• Title/Summary/Keyword: thermodynamic analysis

Search Result 642, Processing Time 0.025 seconds

Finite Element Analysis of Elasto-Plastic Large Deformation considering the Isotropic Damage (the 1st Report) -Development of Elasto-Plastic Damage Constitutive Model- (등방성 손상을 고려한 탄소성 대변형 문제의 유한요소해석(제1보) -탄소성 손상 구성방정식 개발-)

  • 노인식
    • Journal of Ocean Engineering and Technology
    • /
    • v.14 no.2
    • /
    • pp.70-75
    • /
    • 2000
  • In this paper a new constitutive model for ductile materials was proposed. This model can describe the material degradation due to the evolution of isotropic damage during elasto-platic deformation. The plastic flow rule was derived under the framework of thermodynamic approach of continuum damage mechanics(CDM) in which plastic strain hardening parameters and isotropic damage were taken as thermodynamic state variables. And the process to determine material constants for constitutive model using an experimental data was presented.

  • PDF

A Numerical Study on the Laminar Flow Field and Heat Transfer Coefficient Distribution for Supercritical Water in a Tube

  • Lee Sang-Ho
    • International Journal of Air-Conditioning and Refrigeration
    • /
    • v.13 no.4
    • /
    • pp.206-216
    • /
    • 2005
  • Numerical analysis has been carried out to investigate laminar convective heat transfer at zero gravity in a tube for supercritical water near the thermodynamic critical point. Fluid flow and heat transfer are strongly coupled due to large variation of thermodynamic and transport properties such as density, specific heat, viscosity, and thermal conductivity near the critical point. Heat transfer characteristics in the developing region of the tube show transition behavior between liquid-like and gas-like phases with a peak in heat transfer coefficient distribution near the pseudo critical point. The peak of the heat transfer coefficient depends on pressure and wall heat flux rather than inlet temperature and Reynolds number. Results of the modeling provide convective heat transfer characteristics including velocity vectors, temperature, and the properties as well as the heat transfer coefficient. The effect of proximity on the critical point is considered and a heat transfer correlation is suggested for the peak of Nusselt number in the tube.

A Study on the Transient Convective Heat Transfer for Supercritical Water in a Vertical Tube (수직관 내 초임계상태 물의 천이상태 대류열전달현상에 관한 연구)

  • Lee Sang-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.17 no.12
    • /
    • pp.1095-1105
    • /
    • 2005
  • Numerical analysis has been carried out to investigate transient turbulent convective heat transfer in a vertical tube for supercritical water near the thermodynamic critical point. Heat transfer and fluid flow in the tube we strongly coupled due to the large variations of thermodynamic and transport properties such as density, specific heat, and turbulent viscosity. As pressure in the tube approaches to the critical pressure, the properties variation with time becomes larger. Heat transfer coefficient rapidly decreases along the tube near the pseudocritical temperature at the tube wall for $P_R<1.2$. Stanton number variation with time is largely reduced in the region of gas-like phase in comparison with Nusselt number. Turbulent viscosity ratio close to the wall increases near the pseudocritical temperature and it gradually decreases with time.

Thermodynamic and Physical Properties of (NH4)2MnCl4·2H2O by Nuclear Magnetic Resonance Relaxation Times

  • Kim, Yoo Young
    • Journal of the Korean Magnetic Resonance Society
    • /
    • v.23 no.2
    • /
    • pp.40-45
    • /
    • 2019
  • The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

FE Analysis of Hot Press Forming Process considering the Phase Transformation (상변태를 고려한 핫프레스포밍 공정의 유한요소해석)

  • Kang, Gyeong-Pil;Lee, Kyung-Hoon
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2008.10a
    • /
    • pp.226-229
    • /
    • 2008
  • Hot press forming is an advanced forming technology fur manufacturing of complex and crash-resistant automotive parts using ultra high strength steels. The 3-dimensional FE analysis of hot press forming process, in which process the deformation, heat transfer and phase transformation behavior are fully coupled, is carried out. The vast amount of material properties for the FE analysis is obtained from material properties calculation software which is based on thermodynamic calculations. The overall methodology for the FE analysis of HPF process and the analysis results are discussed here.

