Mixing of Compressible Fluids

1961 ◽  
Vol 28 (3) ◽  
pp. 335-338 ◽  
Author(s):  
E. D. Kennedy
Keyword(s):  
Experimental Data ◽  
Compressible Fluid ◽  
Second Law Of Thermodynamics ◽  
Stagnation Pressure ◽  
Compressible Fluids ◽  
The Other ◽  
Second Law ◽  
Conservation Equations ◽  
Dimensionless Parameters ◽  
Constant Area

The problem of the mixing of two streams of the same compressible fluid in a constant-area duct is solved by applying certain dimensionless parameters first used by Kiselev. The extension to dissimilar fluids or to more than two streams is straightforward. Although the analysis is unrestricted, detailed results are given only for the case where one stream is sonic or supersonic and the other sonic or subsonic at the origin of mixing. For this case, the second law of thermodynamics indicates that, of the two solutions of the conservation equations, the subsonic one is always permitted while some of the supersonic solutions are thermodynamically impossible. Upon examination of experimental data, it is further concluded that of the admissible supersonic solutions, only one may be expected to occur. The establishment of this supersonic solution with its relatively high stagnation pressure leads to the conclusion that when the initial temperatures are sufficiently different, there exist thermodynamically possible solutions with a stagnation pressure higher than that of either of the two initial streams.

scholarly journals Reciprocally-Coupled Gating: Strange Loops in Bioenergetics, Genetics, and Catalysis

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 265
Author(s):  
Charles W. Carter ◽  
Peter R. Wills
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Historical Context ◽  
Large Body ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Formal Structure ◽  
Second Law ◽  
Coupled Gating ◽  
Strange Loops

Bioenergetics, genetic coding, and catalysis are all difficult to imagine emerging without pre-existing historical context. That context is often posed as a “Chicken and Egg” problem; its resolution is concisely described by de Grasse Tyson: “The egg was laid by a bird that was not a chicken”. The concision and generality of that answer furnish no details—only an appropriate framework from which to examine detailed paradigms that might illuminate paradoxes underlying these three life-defining biomolecular processes. We examine experimental aspects here of five examples that all conform to the same paradigm. In each example, a paradox is resolved by coupling “if, and only if” conditions for reciprocal transitions between levels, such that the consequent of the first test is the antecedent for the second. Each condition thus restricts fluxes through, or “gates” the other. Reciprocally-coupled gating, in which two gated processes constrain one another, is self-referential, hence maps onto the formal structure of “strange loops”. That mapping uncovers two different kinds of forces that may help unite the axioms underlying three phenomena that distinguish biology from chemistry. As a physical analog for Gödel’s logic, biomolecular strange-loops provide a natural metaphor around which to organize a large body of experimental data, linking biology to information, free energy, and the second law of thermodynamics.

Models and Explanations: Understanding Chemical Reaction Mechanisms

2000 ◽  
Author(s):  
Barry K. Carpenter
Keyword(s):  
Internal Rotation ◽  
Chemical Reaction ◽  
Reaction Mechanisms ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Second Law ◽  
Original Design ◽  
Mechanical Analogy ◽  
Boston College ◽  
Chemical Reaction Mechanisms

In 1997, Ross Kelly and his coworkers at Boston College reported their results from an experiment with an intriguing premise (Kelly et al., 1997; see also Kelly et al., 1998). They had synthesized the molecule shown in figure 12.1. It was designed to be a “molecular ratchet,” so named because it appeared that it should undergo internal rotation about the A—B bond more readily in one direction than the other. The reason for thinking this might occur was that the benzophenanthrene moiety—the “pawl” of the ratchet—was anticipated to be helical. Thus, in some sense, this might be an inverse ratchet where the asymmetry dictating the sense of rotation would reside in the pawl rather than in the “teeth” on the “wheel” (the triptycene unit) as it does in a normal mechanical ratchet. Kelly and coworkers designed an elegant experiment to determine whether their molecular ratchet was functioning as anticipated, and they were (presumably) disappointed to find that it was not—internal rotation about the A—B bond occurred at equal rates in each direction. In 1998 Davis pointed out that occurrence of the desired behavior of the molecular ratchet would have constituted a violation of the second law of thermodynamics (Davis, 1998). With hindsight, I think most chemists would agree that Davis’s critique is unassailable, although the appeal of the mechanical analogy was so strong that I imagine those same chemists would also understand if Kelly et al. had overlooked the thermodynamic consequences of their proposal in the original design of the experiment. But now comes the interesting question: Suppose Kelly et al. had been fully aware that their experiment, if successful, would undermine the second law of thermodynamics, should they have conducted it anyway? Davis, in his critique writes: . . .Some would argue that this experiment was misconceived. To challenge the Second Law may be seen as scientific heresy (a nice irony, considering the Jesuit origins of Boston College), and the theoretical arguments against molecular ratchets and trapdoors are well developed. . . .

