| Topic: |
Science > Physics |
| User: |
"s.morra" |
| Date: |
15 Aug 2005 01:30:50 PM |
| Object: |
Thermal Inductance |
As an example, from page 34 of
http://web.mit.edu/2.151/www/Handouts/EnPwrFlow.pdf (other references easy
to find)
"Thermal Inductance: No significant physical phenomenon has been observed
which corresponds to energy storage due to heat flow in a "thermal inductor".
Thus only one thermal energy storage element, the thermal capacitance, is
defined."
and of course, we have thermal resistance.
So it appears that thermal resistance and thermal capacitance but no thermal
inductance phenomena have been observed. Does anyone know of any cases
where thermal inductance has been observed?
.
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| User: "Helmut Wabnig EmailAddress" |
|
| Title: Re: Thermal Inductance |
15 Aug 2005 02:29:07 PM |
|
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On Mon, 15 Aug 2005 13:30:50 -0500, "s.morra" <s.morra@comcast.net>
wrote:
As an example, from page 34 of
http://web.mit.edu/2.151/www/Handouts/EnPwrFlow.pdf (other references easy
to find)
"Thermal Inductance: No significant physical phenomenon has been observed
which corresponds to energy storage due to heat flow in a "thermal inductor".
Thus only one thermal energy storage element, the thermal capacitance, is
defined."
and of course, we have thermal resistance.
So it appears that thermal resistance and thermal capacitance but no thermal
inductance phenomena have been observed. Does anyone know of any cases
where thermal inductance has been observed?
let us have a look at the characteristics of a capacitor:
(fixed pitch font)
A stepwise increase in Voltage (temperature)
will result in a slowly decreasing current
(a certain resistance assumed in the conductors)
Voltage difference (temperature difference)
_______________
I
I
I
----I
Current (Ampere, calories per sec)
*
I *
I *
I *
---- *
For an inductor we expect the following characteristic
Voltage (temperature)
_______________
I
I
I
----I
current (calories per sec)
*
*
*
*
*
----*
How can we possibly make such an object?
w.
.
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| User: "s.morra" |
|
| Title: Re: Thermal Inductance |
23 Aug 2005 01:46:16 AM |
|
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Thanks for your response, as there have been very few in this (and other
newsgroups). I am asking others about their knowledge of any cases of
thermal inductance being observed, because it is one explanation for an
event that I experienced about 20 years ago. I'll briefly describe the
event.
I was holding a 6 foot long piece of rebar (about 1/2" diameter steel rod,
commonly used to reinforce concrete) at arms length while a friend I was
helping was cutting it in half with an oxy-acetylene torch (I think steel
melts at ~1400 C). It was cut in half and both ends were brightly red hot.
After cutting, I moved my hands towards the ends to hold one 3 foot piece in
each hand at the cool end. There was a D-shaped tank (about 12" wide, 3
feet long, 2 feet high, flat of D facing up) filled with water nearby, about
2 inches from the top. So I dipped one of the hot ends in the water
gingerly a few times to cool it at about a 30 degree angle from the floor.
I didn't want to make a lot of steam quickly, as I thought that rapid
cooling might alter the metal somehow and my friend was going to weld the
two pieces to a piece of angle iron afterwards. The steam ball made was
about 4-6 inches in diameter at most as I recall. Within 15 seconds or so,
the 3 foot rod I was cooling became so hot that I couldn't hold it anymore,
so I dropped it into the tank. I was still holding the other rod in my
other hand (still glowing red hot) and it was only slightly warm where I
held it. I cooled it off too and we went about the next step of welding the
two pieces to the angle iron.
I do not have access to a torch or rebar to recreate the event since then,
but I've often thought about what I experienced ever since. I wonder if I
experienced thermal inductance, analogous to an inductive kick in
electronics. I still wonder about it and would appreciate any considered
explanations you may have (or others in this group).
"Helmut Wabnig" <EmailAddress> wrote in message
news:mlq1g1tjhlfn22ekeotb1sa906isfij694@4ax.com...
On Mon, 15 Aug 2005 13:30:50 -0500, "s.morra" <s.morra@comcast.net>
wrote:
As an example, from page 34 of
http://web.mit.edu/2.151/www/Handouts/EnPwrFlow.pdf (other references easy
to find)
"Thermal Inductance: No significant physical phenomenon has been observed
which corresponds to energy storage due to heat flow in a "thermal
inductor".
Thus only one thermal energy storage element, the thermal capacitance, is
defined."
and of course, we have thermal resistance.
So it appears that thermal resistance and thermal capacitance but no
thermal
inductance phenomena have been observed. Does anyone know of any cases
where thermal inductance has been observed?
let us have a look at the characteristics of a capacitor:
(fixed pitch font)
A stepwise increase in Voltage (temperature)
will result in a slowly decreasing current
(a certain resistance assumed in the conductors)
Voltage difference (temperature difference)
_______________
I
I
I
----I
Current (Ampere, calories per sec)
*
I *
I *
I *
---- *
For an inductor we expect the following characteristic
Voltage (temperature)
_______________
I
I
I
----I
current (calories per sec)
*
*
*
*
*
----*
How can we possibly make such an object?
w.
.
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| User: "AJW" |
|
| Title: Re: Thermal Inductance |
23 Aug 2005 05:15:53 AM |
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I would suggest what happened in your case is the steam rose, condensed
on the rebar you were holding, and heated it. Instead of the heat being
propogated through the thermal diffusion we usually think about, the
energy was converted to steam, then transported that way along the rod.
You could mimic that 'external energy transfer' by holding one rod
vertical, hot end up, the other vertical, hot end down. The hot end
down one would heat air that would move along the rod, heating it. Hot
end up would lose thermal energy to the atmosphere.
.
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