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.

Thermodynamic Analysis of a Multi-Fueled Single Cylinder SI Engine

2011 ◽  
Author(s):  
M. Z. Haq ◽  
M. R. Mohiuddin
Keyword(s):  
Thermodynamic Analysis ◽  
Chemical Properties ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Si Engine ◽  
Gaseous Species ◽  
Single Cylinder ◽  
Engine Cylinder ◽  
Si Engines

The paper presents a thermodynamic analysis of a single cylinder four-stroke spark-ignition (SI) engine fuelled by four fuels namely iso-octane, methane, methanol and hydrogen. In SI engines, due to phenomena like ignition delay and finite flame speed manifested by the fuels, the heat addition process is not instantaneous, and hence ‘Weibe function’ is used to address the realistic heat release scenario of the engine. Empirical correlations are used to predict the heat loss from the engine cylinder. Physical states and chemical properties of gaseous species present inside the cylinder are determined using first and second law of thermodynamics, chemical kinetics, JANAF thermodynamic data-base and NASA polynomials. The model is implemented in FORTRAN 95 using standard numerical routines and some simulation results are validated against data available in literature. The second law of thermodynamics is applied to estimate the change of exergy i.e. the work potential or quality of the in-cylinder mixture undergoing various phases to complete the cycle. Results indicate that, around 4 to 24% of exergy initially possessed by the in-cylinder mixture is reduced during combustion and about 26 to 42% is left unused and exhausted to the atmosphere.

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. . . .

Thermodynamic Analysis of the CO2 Gas Removal Process

2007 ◽  
Author(s):  
Rosa-Hilda Chavez ◽  
Jazmin Cortez-Gonzalez ◽  
Javier de J. Guadarrama ◽  
Abel Hernandez-Guerrero
Keyword(s):  
Thermodynamic Analysis ◽  
Second Law Of Thermodynamics ◽  
Chemical Processes ◽  
Second Law ◽  
Equilibrium Partial Pressure ◽  
Co2 Gas ◽  
Acid Gas ◽  
Removal Process ◽  
Gas Removal ◽  
Carbon Dioxide Co2

The present paper describes the thermodynamic analysis of the carbon dioxide (CO2) gas removal process in two separated columns with absorption/stripping sections respectively. This process is characterized as mass transfer enhanced by chemical reaction, in which the presence of an alkanolamine enhances the solubility of an acid gas in the aqueous phase at a constant value of the equilibrium partial pressure. A very useful procedure for analyzing a process is by means of the Second Law of Thermodynamics. Thermodynamic analyses based on the concepts of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes. Furthermore, they point out where the irreversibilities of the process are located, and provide a generalized discussion from the successful application of the technique.

A Micro Combined Heat and Power Thermodynamic Analysis and Optimization

2010 ◽  
Author(s):  
Ali Gholizadeh ◽  
M. B. Shafii ◽  
M. H. Saidi
Keyword(s):  
Combustion Chamber ◽  
Entropy Production ◽  
Thermodynamic Analysis ◽  
Second Law Of Thermodynamics ◽  
Combined Heat And Power ◽  
Second Law ◽  
Entropy Production Rate ◽  
Prime Mover ◽  
Operation Condition ◽  
Laws Of Thermodynamics

In modeling and designing micro combined heat and power cycle most important point is recognition of how the cycle operates based on the first and second laws of thermodynamics simultaneously. Analyzing data obtained from thermodynamic analysis employed to optimize MCHP cycle. The data obtained from prime mover optimization has been used for basic stimulus cycle. Assumptions considered for prime mover optimization has been improved, for example in making optimum operation condition by using genetic algorithms constant pressure combustion chamber was considered. The exact value of downstream and upstream pressure changes in the combustion chamber reaction has been obtained. After extraction of the appropriate relationship for the primary stimulus cycle, data required for the overall cycle analysis identified, By using these data optimum total cycle efficiency and constructing the first and second laws of thermodynamics has been calculated for it. After reviewing Thermodynamic governing relations in each cycle and using the optimum values that the prime mover has been optimized with, other cycles have been optimized. In best performance condition of cycle, electrical efficiency was 41 percent and the overall efficiency of the cycle was 88 percent, respectively. After using the second law of thermodynamics mathematical model Second law of thermodynamics efficiency and entropy production rate was estimated. Second law of thermodynamics yield best performance against the 45.14 percent and the rate of entropy production in this case equal to 0.099 kW/K respectively.

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.

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.

Thermodynamic Analysis of the First Stage of Heavy Water Production

2006 ◽  
Author(s):  
R. Hilda Cha´vez ◽  
Javier de J. Guadarrama ◽  
Abel Herna´ndez-Guerrero
Keyword(s):  
Thermodynamic Analysis ◽  
Heavy Water ◽  
Second Law Of Thermodynamics ◽  
Chemical Processes ◽  
Second Law ◽  
Water Production ◽  
Entropy Increase

The present paper describes the thermodynamic analysis of the first stage of enrichment of heavy water production by the Girdler Sulfide (GS) process. A very useful procedure for analyzing a proces is by means of the Second Law of Thermodynamics. Thermodynamic analyses based on the concept of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes. Furthermore, this study points out where the irreversibilities of the process are located, and provides a generalized discussion from the successful application of the technique.

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.

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