Subject: Solar heating to an instrument case

From: "Murray E.Moore" <internet:[email-masked]>
Date: 26 Mar 1996 23:32:33 GMT

I am building an air sampling device that will be used in the desert 
near Las Vegas, Nevada this summer.  (120 degrees in the shade!)

There will be an instrument box with a radio, datalogger, etc. as part
of this air sampler.  I am worried about overheating of the 
electronics, and I'm thinking about installing an air conditioner to
keep things cool.  Could I use 300 BTU/ft^2-hr as an estimate for the
solar energy incident on my instrument box?  

I don't have any tables with me, and I got that value from a general
reference book.  

I want to do a heating calculation on the box, then get a rough idea
of the AC unit I would need.  Adequate electricity is not expected 
to be a problem, but I don't want to overkill it on the size of the
system.

Replies can be posted to my e-mail or to the newsgroup.

Murray E. Moore
Los Alamos National Labs
Group ESH-4

---

From: [email-masked] (Jonathan M. Elson)
Date: 27 Mar 1996 22:30:01 GMT

Murray E.Moore (internet:[email-masked]) wrote:
: I am building an air sampling device that will be used in the desert 
: near Las Vegas, Nevada this summer.  (120 degrees in the shade!)

: There will be an instrument box with a radio, datalogger, etc. as part
: of this air sampler.  I am worried about overheating of the 
: electronics, and I'm thinking about installing an air conditioner to
: keep things cool.  Could I use 300 BTU/ft^2-hr as an estimate for the
: solar energy incident on my instrument box?  

Watch out! don't neglect REFLECTED heat (radiated) from the ground!
You might think about a sun-shield to reduce radiation DIRECTLY hitting
the box.

Just a piece of sheet metal above and to the sides (generally E-W) of the
box will catch most of the heat, and transfer most of it to the air.
It will radiate a much smaller amount down to your box.  I have a litle
experience shading environmental sensors from the sun, and a piece of
galvanized steel over the sensor makes a BIG difference.  It is also a
lot cheaper (and maybe more reliable) than mechanical air conditioning.