• 융복합기술연구소 논문집
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• 제2권2호
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• pp.30-34
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• 2012

The SI thermochemical cycle process accomplishes water splitting through distinctive three chemical reactions. We focused on thermodynamic models applicable to the process. Recently, remarkable models based on the assumed ionic species have been developed to describe highly nonideal behavior on the liquid phase reactions. ElecNRTL models with ionic reactions were proposed in order to provide reliable process simulation results for phase equilibrium calculations in Section II and III. In this study, the current thermodynamic models of SI thermochemical cycle process were briefly described and the calculation results of the applied ElecNRTL models for phase equilibrium calculations were illustrated for binary systems.

• Bulletin of the Korean Chemical Society
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• 제7권6호
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• pp.448-453
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• 1986

Two contributions to the activation barrier of the $S_N2$ reaction, intrinsic and thermodynamic, are discussed in connection with the predictive power of various rate-equilibrium relationships. It has been shown that the PES models can only give correct predictions of changes in structure and energy of the transition state if the activation barrier is dictated by the thermodynamic factor. We concluded that the identity and dissociative $S_N2$ reactions are dominated by the intrinsic component while associative $S_N2$ reactions are predominantly of thermodynamic controlled. Thus in the former cases, the PES models fail, whereas in the latter cases predictions based on the intrinsic factor, the quantum mechanical models, fail. Finally in a general case of equal contributions by thermodynamic and intrinsic factors, the $SN_2$ reaction proceeds by a synchronous process with zero net charge on the reaction center, for which predictions of substituent effects will be the same as for the intrinsic control case.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.501-509
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• 1997

In recent papers[Bull. Kor. Chem. Soc. 1996, 17, 735; ibid 1997, 18, 478] we reported results of molecular dynamics (MD) simulations for the thermodynamic, structural, and dynamic properties of liquid normal alkanes, from n-butane to n-heptadecane, using three different models. Two of the three classes of models are collapsed atomic models while the third class is an atomistically detailed model. In the present paper we present results of MD simulations for the corresponding properties of liquid branched-chain alkanes using the same models. The thermodynamic property reflects that the intermolecular interactions become weaker as the shape of the molecule tends to approach that of a sphere and the surface area decreases with branching. Not like observed in the straight-chain alkanes, the structural properties of model Ⅲ from the site-site radial distribution function, the distribution functions of the average end-to-end distance and the root-mean-squared radii of gyration are not much different from those of models Ⅰ and Ⅱ. The branching effect on the self diffusion of liquid alkanes is well predicted from our MD simulation results but not on the viscosity and thermal conductivity.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.735-744
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• 1996

We present results of molecular dynamic (MD) simulations for the thermodynamic and structural properties of liquid n-alkanes, from n-butane to n-heptadecane, using three different models Ⅰ-Ⅲ. Two of the three classes of models are collapsed atomic models while the third class is an atomistically detailed model. Model Ⅰ is the original Ryckaert and Bellemans' collapsed atomic model [Discuss. Faraday Soc. 1978, 66, 95] and model Ⅱ is the expanded collapsed model which includes C-C bond stretching and C-C-C bond angle bending potentials in addition to Lennard-Jones and torsional potentials of model Ⅰ. In model Ⅲ all the carbon and hydrogen atoms in the monomeric units are represented explicitly for the alkane molecules. Excellent agreement of the results of our MD simulations of model Ⅰ for n-butane with those of Edberg et al.[J. Chem. Phys. 1986, 84, 6933], who used a different algorithm confirms the validity of our algorithms for MD simulations of model Ⅱ for 14 liquid n-alkanes and of models Ⅰ and Ⅲ for liquid n-butane, n-decane, and n-heptadecane. The thermodynamic and structural properties of models Ⅰ and Ⅱ are very similar to each other and the thermodynamic properties of model Ⅲ for the three n-alkanes are not much different from those of models Ⅰ and Ⅱ. However, the structural properties of model Ⅲ are very different from those of models Ⅰ and Ⅱ as observed by comparing the radial distribution functions, the average end-to-end distances and the root-mean-squared radii of gyrations.

• 한국수소및신에너지학회논문집
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• 제32권3호
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• pp.189-195
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• 2021

A compressed hydrogen tank is to be repressurized to 40 bar by being connected to a high-pressure line containing hydrogen at 50 bar and 25℃. Hydrogen filling time and the corresponding hydrogen temperature has been estimated when the filling process stopped according to several thermodynamic models. During the process of cooling the hydrogen tank, hydrogen temperature and pressure vs. time estimation was performed using Aspen Dynamics. Filling time, hydrogen temperature after filling hydrogen gas, cooling time and the final tank pressure after tank filling process have been completed according to the thermodynamic models are almost same.

• 대기
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• 제25권2호
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• pp.249-260
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• 2015

The changes in thermodynamic and dynamic aspects on near (2025~2049) and long-term (2075~2099) future climate changes between the historical run (1979~2005) and the Representative Concentration Pathway (RCP) 4.5 run with 20 coupled models which employed in the phase five of Coupled Model Inter-comparison Project (CMIP5) over East Asia (EA) and the Korean Peninsula are investigated as an extended study for Moon et al. (2014) study noted that the 20 models' multi-model ensemble (MME) and best five models' multi-model ensemble (B5MME) have a different increasing trend of precipitation during the boreal winter and summer, in spite of a similar increasing trend of surface air temperature, especially over the Korean Peninsula. Comparing the MME and B5MME, the dynamic factor (the convergence of mean moisture by anomalous wind) and the thermodynamic factor (the convergence of anomalous moisture by mean wind) in terms of moisture flux convergence are analyzed. As a result, the dynamic factor causes the lower increasing trend of precipitation in B5MME than the MME during the boreal winter and summer over EA. However, over the Korean Peninsula, the dynamic factor causes the lower increasing trend of precipitation in B5MME than the MME during the boreal winter, whereas the thermodynamic factor causes the higher increasing trend of precipitation in B5MME than the MME during the boreal summer. Therefore, it can be noted that the difference between MME and B5MME on the change in precipitation is affected by dynamic (thermodynamic) factor during the boreal winter (summer) over the Korean Peninsula.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.179-182
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• 2007

