• Title/Summary/Keyword: Equilibrium-thermodynamic properties

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A Study on the Electrochemical and Thermodynamic Properties of Hydrogen Absorbing Alloys (수소저장합금의 전기화학 및 열역학적 특성에 관한 연구)

  • Park, Chan-Kyo;Cho, Tae-Hwan
    • Journal of Hydrogen and New Energy
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    • v.5 no.2
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    • pp.65-71
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    • 1994
  • Electrochemical and thermodynamic properties of $MmNi_5$ and the related alloys for nickel-metal hydride battery(Ni-MH) were studied in terms of the equilibrium hydrogen pressure. $MmNi_5$ alloy with high equilibrium hydrogen pressure(10~20atm at room temperature), which is usually difficult to charge, was substituted for Al in part. Partial substitution of Al made not only the equilibrium pressure to be reduced remarkably, but also the enthalpy change depending on the formation of metal hydride to be agreed to the value in gas phase reaction and electrochemical reaction. Besides the composition of Al which can be given the maximum discharge capacity was turned out to be between the 0.5~1.0 atoms of Al.

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A Study on the Velocity Distribution of Gas Molecules by the Molecular Dynamics Method (분자동역학법에 의한 기체분자의 속도분포에 관한 연구)

  • 최순호
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.3
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    • pp.441-450
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    • 2004
  • The velocity distribution of gas molecules from the experimental results was confirmed as the same with the Maxwell-Boltzmann's theoretical results within the experimental error. This study is on the realization of the Maxwell-Boltzmann's velocity distribution of gas molecules by the molecular dynamics(MD) method. The Maxwell-Boltzmann's velocity distribution of gas molecules is extremely important to confirm the equilibrium state because the properties of a thermodynamic system shall be obtained from the system's equilibrium configuration in the MD method. This study is the first trial in the successive researches to calculate the properties of a thermodynamic system by the computer simulations. We confirmed that the maxwell-boltzmann's velocity distribution is developed in some transient time after starting a simulation and dependent on the size of a system. Also it is found that the velocity distribution has no relation with an initial configuration of gas molecules.

Viscosity and Thermodynamic Properties of Liquid Sulfur

  • Chang, Man-Chai;Jhon, Mu-Shik
    • Bulletin of the Korean Chemical Society
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    • v.3 no.4
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    • pp.133-139
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    • 1982
  • It has been presumed that the molten sulfur above $159^{\circ}C$ consists of an equilibrium mixture of $S_8$ rings and $S_x$ polymers where the number average degree of polymerization, P, is large. But it is known that admixture of halogens with liquid sulfur greatly reduce the viscosity. Constructing a new equilibrium equation, it is possible to evaluate the viscosity when halogens are added to liquid sulfur. Calculated viscosity is in good agreement with experimental values. Using the proposed model, the thermodynamic properties of liquid sulfur are also calculated over a wide range of temperature which the sulfur exists as the polymer.

Studies on the Estimation of Theromodynamic Properties for the Non-Azeotropic Refrigerant Mixtures (혼합냉매의 열역학적 물성치 추산에 관한 연구)

  • 김민수;김동섭;노승탁;김욱중;윤재호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1337-1348
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    • 1990
  • Estimations of the thermodynamic properties are made for the selected binary non-azeotropic refrigerant mixtures including R13B1/R114, R22/R114, R12/R114, R152a/R114, R13B1/R152a and R13B1/R12 using the Peng-Robinson equation of state and mixing rules. In this study, we find that the binary interaction coefficients for the above mixtures have an effect upon the vapor-liquid equilibria and the thermodynamic properties. As the binary interaction coefficient becomes larger, the deviation from the idealized model, say, Raoult`s rule, is obvious. A correlation is proposed to relate the binary interaction coefficient to the difference between the dipole moments op each pure refrigerant. Vapor-liquid equilibrium are also accurately estimated using the binary interaction coefficient. Pressure-enthalpy and temperature-entropy relations are plotted for a certain composition ratio of each refrigerant mixture. Results show that the estimating method in this study can be applied to the investigation of the thermodynamic properties for the binary non-azeotropic refrigerant mixtures.