  • PDF

Investigation of thermodynamic analysis in GaN thick films gtowth (GaN 후막 증착의 열역학적 해석에 관한 연구)

  • Park, Beom Jin;Park, Jin Ho;Sin, Mu Hwan
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.8 no.3
    • /
    • pp.387-387
    • /
    • 1998
  • This paper reports on a thermodynamic analysis for the GaN thick film growth by vapor phaseepitaxy method. The thermodynamic calculation was performed using a chemical stoichiometric algorism. Thesimulation variables include the growth temperature in a range 400~1500 K, the gas ratios $(GaCl_3)/(GaCl_3+NH_3)$and $(N_2)/(GaCl_3+NH_3)$. The theoretical calculation predicts that the growth temperature of GaN be in thelower range of 450~750 K than the experimental results. The difference in the growth temperature betweenthe simulation and the experiments indicates that the vapor phase epitaxy of GaN is kinetically limited,presumably, due to the high activation energy of thin film growth.

Investigation of thermodynamic analysis in GaN thick films gtowth (GaN 후막 증착의 열역학적 해석에 관한 연구)

  • 박범진;박진호;신무환
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.8 no.3
    • /
    • pp.388-395
    • /
    • 1998
  • This paper reports on a thermodynamic analysis for the GaN thick film growth by vapor phase epitaxy method. The thermodynamic calculation was performed using a chemical stoichiometric algorism. The simulation variables include the growth temperature in a range 400~1500 K, the gas ratios $(GaCl_3)/(GaCl_3+NH_3)$ and $(N_2)/(GaCl_3+NH_3)$. The theoretical calculation predicts that the growth temperature of GaN be in the lower range of 450~750 K than the experimental results. The difference in the growth temperature between the simulation and the experiments indicates that the vapor phase epitaxy of GaN is kinetically limited, presumably, due to the high activation energy of thin film growth.

  • PDF

Studies on the Adsarption Characteristics of Fluoride Ion-Containing Wastewater by Employing Waste Oyster Shell as an Adsorbent (폐굴껍질을 흡착제로 한 불소폐수 처리특성에 관한 연구)

  • Lee, Jin-Suk;Kim, Dong-Su
    • Journal of Korean Society on Water Environment
    • /
    • v.23 no.2
    • /
    • pp.222-227
    • /
    • 2007
  • The adsorption features of fluoride ion on the oyster shell have been investigated for the purpose of the employment of waste oyster shell as an adsorbent for the treatment of fluoride ion-containing wastewater. The major component of oyster shell was examined to be Ca with minor components of Na, Si, Mg, Al, and Fe. As the initial concentration of fluoride ion was raised, its absorbed amount was enhanced at equilibrium, however, the adsorption ratio of fluoride ion compared with its initial concentration was shown to be decreased. Also, adsorption of fluoride ion onto the oyster shell resulted in the formation of $CaF_2$ in the morphological structure of adsorbent. Kinetic analysis showed that the adsorption reaction of fluoride ion generally followed a second order reaction with decreasing rate constant with the initial concentration of adsorbate. Freundlich model agreed well with the adsorption behavior of fluoride ion at equilibrium and the adsorption reaction of fluoride ion was examined to be endothermic. Several thermodynamic parameters for the adsorption reaction were calculated based on thermodynamic equations and the activation energy for the adsorption of fluoride ion onto oyster shell was estimated to be ca. 13.589 kJ/mole.

Kinetic and Thermodynamic Analysis of AChE Inhibition of Solvent Extract Fractions from Inonotus obliquus (차가버섯 용매추출분획의 Acetylcholinesterase 저해활성에 대한 동역학 및 열역학적 해석)

  • Kim, Hak-Kyu;Hur, Won;Hong, Eok Kee;Lee, Shin-Young
    • Food Engineering Progress
    • /
    • v.15 no.4
    • /
    • pp.289-296
    • /
    • 2011
  • Twenty four fractions by solvent extraction and/or acid precipitation from fruit body and culture broth of Inonotus obliquus were prepared, and their inhibitory effect against acetylcholinesterase (AChE) was investigated. Among these fractions, acid (1 M HCl) precipitates from cell-free culture broth and fruit body exhibited the highest inhibitory effect on AChE in vitro. Acid precipitates inhibited AChE activity in a concentration-dependant manner and $IC_{50}$ values of both acid precipitates were 0.53 mg/mL. The inhibition pattern was general non-competitive inhibition. The energetic parameters were also determined by dual substrate/temperature design. Both acid precipitates increased the values of Ea, ${\Delta}H,/;{\Delta}G$ and ${\Delta}H^{\ast}$ decreasing the value of ${\Delta}S$ for AChE. The results implied that the acid precipitates from I. obliquus increased the thermodynamic barrier, leading to the breakdown of ES complex and the formation of products as inhibitory mechanism.