물성테이블 기반 보간 알고리즘을 이용한 작동유체의 열역학적 물성 계산에 대한 연구

김찬중(Chanjoong Kim),최상미(Sangmi Choi),임현정(Hyunjeong Lim),조연주(Yeonjoo Cho),김민성(Minsung Kim) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6

공비혼합냉매의 열역학적 상태량계산을 위한 프로그램개발

박윤철,현명택 제주대학교 공과대학 첨단기술연구소 2002 尖端技術硏究所論文集 Vol.13 No.2

The Montreal Protocol, an international agreement to curtail and, eventually, to eliminate the use of several widely-used chlorofluorocarbons, in particular R11 and R12, gave further impetus to having program of thermodynamic properties for pure refrigerant and their mixture such as Azeotropic refrigerant. The equations which are the basis for this calculation are the equation of state, the equation for the ideal gas heat capacity and the vapor pressure equation. The developed program has been designed to produce tables of thermodynamic properties. This program allows for the calculation of the thermodynamic properties of R410A and R134a refrigerant.

열역학 물성 예측을 위한 분자 시뮬레이션 소프트웨어의 개발

장재언 ( Jae Eon Chang ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.3

By using Monte Carlo simulation method we developed a new molecular simulation software which can be used to predict the thermodynamic properties of organic compounds. Starting from molecular structure and intermolecular potential function, rigorous statistical mechanical principles give a probability distribution for the behavior of a system containing many molecules, which enables us to calculate macroscopic thermodynamic properties of the system. The software developed in this work, cheMC, is based on Windows platform providing with easy access. One can efficiently administrate simulations by using an intuitive interface equipped with visualization tool and chart generation. It is expected that molecular simulations supplement the equation of state approach and will play a more important role in the study of thermodynamic properties.

Influences on the H₂-Sorption Properties of Mg of Co (with Various Sizes) and CoO Addition by Reactive Grinding and Their Thermodynamic Stabilities

Song, MyoungYoup,Lee, DongSub,Kwon, IkHyun 대한금속재료학회 2004 METALS AND MATERIALS International Vol.10 No.1

We attempted to improve the Hn-sorption properties of Mg by mechanical grinding under H2 (reactive grinding) with Co (with various particle sizes) and with CoO. The thermodynamic stabilities of the added Co and COO were also investigated. CoO addition has the best influence and addition of smaller particles of Co (0.5-1.5 pm) has a better effect than the addition of larger particles of Co on the Ha-sorption properties of Mg. The activated Mg+10 wt.%CoO sample has about 5.54 wt.% hydrogen-storage capacity at 598 K and the highest hydriding rate, showing an H₄ value of 2.39 wt.% after 60 min at 598 K, 11.2 bar H₂. The order of the hydriding rates after activation is the same as that of the specific surface areas of the samples. The reactive grinding of Mg with Co or CoO and hydriding-dehydriding cycling increase the Hz-sorption rates by facilitating nucleation of magnesium hydride or a solid solution of Mg and H (by creating defects on the surface of the Mg particles and by the additive), and by making cracks on the surface of Mg particles and reducing the particle size of Mg, thus shortening the diffusion distances of hydrogen atoms. The cobalt oxide is stable even after 14 hydriding cycles at 598 K under 11.2 bar H₂. Discharge capacities are measured for the samples Mg+lO wt.%CoO and Mg+lO wt.%Co (0.5-1.5 pm) with good hydrogen-storage properties.

고엔트로피 합금의 연구동향

박푸른솔,이호준,조영준,구본승,최원준,변종민,Park, Pureunsol,Lee, Ho Joon,Jo, Youngjun,Gu, Bonseung,Choi, Won June,Byun, Jongmin 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.6

High-entropy alloys (HEAs) are generally defined as solid solutions containing at least 5 constituent elements with concentrations between 5 and 35 atomic percent without the formation of intermetallic compounds. Currently, HEAs receive great attention as promising candidate materials for extreme environments due to their potentially desirable properties that result from their unique structural properties. In this review paper, we aim to introduce HEAs and explain their properties and related research by classifying them into three main categories, namely, mechanical properties, thermal properties, and electrochemical properties. Due to the high demand for structural materials in extreme environments, the mechanical properties of HEAs including strength, hardness, ductility, fatigue, and wear resistance are mainly described. Thermal and electrochemical properties, essential for the application of these alloys as structural materials, are also described.