scholarly journals Measurement and calculating of supersonic ejectors

2019 ◽  
Vol 213 ◽  
pp. 02097
Author(s):  
Lukas Vojta ◽  
Vaclav Dvorak
Keyword(s):  
Stagnation Pressure ◽  
The Other ◽  
Ansys Fluent ◽  
Supersonic Ejector ◽  
Air Inlet ◽  
Optimum Position ◽  
Constant Area ◽  
Mixing Chamber ◽  
Nozzle Position ◽  
Fluent Software

This paper deals with numerical and experimental investigation of the flow in an air to air supersonic ejector with constant area mixing chamber. The mixing chamber of previous ejector was completely repaired since a scratch from previous turning had been found. As a result, a new geometry of the mixing chamber was created. Several measurements were conducted with different nozzle position (NP): 1 mm, 2 mm and 3 mm. Furthermore, for a given NP, two different values of stagnation pressure of 200 kPa and 300 kPa at the primary air inlet were investigated in more detail. All numerical simulations were performed in the ANSYS Fluent software. It was found that the influence of the position of the nozzle influences the ejection factor only to a certain extent. For the other parameters of the ejector is also a need to find the optimum position of the nozzle. Repair of the mixing chamber has contributed to reduce the pressure difference at the wall of the mixing chamber.

It's about Time: The Temporal Evolution of Order

2009 ◽  
Vol 34 (2) ◽  
pp. 131-137
Author(s):  
MOSHE PERLSTEIN
Keyword(s):  
Temporal Evolution ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Second Law ◽  
Ethical Values ◽  
Other Hand ◽  
Measure For Measure ◽  
Analyse Time

This article borrows its methodology from physics in order to analyse time in the theatre as evolution of order. Two set designs (both designed by Roni Toren for the Khan Theatre in Jerusalem) are portrayed through this perspective, representing inverse examples. In Measure for Measure, directed by Gadi Roll, the temporal evolution of space is from order to disorder, obeying the second law of thermodynamics. On the other hand, in The Seagull, directed by Ofira Henig, the evolution contradicts that law. The problem of depicting disorder on stage, the possibility of such a contradiction, the implication of the two different perceptions and their ethical values are discussed to prove the effectiveness of a methodology adopted from physics.

scholarly journals Distinguishability of non-orthogonal density matrices does not imply violations of the second law

2019 ◽  
Author(s):  
PierGianLuca Porta Mana
Keyword(s):  
Hilbert Space ◽  
Density Matrix ◽  
Thermodynamic Analysis ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Second Law ◽  
Density Matrices ◽  
Matrix Space ◽  
Von Neumann ◽  
Quantum Thermodynamic

The hypothetical possibility of distinguishing preparations described by non-orthogonal density matrices does not necessarily imply a violation of the second law of thermodynamics, as was instead stated by von Neumann. On the other hand, such a possibility would surely mean that the particular density-matrix space (and related Hilbert space) adopted would not be adequate to describe the hypothetical new experimental facts. These points are shown by making clear the distinction between physical preparations and the density matrices which represent them, and then comparing a "quantum" thermodynamic analysis given by Peres with a "classical" one given by Jaynes.

scholarly journals A General Solution to the Different Formulations of the Second Law of Thermodynamics

2021 ◽  
Vol 82 (2) ◽  
pp. 61-71
Author(s):  
Saeed Shahsavari ◽  
Mehran Moradi
Keyword(s):  
General Solution ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Second Law ◽  
Energy Structure ◽  
New Approach ◽  
General Physics ◽  
Classical Thermodynamics ◽  
Physical Laws ◽  
Energy Components

The second law of thermodynamics is one of the most important physical laws that has been extracted by different formulations. In this paper, a new approach to study different formulations of the second law is extracted based on the energy components of the system as well as introducing the independent and dependent energy components concepts. Also, two main formulations of classical thermodynamics, and also entropy from the perspective of general physics are discussed based on the energy components of the system for constant applied energy to the system in different conditions. Kelvin-Plank and Clausius formulations, as two main classical formulations, are all assertions about impossible processes. Considering the energy structure equation of the system, as an equation to formulate the performed process using activated energy components, it is shown that different formulations of the second law of thermodynamics represent the same concept in the perspective of the energy structure. Finally, a new general formulation to the second law, based on the energy structure of the system is extracted, and the equivalence as the other formulations is shown. The presented formulation is extracted based on the dependent and independent activated energy components, and in fact, shows all possible paths in the considered energy applying to the system.

