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Xtreme Cooling LN2, Dry Ice, Peltiers, etc... All the usual suspects

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Unread 11-19-2005, 04:45 AM   #1
anarion
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pressure resistance !

how much pressure , a tec can take ?

like this scenario ; put a plet between cpu/gpu & with force try to mount hsf on it

btw u guys almost every one of u are; "coolest" ever a forum can get
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Unread 11-20-2005, 08:16 AM   #2
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TEC elements need heaps of clamping pressure, a general rule would be not to exceed 2400kPa.

I don't quite get your wording, are you thinking of mounting a peltier element directly on your cpu? Wouldn't work, the above mentioned pressure is way over-spec for any processor.
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Unread 11-20-2005, 08:29 AM   #3
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You need a coldplate between the processor and the TEC, and if you are going to mount a air cooler on top of the TEC it better be a GOOD cooler aswell. And it has to be attached using screws so that you can adjust the pressure to the processor.
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Unread 11-20-2005, 06:08 PM   #4
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Make that a water cooler, I have tried huge heat pipe air coolers (around .2 C/w maby less) and they dont work. Well that is unless you want temps worse then the cooler alone. Also nugit is right they handle clamping very well but dont twist them they tend to be much weaker that way. One other note you will need around a 250 watt Qcmax pelt for the CPU and 170 watt for the GPU.
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Unread 11-20-2005, 11:21 PM   #5
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You cant really measure the amount of clamping pressure you put on a tec, just clamp it good and tight and make all the torque on all the bolts the same.

You dont wanna strip copper threads, thats for sure.
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Unread 11-21-2005, 02:24 AM   #6
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it seem i'm a tiny noob ,

tnx u all for very nice replys , i get my answer about force-in the plets

but now ; i found a few one :shrug:

FL3JM , u mean i must put somtin between PUs... ; why i can't put plet right there & use thermal paste !

i use all copper heatpipe gigabyte cooler for cool down tec .

an further info greatly tnx in advance ...
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Unread 11-21-2005, 11:02 AM   #7
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Quote:
Originally Posted by FL3JM
You need a coldplate between the processor and the TEC, and if you are going to mount a air cooler on top of the TEC it better be a GOOD cooler aswell. And it has to be attached using screws so that you can adjust the pressure to the processor.
Has anyone checked if the latest clamping pressure would allow to bypass having a coldplate? Not that it would be advisable, just throwing an idea out there.
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Unread 11-23-2005, 07:31 AM   #8
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ill give it a try
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Unread 11-24-2005, 12:38 AM   #9
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Quote:
Originally Posted by bigben2k
Has anyone checked if the latest clamping pressure would allow to bypass having a coldplate? Not that it would be advisable, just throwing an idea out there.
I'm thinking that the higher temp diff across the TEC coupled with the thermal expansion coefficient of the cheramics may lead to cracking of it. Depending ofcourse on IHS vs. pelt size.

However with something like a 40mm square pelt on a IHS you may be fine. Don't expect stellar performance though.
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Unread 12-27-2005, 07:34 PM   #10
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Default Re: pressure resistance !

Quote:
Originally Posted by killernoodle
You cant really measure the amount of clamping pressure you put on a tec, just clamp it good and tight and make all the torque on all the bolts the same.

You dont wanna strip copper threads, thats for sure.
The recommended compression for a TEC assembly is 150 to 300 pounds per square inch of module surface area. Using the following formula, you can calculate the torque setting per screw:

T = (C x D x F x in^2) / (# of screws)

T = torque per screw (in-lbs)
C = torque coefficient; generalized values for copper/mild steel (0.36 dry, 0.18 lubricated)
D = nominal screw size (8 = 0.164, 10 = 0.190, 1/4 = 0.250)
F = Force (lbs / in^2)
in^2 = module surface area (length x width)

Check the torque setting after one hour and retighten if necessary.

Example: Assuming (4) # 8 screws are used to secure a coldplate used with a 62mm (2.44 in) square module surface area and a surface force of 300 lbs per in^2 is required, what is the torque setting required per screw?

T = (0.36 x 0.164 x 300 x 5.95) / 4 = 26.35 in-lbs per screw



If a torque wrench/screwdriver is not available, a properly-ranged pull spring scale attached to the end of an L-shaped hex wrench can be used to establish the screw torque setting. To calculate the required spring scale pull force, apply this formula:

F = T / D

F = Force (lbs)
T = Torque (in-lbs)
D = Distance (in)

Example: What is the spring scale pull force required at the end of a 3.75 inch long L-shaped hex wrench to produce a 26.35 in-lbs screw torque setting?

F = 26.35 in-lbs / 3.75 in = 7.02 lbs pull force

Last edited by DNA; 12-28-2005 at 09:22 PM.
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Unread 12-28-2005, 05:44 PM   #11
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Default Re: pressure resistance !

mmm, "Torque wrench"...
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Unread 12-28-2005, 06:25 PM   #12
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Default Re: pressure resistance !

How can you calculate the coeffecient of friction of the screw? There are different types of screw heads, different materials being used, different material thicknesses, ect. I dont see how it is possible to establish a rudimentary figure like .20 without taking in all the variables.

But 15 in. lbs seems like it would be a good figure in that calculation regardless. I dont think you can hurt a tec by overtightening it.
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Unread 12-28-2005, 08:22 PM   #13
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Default Re: pressure resistance !

Quote:
Originally Posted by killernoodle
I dont see how it is possible to establish a rudimentary figure like .20 without taking in all the variables.
Without making this subject overly complex, I used generalized values for clean copper and mild steel. This calculation has to be considerably more exact than the WAG being used by most.

Last edited by DNA; 12-28-2005 at 09:05 PM.
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Unread 12-29-2005, 01:07 AM   #14
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Default Re: pressure resistance !

Thanks, DNA! I've been looking for a good equation with some decent constants for commonly used bolt sizes/materials. I've replied to other threads with, "it's too complicated" because I didn't have any idea what the nominal values for torque coefficient and "nominal screw size" would be.

Not being a mechanical engineer.... I didn't even know the proper names to be googling.
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