sethoflagos

A good and important point @Ghideon An ice block fresh out of the freezer should be oto -18 oC (0 oF) throughout. Even it has been left a while, the surface may well be at freezing point, but the bulk of the inside may be considerably colder. When it is placed under the cold plate of a Stirling engine, it is effectively insulated from ambient air while it continues to lose heat to the inside of the block. It is entirely consistent for the engine to appear to run well, rejecting a certain amount of heat to the ice interface, while that interface freezes and cools further due to a greater heat loss to the core. The cold reservoir is in this case the core of the ice block and the distribution of its temperature is unknown.

Me neither. Too closely associated in my mind with the Aztec two-step to give the right picture. But we should have a word for it really. In my own internal dialogues I call them 'condensations', but this is the first time I've communicated that to anyone. One person's mental picture doesn't necessarily work for others. This ifdea covers so many different processes and interactions that it's very difficuly to give a general answer that covers everything without quoting most of a thermodynamics textbook. So simple examples are probably the nest way to go. If we take too simplistic a view of entropy, many of the things we see happening around us don't seem to make sense. Take for example a glass jar of muddy water. The silt particles are all over the place so the entropy is relatively high. If we leave it to stand for a few hours most of the particles will settle to the bottom of the jar leaving the water much clearer. This is a lower entropy state and appears at first glance to contradict the 2nd Law of thermodynamics. We've produced 'order' out of 'chaos'. It only makes sense when you realise that as the silt particles settled, they created a bit of heat due to friction. That heat was lost to the surroundings, which raised the entropy of the surroundings by at least as much entropy as was lost from the contents of the jar. So the world starts making sense again. Understanding such simple pictures help you to understand how much more complex processes like photosysnthesis can build trees for example out of a few simple molecules and sunlight.

It's one of Brian Greene's catchphrases. It seems like a catch-all for all processes similar to the crystallisation of a low entropy solid phase out of a higher energy solution. It crops up about a minute or so into this.

You can 'age' exposed concrete structures in the garden (planting troughs for example) by painting the surface with yoghurt. It rapidly incubates a collection of mosses and lichens to help it blend in. A little tip I got from my mother many years ago.

There are, but they are usually behind paywalls. I'd be wary of using viscosity as your parameter. A particularly important viscosity behaviour is that of a binary mixture of water and ethanol. It is highly irregular in certain proportions and certain conditions due to specific interactions between the components. You can get the experimental data easily enough, but then the question is whether Ansys contains an appropriate mixing model for that particular system. Empirical data always trumps predictive modelling. It comes down to what you're exactly trying to achieve. Could you pick entropy instead? It follows a much more predictable path that's quite simple to calculate. Look for a wikipedia page on Entropy of Mixing.

I could do with one of those. We've not had mains supply for 48 hours.

I remind members of the opening few paragraphs of the OP Exactly how much of this are we supposed to accept without question? Given the extraordinary nature of the claims in this OP, I think it quite right and proper that we take a very close look at exactly what it is the OP is trying to do. I note the OP's reluctance for us to do so, and that in itself tells a story. So what exactly should we expect to happen when we fully decouple a Stirling engine from its cold sink. Despite the OP's earnest protestations, I'm going to start with the idealised model because that's how it's done. And let's put some numbers in: Stage 1: Isothermal expansion @ TH The power available from isothermal expansion of an ideal gas from compressed volume VC to expanded volume VE can be expressed as WE = nRTHln(VE/VC) where n & R have their normal IGE meanings. To keep matters simple we can assign it the value of 1 kJ over a certain number of cycles. The source of this energy comes entirely from heat input from the hot source hence QE = WE = 1 kJ Stage 2: Isochoric cooling Adiabatic null process by design. See Stage 4. Stage 3: Adiabatic compression from VE to VC Here we must introduce the ratio of specific heats k (1.40 for air), and can derive: WC = knRTH/(k-1).((VE/VC)^(k-1) -1) >= knRTHln(VE/VC) >= kWE >= 1.4 kJ The approximation tends to equality as VE/VC tends to unity. Since I've introduced inequalities, I'll use absolute values for Q & W to avoid confusion. Stage 4: Isochoric cooling from TA to TH The balance of energy, heat of compression, is returned non-reversibly to the heat sink at TH which is now functioning as a cold sink. QC = WC >= 1.4 kJ Non-ideal behaviour OP is of course correct in asserting that idealised processes can rarely if ever be fully realised in practice. However, that does not make them intractable. Stage 1 may be allowed to have a reasonable adiabatic element by allocating a k value of say 1.04 rather than the implied default of k=1 for ideal isothermal behaviour. This will have the effect of allowing some expansion cooling below TH and slightly increase power output on the expansion stroke. Similarly reducing the k value for Stage 3 from 1.4 to say 1.36 will introduce some isothermal behaviour, reducing TA and slightly reducing the power absorbed by the compression stroke. Which leads us to consider whether the machine is truly decoupled from its cold sink, since if it isn't this will reintroduce Stage 2 cooling and drastically reduce the adiabatic nature of Stage 3. We will return to this. Summary 1) While the Stage 3 compression phase is more adiabatic in nature than the Stage 1 expansion phase, the machine would require a significant work input to continue running for more than a couple of cycles. To this extent the OP prelinary assumption is true. 2) In response to the semi-rhetorical question posed by the OP It is clear that Remains by far the most credible explanation. The OP neglected to respond to this specific comment. What was the goal of the experiment? We need look no further than here Throughout this thread, the OP has treated the following statements as logical consequences of each other: A 100% efficient heat engine transmits no heat to its 0K cold reservoir. A heat engine connected to a 0K cold reservoir is 100% efficient. A heat engine transmitting no heat to a cold reservoir is 100% efficient. By disproving any one of these propositions he imagines he disproves them all.

