Delta T) as well as the additional
> pressure required to force air through the thicker core. I also found that
> the oil cooler was at its limit (due to air flow).  The latter was a
> surprise as I can bump up the "go juice" to higher HP and while oil temps
> increase, it appears that the extra capacity of the evaporator cores
> heat rejection after the oil cooler reaches its limit.  The 1" thick (or
> thinner) large surface area automobile radiators are necessary because of
> the low dynamic pressure at typical auto speeds in a urban area, dynamic
> pressure of course is much higher at the speeds we fly at.  So again what
> works fine designed for one environment is not necessary the "Cats Meaow"
> a different environment.
> These calculations only address the airflow ability to carry away the
> waste heat, not whether the water pump or oil pump is flowing the heat
> carrying medium to the cooling fins fst enough - thats another issue.  If
> the air flow is not sufficient to carry away the heat from the cooling
> then it doesn't matter how much coolant/oil flow you have carrying heat to
> the fins.
> Sorry, get to rambling on at times.
> Ed Anderson
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