cross-posted from: https://piefed.social/c/historymemes/p/1836852/copper
Copper? I don't even know 'er!
this post was submitted on 08 Jul 2026
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Okay, who gets to be the lucky one to calculate the amount of time that thing could heat sink a pegged, modern, 120w TDP CPU before it throttles at 100C? I'll give you a sticker.
Nice try. I’m not googling “copper pegging” again.
Was intrigued, so made a simulation to figure it out.
TLDR: 592.2 seconds, or 9 minutes and 52.2 seconds. Very similar to the other comment - it appears temperature differentials and heat loss to the air have opposite effects on thermal throttle time and mostly cancel themselves out. For the most part, heat transfer and heat loss appear to affect the thermal throttle time less than the sheer heat mass of the block by several multiples
Assumptions:
- Copper's heat conductivity is 400 W/m-K, and specific heat is 0.4 J/g-K, and density is 9000 kg/m^3, and these values do not change over the range of temperatures
- Air's heat transfer coefficient is 20 W/m^2-K and does not change over the range of temperatures
- The surrounding air does not change in temperature and remains at room temperature (25 C)
- The input wattage is actually 120 W and not just random marketing bullshit
- The copper block's size is 4 cm x 4 cm x 16 cm (same as other comment)
- The temperature within the copper block differs only by the vertical axis; it is assumed that temperature does not change if you move horizontally into the block
Modeling conditions:
- The block is sliced into 100 equally-sized slices, stacked vertically.
- Each slice starts off with a temperature of 25 C
- 120 W is input directly into the bottom slice
- Heat transfer is modeled between each slice
- Heat loss into the air is modeled for each slice (top slice has more heat loss due to more contact with the air)
- Temperature changes are calculated per millisecond
- Final time is calculated by the total number of milliseconds it takes for the bottom slice to reach a temperature greater than 100 C
Fun facts I found from playing around with the model:
- According to this model, at the time that the CPU thermal throttles, the top of the block should be 85 C
- If we assume instantaneous heat transfer, time to thermal throttle goes up to 703 seconds (11 minutes and 43 seconds). Difference is about 2 minutes.
- If we assume no heat loss to the air, time to thermal throttle goes down to 500.0 seconds (8 minutes and 20 seconds). Difference is about 1.5 minutes.
- The copper block should be able to prevent throttling as long as the CPU remains idle (30W for AMD CPU's). The CPU should cap out at around 82-83 C.
- The copper block can prevent thermal throttling for a 170 W CPU for 368.1 seconds, or 6 minutes and 8.1 seconds
Respect for taking the time to model that. Goes to show why heat sinks look the way they do, and not just big lumps of metal lol
Numerical methods is cheating! Real men use PDE's!
/s of course, though I was kinda hoping you'd use PDE's
See, I thought about doing that, but then I realized: I don't actually want to do that
Let's assume the dimensions of the copper block are 40mm40mm160mm (I'm not taking the heat spreader into account here)
That results in a volume of 256000mm3, or 256cm3
Copper (at 20C) has a density of 8.935 g/cm3, so that's roughly 2.28736kg of copper
Copper has a specific heat capacity of 384.603 J/(kg K)
Using E=cm∆t, we can figure out that it would take ≈ 70378J of energy to heat the copper block to 100C, starting at 20C
With a TDP od 120W, that means it would take 586 seconds to heat the block to 100C, or 9m46s
This is probably way off but I was bored
Your napkin math is the best we have. We will make all decisions based on it.
They will have entire hard drives explaining KSP Atlas's shitty math in 3 thousand years...
Hmm, I think at minimum calculus will need to be involved here. Because we can't just assume that the heat is spread evenly in the copper - it'll likely be hotter at the bottom, leading to thermal throttling earlier than expected. On the other hand, there's going to be heat dissipation into the air, which will help cool the block somewhat
Heat transfer will not limit much, but heat loss should add a significant amount of time. How did you model that?
I left another comment going into more detail about the model specifications, if you'd like to read into it. But briefly: I took the copper heat conductivity coefficient and the air heat transfer coefficient. I sliced the copper block into thin slices and modeled heat transfer between each slice, as well as heat transfer between each slice and the surrounding air.
It seems that both heat transfer and heat loss do actually matter quite significantly, but they just cancel each other out almost entirely.
If we assume instantaneous heat transfer, thermal throttling time goes up from 592 seconds to 703 seconds (almost 2 minute difference).
If we assume no heat loss to the air, thermal throttling time goes down from 592 seconds to 500 seconds (about 1.5 minute difference).
The conduction in copper is fast enough that there's not much of a difference between the top and bottom.
Copper conductivity is fast, sure, but it's not fast enough to have equal temperatures at the top and bottom for such a big chunk of copper. That does affect the time to thermal throttle pretty significantly, actually. If we assume completely homogeneous temperatures across the block (ie, instantaneous heat transfer), according to my model, it'll take 703 seconds to thermal throttle. With heat transfer, the time drops to 592 seconds - a difference of about 2 minutes
Account for convective loses into air?
I got ~32 watts of convective heat transfer using assuming a uniform surface temperature of 99°C and a case fan speed of 0.2 m/s
https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html
Its going to radiate a little bit too.
Not a fan
That's indeed not a fan. Did we even need to mention that? /j
Yeah man, I dunno what that whiny bitch Nanni was on, but this some good quality copper.
Customer
But is it really copper?
Lets hope CCA doesnt strike again
Till it all gets to temp then it won't do much. It needs some more surface area to convect heat better.
With enough fins you don't need fans.
the other option is
only fans
Would a slow small fan still make a huge difference to the cooling here? Completely passive cooling seems like something that would only make sense in very specific professional environments (like needing an ultra low sound floor in an audiology chamber or recording studio).
I had a roommate who was getting his doctorate in chemical engineering, specifically focused on graphene. He was able to demonstrate how doping the materials in a heat sink to alter their ability to "release" heat, and then organizing these intentional hotspots along the length of the fins, you could create an active airflow using a stationary object.
But then his lab manager killed his grant and instead put him on a project partnered with BMW to make their bumpers more marketable.
Really makes you wonder how many revolutionary ideas have fallen through the cracks because of moron management
Black pilled by monetary interests.
Who knows how many great ideas we have lost because of bad management and capitalism...sigh
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The case has an opening for a vertical fan but it is not needed unless you do heavy gaming and run a high end GPU. For video rendering and other tasks the fins are rated to keep it at a decent temp.
I have good hearing, and a HDD spinning or even a "silent" fan is still audible droning noise to me.
This build is totally silent. The PSU is over-rated on purpose because it has a below 30% max draw mode that is fanless.
So this case makes 0 noise.
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Toblerone Gaming Heat Sink.
Toblerone has one identifier, its triangular shape. ☝️🤓
But there is another.... the convection space between the fins.
I remember when that space was less.... Spacious.
yeah that looks so weird right?
Toblerone has famously been shrinkflating their product for some time.
I remember seeing a comparison post many years ago of a modern one vs one that had been bought years ago and rediscovered in a closet or drawer or something. The older ones had thicker spikes.
A bar of disappoitment
Saturation for the nation
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