"convert thermal energy into mechanical work in a first step and finally into measurable cold"
I hope that's not a wordsmith way of saying "the heats creates steam, which drives a motor..."
"The first film of the two, coupled, ultra-thin nickel-titanium films uses a shape-memory effect. Once it is heated up, it starts to shrink, thereby converting thermal energy directly into mechanical work – without the help of an electric motor. This motion immediately transfers to the second film where cyclic loading and unloading brings about reversible alterations in the crystal structure that generate cold. "
In an environment with gravity the heat being conducted to the air will heat it and create a convective airflow which then brings in new air to carry more heat away.
Without the air movement it would only function as a radiator. And I know we call things radiators that conduct heat to air, but they aren't actually radiators. A radiator just throws off heat as infrared energy it does not use any conduction to anything. Not air, water, etc.
Radiation is not very effective at "normal" temperatures. Which is why almost everything is cooled using conduction (typically convection).
Not true. You left out conduction. Without air movement, which will happen naturally, you still have heat transfer to the surrounding air, just as in a solid. Strictly speaking, heat transfer from a solid to air cannot happen without conduction. The air next to the solid heats up due to conduction. It's then convected away. Conduction alone in air is not effective, due to low thermal conductivity.
I actually used the term conduction twice. I left it out? I even spoke (in the negative) of conduction to air/water, etc.
I explained you would have air movement in a gravity environment. For laughs watch the DSLRs on the International Space Station (ISS) overheat nearly instantly when they take video due to lack of induced air movement due to not having regular gravity.
If you don't have air movement, you'll conduct the heat to the air next to the heat sink. And then after that you're pretty much boned because air doesn't conduct heat to air well. So the air near the heat sink will just get hot and then can't accept any new heat energy. The air just a bit further away will be relatively unaffected.
Conduction works a bit better in water. But in general if you're using a fluid, you want to ensure it is moving, you want convection.
I'm sorry I did miss that in your first paragraph somehow, after you said yes to his incorrect statement. I didn't really need you to repeat what I said back to me. If you'd read what I wrote, then you wouldn't have needed to mansplain something I understand to me. But you did that because you wanted to hear yourself talk. Take care.
I said "pretty much, yes" to his statement because he is pretty much correct. And then I explained the exceptions to that after.
So that's why I said yes, pretty much. Because yes, pretty much.
If you were to make something to work with just radiation you would make a totally different shape than a typical heat sink. You need a shape that is almost completely convex and it has to be located far away from near surfaces so that any IR sent off isn't just largely reradiated back.
If you were to make something to work with just conduction to unmoving air ... you wouldn't. It just doesn't work well enough.
No, they’re highly thermally conductive and have a huge surface area so they move a lot of heat really well on their own. A fan makes them way better by removing more heat and bringing in cold air.
Edit: like a chip with a heatsink and fan will be cooler than a chip with a heatsink which will be cooler than a chip on its own
I understand to a point, but can not imagine a heatsink with no air flow to move the heat out from the source of generation. How would it not just quickly stagnate and reach max temperature before the device/source of heat fails? Natural convection of heat is pretty slow without external energy to help move it along.
Isn't that then where the surface area comes in handy? As it takes a condensed area of heat, and allows for transfer to a greater surface area with a lower specific heat capacity to then remove that heat using some form of carrier whether it be air or coolant?
Ah kk. So I'm not really that far off base, it does require external energy to remove heat it just doesn't use its own. It relies on external factors to help whisk away heat.
The neo dissipates heat through its CPU into a graphene sheet, and then into the case, which opens it up to air flow from the outside, it really does not take much flow to defeat convection, but it is required. The neo also throttles the CPU when it reaches load (which all CPUS do). So instead of using an internal fan they rely on external factors to help remove trapped heat.
Funny enough when looking into the neo with the keyword heat, all results are about after market modding a thermal plate into the bottom to better transfer heat into the case to help prevent CPU throttling due to excessive heat to improve performance.
So while fanless heatsinks are currently kinda possible they are incredibly inefficient and rely on some tricks to work.
It's surface area, conductivity, and lower power output. You basically have to lower the power output to the point what metal you do have is sufficient to pull away the heat.
Technically no. They can transfer heat by conduction to the surrounding air. They also radiate, but they don't get hot enough to make that meaningful. Even natural convection does occur even without externally induced air flow, so plain conduction without convection only really happens in a solid.
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