|
Message
Todd 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 -----
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.
- continuous current draw - 4.3 amps
- max inrush current draw at 100mS - 6.8
amps
- max inrush current draw at 250uS - 13 amps
- 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.
- Max flow 9.3 usg/m 35 l/m
- 12.07 volt battery supply voltage
Second test had no evap
cores in the system. Simply recirced water through pump - engine - header
tank - pump.
- max flow 13.0 usg/m 49 l/m
- 12.06 volt battery supply voltage
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.
- max flow 7.7 usg/m 29 l/m
- 12.4 volts supply voltage (I hooked a trickle
charger to the battery)
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
"The world will always have a place for those that bring hard work and
determination to the things they
do."
|