On Wednesday, May 10, 2017 at 5:45:33 PM UTC-4, Tim Wescott wrote:
On Wed, 10 May 2017 14:00:52 -0400, Carl Ijames wrote:

"rangerssuck" wrote in message
...

The refrigerant pipes in a typical rink are about 10 or 11 miles long
(seriously), and are (sometimes) 5/8 OD thinwall steel, but that's a
variable.

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Just as a sanity check when you do the pressurize with nitrogen test, I
get a volume of 72 cu ft or 2039 L for 10 miles of 1/2" ID tubing. At
STP, 0 C and 101 kPa nitrogen has a density of 1.25 g/L so at STP 72 cu
ft would weigh 5.62 lbs (I'm ignoring the difference between room
temperature and STP for this estimate :-)). If you start at atmospheric
pressure you would need 3x72 cu ft = 216 cu ft to reach 44.1 psig which
should be completely safe since the vapor pressure of R22 at 75 F is 132
psig. So you will need at least a couple of tanks of nitrogen on hand
to be safe, and a refrigeration scale that can do 0.1 lbs at the weight
of a full tank of nitrogen with regulator should let you get an answer
in the 5-10% range. Have fun.

Man, I just know that if I tried this I'd be lucky to be off by a factor
of two, and not 10 or something.

Good luck, and have fun.

Back in grad school, I screwed up the conversion of Pascals
to atmospheres (or Torr?) by a factor of ten. And made my flow impedance
line x10 times too restrictive. ~x10 the work too. But once I found the
mistake in my notebook it was pretty easy to cut the line down to the
right impedance.

George H.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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