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GETTING RID OF THE SECOND LAW OF THERMODYNAMICS



 
 
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  #1  
Old June 21st 13, 12:59 PM posted to sci.astro
Pentcho Valev
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Default GETTING RID OF THE SECOND LAW OF THERMODYNAMICS

Any heat engine converts heat into work by undergoing the following (very roughly described) four-step cycle:

Step 1: The heat engine is manipulated (usually heated) so that its work-producing force increases from F1 to F2.
Step 2: Work W2=F2*L, where L is the respective displacement, is extracted from the heat engine.
Step 3: The heat engine is manipulated (usually cooled) so that its work-producing force decreases from F2 to F1.
Step 4: Work W1=F1*L is done on the heat engine. Its initial state is restored.

The net work extracted from steps 2 and 4 is positive (Wnet=W2-W1) so if there is something that prevents us from abandoning the second law of thermodynamics, this something should be looked for in steps 1 and 3. Traditional education considers exclusively non-isothermal manipulation of the heat engine in steps 1 and 3 (heating and cooling):

http://physics.bu.edu/~duffy/py105/Heatengines.html
"A necessary component of a heat engine, then, is that two temperatures are involved. At one stage the system is heated, at another it is cooled."

http://www.qi.fcen.uba.ar/materias/f...astica%202.pdf
"Figure 2. Thermoelasticity experiments on a stretched elastomer and compressed gas, where W represents a weight. An increase in temperature decreases the length of the elastomer, and increases the volume of the gas."

Yet there are ISOTHERMAL heat engines - the work-producing force is increased or decreased in some chemical way. For instance, there are macroscopic polymers which, when the concentration of hydrogen ions in the solution increases, contract (the work-producing force increases) and lift a weight:

http://www.ncbi.nlm.nih.gov/pmc/arti...00645-0017.pdf
POLYELECTROLYTES AND THEIR BIOLOGICAL INTERACTIONS, A. KATCHALSKY, pp. 13-15: "Let the polymolecule be a negatively charged polyacid in a stretched state and have a length L. Now let us add to the molecule a mineral acid to provide hydrogen ions to combine with the ionized carboxylate groups and transform them into undissociated carboxylic groups according to the reaction RCOO- + H+ = RCOOH. By means of this reaction, the electrostatic repulsion which kept the macromolecule in a highly stretched state vanishes and instead the Brownian motion and intramolecular attraction cause a coiling up of the polymeric chains. Upon coiling, the polymolecule contracts and lifts the attached weight through a distance deltaL. On lifting the weight, mechanical work f*deltaL was performed... (...) FIGURE 4: Polyacid gel in sodium hydroxide solution: expanded. Polyacid gel in acid solution: contracted; weight is lifted."

Here is the four-step ISOTHERMAL cycle:

Step 1: The polymer is initially stretched. We add H+ to the system. The work-producing force (of contraction) increases from F1 to F2.
Step 2: The polymers contracts and lifts a weight. Work W2=F2*L is gained by us.
Step 3: We remove the same amount of H+ from the system. The work-producing force decreases from F2 to F1.
Step 4: We stretch the polymer and restore the initial state of the system. Work W1=F1*L is wasted by us.

Now the situation is much clearer: in order for the second law of thermodynamics to remain valid, the net work GAINED from steps 2 and 4, Wnet=W2-W1, should be neutralized by work WASTED in steps 1 and 3.

Yet it is apparent, even from a superficial examination, that the operations in steps 1 and 3 are symmetrical and therefore it is quite reasonable to assume that the net work involved (in steps 1 and 3) would be zero or close to zero. That is, we don't waste work in steps 1 and 3 and Wnet=W2-W1 turns out to be net work extracted from an ISOTHERMAL cycle, in violation of the second law.

A rigorous analysis would show that isothermal heat engines do indeed violate the second law of thermodynamics.

Pentcho Valev
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  #2  
Old June 21st 13, 05:44 PM posted to sci.astro
Pentcho Valev
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Default GETTING RID OF THE SECOND LAW OF THERMODYNAMICS

https://data.epo.org/publication-ser...9&iepatch=.pdf
Dan Urry (pp. 14-15): "When the pH is lowered (that is, on raising the chemical potential, mu, of the protons present) at the isothermal condition of 37C, these matrices can exert forces, f, sufficient to lift weights that are a thousand times their dry weight."

http://pubs.acs.org/doi/abs/10.1021/jp972167t
J. Phys. Chem. B, 1997, 101 (51), pp 11007-11028, Dan W. Urry, Physical Chemistry of Biological Free Energy Transduction As Demonstrated by Elastic Protein-Based Polymers, p. 11025, fig. 16A

Lowering the pH (increasing the concentration of the hydrogen ion, H+) in the polymer-containing system can be achieved by transferring H+ to the system from another system. Note that one GAINS work as one transfers H+ to the polymer-containing system from a reservoir at higher H+ concentration, but then LOSES work as one moves the same amount of H+ back to the reservoir. If both transfers are performed isothermally and reversibly, the net work involved in these two steps (steps 1 and 3) is zero.

The polymer-containing system and the H+ reservoir can be regarded as the half-cells of a concentration cell - the following reference can be useful:

http://fds.oup.com/www.oup.com/pdf/1...6_chapter1.pdf
Oxford University Press 2010. Peter Atkins and Julio de Paula: Physical Chemistry for the Life Sciences 2e : Thermodynamics of ion and electron transport

A rigorous analysis would show that the net work extracted from steps 1 and 3 is not exactly zero. For the polymers considered by Katchalsky (see reference in my previous posting) it is negative (we LOSE work in steps 1 and 3) but for polymers considered by Urry it is positive (we GAIN work from steps 1 and 3).

Pentcho Valev
  #3  
Old June 22nd 13, 10:25 AM posted to sci.astro
Pentcho Valev
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Posts: 8,078
Default GETTING RID OF THE SECOND LAW OF THERMODYNAMICS

The mythology surrounding the second law of thermodynamics is even more schizophrenic than that surrounding Einstein's 1905 false light postulate. At least the light postulate has a clear formulation; in contrast, "even today, the Second Law remains so obscure that it continues to attract new efforts at clarification":

http://philsci-archive.pitt.edu/archive/00000313/
"Snow stands up for the view that exact science is, in its own right, an essential part of civilisation, and should not merely be valued for its technological applications. Anyone who does not know the Second Law of Thermodynamics, and is proud of it too, exposes oneself as a Philistine. Snow's plea will strike a chord with every physicist who has ever attended a birthday party. But his call for cultural recognition creates obligations too. Before one can claim that acquaintance with the Second Law is as indispensable to a cultural education as Macbeth or Hamlet, it should obviously be clear what this law states. This question is surprisingly difficult. The Second Law made its appearance in physics around 1850, but a half century later it was already surrounded by so much confusion that the British Association for the Advancement of Science decided to appoint a special committee with the task of providing clarity about the meaning of this law. However, its final report (Bryan 1891) did not settle the issue. Half a century later, the physicist/philosopher Bridgman still complained that there are almost as many formulations of the second law as there have been discussions of it (Bridgman 1941, p. 116). And even today, the Second Law remains so obscure that it continues to attract new efforts at clarification."

On the other hand:

http://bip.cnrs-mrs.fr/bip10/valevfaq.htm
"There is probably no law in science that has been tested so thoroughly, by so many people, over such a long period."

Pentcho Valev
 




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