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Tracy my calculations shows your coolant temp drop is
where it should be:
My calculations show that at 7 gph fuel burn you need to
get rid of 2369 BTU/Min through your coolant/radiators. I rounded it off
to 2400 BTU/min.
Q = W*DeltaT*Cp Basic Heat/Mass Flow
equation With water as the mass with a weight of 8 lbs/ gallon and a
specific heat of 1.0
Q = BTU/min of heat removed by coolant mass
flow
Assuming 30 GPM coolant flow = 30*8 = 240 lb/min
mass flow. specific heat of water Cp = 1.0
Solving for DeltaT = Q/(W*Cp) = 2400/(240*1)
= 2400/240 = 10 or your delta T for the parameters specified should
be around 10F
Assuming a 50/50 coolant mix with a Cp of 0.7 you
would have approx 2400/(240 *0.7) = 2400/168 = 14.2F so I would say you do not
fly with
a 50/50 coolant mix but something closer to pure
water. But in any case, certainly in the ball park.
You reported 10-12F under those conditions, so I would say
condition is 4. Normal operation
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews,
NC
----- Original Message -----
Sent: Thursday, August 12, 2004 12:59
PM
Subject: [FlyRotary] Re: coolant
temps
I've got a question regarding coolant temps I hope some of you can help
with.
We've been running the Eagle540 recently, getting ready for
that impending
first flight. Our installed instrumentation on the
coolant side is located on
the higher pressure, high temp engine outlet
side of the coolant circuit...
the flow comes out of the top rear of the
engine to the thermostat housing.
Temp sensor is installed in the
t-stat housing. From there it goes through
the firewall and down
to the radiator, then returns back through the firewall
and on to the
water pump. The water pump forces the coolant into the block
and
the circuit is complete. We are not running 50/50 water/anti-freeze
because of the magnesium components... we are running straight Evans
NPG.
During recent runs (engine RPM about 2000RPM, the rev limiter
is set at 3800,
so we're just over 50%) we're seeing the high temp side
over 230 degrees. NPG
doesn't boil until somewhere around 400, but
we obviously don't have any
desire to operate at that kind of
temperature. For those of you who are
instrumented both before and
after the radiator (evap cores, whatever) what
kind of temperature
spread are you seeing? I suspect I'll eventually be
instrumenting
the cool side of the circuit, but would like to know what to
expect on
the hot side. If we're seeing a 40 degree delta across the radiator
(I imagine) is 250-260 considered too hot as a redline for the hot
side? (Our
oil temps are very well behaved, we still haven't
exceeded 150 on the oil cool
side and TITs are running 1350-1400 at
these reduced power levels... sounds ok
to me, but what do I
know?) TIA for any info you're willing to
share.
<Marv>
My before & after coolant temp delta was surprisingly
low. Only got readings at cruise power settings (6.5 - 7
GPH) where it was only 10 - 12 Deg F. This could mean
several things. 1. Rads are no good. 2.
instrumentation was no good. 3. water goes through system really
fast.
Or (4) it could be normal. I don't think the answer is 1 or
2. I don't have time to do calcs to see if 4 is the case.
Anybody got time to run them? Assume GPH at 30 gpm if you do.
Oil temp delta was higher (expected) at 20 - 50 depending on power
setting.
Tracy
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