Comprehensive review on physical properties of supercritical carbon dioxide calculated by molecular simulation

Gaoliang Liao,Yuntao Du,Feng Zhang,Jiaqiang E 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1

The applications of molecular simulation in supercritical carbon dioxide (S-CO2) and its mixtures are reviewed. First, an overview of physical properties of S-CO2 and CO2 models is given. Secondly, the accuracy of S-CO2 thermodynamic and transport properties calculated by different models is compared. It shows that Zhang’s model has relatively better global accuracy in calculating thermodynamic properties. EPM2, Zhang and Cygan models have similar accuracy when calculating transport properties based on equilibrium molecular simulation (EMD) method, but generally have higher deviations when calculating thermal conductivity. Therefore, EMD and non-equilibrium molecular simulation (NEMD) methods have been compared in calculating thermal conductivity. The results show that NEMD is better than EMD but the process is complicated. The structural properties are also discussed in this part. Thirdly, the applications of molecular simulation in S-CO2 binary organic, binary inorganic and multiple mixtures are reviewed. Finally, the summary and the prospect of future works are given.

Effects of Mn and Mo addition on high-temperature tensile properties in high-Ni-containing austenitic cast steels used for turbo-charger application

Jung, Seungmun,Jo, Yong Hee,Jeon, Changwoo,Choi, Won-Mi,Lee, Byeong-Joo,Oh, Yong-Jun,Kim, Gi-Yong,Jang, Seongsik,Lee, Sunghak. Elsevier Sequoia 2017 Materials science & engineering Structural materia Vol.682 No.-

<P><B>Abstract</B></P> <P>Since turbo-chargers require more excellent high-temperature properties to maintain their structures at further higher exhaust gas temperatures up to 1050°C, a 20wt%-Ni-containing austenitic cast steel (N20 steel) has been suggested as a promising candidate cast steel. However, this steel is very expensive because it contains a large amount of expensive Ni. In order to partly replace expensive Ni by inexpensive Mn and to improve high-temperature tensile properties in the N20 steel, three austenitic cast steels were fabricated by replacing 6wt% of Ni by 6.9wt% of Mn or by adding 2–4wt% of Mo. Thermodynamically calculated fractions of equilibrium phases (austenite, ferrite, and M<SUB>7</SUB>C<SUB>3</SUB> carbide) were matched with experimentally measured fractions, although they were somewhat overestimated. The N14 steel where 6wt% Ni was replaced by 6.9wt% of Mn did not contain any ferrite, and showed comparable or more excellent high-temperature tensile properties than those of the N20 steel, which indicated the successful replacement up to 6wt% Ni by Mn, together with alloying cost reduction of 10%. The Mo addition also favorably affected high-temperature properties because Mo worked for increasing both M<SUB>7</SUB>C<SUB>3</SUB> fraction and austenite matrix hardness. Simultaneously considering mechanical properties and alloying costs, therefore, these Mo-containing N14 steels can be fully adopted for high-performance turbo-chargers requiring excellent high-temperature properties.</P>

3-화학종 대체 혼합물을 이용한 케로신의 열역학적·전달 상태량 예측

조미옥(Miok Joh),김성구(Seong-Ku Kim),최환석(Hwan-Seok Choi) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.11

