Heat & Speeds

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Re: eep

Postby len444 » Sat Jun 07, 2003 11:09 am

triniphen wrote:please rephrase len ?? i dont know of a heated liquid rising, i know they expand, especially when boiling.


i think it's called thermodynamics. wouldn't the spacing of the hotter ('excited') molecules (further apart, and more active) make the heated liquid less dense, causing it to rise as well?
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eep

Postby triniphen » Sat Jun 07, 2003 1:43 pm

well the word was rising not expansion. yeah transistors are switches and as with other circuits when something changes something else changes too, E=I/R. i realize water can evaporate at different temperatures but the orginal conditions were 200C. evaporation was not really an issue, nor sublimation. at 200C the vapor pressure would be hugh. of course boiling is just when the vapor pressure exceeds the surrounding pressure. the liquid volume would expand but w/r/t the vapor volume its effect would be small.
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Postby len444 » Sat Jun 07, 2003 2:35 pm

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eep

Postby triniphen » Sat Jun 07, 2003 3:14 pm

From the Article:
Heat Pipe Operating Principles
A heat pipe is a passive heat transfer device with an extremely high effective thermal conductivity. Its twophase
heat transfer mechanism results in heat transfer capabilities from one hundred to several thousand times that of
an equivalent piece of copper. Heat pipes are sealed vacuum vessels that are partially filled with a working fluid,
typically water in electronic cooling, which serves as the heat transfer media. The heat pipe envelope is made of
copper in a myriad of shapes including cylindrical, rectangular, or any other enclosed geometry. The wall of the
envelope is lined with a wick structure, which provides surface area for the evaporation/condensation cycle and
capillary capability. Since the heat pipe is evacuated and then charged with the working fluid prior to being sealed,
the internal pressure is set by the vapor pressure of the working fluid. As heat is applied to the surface of the heat
pipe, the working fluid is vaporized. The vapor at the evaporator section is at a slightly higher temperature and
pressure than other areas. This creates a pressure gradient that forces the vapor to flow to the cooler regions of the
heat pipe. As the vapor condenses on the heat pipe walls, the latent heat of vaporization is transferred to the
condenser. The capillary wick then transports the condensate back to the evaporator section. This closed loop
process continues as long as heat is applied. The capillary pumping pressure generated by the wick structure is
critical to maintaining the circulation of the fluid against the liquid and vapor flow losses, and against adverse body
forces, such as gravity.

this is just a reflux, with the addition of a wick to help the condensate return. im sure the appartus is built strong enough to contain the pressure of the vapor and of course the initially applied vacuum.

i think the point i was trying to make was misconstrued a bit, no biggie. i just wanted proper terminolgy especially after a comment that placed me in a generalized catagory, which annoys me. dont tell me your a doctor and then explain to me the reason im sick is due to bad air. as for cooling it, i have not made any comments regarding the level of ones education or common sense. ahem...
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Postby atang1 » Sat Jun 07, 2003 8:32 pm

The general description of the heat pipe design is correct. I have seen them used on real time computers of the single board construction, where there are no room for a fan. The concept was used on very small heatsink 1"x1" square, 3/16" dianeter heatpipes were 4" long. After a few years, about three years ago, the wick was added internally. the reason was not letting the liquid fly around. Realtime computers are used on B2 bombers, for instance.

How effective it was? I had my finger on the heat pipe while it was cooling the cpu. My finger can stand 115 degrees F.

Bipopar transistors can stand 200 degrees C. So, no one cools them with water. Air cooling is very effective. Largest SCRs(hocky pucks 2 5/8"dia. x 1" thick) use large aluminum heatsinks with giant fans. I supplied thousand amp scrs to Long Island railroad for their electric trains. after they warmed up the heat transfer would equalize and operate at the same temperature. Thermal resistance due to surface contact under high pressure is a big worrysome problem.

When you don't have actual experience and do analysis, take it easy. You can not prove your manhood here. But write anything you like, does anyone care?
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Postby Tulatin » Sat Jun 07, 2003 9:02 pm

15A? That's odd - i only felt a little shock (and a massive heart rate increase)
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Postby len444 » Sun Jun 08, 2003 3:03 am

Tulatin wrote:15A? That's odd - i only felt a little shock (and a massive heart rate increase)



so what were you doing that you got shocked?

under 1amp can kill a person, esp. if the current goes through the heart (between both hands).
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Postby Tulatin » Sun Jun 08, 2003 11:55 am

Well -after modding the supply (added extra fan, new molex, wire sleeving), i was pluggin it back in (without the top cover of course) and (stupidity at its best here), to help the plug go in (as the back wall was weak, i was pushing on the + and - connects of the plug - it goes in and ZAP!
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Postby atang1 » Tue Jun 10, 2003 7:03 am

Do you need technical support for such a simple job?
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Postby Tulatin » Tue Jun 10, 2003 3:51 pm

I don'f follow you here atang...
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