Here is an idea that pretend to be a perpetum mobile. Please find out where is a problem: - Let say that we have large container of monoatomic ideal gas that is thermally couple with environment - In the center we have a cylinder that is free to rotate around it’s axis positioned vertically. Let assume that cylinder is perfectly isolated and can spin frictionless w/o disturbing container gas. - We have also found a way to install directional nozzle that is able to inject gas jet into the cylinder. Nozzle is stationary with the container and injects gas tangentially at the cylinder circumferential wall. - We start experiment with container in thermal equilibrium with environment and cylinder filled with vacuum spinning very fast. - The gas is going to enter cylinder through the nozzle. Nozzle is going to convert thermal energy of gas into directional stream of atoms. If we are using supersonic Laval nozzle, I can see web references describing jet stream entering vacuum chamber with 7deg angle deviation and 1% of speed variation in other words: very directional jet. - Let assume that cylinder is spinning at the velocity that equals that of entering jet speed at the circumference. Basically what observer sitting inside cylinder will see is only residual speed of dispersing gas. And here is a place where a magic happen: from the point of view of container gas leaving through the nozzle caries high entropy and high temperature. From the point of view of the cylinder it receives gas of very low temperature, with low entropy. - Entering gas is going to be a slowest, coldest point within cylinder confinement. With time gas is going to accumulate and fill container. Assuming that temperature is below evaporation point liquefied gas is going to fill the bottom part of cylinder. The liquid is going to conform to the parabolic shape as per rotational force. Above the liquid gas vapor pressure is going to reach equilibrium with low temperature atoms injected by the nozzle. - Last, we need only to provide a hole in the center of cylinder that is being open once liquid level is higher then pressure inside container. We keep escaping liquid rate equal to the amount of gas introduced to the cylinder. The conservation of the rotational momentum is going to provide spinning torque, since new material is introduced at the cylinder edge with high angular moment, the escaping liquid has almost none. - The escaped liquid is going to evaporate inside container and draw the heat from the environment maintaining constant pressure. And the whole process keeps going, going, …. There are some tricky points here such as lack of friction and perfect insulation. This is just to neglect secondary issues, since I don't want to discuss engineering but physics. I did some back of the envelope calculations to illustrate a point: - Gas Xe - Molecular speed of Xe at 20C(293K) 1atm – 236 m/s in container frame of reference - Residual speed left after nozzle expension – 28m/s corresponding to 5K in cylinder frame of reference - Cylinder with radius 3000m and height of 3000m will maintain while spinning at 0.75 rpm speed of 236 m/s at circumference and centrifugal acceleration 1.9G allowing for paraboloidal liquid surface of 2800m in height to fit inside. -al
Hi ael65, Looking past the complexity, you have a basic problem in thermodynamics. What will happen is that the pressure inside the cylinder will equalise with the pressure outside the cylinder, and the temperature will equalise will the environment. Your spinning cylinder is a red herring - the spin on the cylinder doesn't appear to affect the experiment at all.
Hi Pete, Sorry for complexity, I don's see it working any simpler way. The relative motion between 2 liquids(gases) is a critical part. Think what is happening when you spray paint or press button on an areozol filled container. The moving liquid (or gas) drags the other medium creating negative pressure that is proportional to the square of relative speed. This process is called Bernoulli principle. If stationary cylinder would be left to equalize with container, then after it is sped the inner pressure and temperature will need to increase to maintain equilibrium. Since cylinder is isolated this process is going to be adiabatic with additional mass being added.
Hi ael65, You seem to be approaching this problem in an odd way... the tools you are using don't seem to be well polished and up to the task. For starters, you're not adequately considering the gas pressure inside and outside the cylinder. Luckily, well tested tools are available. The field of science that is used to analyse this kind of problem is thermodynamics. I'm a bit rusty on how to apply thermodynamics theory quantitatively, but I don't think it's all that difficult to learn. Now, about this spinning cylinder. Is it frictionless on both the inside and the outside? Is the nozzle stationary in the container, or does it spin with the cylinder?