Estimation of Thermodynamic Properties of Refrigerant Mixtures Using a Modified Carnaha-Starling Equation of State (수정된 Carnahan-Starling 상태방정식을 이용한 혼합냉매의 물성계산)

  • 김민수;김동섭;노승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.2189-2205
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    • 1991
  • Thermodynamic properties of binary nonazeotropic refrigerant mixtures are estimated by using a modified Carnhan-Starling equation of state. In this study, pure component refrigerants such as R14, R23, R13, R13 B1, R22, R12, R134a, R152a, R142b, RC318, R114, R11, R123 and R113 are chosen and the thermodynamic properties of enthalpy and entropy are calculated in terms of relevant variables. The modified Carnahan-Starling equation of state is compared with the carnahan-Staring-De Santis equation of sate. Results show that the relative errors become slightly smaller with the equation of state proposed in this study. Correlations are obtained for the mixtures of which the vapor liquid equilibruim data are available to us in the literature. Those mixtures are R14/R23, R23/R12, R13/R12, R13/R11, R13B1/R22, R13B1/RC318, R12/RC138, R12/R114 and R12/R11. The binary interaction coefficients are found under the condition of minimizing the pressure deviations at the vapor liquid equiblibrium state and the estimation of the vapor liquid equilibrium for the refrigerant mixtures is done. Pressure-enthalpy and temperature-entropy diagrams are plotted for the refrigerant mixtures of specific composition.

Molecular Diffusion of Water in Paper(III) -Theoretical analysis on vapor sorption properties of fiber surface - (종이내 수분확산 (제3보) -종이 표면의 수증기-흡습성에 관한 이론적 고찰-)

  • Yoon, Sung-Hoon;Jeon, Yang;Park, Jong-Moon
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.1
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    • pp.61-71
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    • 1999
  • The study aimed at the theoretical analysis of vapor sorption properties of, pp.rmaking fibers. Water vapor affinity and sorption thermodynamic properties of fiber constituents were evaluated based on Henry's law and Hildebrand's solubility theory. Theoretical equilibrium moisture content(ThEMC) on fiber surface was estimated using functional group contribution. Crystallinity of cellulose in fiber significantly controlled the water vapor solubility. Comparisons of the measured equilibrium moisture content data and the estimated ThEMC data coincidently suggested the fact that crystallinity of cellulose in fibers was around 60% to 70%. Carbohydrates constituents including amorphous cellulose and hemicellulose in fibers showed higher vapor solubility than lignin molecules. High correlation existed between ThEMC and vapor solubility as well as between ThEMC and solubility parameter. In the thermodynamic analysis on water-vapor sorption process in fibers, the sorption enthalpy increased as RH increased, whereas sorption entropy and free energy decreased with increasing RH.

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A study on the physical behavior of arc plasmas in transferred-type Torch (이행형 토치에서의 아크 플라즈마의 물리적 거동에 관한 연구)

  • 김외동;고광철;강형부
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.45 no.3
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    • pp.415-425
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    • 1996
  • This study presents an analytical method of solving the behaviors of arc plasma in a nozzle constricting transferred-type torch and purposes to obtain the basic data for the design of a plasma torch, which can be obtained from the temperature, pressure, velocities and voltage distributions. We have to solve some conservation equations simultaneously and need to know the exact thermal gas properties in order to obtain the correct behaviors of arc plasma. It is also necessary to give the relevant physical or geometric boundary conditions. For the simplicity of analysis, we assumed that (a) the plasma flow is laminar, (b)the local thermodynamic equilibrium, i.e. LTE, prevails over the entire arc column region. The electrode sheath effects were neglected and the nozzle area was excluded from the analysis by assuming that the current flow into the nozzle is zero. We solved the momentum transfer equation including the self-magnetic pinch effect, and obtained the temperature distribution from the energy conservation equation. From this temperature, we could get arc voltage distribution. (author). refs., figs., tabs.