COMS (Communication, Ocean and Meteorological Satellite) is a geosynchronous satellite and has been developing by KARI and Astrium for Ka-band communication, ocean observation and meteorological observation. COMS Chemical Propulsion System (CPS) uses a bipropellant propulsion subsystem, which is applied for transferring COMS from GTO to GEO (mission orbit) and implementing station-keeping manoeuvres. In this paper COMS CPS is briefly introduced for understanding. A few of mathematical thermodynamic modelings of bipropellant propulsion system in literatures are reviewed and authors has studied those models for developing a computer program, which predicts variations of thermodynamic properties such as temperature and pressure histories in the helium pressurant tank, MMH propellant tank and NTO propellant tank during LAE firing and on-orbit manoeuvrings. The CPS thermodynamic model may be used to compute pressurant and propellant masses and to size tank volumes.

• Korean Chemical Engineering Research
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• 제62권2호
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• pp.173-180
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• 2024

Under ordinary atmospheric circumstances, the gravimetric technique was used to measure the solubility of L-cysteine (L-Cys) and L-alanine (L-Ala) in various solvents, including methyl alcohol, ethyl acetate, and mixtures of the two, in the range o 283.15 K to 323.15 K. Both individual solvents and their combinations showed a rise in the solubility of L-Cys and L-Ala with increasing temperature, according to the analyzed data but when analyzed at a constant temperature in the selected mixed solvents, the solubility declined with decreasing of initial mole fractions of methyl alcohol. To further assess, the relative utility of the four solubility models, we fitted the solubility data using the Jouyban-Acree (J-A), van't Hoff-Jouyban-Acree (V-J-A), Apelblat-Jouyban-Acree (A-J-A), and Ma models followed by evaluation of the values of the RAD information criteria and the RMSD were. The dissolution was also found to be an entropy-driven spontaneous mixing process in the solvents since the thermodynamic parameters of the solvents were determined using the van't Hoff model. In order to support the industrial crystallization of L-cysteine and L-alanine and contribute to future theoretical research, we have determined the experimental solubility, correlation equations, and thermodynamic parameters of the selected amino acids during the dissolution process.

• Nuclear Engineering and Technology
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• 제25권2호
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• pp.265-275
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• 1993

증기폭발이 발생하면 파괴적인 동력에너지가 방출될 가능성이 있으므로. 이 현상은 원자력 발전소 안전성 연구 분야에서 중요한 현상으로 지목되어 왔다. 따라서 증기폭발이 미치는 영향을 분석하기 위해서는 폭발시 수반되는 열에너지가 동력에너지로 전환되는 비율을 정확히 해석할 수 있어야 한다. 그러나, 정확한 해석 방법의 개발이 이루어지지 않은 현 상황에서는 순수히 이론에 근거한 열역학적 해석 방법 등을 이용할 수 있으며 이러만 접근 방식은 그 결과가 보수적이라는데 그 의미가 있다. 본 논문에서는 현재까지 알려진 열역학적 해석 방법들을 정리하였고. 이론적으로 모순된 부분을 수정하여 비교하였다. 지금까지 알려진 바와는 달리. Hicks-Menzies 모델과 Board-Hall 모델은 에너지 전환율에서 동일한 결과를 나타냄을 보였다. 또한 증기폭발에서 냉각수 포기 기공율의 영향을 계산, 검토하였으며, 금속의 발열반응의 영향을 분석할 수 있는 열역학적 모델을 제시하였다.

• 자원환경지질
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• 제56권5호
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• pp.515-532
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• 2023

벤토나이트는 고준위 방사성폐기물 처분을 위한 심층처분 시스템에서 처분용기와 암반 사이를 메우는 완충재로 고려되는 팽창성 점토이다. 벤토나이트는 높은 양이온교환능과 비표면적을 가지고 있기 때문에, 처분용기로부터 핵종이 누출될 경우, 수착하여 암반으로의 유출을 지연시키는 역할을 한다. 본 연구에서는 여러 선행연구에서 8종류의 벤토나이트를 사용하여 수행된 U, Am, Se, Eu 핵종의 수착실험 및 모델 자료를 취합하고, 각 연구에서 설정된 실험 조건들을 기반으로 열역학적 수착모델의 특성을 평가하였다. 핵종과 벤토나이트 간의 수착 거동 해석에 중요한 역할을 하는 열역학적 수착모델은 벤토나이트의 광물학적 특성뿐만 아니라 핵종 농도, 용액의 이온강도, 주 양이온, 온도, 고액비, 용존 탄산 농도 등 세부적인 실험 조건과 밀접하게 연관되어 있는 것으로 확인되었다. 이러한 결과는 특정 실험 조건에서 수행된 수착실험 및 모델의 최적화로 제안되는 수착 반응식과 반응상수가 다양한 환경 조건에 적용하기에 불확실성이 크다는 것을 의미한다. 따라서, 심층처분 시스템에 적용가능한 열역학적 수착모델을 구축하기 위해서는 현장 조사 및 실험이 함께 수행되어야 한다.