It appears that I can't post images here since my count is too low. You can seep picture at http: //f7.yahoofs.com/users/4600994bz13c238e/69ccre2/__sr_/f7b5re2.jpg?phQBRWGBq4UhwNBW There are 5 steps of the process: A) Hot gas is injected into low pressure supersonically spinning cylinder along very narrow jet. B) Hot gas in compartment frame of reference becomes low temperature gas in spinning cylinder frame of reference. C) Low temperature gas accumulates inside cylinder and undergoes liquefaction. D) After converting angular momentum into torque liquid is allowed to leave cylinder E) Cold liquid escaped from cylinder draws heat within compartment, evaporates and can be recycled back into stage A. Let’s review each step: A) I don’t have an opinion on a process of creating supersonic narrow gas jet using Lavel nozzle. I can only cite references which describe such a jet with 7deg angular spread and 1% of speed variation. This data sounds good to me, and I have no reason to doubt it. Also, because the speed of cylinder is higher then molecular speed of gas it holds there is no backpressure that affects jet, same as injecting into vacuum. C) Assuming that gas is a low temperature (below melting point) and is introduced into well isolated cylinder at the angular speed matching speed of spinning cylinder, one can expect that with time dynamic equilibrium is going to be reached between liquid and it’s saturated vapors. (flat portion on the PV curve). E.g. based on wiki data if my favorite Xe is used and kept at 165K the pressure is around 100kPa (~1atm). Adding more cold gas under those conditions will cause raise of pressure and subsequently convert more of vapors into liquid. D) Exchanging angular momentum for torque, simple enough. E) Evaporation draws extra heat from environment, simple enough. B) Postulating conversion of the narrow jet at hot temperature and one frame of reference into a cold puff into spinning frame of reference is a key concept. This is the only risky assumption in my opinion into the whole thing, the rest is textbook thermodynamics. I expect someone to point out an obvious reason while it can’t be done, because otherwise we will not need anymore those overpaid oil executives. In short, I propose that temperature and entropy are dependent on the frame of reference and the second low of thermodynamics is not universally applicable, but only applicable with given frame of reference. -al
Pete, What I mean is this: consider observer A that has N atoms of a gas at tempreture Ta. From the point of view of a moving observer B at the speed V such a system can't be adequatly described as an object of internal energy NkTa and kinetic energy NmV^2/2. Instead, the average speed of melucules with respect to B should be considered, say Vb, and B is reporting system of NkTb internal energy and NmVb^2/2 kinetic. Since energy is preserved, the difference V-Vb is going to be complemented by difference in Tb. Because of chaotic motions of particles typically there is no difference in Vb and V. If you manage to line up particles perfectly (like being shot from a gun) then you can convert a whole thermal energy into kinetic. Mind you, this description supposed to be true for a monoatomic ideal gas. -al
Hi ael65, I'm very rusty on thermodynamics, but it seems to me that you are saying here that for any significant volume of gas, V=Vb, so Ta=Tb, and so it follows that temperature and entropy are not frame dependent.
Pete, Not quite. It is not only the size of the system that maters but also the degree or randomness. The point I’m making is that it appears to me (still haven’t heard argument that unhorse this concept) that with available technology you can convert a 3D thermodynamic (and 2’nd low bound) case into basically a 1D case which permits easy conversion into kinetic energy. Can someone bring my picture into the threat from my previous post ? This will improve a quality of discourse. -al
That's precisely what I thought about when I read the first few lines of his idea (before dumping the whole thought.) Please Register or Log in to view the hidden image! What he's proposing is every bit as impractical - and I can't imagine why he cannot see that.
Why Maxwell Demon ? I find John Gamgee's ammonia motor much more relevant, too relevant for comfort indeed. The scheme I like the most is this: assuming existence of a perfect mass to energy converter, why not to beam up light at some height and then gather free energy when converted mass falls back ? The problem with scheme is the same as with John Gamgee motor: you can't cool gas tempreture low enough to liquify all of it by adiabatic decompression. The reason is that evaporation heat is 3 orders of magnitude higher than specific heat. The only substance I found that could do this trick is H2, but this needs to be cooled to 4K. -al
And Gamgee's Zeromotor had no more chance of working than your own idea. Do you have any idea why the second law of thermodynamics is so useful and impossible to defeat? Actually, are you even familiar with it? And I'm not trying to be a smart-alec, I'm asking you an honest question.
