Heat Temperature and Stirling Engines...

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Heat Temperature and Stirling Engines...

Postby clayyts » Tue Jan 06, 2004 12:59 pm

I am at my wits end. Honestly...I have been building Beta type
Stirling engines for the last four or so years since I was introduced
to them buy word of mouth.

Even thought my engines work rather well.. I STILL don't really
understand what is happening. What I do understand is that
temperature is different than heat. Heat can be seen as a fluid that
moves depending on the temperature differential..so far as it will
always try to find the nominal temperature from (so they tell me)low
pressure (or temp) to high!!! I have explored the internet to my max
capabilities for a good explaination, but all that I can come up with
(that makes sense to me) is my own idea (given my past learnings)that
Temperature correspongs to Volts (pressure) Currect corresponds to
heat (amount of STUFF-vibrational energy) and that anything that
comes between these two factors is resistance being the transferral
of heat (working fluid) trying to find it's nominal temperature
(being controlled buy whatever physics that says there has to be a
voltage potential - or difference at all ???)

I'm just really confused. However I am happy. My current engine is
made from one sheet of Aluminium folded into the chassis with slits
that direct the power and displacer rods from rotary to linear
motion. The displacer is a red bull can and the cylinder is an olive
can the crank and ajoining joints is simply No 8 wire. A tea light
candle will work my engine at 700rpm however I do not know the
efficiency as don't know how to calc input given degree celcius of
external source?? and how to measure that source given the
temperature that is dissipated throught ordinary atmosphere of
garage :o) ..So anyways if anybody could reply to this email would be
greatfully appreciated..

PS Even if I did know how to calc input,I am not sure of how to calc
output in watts (so as to calc eff) as I am a bit iffy about the mass
aspect ...so far as do I measure the crank as well as mech weight
then mult by the radius to get force (F=m.a) or just the crank weight
by its self.

Clayton Martini

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Response to Heat Temperature and Stirling Engines...

Postby stan.hornbaker » Wed Jan 07, 2004 9:19 am

The total energy going into any engine must equal the total energy going out. Q represents energy.

Q IN = Q OUT

Stated another way all the energy going into the system (engine) must be accounted for. The energy leaves the system as work and/or heat energy.

Q IN = W OUT + Q OUT

A heat source is applied to the hot end or heater which heats the gas inside causing it to rise in temperature and expand, flow past the displacer, and push the power piston outward removing work energy. The displacer is already moving toward the crank or cold end under the influence of its connecting rod. As the air continues to heat and increase in temperature the displacer moves toward the cool end, 60 to 90 degrees before the power piston reaches TDC. The air contracts in the cool end allowing the power piston to move inward. All of these processes are occurring consecutively in a very short time frame and repeating rapidly. Some of the work of the piston is returned into the system in moving the displacer. Continuity and smooth operation is the function of the flywheel.

The output work or power is quite small and for small engines requires ingenuity and/or sensitive measuring equipment. Dynamometers or pony (prony) brakes are used to measure output in the laboraty.
Measuring and/or calculating the input energy is much more difficult.

An article on the dynamometer is at URL:
http://inventors.about.com/gi/dynamic/offsite.htm?site=http://86.1911encyclopedia.org/D/DY/DYNAMOMETER.htm
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