• Title, Summary, Keyword: Thermodynamic parameters

Search Result 463, Processing Time 0.036 seconds

An Investigation on Local Thermodynamic Equilibrium Assumption of Natural Convection in a Porous Medium (다공성 물질 안에서의 자연대류 현상에 대한 열역학적 국소평형상태 가정의 고찰)

  • Kim, In-Seon;Nam, Jin-Hyun;Kim, Charn-Jung
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.112-117
    • /
    • 2000
  • A numerical study on natural convection in a vertical square cavity filled with a porous medium is carried out with Brinkman-Forchheimer-extended Darcy flow model, and the validity of local thermodynamic equilibrium assumption is studied. The local thermodynamic equilibrium refers to the state in which a single temperature can be used to describe a heat transfer process in a multiphase system. With this assumption, the analysis is greatly simplified because only one equation is needed to describe the heat transfer process. But prior to using this assumption, it is necessary to know in what conditions the assumption can be used. The numerical results of this study reveal that large temperature difference between fluid phase and solid phase exists near wall region, paticularily when the convection becomes dominant over conduction. And the influence of flow parameters such as fluid Rayleigh number, fluid Prandtl number, dimensionless particle diameter and conductivity ratio are investigated.

  • PDF

Thermodynamic Behavior of Si in Mn-Si Melts (Mn-Si 용탕내 Si의 열역학적 거동)

  • Paek, Min-Kyu;Jang, Jung-Mock;Kang, Youn-Bae;Pak, Jong-Jin
    • Korean Journal of Metals and Materials
    • /
    • v.50 no.2
    • /
    • pp.116-121
    • /
    • 2012
  • Equilibria between Mn-Si melts and $MnO-SiO_2$ slags were studied at 1673 K and 1773 K in MnO crucibles to accurately determine the thermodynamic property of the Mn-Si melts. The Unified Interaction Parameter Formalism (UIPF) was used to describe the thermodynamic property of the Mn-Si liquid. Using the UIPF, the experimental results obtained in the present study were thermodynamically analyzed to determine the activity coefficient of Si at infinite dilution and the 1st- and 2nd-order self-interaction parameters of Si in the Mn-Si melts.

Dynamics of multilayered viscoelastic beams

  • Roy, H.;Dutt, J.K.;Datta, P.K.
    • Structural Engineering and Mechanics
    • /
    • v.33 no.4
    • /
    • pp.391-406
    • /
    • 2009
  • Viscoelastic materials store as well as dissipate energy to the thermal domain under deformation. Two efficient modelling techniques reported in literature use coupled (thermo-mechanical) ATF (Augmenting Thermodynamic Fields) displacements and ADF (Anelastic Displacement Fields) displacements, to represent the constitutive relationship in time domain by using certain viscoelastic parameters. Viscoelastic parameters are first extracted from the storage modulus and loss factor normally reported in hand books with the help of Genetic Algorithm and then constitutive relationships are used to obtain the equations of motion of the continuum after discretizing it with finite beam elements. The equations of motion are solved to get the frequency response function and modal damping ratio. The process may be applied to study the dynamic behaviour of composite beams and rotors comprising of several viscoelastic layers. Dynamic behaviour of a composite beam, formed by concentric layers of steel and aluminium is studied as an example.

Biochemical and Thermal Stabilization Parameters of Polygalacturonase from Erwinia carotovora subsp. carotovora BR1

  • Maisuria, V.B.;Patel, V.A.;Nerurkar, A.S.
    • Journal of Microbiology and Biotechnology
    • /
    • v.20 no.7
    • /
    • pp.1077-1085
    • /
    • 2010
  • With an emphasis on its thermal behavior with different pHs and salts, the kinetic and thermodynamic parameters of the purified polygalacturonase (PG) from E. carotovora subsp. carotovora (Ecc) BR1 were studied, as the characterization of an enzyme is significant in the context of burgeoning biotechnological applications. The thermodynamic parameters for polygalacturonic acid hydrolysis by the purified PG were ${\Delta}H^*$=7.98 kJ/mol, ${\Delta}G^*$=68.86 kJ/mol, ${\Delta}S^*$=-194.48 J/mol/K, ${\Delta}G_{E-S}$=-1.04 kJ/mol, and ${\Delta}G_{E-T}$=-8.96 kJ/mol. In addition, its turnover number ($k_{cat}$) was 21/sec. The purified PG was stable within a temperature range of $20-50^{\circ}C$ and was deactivated at $60^{\circ}C$ and $70^{\circ}C$. The thermodynamic parameters (${\Delta}H^*$, ${\Delta}G^*$, ${\Delta}S^*$) for the irreversible inactivation of the PG at different temperatures ($30-60^{\circ}C$) were determined, where the effectiveness of various salts and different pHs (4-8) for the thermal stability of the PG were also characterized. The efficacy of various salts for the thermal stability of the PG was in the following order: $MgCl_2$ > $BaCl_2$ > KCl > $CaCl_2$ >NaCl. Therefore, the present work presents the biochemical, substrate hydrolysis thermodynamics and the thermal stabilization parameters of the PG from Ecc.

