Here is a plot of temperature
data, all taken with CHT thermocouples.
Rad_in is clamped to the water
pipe just before it splits to go to the two
radiators
Rad_out is clamped to the exit
water pipe after the flow from the two rads has been
recombined.
Oil_filter is clamped to the oil
line as it exits the filter and enters the engine,
and
Oil Cool left end is bonded to
the end away from the entrance/exit on the oil cooler to tests that the oil
cooler is working. As you know the standard Mazda oil cooler sends the oil
down to the end and back. I was getting high oil temperatures on one
of my (non thermocouple ) oil sensors, and wanted to verify that the oil
cooler was working.
Bill Schertz
KIS Cruiser
#4045
N343BS
Phase I testing
Sent:
Friday, May 14, 2010 5:32 PM
Subject:
[FlyRotary] Re: alternative water pump
Hi
Bill,
Had seen your nice
data before, but one thing finally awoke in my old brain when I looked at it
this time that I had not considered before. We know that parallel
cores give slightly better efficiency than a serial core set because the
DT decreases for the
second core in the series compared to both parallel cores having the same
DT (at least in
theory). However, what jumped out at me this time was the real
significance of the parallel cores in cooling. In this case, I am
assuming no thermostat in the coolant flow.
If
I understood your graphs correctly, it looks like you are getting around 20
gpm flow with a single core (so presumably you would get a bit less with two
cores in series – but perhaps not significantly), but looks like with
parallel cores you are getting around 32 gpm flow. That is a 20/32
= approx 37 % more mass coolant flow through the
engine. That means (all else being equal), you should transfer
37% more heat out of the engine per unit time with the parallel cores
compared to the serial cores (assuming cores of same type and size).
Now the engine is
producing X amount of waste heat at Y HP that it needs to get rid of.
That won’t change for a given power setting Y. So Q (waste heat X)
produced by the engine should be a constant at Y Hp.
So
taking Q = M*Dt/Cp and since Q
(waste heat) = constant at power setting Y, then with M (mass flow up
37%) implies that in this case Dt = (Temp of
coolant out of engine – temp of coolant into engine) should decrease
by 37%. When you increase the mass flow and are removing the same
quantity of heat, the DT is of necessity a
lower value.
If
that is the case, then the question is - does this mean the temp of
coolant into the engine
increases – not necessarily
desirable, or does the Temp of coolant out of the engine decrease? Or a bit of both? I
suspect it’s a bit of both depending on the radiator’s performance. If
your radiators/air flow are the limiting factors, then transferring more
heat per unit time to the radiators is not going to buy you much. The
reason is that if it is not able to get rid of the heat at the faster rate
and the DT between the coolant and air will be less.
But, my guess is
that this theoretical increase in heat removal by using parallel cores could
be useful in some situations – again if you are already limited in the
airflow situation, then this won’t make much difference. It does
suggest that using parallel cores could result in the need for core sizes
37% smaller. OR did I miss something here?
Like your
data in any case
Ed
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Schertz
Sent: Thursday, May 13, 2010 10:39
AM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Re: alternative water pump
Back in 2002 I measured the flow
from a 13-B pump, attached to the engine but driven with an electric motor.
The curve is attached. I ran the pump at 3 different RPM, established by
changing the pulley size on the motor. At 5594 rpm, the pump produced 19 psi
at zero flow, and 44 gpm at 0 psi. At lower RPM, the pump of course pumps
less.
The other test I did was to
measure the flow through one core of the two I was using for my
installation. That is the curve going up to the right with the red dots as
the experimental points. Since I am running my cores in parallel, the right
hand rising curve is a 'calculated' flow response for the parallel
cores.
Finally, I hooked up the cores
to the system, and pumped water through them. The single large point
represents where the flow and pressure came out, very close to the
calculated expected response.
All flow measurements were done
by the "bucket and stop-watch" technique, with multiple runs to get the
flow.
Bill Schertz
KIS Cruiser
#4045
N343BS
Phase I testing
Sent:
Wednesday, May 12, 2010 11:54 AM
Subject:
[FlyRotary] Re: alternative water pump
Al,
Are you sure of the
40 GPM? That seems like a lot. My radiator in/out is 1.25
inches, so the water would be traveling at 628 feet per minute at that flow
rate. That is over 7 miles per hour!
Bill
B
When my 20B (with
a 13B pump that Atkins referred to as ‘high flow’) was on the dyno the
measured flow was 48 gpm with the standard pulleys. I expect the dyno
cooling loop was fairly low pressure drop compared to our typical systems,
so I’m just guessing 40 gpm is in the ballpark. 628 fpm (10.5 ft/sec)
would not be considered very high - - above 15 ft/sec I’d consider
high.
Al