exchemist

Was this item the only one made of this "slate", or were other objects made of it as well? And was it really slate, or could it have been siltstone? Real slate flakes easily into layers and is not ideal for carving, whereas siltstone is much more suitable. I quote an extract from the Wikipedia article on the Narmer Palette, which was thought to be made of slate but is actually siltstone. The Narmer Palette is a 63-centimetre-tall (2.07 ft), shield-shaped, ceremonial palette, carved from a single piece of flat, soft dark gray-green siltstone. The stone has often been wrongly identified, in the past, as being slate or schist. Slate is layered and prone to flaking, and schist is a metamorphic rock containing large, randomly distributed mineral grains. Both are unlike the finely grained, hard, flake-resistant siltstone, whose source is from a well-attested quarry that has been used since pre-dynastic times at Wadi Hammamat.[13] This material was used extensively during the pre-dynastic period for creating such palettes and also was used as a source for Old Kingdom statuary. A statue of the 2nd dynasty pharaoh Khasekhemwy, found in the same complex as the Narmer Palette at Hierakonpolis, also was made of this material.[1 From: https://en.wikipedia.org/wiki/Narmer_Palette

Yes it's on this thread a couple of pages back. I was referring to the mechanism that causes frost shattering of rock. Water gets into cracks, freezes at night, jacking open the crack, thaws again, refreezes and jacks it open a bit more, etc. I was being a bit figurative, as it is not a constructed engine as such, but it does operate in a cycle, exploits a heat source and heat sink and does mechanical work, using water as the working fluid, by exploiting the ice/water phase change. So if you put it like that, it has all the elements of an engine. That's because videos are a crap way of communicating experiments. To analyse what you did, we need to see a precise description of the exact set up, with a diagram. Whatever you did, you did NOT run it without a heat sink. That I guarantee.

Yes, that would be the principle employed by the natural ice engines you get at the tops of mountains or in deserts, as @sethoflagospointed out a while back. You can certainly exploit the temperature difference between day and night to run an engine. Just don't imagine you can run a heat engine with only a heat source and no heat sink. That is wacko - like poor Tesla.

However the electricity you use to run the freezer will exceed the power output of the ice engine.

Nor has anyone. And there is no reason to think that is what is depicted in these carvings.

Bingo! You've got it - except that in fact you have to add back MORE heat than was taken away, in order to complete the cycle. So yup, its thermodynamics are just like any other heat engine. Exactly. The intermolecular force in the case of water comes mainly from hydrogen bonding. It happens that, because of the relative positions and angles the molecules need to take up, to maximise the energy released by forming these bonds, they have to move apart somewhat, compared to their average spacing in liquid water. Hence we get expansion on freezing. (One or two other materials also expand on freezing, but it is very unusual.)

Not so much weaponised by the wealthy as by the marketing departments of consumer goods companies, I'd have thought. Whole industries have been built on creating and fanning the flames of dissatisfaction. It is a commonly observed fact that poor rural families with very little by way of possessions often seem far happier and more contented than blokes in jags. I myself remember when I got rid of my old Morris Minor, in favour of an MGB roadster, that I was suddently assailed by worries about it getting scratched or stolen, whereas before I couldn't have cared less about the rusty old Minor. Same when I bought my first house.

....and we are where, now, exactly????

Agreed. They are obviously aubergines.

When you say your proposed machine converts atmospheric heat in useful power (electricity I suppose), where is the waste heat rejected? Into water cooler than the air, or something?

Because if you are not not a rabbit, then you are a rabbit. It's just logic.

This seems to have dissolved into rambling incoherence. I don't think there's much point in me continuing this discussion.

Some of these "Mysteries-of-the-Ancients", von Daniken loonies insist they are Crookes tubes!

No I think you re complicating this unnecessarily. The way I envisage this, for simplicity, is that the ratchet acts to stop the load pressing on the ice the moment it starts to melt, i.e. it engages immediately to support the load. So NO work is done on it by the load during what you might call the "return stroke" of the engine. So ignore the ratchet: its function in this scenario is to make things simple. Regarding the atmosphere, yes, a tiny bit of work is done by the atmosphere when the ice melts, sure. But we can forget that too, since it is (i) very small and (ii) an equal and opposite amount of work is done against it during the expansion "power stroke". The ice has not only to push up the load, but also push back the atmosphere too, right? So it makes no net difference to anything. So again, forget it, to make things simple. Also ignore taking machines in and out of freezers and all that jazz. You have a warm reservoir at T1 and a cold one at T2 and you put the engine in contact with each alternately: it does not matter how. Forget the engineering. It does not matter a toss and it is preventing you seeing the essence of the scenario clearly. The point is that, stripped to its essentials, you have a standard heat engine, to which the Carnot cycle principle can be applied, as it can to any other heat engine. As to what does the work during the expansion "power stroke", it is chemical energy. As ice crystallises, chemical bonds are formed as the molecules move to a lower energy state. This releases energy, which emerges in the form of both heat and in any work that has to be done to push the molecules apart, as they start to take up the more open but bonded, rigid structure they have in solid ice. During the return stroke, heat has to be added to give the molecules the thermal kinetic energy to break those bonds again.

