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>
> The EWP is the same game. Pump a lot of water and
restrict what you
> don't need. Simple old school thinking.
Don't hink of the EWP as 57
> times more efficient, think of it as only
pumping the 1/57th of
> coolant that is actually needed at 6000RPM vs
800RPM.
It will, of course be very interesting to see
the mesured flow rates. But we must be aware that in the aircraft
application, the power output is pretty much a function of the RPM. And
the heat rejection requirement is a function of power output. So the
higher the RPM, the higher the flow requirement. And we do run at much
higer sustained percent of max power levels than street auto, and higher than
most race applications. We never let up on the gas to go into the turn;or
run like hell for a 1/4 mile and shut it down.
In a cooling system with NO head, it will pump 80 litres per
minute. Assuming about 3" of head, allowing for cooling system
boundary layer friction, it will still pump about 75 litre a minute at
full tilt. (which is still about a full RX7 tank of water every
minute!!)
It is NOT the FLOW of water through the engine or the heat
exchanger that is the issue.
It is actually an issue. Water has a certain
capacity for carrying heat (about 11 Btu/min-F), and ethylene-glycol, much less.
Assuming you have an effective air side flow in your rad, you're going to
get somewhere in the range of 15-30 degrees F temp drop in the coolant on a
warm day. Knowing this, and the power output it is quite straight forward
to comput the amount of flow you will need to reject to heat.
A 20 F drop coolant drop across the rad will
require a flow rate of 32 gpm of water (or 45 gpm of 50/50 water-eg mix) to
handle the heat load at an engine power level of 200 Hp. A 30 degree drop
(difficult to achieve on a hot day) requires two thirds that much - 21 and 30
gpm. So if the max flow of the EWP is going to be about 23gpm; I'd
suggest not planning on it for your 20B or your turboed 13B. On
a NA 2-rotor, could be fine.. If, of course, it will run reliably at or
near it's max output for long periods of time.
From what little data I was able to find for the water
pump on the 20B, it will pump about 35 gpm at engine RPM of 6000.
Marginal, at best, for that climbout on a 90 degree day. At altitude, at
cruise; the EWP may be able to handle it.
No; I don't have measured data on my airplane because
I'm not flying yet. But having spent years doing engineering analysis on
various nuclear power systems, including some for space application, and
where the analysis had to be backed up by test data; I think I have at least
a reasonable handle on this thing. But if experience with the EWP can
prove me wrong - great.
Al Gietzen
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