• Title/Summary/Keyword: 열역학

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連續體力學의 基礎的 槪要(II)

  • 박진무
    • Journal of the KSME
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    • v.26 no.3
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    • pp.214-218
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    • 1986
  • 제 4절에서 얻은 연속체 일반의 장방정식들을 제 5절에서와 같이 각종 물질의 구성방정식으로 보충하므로써, 탄성이론, Newton 유체역학, 비 Newton 유체역학, 소성이론, 점탄성이론, 비균질 체역학, 연속체 일반의 열역학 ...등의 기본적 이론체계를 구성할 수 있다. 또 합당한 경계조건과 함께 구체적 해를 얻는 다양한 연구로 이어진다. 이에 대한 독자의 편의를 위하여 몇 개의 문 헌을 뒤에 나열한다. (8,15,16,17,18,19) 공학의 한 분야에 전문적인 지식을 얻기 위해서는 공학 일반(engineering science)에 대한 선명한 이해가 필수적이며 이를 위해 연속체이론이 꾸준히 연구되고 있다. 그러나 이와 같은 방대한 체계를 $E_{3}$ 해석학의 틀 속에서 선명하게 파악 하려하는 것은 어려운 일이다. 결국 대역적해석학(global analysis)의 응용(3,5,20,21,22)이 불가 피하지 않나 생각된다. 이 방향의 연구가 선진국에서도 아직 소수의 학자들에 국한된 실정이나, 우리 공학의 획기적 발전을 위하여 독자들의 노력이 계속되었으면 한다.

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Computational Fluid Dynamics for Proton Exchange Membrane Fuel Cell (PEMFC) (고체고분자전해질연료전지의 해석을 위한 전산유체역학)

  • Kim, Sunhoe
    • Prospectives of Industrial Chemistry
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    • v.22 no.4
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    • pp.20-34
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    • 2019
  • 수소경제 시대의 도래와 함께 연료전지에 관한 연구가 크게 주목받고 있다. 그중 실험적으로 분석이 어려운 부분에 관하여 비용과 시간이 요구되는 실험적인 방법을 배제할 수 있는 모델링 기법인 전산유체역학(computational flow dynamics, CFD)이 큰 관심을 받고 있다. 연료전지의 연구에 주로 사용되는 전산유체역학에 관한 연구는 열분포, 유체의 흐름, 각종 반응물의 농도, 그리고 전기화학반응 등의 실험적인 분석이 현실적으로 불가능한 부분의 분석으로 통하여 실험을 줄이고도 많은 결과를 얻을 수 있는 연구가 활발하게 진행되고 있다. 본 기고문에서는 전산유체역학을 이용한 연료전지 내부에서 벌어지고 있는 각종 유체, 열, 전기화학반응 등에 관한 연구동향을 소개하고자 한다.

Thermal-Hydro-Mechanical Behaviors in the Engineered Barrier of a HLW Repository: Engineering-scale Validation Test (고준위폐기물처분장 공학적방벽의 열-수리-역학적 거동 연구: 엔지니어링 규모의 실증실험)

  • Lee, Jae-Owan;Cho, Won-Jin
    • Tunnel and Underground Space
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    • v.17 no.6
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    • pp.464-474
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    • 2007
  • An enhancement in the performance and safety of a high-level waste repository requires a validation of its engineered barrier. An engineering-scale test (named "KENTEX") has been conducted to investigate the thermal-hydro-mechanical behaviors in the engineered barrier of the Korean reference disposal system The validation test started on May 31, 2005 and is still under operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the thermal-hydro-mechanical behaviors in the bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying-wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. Near the heater region, there was also a significant contribution of the thermal expansion of bentonite and the vapor pressure in the pores of the bentonite blocks.

