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"Thermodynamic"
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Thermodynamic Analysis and Experimental Research of Water-Cooled Small Space Thermoelectric Air-Conditioner
This paper aims to find a more general analysis method for the refrigeration performance, and to design a high efficiency modular cooling structure of water-cooled plate. A new analysis method, namely current and refrigeration rate density analysis, is proposed. The general refrigeration performance calculation equations are obtained. A finite-time thermodynamic model of the thermoelectric device is established considering Thomson effect. The basic structure of water-cooled thermoelectric air-conditioner is designed and the specific calculation method is given. The influences of input current density, filling factor and heat transfer conditions on refrigeration performance of the thermoelectric air-conditioner are analyzed, which is compared with refrigeration performance of air-cooled thermoelectric air-conditioner. The results show that the maximum refrigeration rate density of the water-cooled thermoelectric air-conditioner is 8.65 kW/m2, and the maximum coefficient of performance (COP) is 2.27 in the case of the cooling temperature difference ΔT=5 K. Compared with ΔT=5 K, the maximum refrigeration rate density and the maximum COP of ΔT=15 K decreases by 27.98% and 76.65%, respectively. At the filling factor θ=0.43, the refrigeration rate density and COP are 2.57 kW/m2 and 1.24, respectively. The experimental device of thermoelectric air-conditioner is established to verify the model. The experimental results show that the maximum value of input current and COP is 4 A and 0.95 with the efficient water-cooling method, respectively. The experimental data coincides with the theoretical calculation, which shows the validity of the analysis method and cooling method.
Journal Article
Molecular Dissipative Structuring: The Fundamental Creative Force in Biology
The spontaneous emergence of macroscopic dissipative structures in systems driven by generalized chemical potentials is well established in non-equilibrium thermodynamics. Examples include atmospheric/oceanic currents, hurricanes and tornadoes, Rayleigh–Bénard convection cells and reaction–diffusion patterns. Less well recognized, however, are microscopic dissipative structures that form when the driving potential excites internal molecular degrees of freedom (electronic states and nuclear coordinates), typically via high-energy photons or coupling with ATP. Examples include dynamic nanoscale lipid rafts, kinesin or dynein motors along microtubules, and spatiotemporal Ca2+ signaling waves propagating through the cytoplasm. The thermodynamic dissipation theory of the origin of life asserts that the core biomolecules of all three domains of life originated as self-organized molecular dissipative structures—chromophores or pigments—that proliferated on the Archean ocean surface to absorb and dissipate the intense “soft” UV-C (205–280 nm) and UV-B (280–315 nm) solar flux into heat. Thermodynamic coupling to ancillary antenna and surface-anchoring molecules subsequently increased photon dissipation and enabled more complex dissipative processes, including photosynthesis, to dissipate lower-energy but higher-intensity UV-A and visible light. Further thermodynamic coupling to abiotic geophysical cycles (e.g., the water cycle, winds, and ocean currents) ultimately led to today’s biosphere, efficiently dissipating the incident solar spectrum well into the infrared. This paper reviews historical considerations of UV light in life’s origin and our proposal of UV-C molecular dissipative structuring of three classes of fundamental biomolecules: nucleobases, fatty acids, and pigments. Increases in structural complexity and assembly into larger complexes are shown to be driven by the thermodynamic imperative of enhancing solar photon dissipation. We conclude that thermodynamic selection of dissipative structures, rather than Darwinian natural selection, is the fundamental creative force in biology at all levels of hierarchy.
Journal Article
Energy and exergy analyses and optimizations for two-stage TEC driven by two-stage TEG with Thomson effect
Based on the non-equilibrium thermodynamics and energy and exergy analyses, a thermodynamic model of two-stage thermoelectric (TE) cooler (TTEC) driven by two-stage TE generator (TTEG) (TTEG-TTEC) combined TE device is established with involving Thomson effect by fitting method of variable physical parameters of TE materials. Taking total number of TE elements as constraint, influences of number distributions of TE elements on three device performance indictors, that is, cooling load, maximum COP and maximum exergetic efficiency, are analyzed. Three number distributions of TE elements are optimized with three maximum performance indictors as the objectives, respectively. Influences of hot-junction temperature of TTEG and cold-junction temperature of TTEC on optimization results are analyzed, and difference between optimization results corresponding to three performance indicators are studied. Optimal performance intervals and optimal variable intervals are provided. Influences of Thomson effect on three general performance indicators, three optimal performance indicators and optimal variables are comparatively discussed. Thomson effect reduces three general performance indicators and three optimal performance indicators of device. When hot- and cold-junction temperatures of TTEG and TTEC are 450, 305, 325 and 295 K, respectively, Thomson effect reduced maximum cooling load, maximum COP and maximum exergetic efficiency from 9.528 W, 9.043×10
−2
and 2.552% to 6.651 W, 6.286×10
−2
and 1.752%, respectively.
