MessageTodd has provided some very interesting and valuable information on the performance of the EWP.

If the pump, flowing through the Ford evaporator coils, flows 9.3 gallons/min, we can determine some things about the performance.  The attached PDF file shows how to calculate flow vs. water temperature and air temperature drop as a function of horsepower generated.

At 9 gallons per min, if Todd's engine generates 150 horsepower to the prop, and the engine is successfully cooled, then the temperature rise across the engine (and drop across the radiators) must be a little more than 50 degrees F. In other words, at 180F out of the engine, the coolant entering the engine must be below 130F.

At 100 horsepower to the prop, it is about 40 degrees temperature drop.

Now, to get 50+ degrees drop on the coolant side, means that the heat has to be transferred to the air.  In a first approximation, the temperature of the air leaving the radiators cannot be hotter than the temperature of the water leaving the radiators, so the air can only be heated to some-what less than 130F. If we operate on a hot day, (100F), we only have 30F available to heat the air. Looking at the second chart in the attachment, we can see that at 150 horsepower, we will have to be flowing about 8,000 ft^3/min through the radiators. Is that possible? If we *assume* that he has about 50 in^2 of opening in the cowl feeding the two evaporator cores ( a little bigger than 3x8 openings x 2) then the area of the opening is 50/144 = 0.347 ft^2. To cram 8000 ft^3 of air through this opening the air must be moving at 8000-ft^3/min /0.347 ft^2 = 23040 ft/min

(23040 ft/min)/(60 sec/min) = 384 ft/sec.  Now, 60 miles per hour = 88 ft/sec, so the air moving through the openings must be moving at 384*60/88 = 262 miles per hour.  This doesn't seem possible in a 150 mph plane.

So, does this mean that the EWP does not work? NO, what is means is one of several possiblities, maybe in combination.

1. Todd may be developing less that 150 horsepower
2. Todd may be flying in much cooler climate.
3. Todd may be letting the water go to a higher temperature than 180F

The combination of the above 3 items, hotter water temperature, cooler ambient temperature, and less horsepower would allow the EWP to work within the parameters reported by Todd. However, someone considering putting an EWP in a 3 rotor engine, generating well over 200 horsepower may not be pleased with the result.

Todd, do you have fuel burn or horsepower numbers for your flights?

Bill Schertz
KIS Cruiser # 4045
  ----- Original Message -----   From: Todd Bartrim   To: Rotary motors in aircraft   Sent: Saturday, November 06, 2004 3:27 PM
  Subject: [FlyRotary] Re: EWP


  Whoaa, before anybody gets worked up over my current draw figures, I'd made a mistake in my report and had sent another post correcting it the next day. Below is the corrected post.... hmmnn, is there a way of going back into the archives to correct erroneous data, as this same issue came up once before based on my incorrect data post.

  Hi Guy's
          I had a hard time believing the current draw for the pump so I brought home my good "Fluke" multimeter from work. The one I used last night was a cheap Digital meter from "Canadian Tire". I seldom use this one, so I'm not familiar with it but since it is very similar in outward appearance to my "Fluke 87" I assumed the same functions would apply. They don't.

   OK,OK, enough excuses, now for the real current draw.

    a.. continuous current draw - 4.3 amps     b.. max inrush current draw at 100mS - 6.8 amps     c.. max inrush current draw at 250uS - 13 amps     d.. continuous current draw at minimum controlled flow - .2 amps
  The max inrush current is not really relevant to our concerns, but there it is for those that care.
  This higher current flow is still well within acceptable limits for my needs, and I expect that while in cruise flight, the controller will be reducing pump speed and current draw.

  I've reposted the flow measurements along with this post with the incorrect current draw deleted. I hope this clears up any confusion about EWP current requirements. I           I ran the first test with the Ford evap cores in the system, plumbed in parallel.
      a.. Max flow 9.3 usg/m  35 l/m       b.. 12.07 volt battery supply voltage       c..         Second test had no evap cores in the system. Simply recirced water through pump - engine - header tank - pump.
      a.. max flow 13.0 usg/m   49 l/m       b.. 12.06 volt battery supply voltage       c..         Third test, I plumbed in a set of GM (Harrison) evap cores in parallel, into the system. I hung them just below my mounted Ford cores, using they same pipe sizes in an effort to have comparable test conditions.
      a.. max flow 7.7 usg/m   29 l/m       b.. 12.4 volts supply voltage (I hooked a trickle charger to the battery)       c..         In each test configuration test results are with heater valve closed. Heater core added .5 usg/m in each case.

        In all of the above tests the electronic pump controller was bypassed to give full battery voltage to the pump. With the pump controller in use, as the water was cold well water, controller had pump at minimum flow which was measured at .6 usg/m - 2.2 l/m.     I've just been lurking since returning from school as I've got allot to catch up on around here, so am trying not to get distracted with the list, however I needed to jump in on this one. I need to head out to the airport today to install my new radio and hopefully get out for a flight, as they are calling for 5" of snow tonight.

    Todd Bartrim

    RV9Endurance
    13B Turbo Rotary
    C-FSTB
    http://www3.telus.net/haywire/RV-9/C-FSTB.htm

                 "The world will always have a place for those that bring hard work and determination to the things they do."
     

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