[wxqc] Opinions please -- New design for solar radiation shielding

[jim]

Bryce
I am in Bullhead City AZ. and I had a problem with shielding also. after
talking with a couple of people on this list I came to the conclusion
because of the conditions in the summer in  AZ. you need a fan aspirated
shield period.
I constructed a shield out of 4" PVC "sewer pipe" and 2  90 degree L's
forming a "U" shape with a  12V 4" computer fan sucking the air from the
opposite end from the sensor. I used 4" PVC because of the size of the fan
and the sensor housing you can adjust the size to fit your requirements.
I placed this in a "Bird house" with the input end in the bottom of the bird
house at approx. 5' height. I also insulated the bird house on the inside
with garage door insulation.  pictures are on my QC summery page. I can
provide more pictures if you need them or questions. contact me at
jimwc at frontiernet.net

Jim
CW4367
  -----Original Message-----
  From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net]On Behalf Of Bryce Alexander
  Sent: Friday, May 04, 2007 4:55 PM
  To: wxqc at lists.gladstonefamily.net
  Subject: [wxqc] Opinions please -- New design for solar radiation
shielding


  After reading all the material that the CWOP program references about
solar radiation shields I had a brainstorm for a different design.

  In essence it is a six inch pipe, open at either end, with the pipe set at
an angle such that it is oriented on a North/South plane with the north end
higher than the south end. Both ends of the pipe are cut at angles so that
no sun is able to enter the bottom half of the pipe regardless of the
seasonal angle of the sun's ecliptic. I used nylon screws to mount the
instruments to the inside of the pipe to prevent heat transmission from the
outside of the pipe through the screws.

  Take a look at the Flickr images on
http://weather.gladstonefamily.net/site/C7166  to see how my prototype is
constructed and to make sense of the above description.

  The thinking is, that because the north end of the pipe is elevated we
will get a chimney effect of the warmer air rising upward at the North end
and the cooler air "falling" out the south end of the pipe. The theory is
that there is very little chance of air stagnating in this configuration.

  One thing I noticed right away is that the temperature and humidity seems
much more dynamic (or in other words, more changes during a given time
frame) which seems to indicate that I am indeed reducing the incidence of
air stagnation I was seeing with a gill style solar shield.

  The one down side I see right now is that a driving rain from the North
might get the instrument package wet. I will have to create some kind of
barrier or hood that will not interfere with the convective flow. The nice
thing is that I believe this can remain passive (not fan aspirated) even
during the worst of the Arizona heat, we will see this summer.  I do notice
some slightly higher temps during the day, but they are not the same thing I
was seeing when I had a solar radiation problem. I would attribute that to
the microclimate of being between Stucco houses, with cinder block fences
and tile roof in proximity to the sensor.

  If anyone wants to go back into my historical data I added the shield on
April 21 and tweaked my humidity about four days ago.

  Let me know what you think, I welcome any suggestions or comments,
positive or negative.



  Feel free to use this design for hobby or research purposes with proper
attribution, anything else by permission.




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