Thermal conductivity

[cirthix]

8rdavcore is a good nforce2 program that automatically adjusts fsb, voltage, fans, mem timings, etc from windows automatically and is free, just google for it and dl it, but be sure to try both versions, .85 or sumthin is stable for me, but not for my friend, who uses .87 dev. just try both and find whats best for you. more background info: i have a watercooling system taht i made all myself, wb, res, everything but pump and hoses that performs nicely. i'm a person who likes to conserve energy and stuff like taht but also into overclocking (interesting paradox eh?) so to save energy and still have a good system, i thought for a long time so heres my idea: when cpu is idle/low usage, use 8rdavcore to clock cpu to 1ghz at 1.2 volts maybe even lower, but when usage is up, clock to full speed of 2.6+ghz at 2 volts. big difference in speeds and everything, but the real idea is this: when the cpu is clocked low, have the peltier turn off and just use the watercooling system. i have a big rad, so i could even turn off the fans (2ghz stable with all fans off, just natural convection with temps below 50c) as of now, i have no peltier unit but if this could work, i would get one and slap it on my waterblcok

i guess what i'm asking is how well a pelt transfers heat while its off and how i would impliment such a scheme.
Current rig:
2600+ mobile barton
dfi infinity stable 260+fsb +sb cooling and active nb coolling
1*512mb geil ddr4400
9700pro not overclocked...... yet
thermaltake 420w psu modded with a 120mm fan, 160gb hard drive, cd burner, hardcano2, awesome homemeade watercooling setup using heatercore off some old car i forget what
generic case modded with big 120mm fans... everywehre, some other random stuff
Clocking my cpu down to 500mhz at 1.1 volts will drop power usage of the cpu to 6 watts or so. Clocking it down to 1ghz at 1.2v will drop power usage down to 16 watts, as opposed to the stock wattage rating of 47! less than 1/9th of the power usage sounds good to me! especially if that means that its putting out less heat than my northbridge and can be passive cooled. You have a point about cooling the water with the pelt, but i dont want to have to deal with the pump's heat along with the heat from the cpu, adding 27w when cpu is using 5 dosent sound good to me, because i'll have to have something cooling the pelt seperately. not fun when i have a small case.


sorry if i seem kind of thinking all at once in every direction, but thats the way i aim. i can clarify if you ask about anything
a gmail invite goes to whoever answers the best

 

[cirthix]

btw, thsi is the pelteir i'm talking about
http://cgi.ebay.com/ws/eBayISA...em=3836163052&rd=1
and i'm current running 250mhz fsb because i think i have an air bubble under sb heatsink that causes trouble under heavy load ( worked ok, then i changed heatsink, got faster fsb, then it came loose, and when i reseated it, some problems started) anyone have some thermal epoxy i could have because im using superglue and defective ceramique(it never hardened, even after 2 months on my video card ramsinks, so i had to take those off too)

 

[TuxDave]

Sorry.. due to my ADD, my eyes glazed over. Can you highlight the basic question?

 

[cirthix]

what is the thermal conductivity of http://cgi.ebay.com/ws/eBayISA...em=3836163052&rd=1 when no power is appllied?

 

[Mday]

No, it doesnt belong in this forum.

Originally posted by: cirthix
what is the thermal conductivity of http://cgi.ebay.com/ws/eBayISA...em=3836163052&rd=1 when no power is appllied?

It's USELESS when there is no power applied. Does that help?

Try to imagine if it had good thermal conductivity when no power is applied. That means if power is applied, there is still good thermal conductivity. This means that the COOL side will PERPETUALLY be cooling the HOT side. So, it'd just get hotter and hotter due to the laws of thermodynamics.

 

[cirthix]

if power is applied, the tempearature of the hot side increases and the cold side decreases even below ambient. if i clock the cpu down from 2.7ghz too 500mhz, and drop the voltage from 2 to 1.1, as well as turning off the peltier, i will be saving 170w from the peltier(a little more becasue it will actually generate juice due to the the seebeck effect) as well as about 115w from the cpu. thats a 285w decrease in overall power use of the compter. What i'm asking is if the peltier can have 6w applied to the cold side and have the hot side cooled with an effeciency of .07C/W(homemade watercooling), with no power supplied, and keep the core temperature below 55celcius?