Many thanks for that Joss. I've been a subscriber to that channel for a couple of years and it rarely disappoints.

An 'avatar' of the local Cernovii (possibly 'horned ones') iron age tribe as suggested seems quite credible. Can't find any info on its physical size, but similar stones are often boundary markers carrying the implicit message 'Our land. Trespassers may be poked with a pointy thing and ritually garrotted.'

Then I suggest you don't waste your valuable time in composing one of your usual 500+ word rambles. I summarised your proposed cycle in about 50 words. Your alternative proposed wording should be similarly concise. Don't link to external sources. Just plain simple wording for all to see.

Fish are pretty isothermal. As is a bucket of iced water. Why are you running scared of the isothermal assumption, Tom? If anything it works to your favour by maximising the efficiency of your machine. I'm perfectly happy with 'nearly isothermal', or 'not even nearly isothermal' or even 'adiabatic' if you want the lowest possible efficiency. Your choice. But I do insist that you make a choice. It's spelt 'isochoric' and means 'conducted at a constant volume'. I'll only accept 'very nearly isochronic' since it's pretty easy to ensure machinery isn't too elastic. But again, the theoretical ideal works to your advantage. Your choice. But I do insist that you make a choice. 'Isochronic' is something entirely different.

Just to clarify, the intent is to make the following changes to the Stirling Cycle. 1. The isothermal expansion stage at TH stays as is outputting power WE. 2. Isochoric cooling stage becomes a null event since it is adiabatic. QC = 0. 3. The isothermal compression at TC stage becomes an adiabatic compression from TH to TA absorbing power Wc. 4. The isochoric heating stage from TC to TH becomes an isochoric cooling from TA to TH. Are we all in agreement? I do know that you've read this, so I'll take your failure to respond as concurrence.

Just to clarify, the intent is to make the following changes to the Stirling Cycle. 1. The isothermal expansion stage at TH stays as is outputting power WE. 2. Isochoric cooling stage becomes a null event since it is adiabatic. QC = 0. 3. The isothermal compression at TC stage becomes an adiabatic compression from TH to TA absorbing power Wc. 4. The isochoric heating stage from TC to TH becomes an isochoric cooling from TA to TH. Are we all in agreement?

Exactly.

Just one example of many similar cases. What would be the result of your conscious self being able to manipulate at will the hard wiring of your visual cortex and alter the (currently subconscious) pre-processing of the information coming from your eyes? As there are many, many more ways of making a mistake than of making an improvement, any change you made would almost certainly be destructive with consequences for your future survival. May it therefore be reasonable to assume that evolution would try to make it as difficult as reasonably possible to do this? On a more general scale, wouldn't it be a good idea for evolution to limit the scope of your consciousness to the minimum necessary for survival and reproduction? We should perhaps be grateful for having sufficient conscious awareness to provide the opportunity to enjoy our friendships, interests and cultures free of the endless computational burden of having to consciously process every single nerve impulse occurring in our body. So no, our sense of self and our total brain functionality cannot operate on an equal footing. Our survival demands that most of the complex computational processing and maintainance of vital service runs subconsciously in the background, leaving our consciousness intelligence to tackle changing conditions and novelties that evolution is ill-equipped to anticipate.

