Jump to content


Senior Members
  • Posts

  • Joined

  • Last visited

  • Days Won


Everything posted by exchemist

  1. No idea. Can you give some context, please?
  2. I am no biologist but I don't think plants can get nutrition from proteins in milk or yogurt, saccharides in the starch in flour or sugars in orange juice, or triglyceride fats in cooking oil. These are all, so far as I know, types of substance they synthesise for themselves. They will take up water and minerals from the soil, but I think that's all. However, there are plenty of bacteria and fungi that can make use of some of these types of substance.
  3. Yes you are quite right. Your diagram represents the Carnot cycle efficiency formula in the the form η=(TH - TL) / TH . The length of the line from absolute zero to TH is 100% and, using the temperatures you have chosen, the length of it to TL is 80%. That's all it is. However what I think some other posters have been trying to do is explain how that very simple formula for the maximum possible efficiency is derived. That too is fairly simple, but it does require you to understand the gas laws and what an isothermal and an adiabatic process are. The Carnot cycle simply applies these to a fixed amount of gas doing work by expanding against a piston and then being cooled so that it can repeat the cycle and do more work. So if the gas laws are true, the Carnot efficiency formula is true. More detail here: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html
  4. But important to keep in mind that alcohols are a whole family of organic substances, in which there is a hydrocarbon backbone and one or more hydroxyl groups (-OH) attached. There is only one of these that can be drunk safely (within modest limits), namely ethanol, C2H5OH, as @chenbeier says. All the others are poisonous. Commercial sprits are usually 40% ethanol, the rest being water. Wine is about 13% and beer 4-5%.
  5. I'm surprised you were not also Nebuchadnezzar and Rameses II. Funny how these reincarnation nuts are never reincarnations of ordinary people.
  6. And for 150 years, all engine designers have been failing to apply common sense, in your expert opinion, based on some half-arsed experiments you've done with a $200 toy Stirling engine? Stroll on! 😁
  7. Assuming "revenge" = "continent", I am not aware we know of any other planets with plate tectonics. Without that, the whole idea of continents becomes fairly meaningless. Continents are lighter portions of lithosphere that float on a denser layer. They seem to arise by a process of fractionation, due to volcanic activity. So if those elements are not present, you won't expect there to be identifiable blocks of crust that you could call continents.
  8. Wrong. Industrial diesel engines (low speed, two stroke, with an energy recovery turbine in the exhaust) can get over 50% efficiency, and combined cycle turbine installations even getting on for 60%: https://en.wikipedia.org/wiki/Combined_cycle_power_plant The opening few paragraphs go into this a bit and even refer to how close to Carnot cycle efficiency they can get.
  9. They know the temperature of combustion inside their machines. They have to, to choose the right alloys, calculate expansion, estimate expected NOx generation for emissions compliance, and all manner of other things. You have no conception of how much detailed work goes into the design of an industrial engine or turbine. A power turbine does not put out exhaust below ambient, obviously. You are, as you so often do, introducing irrelevant anecdotes to muddy the discussion. You can get obviously get Joule-Thomson cooling by expansion from the outlet of a compressed air supply. But we are not, I say again NOT going to get distracted by that latest irrelevance of yours. What are you doing here, Tom?
  10. Do you really think the designers of heat engines don't measure their efficiency? I spent the last decade of my career talking to designers of engines and turbines for ships and power plants. I can assure you that the fuel efficiency of their machines was one of their top preoccupations, and that comes down to thermal efficiency, which was often quoted. Every power plant operator knows the efficiency of their generation plant. It is absolutely central to their business. Unlike you, they were not just futzing about with hair dryers. 😁
  11. I think we can guess the agenda from Tom's previous thread on the "ice bomb engine": https://www.scienceforums.net/topic/124996-the-ice-bomb-thermal-engine/page/2/#comments As often with the crank fraternity, Tesla is behind it. In this case though, interestingly, it is not the usual misunderstood magnetism but another notion Tesla had, which was to create an engine that rejected no waste heat. So it's perpetual motion of the second kind. Which is more fun than a mere violation of conservation of energy, admittedly. The ice engine was great - I enjoyed it immensely.
  12. Nobody has ever made a Carnot cycle engine, for one very obvious reason - which you would have realised if you had learnt the necessary thermodynamics. Because the essence of a Carnot cycle is that it is 100% reversible, with no losses, all its processes have to take place infinitely slowly. It also has to be perfectly insulated, so that the adiabatic stages can be exactly adiabatic. So such a machine can't be made. Its cycle can only be calculated on paper. The best we can do is assess the efficiency of real machines compared to the idealised Carnot efficiency. 150 years of engineering experience confirms that no heat engine has ever equalled or exceeded the Carnot efficiency. So, not only does it appear to be correct on theoretical grounds but practical experience also indicates it seems to be right.
  13. Do you think all value judgements are subjective, then?
  14. "Officially"? Where do you think the subjectivity comes in, in the practice of requiring reproducibility in observations? What is subjective about thinking this is a good practice to adopt?
  15. Because it is collective, rather than individual, is not specific to a group or a way of thinking it is a reasoned technique for achieving objectivity. But if you think it is subjective, what would you say is subjective about it?
  16. No. For instance, in science we demand reproducible observations. That is a collective requirement the science community as a whole has adopted, in an attempt to achieve objectivity. That has not been arrived at subjectively.
  17. The article seems to be Chopraesque quantum woo. In other words, meaningless ballocks. 😁 Unless, perhaps, you can unpack it for me and explain what it actually says that has some science content to it.
  18. Haven't you noticed electric cars, wind turbines and soar panels all over the place?
  19. Yes, Tom is a perpetual motion machine of the second kind devotee. He thinks all heat can be converted to work, with no waste heat rejected.
  20. If your magnetic dipole is made of gas (though hard to see how this could be managed) you won't get any radiation. If it is made of a metallic conductor, in which the conduction band electrons are free to move within the conductor, then I suppose in theory you might, since the electron flow in a metallic conductor is more or less classical. Do not muddle up the two.
  21. The problem is you can't do the Stern-Gerlach experiment with a solid array of atoms. In a solid, the atoms are in a much more complex potential field. Changes to their alignment will depend on interactions with the lattice as well as any external field. You seem to think that there will be radiation from a compass needle oscillating about North position. Maybe that's right. But you are dealing with a conductor, that is with a sea of electrons in the conduction band of a metal.
  22. What you are overlooking is that spontaneous emission has a probability that goes up with the cube of frequency. The atoms in the higher energy alignment states can't just radiate freely. The transition would involve microwave emission and the probability of this occurring spontaneously is very low, because the frequency of the emitted photons would be so low. The atoms in the higher states are trapped there, until something interacts with them to allow them to lose energy.
  23. The passage you quoted is not a classical treatment, but a QM treatment. That's what the wave function integral is about. There is no way for a classical treatment to give you a series of beams, corresponding to discrete orientations. You would get a continuum, since all possible orientations are allowed - or just one spot if the particles had time to orient themselves with the field before exiting it.
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.