Jeff Spitzer wrote:

Neil A. Kruiswyk wrote:

Paul,

    You missed my note about extrapolating the data to flight
 conditions....
(Otherwise you'd better find a pickup that will do 250mph.)

    If you can measure temp drop of the water through the rad given a
certain flow rate of water and measure the temp rise of air going through
the rad given a certain flow rate...  you can expand these numbers.

Come to think of it...  Bruce has the right idea...  Go ask someone who
has already done the work.  I.e., Griffin. http://www.griffinrad.com

Neil

Two points:

1) I have asked a long time ago and they couldn't give me the answers I was
looking for.  Can anyone get the first two charts that Paul recently posted
(my hand drawn) from any racing radiator manufacturer?  If so, great, I'd
pay the money for the racing stuff to know what I'm getting in both
performance and quality.  My opinion is that the performance of these cores
is no better than what you can pull out of the junkyard and all you're
paying for is welded aluminum at low economies of scale.

2) The data from the cartop or fan and heater test can both be usable.  The
max heat rejection requirement for the A/C is probably hot day climbout.
Most of us don't climb at 250 MPH.  In fact, 100 MPH may be a little high
for most for best rate of climb.  You do want your installation to cool
adequately at max rate of climb don't you?  Once you figure out how fast
(slow) you will be going at worst case cooling conditions then you can
assign a value to ram pressure and therefore max pressure drop across the
core.  Next, you have to subtract out ducting losses to find out what net
pressure you expect to have across the core.  Now you know what you need to
test.  The answer is you have something less than about 3" of water to work
with.  

This can be generated in Paul's test at about 78 MPH at sea level
(the rig shown has essentially zero duct losses).  The challenge with
Paul's test is to get scientifically valuable data because coolant flow
changes with engine speed and thermostat position.  Further, if you slow
down to reduce the airflow through the radiator then the heat load goes
down unless you adjust the parachute.  It's kinda difficult.  Neil's test
is also valid but as Paul points out you need a lot of heat.  The option
here would be to use only a small section of the radiator but you must have
representative water flow and air flow.  The choice of a squirrel
cage fan is good because those are typically capable of more pressure 
then std axial fans.  

The aftermarket radiator fan you buy at Pep Boys will barely
make 2" of water at 18 volts.  I think a heater fan from a big car or
truck may give what your looking for, Neil, if you limit the cross section
under test to maybe 10-20% of the actual radiator.  The main point is that
you cannot extrapolate along "curve #2" in my sketches because you don't
know the function.  Further, the same curve exists for heat rejection vs.
water flow so better to just have the right water flow for the 13B then to
get into multidimensional testing.

Jeff Spitzer

Maybe several small parachutes would ease the adjustment problem.

PL
 
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