 

[f95toli]

In order to answer that question you need to measure the thermal conductivity the element,
I know that is the question but unless someone has a datasheet with that kind of information it is not possible to answer. Besides, even if you had that data it is still difficult to calculate how much heat you will dissipate with any real accuracy (unless you use modellng software like FEMLAB)l

Wouldn't it be possible to just try? You know how much power the CPU is generating, replace the CPU wiith somehing else which generates roughly the same amount of heat and then measure the temperature of the element, if it gets hot it probably won't work with the real CPU either.

 

[TuxDave]

Why are you even using a peltier in the first place?

 

[cirthix]

erm, to get temps in the -10c range under load without phase change.. i'm not rich enough to afford it!

 

[Mday]

Originally posted by: cirthix
if power is applied, the tempearature of the hot side increases and the cold side decreases even below ambient. if i clock the cpu down from 2.7ghz too 500mhz, and drop the voltage from 2 to 1.1, as well as turning off the peltier, i will be saving 170w from the peltier(a little more becasue it will actually generate juice due to the the seebeck effect) as well as about 115w from the cpu. thats a 285w decrease in overall power use of the compter. What i'm asking is if the peltier can have 6w applied to the cold side and have the hot side cooled with an effeciency of .07C/W(homemade watercooling), with no power supplied, and keep the core temperature below 55celcius?

water block
peltier
CPU (may need flat metal surface to work with)

With the power off in the peltier, what you have is an oxide\cermaic between the CPU and the waterblock.

Without knowing the technical specifications of the peltier, you cant find the information. You need to find out who makes it, and then what it's made of (materials) then look up the thermal conductivity of hte materials.

 

[cirthix]

k, i'll go ask the company that makes them. i was just wondering if anyone here had specs/knew/ had experince/did taht kinda stuff.

 

[Mday]

Originally posted by: cirthix
k, i'll go ask the company that makes them. i was just wondering if anyone here had specs/knew/ had experince/did taht kinda stuff.

yeah, there are too many manufacturers of pelts. And no one uses them when they are off. Don't think I didnt try looking.

 

[CTho9305]

Every overclocker I've talked to says that if the peltier is off and your CPU isn't, your CPU is going to cook.

 

[icarus4586]

Erm... doesn't sound like a very good idea. Turning the pelt off, no matter how little heat the CPU is giving off, probably won't be able to keep the CPU below 55C. Running the CPU at 2.0v isn't a real good idea, either, no matter how good cooling you have.

 

[Tiamat]

Originally posted by: cirthix
erm, to get temps in the -10c range under load without phase change.. i'm not rich enough to afford it!

Sorry, i got lost when reading... Why do you need -10C?


as far as I know, Peltiers require electricity in order to function, thus why they are Thermal-Electric modules and not just Thermal modules. They are also very very inefficient. If your electricity bill is too high, just get rid of the peltier all together and get something that either is a very good conductor of heat (good heat sink like XP120, or XP90) or is a very good remover of heat (good water cooling)

 

[iwantanewcomputer]

that makes sense that they would want it to have bad thermal conductivity to slow the transfer from the hot side to the cold side. it doesn't seem like it would be able to be turned off an still allow your processor to be cooled by the water. i thought about doing this a while back but i didn't want to have to have the peltier on all the time.

Alternative. use the peltier, or multiple ones, to chill the water you are pumping throught he system. it's not as effective per peltier power, but you would be able to turn it off and on without cooking your system. heres what i mean

pump(s)->radiator(s)-> peltier water chiller-> waterblock(s)

the chiller would be some kind of copper tubing for the water to flow through with peltiers attached to the outside of the tubes. the peltiers have heat sinks on the hot side. the copper tubing could split up into a bunch of smaller tubes in parallel with the peltier welded? or something to the sides to cool the water better.

from what i've heard these don't actually make much diference when it gets to the cpu temp though

 

[Mday]

I tried talking some sense into him, but he didnt listen.

 

[phisrow]

Unpowered Peltiers are rather good insulators, so your chip will probably crash quite quickly if you power one off during use. Even better, overheating tends to kill peltiers. Dansdata has some good introductory stuff about peltier cooling, check here and here for starters.
If you do want variable cooling power, I second the suggestion of peltier cooling your cooling fluid(be sure to dope your coolant with antifreeze and insulate the pipes to prevent condensation) given by iwantanewcomputer.

 

[gsellis]

If folks are going to go to this much trouble, there has to be a market for Arctic Gold and a 24kt heat sink