arkie87

Was wondering if anyone had any particularly good methods (besides putting it in a bigger pot of ice) of cooling hot pots of soup so they can be put in the fridge without spoiling everything inside. The way i see it, the pot has a lot of thermal mass, and once the top layer of liquid cools, the steaming stops, so the heat is trapped in. Today, i had the idea to put wet paper towels on the sides of the pot. The hot pot quickly dries the towels, which essentially, allows the pot to continue to steam. What do you guys think? P.S. I've also found an idea for filling a glass bottle with water and sticking in the freezer. The glass bottle can then be placed into the soup to cool the internal part rapidly.

Not sure what you mean here. If you could (magically) apply the minimum layer to fill the roughness, then TIM would be better, even for lapped surfaces. And it should reduce total interfacial resistance significantly (at least a factor of 2).

Properly applied TIM is always better. With lapped surfaces, it is probably very difficult to apply the "proper" amount (to fill roughness but no more). TIM conductivity is still 100x larger than air (and solder is 10-100x higher than TIM). And yes, it is pretty easy to apply too much TIM, even for unlapped cpus

This isnt correct. Even if they are so flat, that they float on top of each other and stick together, only a small fraction of the surfaces are actually touching, which is what thermal interface resistance is. Roughness is still on the order of 100-200nm even after lapping, and i havent heard of anyone who can go lower (surely not if you are hand lapping the chip yourself). Of course, it is better than if the surfaces werent lapped, but it is still too large (and not better than unlapped but with TIM). I agree. Just go with commercially available products, unless you want to make your own project out of it (and possibly destroy your cpu).

Lapped CPU's still have thermal interface resistance; thus, they still need TIMs, albeit a much smaller volume (probably not even possible to deposit that little). And as a side, most silicon is already lapped and polished; its the heat sink and case that needs lapping. My guess is it will take a while before it is necessary for consumer CPU's. Right now, its mostly applicable to other high flux electronics, like laser diodes and power amplifiers. CPU's have been getting more efficient (less heating per flop), so that bypasses the thermal limits.

If TIM becomes limiting factor, then you can simply remove TIM It's called embedded cooling It is actually the project i am working on

By active cooling, you mean refrigeration and/or cryogenic fluids? Liquid cooling with a pump is also "active" when comparing it to passive heat pipes.

Are you saying heat sink to air is the bottleneck OR that when it is, switching to liquid cooling helps? Pumped liquid cooling and heat pipes can easily achieve thermal conductances greater than the TIM, making the TIM the bottleneck. If the TIM is not the bottleneck, then switching to liquid cooling should give significant improvement, no?

Even heat pipes wont help if a TIM is thermal bottleneck. Microchannel water coolers can be just as good if not better than heat pipes, though heat pipes are passive (which is both an advantage and a disadvantage).

I am mostly concerned with the cause of the limit, rather than the specific value of the limit. I dont understand the logic here. Water is 20x better than air at transferring heat (0.5 W/mK vs 0.025 W/mK thermal conductivity). A well designed water cooler should be able to keep the temperature much lower than an air cooled one. The only reason this wouldnt be the case is because of the thermal interface materials (TIMs) which might account for the bulk of the thermal resistance; in this case, you either have to bypass the TIM or use cryogenic fluids.

Sorry, may not have read in full. Got a lot of responses... What limits the gains to 400 MHz? Chip voltages and/or computer crashes? Or chip temperature i.e. liquid cooling isnt much better than a well-designed air heat sink...

Makes sense. Comparable Intel and AMD cpus might be priced (linearly) proportional to their performance, but higher end, it becomes non-linear. Thanks for the info.

Thanks for all the replies. I'm not really sure if i have an answer. Why is AMD 10x cheaper than Intel? Are AMD's also 10x worse? Also, w.r.t. liquid cooling: does one buy separate kits for CPU and GPU or do GPU's not allow for liquid cooling? Also, does one need to buy a CPU meant for liquid cooling, or can any CPU be modified (by just removing the heat sink) for liquid cooling? - - - Updated - - - Is this really true? While it is true that all heat is eventually rejected to air, liquid cooling is supposed to keep the processor a lot cooler, since the heat is removed more efficiently from the chip... I thought 1.1 with unity 5 was supposed to change all that. Multithreaded physics... everything i've read so far has said that bigger ships will perform better. Do you have a reference to suggest it wont?