Journal Article
A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles
Given significant challenges with available measurements of aerosol acidity, proxy methods are frequently used to estimate the acidity of atmospheric particles. In this study, four of the most common aerosol acidity proxies are evaluated and compared: (1) the ion balance method, (2) the molar ratio method, (3) thermodynamic equilibrium models, and (4) the phase partitioning of ammonia. All methods are evaluated against predictions of thermodynamic models and against direct observations of aerosol–gas equilibrium partitioning acquired in Mexico City during the Megacity Initiative: Local and Global Research Objectives (MILAGRO) study. The ion balance and molar ratio methods assume that any deficit in inorganic cations relative to anions is due to the presence of H+ and that a higher H+ loading and lower cation / anion ratio both correspond to increasingly acidic particles (i.e., lower pH). Based on the MILAGRO measurements, no correlation is observed between H+ levels inferred with the ion balance and aerosol pH predicted by the thermodynamic models and NH3–NH4+ partitioning. Similarly, no relationship is observed between the cation / anion molar ratio and predicted aerosol pH. Using only measured aerosol chemical composition as inputs without any constraint for the gas phase, the E-AIM (Extended Aerosol Inorganics Model) and ISORROPIA-II thermodynamic equilibrium models tend to predict aerosol pH levels that are inconsistent with the observed NH3–NH4+ partitioning. The modeled pH values from both E-AIM and ISORROPIA-II run with gas + aerosol inputs agreed well with the aerosol pH predicted by the phase partitioning of ammonia. It appears that (1) thermodynamic models constrained by gas + aerosol measurements and (2) the phase partitioning of ammonia provide the best available predictions of aerosol pH. Furthermore, neither the ion balance nor the molar ratio can be used as surrogates for aerosol pH, and previously published studies with conclusions based on such acidity proxies may need to be reevaluated. Given the significance of acidity for chemical processes in the atmosphere, the implications of this study are important and far reaching.
Journal Article
Thermodynamic Assessment of the P2O5-Na2O and P2O5-MgO Systems
Knowledge about the thermodynamic equilibria of the P2O5-Na2O and P2O5-MgO systems is very important for controlling the phosphorus content of steel materials in the process of steelmaking dephosphorization. The phase equilibrium and thermodynamic data of the P2O5-Na2O and P2O5-MgO systems were critically evaluated and re-assessed by the CALPHAD (CAlculation of PHAse Diagram) approach. The liquid phase was described by the ionic two-sublattice model for the first time with the formulas (Na+1)P(O−2, PO3−1, PO4−3, PO5/2)Q and (Mg+2)P(O−2, PO3−1, PO4−3, PO5/2)Q, respectively, and the selection of the species constituting the liquid phase was based on the structure of the phosphate melts. A new and improved self-consistent set of thermodynamic parameters for the P2O5-Na2O and P2O5-MgO systems was finally obtained, and the calculated phase diagram and thermodynamic properties exhibited excellent agreement with the experimental data. The difference in the phase composition of invariant reactions from the experimentally determined values reported in the literature is less than 0.9 mol.%. The present thermodynamic modeling contributes to constructing a multicomponent oxide thermodynamic database in the process of steelmaking dephosphorization.