Characterization of Thickness and Thermoelastic Properties of Interphase in Polymer Nanocomposites using Multiscale Analysis (멀티스케일 해석을 통한 고분자 나노복합재의 계면 상 두께와 열탄성 물성 도출)

  • Choi, Joonmyung;Cho, Maenghyo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.6
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    • pp.577-582
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    • 2016
  • In this study, a multiscale method for solving a thermoelasticity problem for interphase in the polymeric nanocomposites is developed. Molecular dynamics simulation and finite element analysis were numerically combined to describe the geometrical boundaries and the local mechanical response of the interfacial region where the polymer networks were highly interacted with the nanoparticle surface. Also, the micrmechanical thermoelasticity equations were applied to the obtained equivalent continuum unit to compute the growth of interphase thickness according to the size of nanoparticles, as well as the thermal phase transition behavior at a wide range of temperatures. Accordingly, the equivalent continuum model obtained from the multiscale analysis provides a meaningful description of the thermoelastic behavior of interphase as well as its nanoparticle size effect on thermoelasticity at both below and above the glass transition temperature.

Real Gas Speeds of Sound and Approximate Riemann Solver (실제 기체 음속과 근사 리만 해법)

  • Moon, Seong-Young;Han, Sang-Hoon;Choi, Jeong-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.1
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    • pp.1-11
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    • 2010
  • The definition of the speed of sound is reexamined since it is crucial in the numerical analysis of compressible real gas flows. The thermodynamic speed of sound (TSS), $a_{th}$, and the characteristic speed of sound (CSS), $a_{ch}$, are derived using generalized equation of state (EOS). It is found that the real gas EOS, for which pressure is not linearly dependent on density and temperature, results in slightly different TSS and CSS. in this formalism, Roe's approximate Riemann solver was derived again with corrections for real gases. The results show a little difference when the speeds of sound are applied to the Roe's scheme and Advection Upstream Splitting Method (AUSM) scheme, but a numerical instability is observed for a special case using AUSM scheme. It is considered reasonable to use of CSS for the mathematical consistency of the numerical schemes. The approach is applicable to multi-dimensional problems consistently.

Application of Statistical Model and Thermodynamic Analysis on Sorption of Heavy Metals by Bentonite (벤토나이트의 중금속 흡착에 대한 통계모델의 적용 및 열역학적 해석)

  • 정찬호;김수진
    • The Journal of Engineering Geology
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    • v.12 no.2
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    • pp.203-214
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    • 2002
  • The statistical model was introduced to satisfy various experimental condition on the sorption of heavy metals (Pb, Cu, Cd, and Zn) by bentonite. The Box-Behnken model designed statistically was applied to determine relative impact among three variables such as pH, HCO$_3$ contents and heavy metal concentrations on the sorption. The SAS program was used to obtain the statistical solution. The statistical surface response analysis indicates that initial concentration of heavy metals and pH have an important effect on the sorption, and bicarbonate is not a serious variable. The sorption capability about heavy metals of bentonite is in the order of Pb>Cu>Zn>Cd. The precipitation as hydroxyl and carbonate complexes of heavy metals was thermodynamically analyzed as major mechanism of sorption under alkaline pHs and high bicarbonate solution. It was found that there is a little difference between the model prediction on the precipitation of heavy metals and the results of batch sorption experiment. The thermodynamic data of the programs have to revise to obtain the best fit condition between the model prediction and the experimental results.

Development of Thermomechanical Coupled Numerical Model for Energy Slab (에너지 슬래브의 열-역학적 수치해석 모델 개발)

  • Park, Sangwoo;Choi, Hangseok;Lee, Seokjae
    • Journal of the Korean Geotechnical Society
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    • v.40 no.1
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    • pp.55-63
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    • 2024
  • In this study, a thermomechanical numerical model was developed to evaluate the stability of energy slabs. First, a wall-type energy slab was installed in a residential underground parking lot, and thermal performance tests were conducted. Based on the tests, a numerical thermohydraulics model of the energy slab was developed to accurately simulate the thermal behavior in thermal performance tests. Finally, utilizing the temperature data acquired using the developed model, a thermomechanical numerical model of the energy slab was established. The thermomechanical model was then used to simulate the thermal stresses induced by operating the energy slab. The results demonstrated a maximum thermal stress of 5,300 kPa, which highlights the need to utilize cement mortar with sufficient tensile strength to realize stable operation of the energy slab.