Self Diffusions and Rheological Properties of Polyamide Polymer Materials in Various Solvents (용매 환경에서의 폴리아미드 고분자 재료의 자체확산과 유변학적인 특성)

  • Kim, Nam Jeong
    • Journal of the Korean Applied Science and Technology
    • /
    • v.36 no.4
    • /
    • pp.1050-1059
    • /
    • 2019
  • The self diffusion, hole volume, and flow thermodynamic parameters of polyamide fibers were calculated from rheological parameters and crystallite size in order to study of flow segments in amorphous region. The stress relaxation of polyamide filament fibers were carried out in air and various solvents at various temperatures using the tensile tester with the solvent chamber. The rheological parameters were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model. It was observed that the rheological parameters of these polyamide filament fibers are directly related to the relaxation spectra, self diffusion, viscosities, and activation energies of flow segments.

Self Diffusion Coefficients and Free Hole Volumes of Poly(acrylonitrile)-poly(vinyl chloride) Copolymers (Poly(acrylonitrile)-poly(vinyl chloride) 공중합체의 자체 확산 계수와 유동 자유 홀부피)

  • Kim, Nam-Jeong
    • Elastomers and Composites
    • /
    • v.46 no.3
    • /
    • pp.245-250
    • /
    • 2011
  • The self diffusions and hole volumes of amorphous region of poly(acrylonitrile)-poly(vinyl chloride) fibers were investigated by experiments of stress relaxation. The experiments of stress relaxation were carried out using the tensile tester with the solvent chamber. The flow parameters of filament fibers were obtained by applying the experimental stress relaxation curves to the theoretical equation of stress relaxation. From the flow parameters, the hole volumes, self diffusions, viscosities and thermodynamic parameters of solid polymers were calculated. It was observed that the flow parameters of these samples are directly related to the hole volumes, self diffusions and flow activation energies of flow segments.

Adsorption of Pb(II) Ions from Aqueous Solution Using Activated Carbon Prepared from Areca Catechu Shell: Kinetic, Isotherm and Thermodynamic Studies

  • Muslim, A.;Aprilia, S.;Suha, T.A.;Fitri, Z.
    • Journal of the Korean Chemical Society
    • /
    • v.61 no.3
    • /
    • pp.89-96
    • /
    • 2017
  • This study proposed adsorption of Pb(II) ions from aqueous solution using activated carbon prepared from areca catechu shell (ACS AC) using Timphan Method. The effects of independent variables on adsorption kinetic and isotherm have been investigated by conducting experiments in batch mode at neutral pH. The structural characterization of adsorbent was done by FT-IR and SEM analysis. The Pb(II) adsorption was correlated very well with the pseudo second-order kinetic (PSOKM) and Langmuir isotherm models (LIM). Increasing NaOH mass for activation and adsorption temperature increased weakly all the parameters of adsorption kinetic and isotherm. The Pb(II) ions adsorption capacity of the ACS AC at 27 and $45^{\circ}C$ was 50.51 and 55.25 mg/g, respectively. Thermodynamic parameters were determined, and the results confirmed the Pb(II) ions adsorption should be endothermic and spontaneous process, and both physical and chemical adsorption should be taken place.

Study of Performance Diagnostics of Turbo-Shaft Engine for SUAV Using Thermodynamic Sensitivity (열역학적 민감도를 이용한 스마트 무인기용 터보축 엔진의 성능진단 연구)

  • Lee Daewon;Roh Taeseong;Choi Dongwhan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • v.y2005m4
    • /
    • pp.252-255
    • /
    • 2005
  • The operation of a gas-turbine engine gradually deteriorates the performance of its main components and often generates the defects of its components. The GPA method has been usually used for the diagnosis of the deterioration. In this study, the diagnostic code of the engine performance using the thermodynamic sensitivity between the sensed parameters and the health parameters has been developed without an application of the commercial program. The single performance deterioration of the turbo-shaft engine for SUAV has been estimated with this code.

  • PDF