Journal Article
Assessing the Nonequilibrium Thermodynamics in a Quenched Quantum Many-Body System via Single Projective Measurements
We analyze the nature of the statistics of the work done on or by a quantum many-body system brought out of equilibrium. We show that, for the sudden quench and for an initial state that commutes with the initial Hamiltonian, it is possible to retrieve the whole nonequilibrium thermodynamics via single projective measurements of observables. We highlight, in a physically clear way, the qualitative implications for the statistics of work coming from considering processes described by operators that either commute or do not commute with the unperturbed Hamiltonian of a given system. We consider a quantum many-body system and derive an expression that allows us to give a physical interpretation, for a thermal initial state, to all of the cumulants of the work in the case of quenched operators commuting with the unperturbed Hamiltonian. In the commuting case, the observables that we need to measure have an intuitive physical meaning. Conversely, in the noncommuting case, we show that, although it is possible to operate fully within the single-measurement framework irrespectively of the size of the quench, some difficulties are faced in providing a clear-cut physical interpretation to the cumulants. This circumstance makes the study of the physics of the system nontrivial and highlights the nonintuitive phenomenology of the emergence of thermodynamics from the fully quantum microscopic description. We illustrate our ideas with the example of the Ising model in a transverse field showing the interesting behavior of the high-order statistical moments of the work distribution for a generic thermal state and linking them to the critical nature of the model itself.
Journal Article
Thermodynamic Assessment of Slag–Matte–Metal Equilibria in the Cu-Fe-O-S-Si System
Equilibria among the slag, matte and metal phases in the Cu-Fe-O-S-Si system are critically assessed using thermodynamic modeling. The relationships among matte grade, temperature, partial pressure of SO
2
, Fe/SiO
2
in the slag, and the copper concentration in the slag are described by the model, as well as the concentrations of other elements in all phases. A thermodynamic database is created, which can be used for understanding and improving the pyrometallurgical production of copper. An extensive experimental dataset includes the most recent results obtained by the equilibration/quenching/EPMA analysis technique. These data allow to distinguish the physical entrainment of the matte and solid phases in the slag from chemical solubility. As a result, it is possible to describe the copper solubility in the slag with high accuracy and establish the relationship between copper and sulfur in the slag. The thermodynamic database of the present study is consistent with previously reported thermodynamic evaluations of binary, ternary and quaternary subsystems. The slag phase is modeled using the two-sublattice modified quasichemical model in the quadruplet approximation. The matte and metal liquid phases are modeled as one solution using the single-sublattice modified quasichemical model in the pair approximation.
Journal Article
VapoRock: Thermodynamics of Vaporized Silicate Melts for Modeling Volcanic Outgassing and Magma Ocean Atmospheres
Silicate vapors play a key role in planetary evolution, especially dominating early stages of rocky planet formation through outgassed magma ocean atmospheres. Our open-source thermodynamic modeling software “VapoRock” combines the MELTS liquid model with gas-species properties from multiple thermochemistry tables. VapoRock calculates the partial pressures of 34 gaseous species in equilibrium with magmatic liquid in the system Si–Mg–Fe–Al–Ca–Na–K–Ti–Cr–O at desired temperatures and oxygen fugacities (fO2, or partial pressure of O2). Comparison with experiments shows that pressures and melt-oxide activities (which vary over many orders of magnitude) are reproduced to within a factor of ∼3, consistent with measurement uncertainties. We also benchmark the model against a wide selection of igneous rock compositions including bulk silicate Earth, predicting elemental vapor abundances that are comparable to (Na, Ca, and Al) or more realistic than (K, Si, Mg, Fe, and Ti) those of the closed-source MAGMA code (with maximum deviations by factors of 10–300 for K and Si). Vapor abundances depend critically on the activities of liquid components. The MELTS model underpinning VapoRock was calibrated and extensively tested on natural igneous liquids. In contrast, MAGMA’s liquid model assumes ideal mixtures of a limited set of chemically simplified pseudospecies, which only roughly approximates the nonideal compositional interactions typical of many-component natural silicate melts. Finally, we explore how relative abundances of SiO and SiO2 provide a spectroscopically measurable proxy for oxygen fugacity in devolatilized exoplanetary atmospheres, potentially constraining fO2 in outgassed exoplanetary mantles.
Journal Article
Optimal Thermodynamic Uncertainty Relation in Markov Jump Processes
We investigate the tightness and optimality of thermodynamic-uncertainty-relation (TUR)-type inequalities from two aspects, the choice of the Fisher information and the class of possible observables. We show that there exists the best choice of the Fisher information, given by the pseudo entropy production, and all other TUR-type inequalities in a certain class can be reproduced by this tightest inequality. We also demonstrate that if we observe not only generalized currents but generalized empirical measures, the TUR-type inequality becomes optimal in the sense that it achieves its equality in general nonequilibrium stationary systems. Combining these results, we can draw a hierarchical structure of TUR-type inequalities.
Journal Article