A Study on Characteristics of Jointed Rock Masses and Thermo-hydro-mechanical Behavior of Rock Mass under High Temperature (방사성 폐기물 저장을 위한 불연속 암반의 특성 및 고온하에서의 암반의 수리열역학적 상호작용에 관한 연구)

  • 이희근;김영근;이희석
    • Tunnel and Underground Space
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    • v.8 no.3
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    • pp.184-193
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    • 1998
  • In order to dispose radioactive wastes safely, it is needed to understand the mechanical, thermal, fluid behavior of rockmass and physico-chemical interactions between rockmass and water. Also, the knowledge about mechanical and hydraulic properties of rocks is required to predict and to model many conditions of geological structure, underground in-situ stress, folding, hot water interaction, intrusion of magma, plate tectonics etc. This study is based on researches about rock mechanics issues associated with a waste disposal in deep rockmass. This paper includes the mechanical and hydraulic behavior of rocks in varying temperature conditions, thermo-hydro-mechanical coupling analysis in rock mass and deformation behavior of discontinuous rocks. The mechanical properties were measured with Interaken rock mechanics testing systems and hydraulic properties were measured with transient pulse permeability measuring systems. In all results, rock properties were sensitive to temperature variation.

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Finite Element Method for Evaluation of Wave Forces (파랑하중의 산정을 위한 유한요소법)

  • 박우선
    • Computational Structural Engineering
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    • v.3 no.2
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    • pp.9-12
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    • 1990
  • 유한요소법은 구조물의 변위 또는 응력 등을 해석하기 위한 구조해석 분야에서 뿐만 아니라, 유체역학, 열역학 및 전자기학 등 각종 공학문제의 수학적 모형에 대하여 구해진 미분방정식을 푸는 기법으로 널리 사용되고 있다. 특히, 컴퓨터 기술의 급속한 발달로 인한 유한요소법의 적용범위는 더욱 확장되고 있다. 본 고는 유한요소법이 타 공학문제, 특히 유체에 관련된 문제에서 어떻게 이용되고 있는가를 소개하려 한다. 구체적으로, 해양구조물의 설계에 있어서 선결되어야 할 주요사항인 파랑하중 산정문제를 예로 들어, 유한요소법을 이용한 이의 수식화과정을 간략히 설명하였다.

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Numerical Modeling of Coupled Thermo-hydro-mechanical Behavior of MX80 Bentonite Pellets (MX80 벤토나이트 펠렛의 열-수리-역학적 복합거동 모델링)

  • Lee, Changsoo;Choi, Heui-Joo;Kim, Geon-Young
    • Tunnel and Underground Space
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    • v.30 no.5
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    • pp.446-461
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    • 2020
  • Numerical simulations of CIEMAT column test in Spain are performed to investigate the coupled thermo-hydro-mechanical (THM) behavior of MX80 bentonite pellets using TOUGH2-FLAC3D. The heater power and injection pressure of water in the numerical simulations are identical to those in the laboratory test. To investigate the applicability of the thermo-hydraulic (TH) model used in TOUGH2 code to prediction of the coupled TH behavior, the simulation results are compared with the observations of temperature and relative humidity with time. The tendencies of the coupled behavior observed in the test are well represented by the numerical models and the simulator in terms of temperature and relative humidity evolutions. Moreover, the performance of the models for the reproduction and prediction of the coupled TH behavior is globally satisfactory compared with the observations. However, the calculated stress change is relatively small and slow due to the limitations of the simple elastic and swelling pressure model used in numerical simulations. It seems that the two models are insufficient to realistically reproduce the complex coupled THM behavior in the bentonite pellets.