• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.883-888
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• 2007

As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, $T^*=0.685$, is close to that of the experiment with only 2% error.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.204-206
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• 1998

The Gibbs free energy of formation of $BaThO_3$ from elemental oxides has been measured at temperatures between 853 and 903 K using a $CaF_2$ solid electrolyte galvanic cell. The galvanic cell consisted of Pt, $O_2, CaO+CaF_2 \parallel CaF_2 \parallelBaThO_3+ThO_2+BaF_2, O_2$, Pt EMF gave the standard Gibbs free energy for the reaction $CaF_2+BaThO_3=CaO+BaF_2+ThO_3$ as $\DeltaG^o$,/TEX>=124111.031-117.597 T(J/mol).

• Nuclear Engineering and Technology
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• v.45 no.1
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• pp.107-114
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• 2013

It is required that the pH of the sump solution should be above 7.0 to retain iodine in a liquid phase and be within the material compatibility constraints under LOCA condition of PWR. The pH of the sump solution can be determined by conventional chemical equilibrium constants or by the minimization of Gibbs free energy. The latter method developed as a computer code called SOLGASMIX-PV is more convenient than the former since various chemical components can be easily treated under LOCA conditions. In this study, SOLGASMIX-PV code was modified to accommodate the acidic and basic materials produced by radiolysis reactions and to calculate the pH of the sump solution. When the computed pH was compared with measured by the ORNL experiment to verify the reliability of the modified code, the error between two values was within 0.3 pH. Finally, two cases of calculation were performed for the SKN 3&4 and UCN 1&2. As results, pH of the sump solution for the SKN 3&4 was between 7.02 and 7.45, and for the UCN 1&2 plant between 8.07 and 9.41. Furthermore, it was found that the radiolysis reactions have insignificant effects on pH because the relative concentrations of HCl, $HNO_3$, and Cs are very low.

• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.53-58
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• 2001

Sulfonated poly(phenylene sulfide) (SPPS) polymers were prepared by sulfonation of poly[methyl[4-(phenylthio) phenyl]sulfonium trifluoromethanesulfonate] (PPST) with fumic sulfonic acid (10% $SO_3-H_2SO_4$) and demethylation with aqueous NaOH solution. The equilibrium constants of ion exchange reactions between alkali metal cations ($Li^+,\;Na^+,\;and\;K^+$) and SPPS ion exchanger in organic solvents such as tetrahydrofuran (THF) and dioxane were measured. The equilibrium constants of ion exchange reactions increased as the polarity of the solvent increased, and the reaction temperature decreased. The equilibrium constants of the ion exchange reaction ($K_{eq}$) also increased in the order of $Li^+,\;Na^+,\;and\;K^+$. To elucidate the spontaneity of the exchange reaction in organic solvents, the enthalpy, entropy, and Gibbs free energy were calculated. The enthalpy of reaction ranged from -0.88 to -1.33 kcal/mol, entropy ranged from 1.42 to 4.41 cal/Kmol, and Gibbs free energy ranged from -1.03 to -2.55 kcal/mol. Therefore, the exchange reactions were spontaneous because the Gibbs free energies were negative. The SPPS ion exchanger and alkali metal ion bounding each other produced good ion exchange capability in organic solvents.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.345-351
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• 1999

The structures, the energetics, and the spectra of K+(H2O)3 have been studied at HF and MP2 levels with the basis set of triple-zeta plus two sets of polarization functions (TZ2P) for water molecules. Two structures considered are 3+0 (D3), and 2+1 (C2v). The 2+1 (C2v) has two hydrogen bonds between the primary hydration and the secondary hydration shell water molecules. They have similar binding energy and enthalpy. The most stable conformation of K+(H2O)3 is entropy driven as shown in Na+(H2O)5 and in Na+(H2O)6 cases. The 3+0 (D3) conformation is the most stable at 298 K and at 1 atm, based on Gibbs free energy changes (ΔGr). The thermal contributions to the enthalpy and the Gibbs free energy are corrected for the low frequency modes. The corrected ΔGr is in good agreement with the experimental value. Vibrational frequencies of two conformations are revealed as their characteristics.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1143-1152
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• 2019

In order to study the solubilization of aniline by cationic surfactants (DTAB, TTAB and CTAB), the solubilization constant (K_s) and thermodynamic functions were measured and calculated by using the UV-Vis method. The solubilization constants of aniline with the change of temperature were measured, and the effects of addition of ionic salts and organics on the solubilization constants were investigated. These effects of additives and temperature changes were compared and analyzed for each type of surfactant, and the solubilization of aniline was analyzed microscopically by comparing and evaluating the thermodynamic functions obtained from the solubilization constants. As a result, the Gibbs free energy and enthalpy changes were both negative and the entropy changes were positive within the measured range for the solubilization of aniline by cationic surfactants. The solubilization constant value decreased with increasing temperature and increased with increasing carbon chain length of the surfactant. As the concentration of ionic salts increased, the Gibbs free energy change increased at first and then decreased. In n-butanol solution, the Gibbs free energy change tended to increase continuously with increasing the concentration of n-butanol.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.104-105
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• 2000

High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, T$_{sub}$, and ozone gas pressures, PO$_3$. The correlation diagrams of the BSCCO phases appeared against T$_{sub}$ and PO$_3$are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 phases as well as Bi2212 one come out as stable phases depending on T$_{sub}$ and PO$_3$. From these results, the thermodynamic evaluations of ΔH and ΔS which are related with Gibbs'free energy change for single Bi2212 or Bi2223 phase are performed.ormed.i2212 or Bi2223 phase are performed.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.543-550
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• 1998

From the power plant in a steel plant, environment pollutants such as $SO_x$, $NO_x$, CO and $CO_2$ are emitted by combustion reactions of the fuels which are by-product gases, oil and liquefied natural gas(LNG). To reduce the amounts of the pollutants, it is important to build a predictive model for the emission of the pollutants. In this paper, model that predict the amounts of generated pollutants for the used fuel is developed by using Gibbs free energy minimization method[1] with the temperature correction technique. For some data set, the calculation results from this model are compared with the real emission amounts of $SO_x$, $NO_x$, and the result of the calculation by both ASPEN PLUS which is a commercial simulation software. This model shows good results and can be applied to other power plants.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.134-138
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• 2004

The discrepancies between theoretical values and measured data of PEFC(Proton Exchange Fuel Cell) is carried out for the machine tool power generation. Rudimental approach of theoretical fuel cell open circuit potential using Gibbs free energy is employed for the examination of PEFC module. The stack temperature, stack voltage and stack current are measured during the operation of PEFC module. It is found that stack voltage and current values show the pronounced discrepancy with the results calculated by Gibbs free energy approach. It is analysed that the discrepancy is due to activation polarization, concentration overvoltage and ohmic overvoltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.304-307
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• 2001

High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $PO_3$. The correlation diagrams of the BSCCO phases appeared against $T_{sub}$ and $PO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi220l and Bi2223 phases as well as Bi2212 one come out as stable phases depending on $T_{sub}$ and $PO_3$. From these results, the thermodynamic evaluations of ${\Delta}H$ and ${\Delta}S$ S, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase are performed.