I'm assuming you meant 'all the earth's land masses ended up in one continent'. The idea's a bit of a nonsense I'm afraid. The geological record in Britain (excluding Scotland and Northern Ireland) for the 200 million years leading up to the formation of Pangaea is practically complete and has been extensively studied. It has it's action moments but these are no more extreme than eruptions from a volcanic island chain along the north-west coast. The rest is almost entirely quiescent marine deposition. No evidence whatsover of planetary collision. Various lines of evidence indicate a slow journey from mid-southern latitudes until close to the equator where we had a three way collision with Canada (who gave us Scotland and Northern Ireland), and much of Scandinavia (who then similarly obtained Norway). Subsequently most of continental europe rear shunted us as they were pushed forward by the great land mass of Africa moving north. I remember this basic sequence being cautiously developed through the 1970's, but as the detailed geology of more parts of the world became available, it all seemed to fit in with the same picture and confidence grew in it being a pretty accurate representation of actual events. There certainly remain a few last lingering details to work out particularly with the more complex and exotic terranes, but the general plan is seen as very sound. Hence wildly different versions of events presented with no supporting evidence (such as the OP) can be safely classified as lunatic fringe.

That post wasn't addressed to you. But perhaps there's no harm in reminding you that this body of theory that you are constantly sneering at is in everyday use in the design of serious real world applications where getting it wrong can seriously damage your career. Steep learning curve.

No shaft work exiting the system so your 'work' is just more heat. Deja vu.

Since I was Lead Process Engineer for Stone & Webster on the design of https://en.wikipedia.org/wiki/Sutton_Bridge_Power_Station, I can confirm this. The minimum required thermal efficiency was written into the contract, and was no small challenge to meet given they insisted we used an air-cooled condenser for the steam cycle. As a side note this was the last CCGT plant to be built in the UK before the government put a moratorium on gas-fired power plant, which was one of the factors that encouraged me to leave for sunnier shores.

An efficiency of zero because you seem to have no means of extracting work from the system. The machine still operates therefore there is enough heat flow to keep it operating.

You were advised: And yet a couple of hours later you continued with: And were again corrected: Now you say: We are going around and around in circles because you fail to understand the difference between an actual real world efficiency and a theoretical limit, despite having this explained to you by several parties. What are you really doing here?

No it isn't. You can't play the victim card when you're the aggressor. I'm simply calling you out. No. You continually misdirect the discussion by ignoring central themes and cherry picking peripheral trivia to have a snipe at. You're bringing absolutely nothing to the table to support your views other than blind persistence. Call it belief, faith, or just plain trolling: the one thing it isn't is science. Your opinion carries less weight here than you imagine. I see no point in trying to share knowledge with someone who has no interest in it. What are you doing here, Tom?

A deliberate refusal to acknowledge the points of view of others when they challenge with your own 'faith'. Deliberate misdirection of the discussion and wrong. The vast majority of collisions are not head on. Kinetic energy gets shared out. There is a nett flow of heat to the cold sink. Conspiracy theory. Irrelevant historical detail. You really don't have the slightest interest in being enlightened do you? Why exactly are you here?

You could start by doing a literature search for current work referencing these citations: Milgram, J. H. 1965 Compliant water-wave absorbers. M.I.T. Department of Naval Architecture and Marine Engineering Report no. 65–13. Ursell, F., Dean, R. & Yu, Y. 1960 Forced small amplitude water waves; a comparison of theory and experiment. J. Fluid Mech. 7, 33–52.

Because it didn't "GO MISSING"! 500 kJ of heat @ 500 K has been transformed to 100 kJ of Shaftwork plus 400 kJ of heat @ 400 K It's still there but at a lower temperature. Add a second machine operating between 400 K and 300 K and that 400 kJ of heat @ 400 K can be further transformed into another 100 kJ of Shaftwork plus 300 kJ of heat @ 300 K On some space base for example with ready access to a cryogenic heat sink, you can potentially recover almost all of the original 500 kJ of thermal energy. Just recognise that extracting the kinetic energy from slow moving particles requires contact with particles that are almost stationary. I think one of the main issues is a very confusing terminology. In the above example we have one (ideal) machine with a 'thermal efficiency' of 0.20 coupled to another with a 'thermal efficiency' of 0.25. Normally when we combine various efficiencies in series we multiply them together and would expect an overall efficiency of 0.05. And yet here we get an overall 'thermal efficiency' of 0.40. It sends a very odd message. To a practical layman, a low efficiency figure implies some failings in the design that can be incrementally improved with a little attention to detail. This is an entirely understandable viewpoint to take. But the above examples are idealised, 'perfect' machines with no avoidable losses. By any reasonable definition they should be classed as 100% efficient. As they would be if instead of W/QH we accepted the Carnot limit for what it is and used Machine Efficiency = W/QH x TH/(TH - TC)