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simple stirling hot air engine made at home with simple tools ,2 cans a baloon - Page 9

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Posted by Curbie on January 4, 2012, 4:56 am
 
Ralph,

I haven't heard of  "resistance temperature detector" are they also
referred to as thermistors(sp)?

Curbie


Posted by Jim Wilkins on January 4, 2012, 2:59 am
 


I've done a lot of temperature testing of the environmental test chambers I
built and always had a hard time with the thermocouples. The twisted wires
don't make good contact with flat hot surfaces so some of the heat leaks
away to the air or down the wires. Tying them down under insulation helps
somewhat. I have the best results with thermocouples tightly jammed into
drilled holes that are deep enough to heat the lead wires. The thermowell I
made yesterday to measure flue temperature is a 3/4" long bolt drilled down
the center from the head end 0.500 deep at 0.140" to clear the insulation,
then a further 0.200" at 0.075" diameter to jam in the bare twisted 20AWG
wires.

The ones I checked with boiling water didn't agree until I stuck them all in
about four inches through the teapot's whistle vent, in the steam above the
water. The bottom of the kettle read about 101C.

I use all type K because my most demanding use is checking the annealing and
hardening temperatures of tool steel. Other types like E, J or T may be
better for you.
http://www.omega.co.uk/temperature/pdf/Thermocouple_Tolerance.pdf

After welding the wires together you can hammer them flat.

jsw



Posted by Curbie on January 4, 2012, 4:48 am
 Thanks to Jim and Ralph for the info but, my automated distillation
project is coming along just fine, slow, but just fine.

A question about long-term hydrogen embrittlement for Jim, doesn't
hydrogen embrittlement take a long time under constant pressure? My
question stems from Morris's pressure issues; for testing purposes,
could he use multiple cheapo pressure sensors, checking that they are
all in basis pressure agreement and scram if not.

It seems for testing, you could waste a whole bunch a cheapo pressure
sensors for $00, after all, he just lookimh for answers?

Curbie


Posted by Morris Dovey on January 4, 2012, 5:16 am
 On 1/3/12 10:48 PM, Curbie wrote:


If it were air being heated in a sealed (constant) volume, where the
Ideal Gas Law could be applied, I would expect to see pressure climb as
in this plot:

    http://www.iedu.com/Solar/Engines/Fluidyne/IdealGas.png

I'll do the same plot for H2 (but not tonight) - and expect that it
won't look much different. If the pressure at 374C is in the ballpark
of 2.2 atmospheres, I don't think pressure will be much of a problem.

Things could be a little dicey if there's any significant amount of
moisture in the reaction chamber - but I think evacuating the chamber
before starting should take care of that.

--
Morris Dovey
http://www.iedu.com/Solar/
http://www.facebook.com/MorrisDovey

Posted by Morris Dovey on January 4, 2012, 2:49 pm
 On 1/4/12 12:32 AM, Bob F wrote:

It may be, but I'm planning to begin with low pressure and low
temperature and work my way toward higher pressures and temperatures by
small increments.

Perhaps I'm being overly-cautious, but I have a low degree of confidence
in the accuracy of both device and operational descriptions of Rossi's
E-CAT. It's supposed to be fully self-sustaining but the /observed/
shutdown procedure begins with turning off a heater...

There're enough little things like that to make me nervous, so I'll at
least begin with low (< 3 atm) testing.

--
Morris Dovey
http://www.iedu.com/Solar/
http://www.facebook.com/MorrisDovey

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