So, i'm thinking about building a new gaming PC, and came across the fact that Intel 8 cores are $1000 while AMD's are <$200. Why is that? How much worse could an AMD 8 core be? Also, would appreciate any references on building PC's, specifically, on liquid cooling. Thanks!

Yeah, its old. Something around 0.23. The aerodynamics is original stock aero too. Or else, there is no way i would slow down from 11 km/s - - - Updated - - - Thanks! Yeah, some classical would work well too.

So a while ago, i had this idea to make this video of me playing KSP with this epic space music. Here it is; what do you guys think? What do you think is the best KSP space music? Note how well i tried to time the game events to changes in the music tempo

If the absorption lines become saturated, can we still tell how thick the gas clouds are? Or we tell by band widening? How does it work? How do we detect clouds if there are no stars behind it or how do we know the cloud is in our galaxy and not on the outskirts of another galaxy, if the stars we observe are in another galaxy? Thanks for your response(s)

I understand that; my question is: why is that our conclusion. Isnt the answer i proposed simpler (and thereby, satisfies Occam's Razor)? How can we really know the density of of interstellar space? - - - Updated - - - In what way(s)?

A question i've had for a long time: It is my understanding that after inputting galaxies into computer simulations, and giving stars velocities similar to the measured ones, the galaxies flung themselves apart in stark contract to reality. Accordingly, physicists have suggested that there is dark matter, which cannot be directly observed. My question, therefore, is: why cant this dark matter be just that: dark matter. The sun constantly gives off solar wind (and i assume most starts do). If it has been burning for billions of years, it might have lost a significant amount of mass, which has cooled and is floating around the solar system (but is un-observable). From Wikipedia: Mass of Observable Universe: 1e53 kg Volume of Observable Universe: 4e80 m3 Average Density: 2.5e-28 kg/m3, which is approximately equal to 1/7th of a proton per cubic meter The average density of interstellar space is 0.1-1000 atom (i assume this means proton) per cubic centimeter: i.e. 1e-22-1e-18 kg/m3 The Mass of the Milkyway galaxy: 3e42 kg The volume of the Milkyway galaxy: 1e61 m3 The average density of the milkyway galaxy is 6e-19 kg/m3 Thus, the upper limit of average density of interstellar space is close to the average density of the milkway galaxy, and so, rarefied gas could be some dark matter? Am i failing to consider something, or worse, miscalculating something?

Why is fourth acceleration due to change in ISP? If it is a change in acceleration, it is still "jerk", no? It would have to be a change in jerk to be a jounce.

You should quote him exactly. I think, when i read what he wrote, it seemed he was implying that water absorbs solar radiation as well as infrared, but actually (after i re-read what he wrote a few times), it appears he was actually implying that the sun emits a significant portion in IR spectrum (and he provided a reference), which is contrary to the source i supplied. Here is the passage im talking about: I didn't. I meant water vapor below cloud level, in its transparent (and invisible) form. Non-cloud water vapor absorbs strongly in the infrared range This might imply that Wedge thinks non-cloud water vapor can absorb visible light; however, it appears he doesnt think that, but rather, that 50% of the solar flux is in the IR spectrum (which water vapor obviously absorbs). I'm not sure how this is possible (unless our two definitions of IR spectrum are different i.e. 10um vs 1 um) See his response:

I guess you will find out? Has he PM'ed you?

I was referring to temperature, not CO2; hence "warming"

Are we sure the current rate of warming is unprecedented? The climate trends for the past 400,000 years (from ice core data) do not appear smooth. If you zoom in, you might find short periods of time (and by short, i mean thousands of years), where climate was warming (and cooling) as rapidly as now, even though the longer term trend was much smoother/less steep.

Neither of those are true at all! i.e. you dont need the word "strictly" Well, in their defense, if CO2 is responsible for only 25-33% of the warming, and the water vapor feedback loop doesnt actually exist or is severely damped (due to the presence of negative feedback loops), then the greenhouse effect becomes a lot less scary, at least, in immediate terms (i.e. our lifetime). Anyway, thanks for being respectful throughout this thread!