Al Gietzen wrote:

Attached are photos of my air flow test setup to measure flow

distributions

and pressure drops.  It is shown here with the scoop and custom Ron

Davis

radiator.  This is one of two radiators for my 20B, this one goes in

the

cowling of my Velocity pusher, and another of different

configuration is in

the wing root.  This is an "armpit" scoop (under the wing at the

fuselage),

and has a diffuser ratio a bit over 4 to 1.

I measured flow and flow distribution with a small handheld

anemometer from

Radioshack; a very cool little instrument that gives digital readout

of air

speed (see at their website); pressure measurements with water

manometer.

The output from the centrifugal blower unfortunately turned out to

be about

half my design point for the rad, but it gave me some very useful
information on placing some vanes internal to the scoop/diffuser in

order to

get a good flow distribution through the rad.

The max flow rate from the blower through the rad was 1300 cfm.  The

design

point for the installation is 2600 cfm.  The radiator is a two row

1" tubes

with 16 fins per inch and  a core thickness of about 2 ½ ".   The

core

is 16

x 11.5 for an area of 184 sq in.  The measured pressure drop across

the

core

at this flow rate was only 0.4 in water.  I think the pressure drop

goes

roughly as the cube of flow rate, so at design point flow, the drop

would

be about 3.2" water.  This compares favorably with Ron Davis'

computed

value

of 3.7".

 Note the length of duct from the blower to the scoop.  The output

from a

centrifugal blower is very turbulent, so if you want meaningful

measurement

of flow distribution, be sure to use a length of duct to help

straighten

things out.

Al,

  Got any pictures of those vanes you had to add? Just curious. Your

test

setup looks really impressive. I've got to find the time to get up there
and see your project.

Mike Wills

Actually I did take some, but then lost that camera over the holidays
(fortunately not a real expensive one), and the pictures went with it.  The
unit is now installed on the airplane, but will come off again, at which
time try to remember to take some.  If you get a chance to get by, we can
take the scoop off and have a look.

Al

 
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