Numerical Computation of Flow in Rotating Ducts

1977 ◽  
Vol 99 (1) ◽  
pp. 148-153 ◽  
Author(s):  
A. K. Majumdar ◽  
V. S. Pratap ◽  
D. B. Spalding
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Finite Difference ◽  
Numerical Computation ◽  
Cross Section ◽  
Dissipation Rate ◽  
Rectangular Cross Section ◽  
Longitudinal Direction ◽  
The Other ◽  
Constant Area

A finite-difference procedure is employed to predict the turbulent flow in ducts of rectangular cross-section, rotating about an axis normal to the longitudinal direction. The flows were treated as “parabolic” and the turbulence model used involved the solution of two differential equations, one for the kinetic energy of the turbulence and the other for its dissipation rate. Agreement with experimental data is good for a constant-area duct at low rotation, but less satisfactory for a divergent duct at larger rotation. It is argued that a “partially-parabolic” procedure will be needed to predict the latter flow correctly.

scholarly journals Realization of Maxwell’s Hypothesis: A Heat-Electric Conversion in Contradiction to the Kelvin Statement

2016 ◽  
Author(s):  
Xinyong Fu ◽  
Zitao Fu
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Room Temperature ◽  
Electric Energy ◽  
Second Law Of Thermodynamics ◽  
Ambient Air ◽  
The Other ◽  
Second Law ◽  
Heat Reservoir ◽  
Static Uniform Magnetic Field

In a vacuum tube, two identical and parallel Ag-O-Cs surfaces, with a work function of approximately 0.8eV, ceaselessly emit thermal electrons at room temperature. The thermal electrons are so controlled by a static uniform magnetic field that they can fly only from one Ag-O-Cs surface to the other, resulting in a potential difference and an electric current, and transferring a power to a resistance outside the tube. The ambient air is a single heat reservoir in the experiment, and all the heat extracted by the tube from the air is converted into electric energy without producing any other effect. The authors maintain that the experiment is in contradiction to the Kelvin statement of the second law of thermodynamics.

scholarly journals The Landauer Principle: Re-Formulation of the Second Thermodynamics Law or a Step to Great Unification?

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 918 ◽  
Author(s):  
Edward Bormashenko
Keyword(s):  
Experimental Verification ◽  
Energy Cost ◽  
Minimum Energy ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Second Law ◽  
Narrow Sense ◽  
Energy Equivalent ◽  
Meaning Interpretation ◽  
Minimum Energy Cost

The Landauer principle quantifies the thermodynamic cost of the recording/erasure of one bit of information, as it was stated by its author: “information is physical” and it has an energy equivalent. In its narrow sense, the Landauer principle states that the erasure of one bit of information requires a minimum energy cost equal to kBT ln2, where T is the temperature of a thermal reservoir used in the process and kB is Boltzmann’s constant. The Landauer principle remains highly debatable. It has been argued that, since it is not independent of the second law of thermodynamics, it is either unnecessary or insufficient as an exorcism of Maxwell’s demon. On the other hand, the Landauer principle enables the “informational” reformulation of thermodynamic laws. Thus, the Landauer principle touches the deepest physical roots of thermodynamics. Authors are invited to contribute papers devoted to the meaning, interpretation, physical roots, experimental verification and applications of the Landauer principle. Papers devoted to the quantum and relativity aspects of the Landauer principle are encouraged.

scholarly journals Reciprocally-coupled Gating: Strange Loops in Bioenergetics, Genetics, and Catalysis

2021 ◽  
Author(s):  
Charles W. Carter, Jr ◽  
Peter R Wills
Keyword(s):  
Free Energy ◽  
Historical Context ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Formal Structure ◽  
Second Law ◽  
Genetic Coding ◽  
Coupled Gating ◽  
Strange Loops

Bioenergetics, genetic coding, and catalysis are all difficult to imagine emerging without pre-existing historical context. That context is often posed as a “Chicken and Egg” problem; its resolution is concisely described by de Grasse Tyson: “the egg was laid by a bird that was not a chicken”. The concision and generality of that answer furnish no details—only an appropriate framework from which to examine detailed paradigms that might illuminate paradoxes underlying these three life-defining biomolecular processes. We examine experimental aspects here of five examples that all conform to the same paradigm. The paradox in each example is resolved by coupling if, and only if, conditions for two related transitions between levels. One drives, and each restricts fluxes through, or “gates” the other. That reciprocally-coupled gating, in which two gated processes constrain one another, maps onto the formal structure of “strange loops”. That mapping may help unite the axiomatic foundations of genetics, bioenergetics, and catalysis. As a physical analog for Gödel’s logic, biomolecular strange-loops provide a natural metaphor around which to organize these data, linking biology to the physics of information, free energy, and the second law of thermodynamics.

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