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In-situ Raman Spectroscopic Study of Nickel-base Alloys in Nuclear Power Plants and Its Implications to SCC

  • Kim, Ji Hyun;Bahn, Chi Bum;Hwang, Il Soon
    • Corrosion Science and Technology
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    • v.3 no.5
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    • pp.198-208
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    • 2004
  • Although there has been no general agreement on the mechanism of primary water stress corrosion cracking (PWSCC) as one of major degradation modes of Ni-base alloys in pressurized water reactors (PWR's), common postulation derived from previous studies is that the damage to the alloy substrate can be related to mass transport characteristics and/or repair properties of overlaid oxide film. Recently, it was shown that the oxide film structure and PWSCC initiation time as well as crack growth rate were systematically varied as a function of dissolved hydrogen concentration in high temperature water, supporting the postulation. In order to understand how the oxide film composition can vary with water chemistry, this study was conducted to characterize oxide films on Alloy 600 by an in-situ Raman spectroscopy. Based on both experimental and thermodynamic prediction results, Ni/NiO thermodynamic equilibrium condition was defined as a function of electrochemical potential and temperature. The results agree well with Attanasio et al.'s data by contact electrical resistance measurements. The anomalously high PWSCC growth rate consistently observed in the vicinity of Ni/NiO equilibrium is then attributed to weak thermodynamic stability of NiO. Redox-induced phase transition between Ni metal and NiO may undermine the integrity of NiO and enhance presumably the percolation of oxidizing environment through the oxide film, especially along grain boundaries. The redox-induced grain boundary oxide degradation mechanism has been postulated and will be tested by using the in-situ Raman facility.

Estimation of characteristic parameters of refrigerants by group contribution method (집단 기여법에 의한 냉매의 특성인자 예측)

  • Kim, Y.I.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.1
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    • pp.125-132
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    • 1999
  • Studies are being done to replace conventional refrigerants with alternatives that have low or no ozone depletion and greenhouse warming Potentials, yet possess appropriate pro perties for a refrigeration cycle. To achieve this goal, a consistent set of thermodynamic properties of the working fluid is required. A common problem with the possible alternative refrigerants is that sufficient experimental data do not exist, thus making it difficult to develp complete equations of state that can predict properties in all regions including the vapor-liquid equilibrium. One solution is the use of the generalized equation of state correlations that can predict thermodynamic properties with a minimum number of characteristic parameters. Characteristic parameters required for the generalized equation of state are, in general, critical temperature, critical pressure, critical volume and normal boiling temperature. In this study, estimation of these characteristic parameters of refrigerants by group contribution method is developed.

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Kinetics and Thermodynamic Properties Related to the Adsorption of Copper and Zinc onto Zeolite Synthesized from Coal Fly Ash

  • Lee, Chang-Han;Ambrosia, Matthew Stanley
    • Journal of Environmental Science International
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    • v.22 no.10
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    • pp.1327-1335
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    • 2013
  • Na-A zeolite (Z-Cl) was synthesized from coal fly ash, which is a byproduct of coal combustion for the generation of electricity. The adsorption of $Cu^{2+}$ and $Zn^{2+}ions$ onto Z-C1 was investigated via batch tests over a range of temperatures (303.15 to 323.15 K). The resultant experimental equilibrium data were compared to theoretical values calculated using model equations. With these results, the kinetics and equilibrium parameters of adsorption were calculated using Lagergren and Langmuir-Freundlich models. The adsorption kinetics revealed that the pseudo second-order kinetic mechanism is predominant. The maximum adsorption capacity ($q_{max}$) values were 139.0-197.9 mg $Zn^{2+}$/g and 75.0-105.1 mg $Cu^{2+}/g$. Calculation of the thermodynamic properties revealed that the absorption reactions for both $Cu^{2+}$ and $Zn^{2+}$ were spontaneous and endothermic. Collectively, these results suggest that the synthesized zeolite, Z-C1, can potentially be used as an adsorbent for metal ion recovery during the treatment of industrial wastewater at high temperatures.