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Thermodynamic non-equilibrium and anisotropy in Mars atmosphere entry
Zuppardi, Gennaro Techno-Press 2021 Advances in aircraft and spacecraft science Vol.8 No.1
Mars exploration demands aerodynamic computations for a proper design of missions of spacecraft carrying instruments and astronauts to Mars. Both Computational Fluid Dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) method play a key role for this purpose. To the author's knowledge, the altitude separating the fields of applicability of CFD and DSMC in Mars atmosphere entry is not yet clearly defined. The limitations in using DSMC at low altitudes are due to technical limitations of the computer. The limitations in using CFD at high altitudes are due to thermodynamic non-equilibrium. Here, this problem is studied in Mars atmosphere entry, considering the Mars Pathfinder capsule in the altitude interval 40-80 km, by means of a DSMC code. Non-equilibrium is quantified by the relative differences between translational temperature and: rotational (θt-r), vibrational (θt-v), overall (θt-ov) temperatures, anisotropy is quantified by the relative difference between the translational temperature component along x and those along y (θx-y) and along z (θx-z). The results showed that θt-r, θt-v, θx-y, θx-z are almost equivalent. The altitude of 45 km should be the limit altitude for a proper use of a CFD code and the altitude of 40 km should be the limit altitude for a reasonable use of a DSMC code.
Nonequilibrium thermodynamics for a harmonic potential moving in time
Lee Hyun Keun,Kwon Youngchae,권철안 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.83 No.5
We investigate non-equilibrium thermodynamics externally driven by moving the center of harmonic potential in time. We present the theoretical formalism for an arbitrary motion in underdamped dynamics. We provide the formulas to find thermodynamic quantities such as work, heat and entropy production produced for time period, which are main quantities in non-equilibrium studies. For sinusoidal driving with external frequency Ω, we observe a resonance for work production where the average rate for infinite period is maximized at Ω = ω0 that is the internal frequency of the harmonic oscillator. It may be used for an alternative way to measure the stiffness of an optical trap potential. We confirm the thermodynamic uncertainty relation newly found for underdamped dynamics subject to general time-dependent protocols for a specific example of driving.
Lim, Y.i.,Lee, U.D. Elsevier Scientific Pub. Co 2014 Fuel processing technology Vol.128 No.-
Gasification is one of the most promising technologies for converting biomass into a fuel. This study presents a simple and practical biomass gasification model based on thermodynamic equilibrium to find effective operating conditions of the air-steam gasification system in fluidized-beds. The carbon conversion fraction empirically obtained was involved in a global gasification reaction. Two empirical equations as the non-equilibrium factor expressing the deviation from equilibrium were derived as the function of the equivalence ratio (ER) from 43 experimental data sets of various operating conditions and different feedstocks. One energy balance was also solved for determining the gasification temperature (T). After the producer gas composition with respect to ER and steam to biomass ratio (SBR) was obtained from the air-steam biomass gasification (ASBG) model, process performances such as lower heating value, heat efficiency, net heat efficiency, and H<SUB>2</SUB>/CO molar ratio were evaluated. An effective operating area was suggested from the contour plot of the process performances with respect to ER and SBR in the auto-thermal gasification temperature from 700 to 830<SUP>o</SUP>C.
오영기 배재대학교 자연과학연구소 2013 自然科學論文集 Vol.24 No.1
Strong shock waves are non-equilibrium phenomena far out of equilibrium, which can not be interpreted by the near equilibrium linear thermodynamic theories. One of the obvious problems remained to be answered in this subject is the temperature profile, although many efforts have been done to extend the limit of linear theories. The temperature profile obtained by existing theories and computer experiments of Monte Carlo simulations overshoots in the shock layer. The overshoot does evidently violate the second law of thermodynamics, however, it has not yet been resolved. The problem seems to be arisen by the improper use of heat capacity of gases, which defines the local temperature by the relation (internal energy–heat capacity-temperature). In this study, we use the relation (heat flux-heat conductivity-temperature gradient) to introduce the local temperature. In order to obtain the temperature profile, the iterative method for the solution of Boltzmann equation has been employed. The results of the first iteration gives a temperature profile which does not overshoot in the shock layer, i.e., the result which is consistent with the thermodynamic law. Also the obtained temperature profile shows correct limiting property for weak shocks. The theory provides formulas for transport coefficients in the shock layer, however, the limiting properties of weak shock transport coefficients do not consistent with the linear theory, which should be reexamined in the future study.
Transport Properties of Charged Mosaic Membrane Based on Non-equilibrium Thermodynamics
Song, Myung-Kwan,Yang, Wong-Kang The Membrane Society of Korea 2005 Korean Membrane Journal Vol.7 No.1
It is well known as the role of ion exchange membrane with functional group in membrane matrix. Recently, we were reported that the charged mosaic membrane within parallel array of negative and positive charge groups. In this study we are reported the properties for the various transport coefficients of metal and heavy metal ions across charged mosaic membrane based on non-equilibrium thermodynamics is not based on equilibrium state.
Microwave-assisted urea-modified sorghum biomass for Cr (III) elimination from aqueous solutions
Muhammad Salman,Makshoof Athar,Umar Farooq,Huma Nazir,Anam Noor,Saba Nazir 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.6
The present study concentrated on the use of an agro-waste biodegradable sorghum biomass in its simple and modified forms for the binding of Cr (III) ions. A relatively new method of modification was adopted using urea under microwave irradiation. FTIR analysis showed the presence of oxygen and nitrogen bearing functional groups in unmodified (UMS) and modified (MS) sorghum biomass. The appearance of new bands and shifts in the peaks confirmed the modification. The influence of different process parameters such as the adsorbent dose, solution pH, contact time, agitation speed and initial metal ion concentration was studied thoroughly to evaluate optimum conditions for adsorption. Maximum adsorption for Cr (III) ions occurred at pH 5.0-6.0 using UMS and MS. Langmuir, Freundlich,Temkin, and Dubinin-Radushkevich isotherm models in a non-linear fashion were used to explain the phenomenon. Maximum adsorption capacity was 7.03 and 16.36 mg of Cr (III) per gram of UMS and MS, respectively. Adsorption mechanism was explored by pseudo-first- and pseudo-second-order kinetic models, and it was found that the process followed pseudo-second-order kinetics. Thermodynamic study indicated the process favorability. The study concluded that urea modification under microwave irradiation produces a non-toxic and more effective adsorbent for Cr (III) remediation by inducing new nitrogen bearing functional groups to sorghum biomass.
Thermodynamic Formalism for Hyperbolic Dynamical Systems
이현덕 청주대학교 학술연구소 2018 淸大學術論集 Vol.31 No.-
본 논문은 비균일 쌍곡 동역학계에서의 열역학적 형식주의 이론 중 기하학적 접근방법을 이용하여 평형측도를 구축하고 그 측도에 대한 통계학적 성질과 에르고딕(ergodic)한 성질을 중점적으로 연구하였다.