한국형발사체(KSLV-Ⅱ) 각 단 엔진의 연료로 사용되는 케로신(Jet A-1)은 추력실 재생냉각 및 연료 막냉각 과정에서 냉각유체로도 기능하게 된다. 본 연구에서는 Jet A-1의 열물리적 특성을 재현하기 위한 대체 혼합물 모델을 선정하고, SUPERTRAPP(NIST SRD4)을 이용하여 초임계압 영역을 포함하는 고압 영역에서 모델 연료의 열역학적·전달 상태량을 예측하였다. 측정값과의 비교 결과 액체로켓 엔진 추력실의 복합 열전달 해석 수행 시 Jet A-1 상태량을 추출하기 위한 데이터베이스로 활용 가능한 것으로 판단되며, 향후 연소 시험 결과와의 비교를 통하여 케로신 대체 모델의 상태량 정보를 이용한 재생냉각 추력실의 연소·냉각 성능 통합 해석 결과를 지속적으로 검증해 나갈 계획이다. Kerosene(Jet A-1), one of the propellants for each stage’s engine of the Korea Space Launch Vehicle-Ⅱ(KSLV-Ⅱ), functions as coolant at the same time as it flows inside the cooling jacket of the combustion chambers and is injected through the film cooling holes. A physical surrogate mixture model to reproduce the thermophysical characteristics of Jet A-1 has been selected and the thermodynamic/transport properties of the model fuel under high pressure including supercritical conditions have been estimated using SUPERTRAPP(NIST SRD4). Comparisons with the measured properties suggest that proposed database can be used to extract properties of Jet A-1 for conjugate heat transfer analysis of liquid propellant rocket engine thrust chambers. Predicted combustion/cooling performance of regeneratively cooled thrust chambers shall be validated through comparisons with upcoming firing test results.

Size-Dependent Thermodynamic Properties of the Reaction of Nano-ZnO with Benzoic Acid

Shuting Wang,Zixiang Cui,Yongqiang Xue 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.7

Studying the thermodynamic properties of the reaction of nanoparticle with organic substance is significant for the application of nanomaterial in organic fields. In this work, by using the reaction of nano-ZnO with different particle sizes with benzoic acid as a research system, the size-dependent standard equilibrium constant and reaction thermodynamic properties were analyzed theoretically, and the influence regularities of the particle size on the standard equilibrium constant and the reaction thermodynamic properties were studied. The excellent agreement between the experimental results and theoretical analysis shows that the particle size has remarkable influence on the standard equilibrium constant and the thermodynamic properties of the reaction; with the decrease of the particle size, the standard equilibrium constant increases, while the standard molar reaction Gibbs energy, the standard molar reaction enthalpy and the standard molar reaction entropy decrease. Furthermore, the logarithm of the standard equilibrium constant and the thermodynamic properties present linear relations with the reciprocal of the particle diameter, respectively. The theory and the influence regularities will provide useful tools to lead better and broader application of nanomaterial in organic fields.

Applicability of special quasi-random structure models in thermodynamic calculations using semi-empirical Debye–Grüneisen theory

Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.650 No.-

<P><B>Abstract</B></P> <P>In theoretical calculations, expressing the random distribution of atoms in a certain crystal structure is still challenging. The special quasi-random structure (SQS) model is effective for depicting such random distributions. The SQS model has not been applied to semi-empirical thermodynamic calculations; however, Debye–Grüneisen theory (DGT), a semi-empirical method, was used here for that purpose. The model reliability was obtained by comparing supercell models of various sizes. The results for chemical bonds, pair correlation, and elastic properties demonstrated the reliability of the SQS models. Thermodynamic calculations using density functional perturbation theory (DFPT) and DGT assessed the applicability of the SQS models. DGT and DFPT led to similar variations of the mixing and formation energies. This study provides guidelines for theoretical assessments to obtain the reliable SQS models and to calculate the thermodynamic properties of numerous materials with a random atomic distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Various material properties are used to examine reliability of special quasi-random structures. </LI> <LI> SQS models are applied to thermodynamic calculations by semi-empirical methods. </LI> <LI> Basic calculation guidelines for materials with random atomic distribution are given. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>