I certainly can't - and I doubt anyone else can since it seems, from the link I gave you earlier in the thread, to depend on what borate product you are using. The DOT product in the link is said to give a more or less ideal pH on its own. At least, that is how I interpret this passage: "When used in pools at typical dilution, the new formulation has an ideal pH of ≈7.6. Above pH 8, the chlorine becomes much less effective as a sanitizer, but below pH 7.4 the equilibrium trends toward hypochlorous acid and chlorine is lost more rapidly." So, as I say, I think the best bet is to check with the supplier's recommendations for whatever borate product you are using - or have in mind to use.

Tell us what you think about it first and then maybe we can guide you a bit.

What I mean by normal is that the principle of the Carnot cycle still applies. You have heat flowing from higher temperature T1 to a lower temperature T2, and some of it gets converted to mechanical work. The Carnot cycle says nothing about the means you choose to use to make the conversion. It just lays down the maximum efficiency achievable in theory, over any heat engine cycle. There is no "corruption" of anything that I can see, nor any reason to suppose that thermodynamics ceases to apply, just because we are dealing with a substance that expands on cooling. I can see, though, that it could be interesting, in an academic sort of way, to work out exactly how the efficiency limitations manifest themselves, in this unusual form of heat engine.

Indeed. But we can forget that effect here. The J-T coefficient for N2 is 0.2K/bar and 10mmHg is ~ 0.13bar, so we're looking at cooling of 0.025K or so due to the Joule Thomson effect. The intermolecular attractions of N2 and O2 are not very strong, so air does not deviate that much from an ideal gas.

I don't think even the Russians would see military potential in this ice engine of yours! But I was thinking about it this afternoon. It could be interesting to distill it down to its simplest. You have a vertical cylinder with water in it, a piston and a ratchet so that when it freezes it lifts a weight and when it melts, the weight can't fall back down. You alternately connect the cylinder to a warm reservoir at say 20C and a cold reservoir at say -20C. The warm reservoir provides heat to melt the ice and the cold reservoir freezes it again. What happens? You start with water, connect to the cold reservoir and freeze the water. Heat flows into it, corresponding to Latent Heat of Fusion minus the work done in lifting the weight. Then you connect to the warm reservoir. Heat flows from it to the cylinder to melt the ice, this time the full Latent Heat of fusion, as the water is no longer under pressure, thanks to the ratchet. So you have a heat flow from warm to cold, with some of the heat being converted to mechanical work. It's a normal heat engine, really, isn't it?

Ah, so it was Tesla, again. Here we go.... And he was looking for a perpetual motion machine of the second kind, that is to say one operating with only a heat source and no heat sink. Fine, we all know how that ends. But I see you are personally quite serious about this: https://experiment.com/projects/hohohltuqpivlpspyewk/methods Now I understand why you talk of getting banned, men in black etc.

You know the pressure change is not significant from the tension or lack of it in your cheeks. But I looked it up and, in pursed lip breathing exercises for medical conditions, patients typically generate a pressure of the order of 15cm H2O, i.e. ~10mmHg. I leave it to you to calculate the temperature drop from adiabatic expansion by this amount, if you think it is significant.

It seems to me @Bufofrog has got it pretty well spot-on. Air entrainment will account for the faster stream of air being a bit cooler. There is negligible pressure drop across pursed lips, so adiabatic cooling won't be relevant. Cooling by evaporation - accelerated by rapid removal of evaporated vapour - will be very important in the soup/tea case. A cup of tea drunk outside cools a lot faster than indoors at the same temperature, if there is a bit of a breeze.

I think that has to be right. In science we make models of the "real" physical world, to predict what we should expect to observe. There comes a point, certainly in QM as I remember it, at which the mathematics is the model. Is it real? The honest answer has to be that we don't know. All our models are subject to change and further refinement, so we can never say they are 100% real, but only approximations to reality.

Are we all barking up the wrong tree because of your initial choice of term for the machine you have mind? Are you perhaps thinking of a hydraulic intensifier: https://en.wikipedia.org/wiki/Hydraulic_intensifier ?

Haha, I did wonder if you were a closet free energy crank, what with all your talk of being banned and everything. Can you refer me to a link to this 1900 fellow? Clearly he wasn't quite as smart as all that - or maybe he wanted to pull a few people's legs. Like you perhaps.