• Title, Summary, Keyword: temperature gradients

Search Result 270, Processing Time 0.036 seconds

Considerations on the Temperature Distributions and Gradients in the Filter During Regeneration in Burner Type Diesel Particulate Trap System (버너방식 DPF 시스템의 재생과정 중 발생하는 내부 온도분포 및 온도구 배에 관한 고찰)

  • 박동선;김재업;김응서
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.4 no.6
    • /
    • pp.78-84
    • /
    • 1996
  • In order to eliminate TPM(Total Particulate Matter) from a diesel engine, we designed and developed a particulate trap system using a burner, which was named as AEFR(Active Exhaust Feeding Regeneration) system. We have considered the temperature distributions and gradients in the filter being regenerated according to regeneration control schemes Ⅰ, Ⅱ and Ⅲ. Schemes Ⅲ has shown the most desirable peak temperature and temperature gradients in AFER system. Finally, it was concluded that much lower peak temperature and temperature gradients in the filter could be obtained than that of other advanced research results by our AEFR system.

  • PDF

Analysis of three-dimensional thermal gradients for arch bridge girders using long-term monitoring data

  • Zhou, Guang-Dong;Yi, Ting-Hua;Chen, Bin;Zhang, Huan
    • Smart Structures and Systems
    • /
    • v.15 no.2
    • /
    • pp.469-488
    • /
    • 2015
  • Thermal loads, especially thermal gradients, have a considerable effect on the behaviors of large-scale bridges throughout their lifecycles. Bridge design specifications provide minimal guidance regarding thermal gradients for simple bridge girders and do not consider transversal thermal gradients in wide girder cross-sections. This paper investigates the three-dimensional thermal gradients of arch bridge girders by integrating long-term field monitoring data recorded by a structural health monitoring system, with emphasis on the vertical and transversal thermal gradients of wide concrete-steel composite girders. Based on field monitoring data for one year, the time-dependent characteristics of temperature and three-dimensional thermal gradients in girder cross-sections are explored. A statistical analysis of thermal gradients is conducted, and the probability density functions of transversal and vertical thermal gradients are estimated. The extreme thermal gradients are predicted with a specific return period by employing an extreme value analysis, and the profiles of the vertical thermal gradient are established for bridge design. The transversal and vertical thermal gradients are developed to help engineers understand the thermal behaviors of concrete-steel composite girders during their service periods.

3-D Simulation of Air Flow in Cold Storage Room for Uniform Temperature Distribution (저온저장고 내부의 균일한 온도분포를 위한 3차원 공기유동 분석)

  • 성제중;고학균;조성인;양길모
    • Journal of Biosystems Engineering
    • /
    • v.25 no.4
    • /
    • pp.279-286
    • /
    • 2000
  • Most of the domestic cold storage rooms are inefficient for agricultural products because of temperature gradients inside the storage rooms. Temperature gradients are developed mainly by improper airflow pattern inside the storage room, which is a main cause of the spoilage of the agricultural products. There proper airflow pattern is essential to minimize these temperature gradients and the spoilage. The performance and characteristics of a cold storage room were determined as a function of airflow pattern and temperature distribution in forced circulation cold storage room. A commercial CFD(computational fluid dynamics) code was used to simulate 3-D airflow in the cold storage room. Solving the flow equations for the storage room, a standard k-$\varepsilon$ turbulent model was implemented to calculate steady state turbulent velocity distribution. The CFD prediction results were compared with temperature measurements inside the cold storage room. In case of pallet storage, Temperature gradients inside pallet storage was reduced because the contact area of cold air expanded through an alley of airflow in storage. But is case of bulk storage, the last temperature of storage considerably rose more than the initial temperature of storage. The reason was that bulk storage didn't include any alley of airflow in storage.

  • PDF

Oxygen Potential Gradient Induced Degradation of Oxides

  • Martin, Manfred
    • Journal of the Korean Ceramic Society
    • /
    • v.49 no.1
    • /
    • pp.29-36
    • /
    • 2012
  • In many applications of functional oxides originally homogeneous materials are exposed to gradients in the chemical potential of oxygen. Prominent examples are solid oxide fuel cells (SOFCs) or oxygen permeation membranes (OPMs). Other thermodynamic potential gradients are gradients of electrical potential, temperature or uni-axial pressure. The applied gradients act as generalized thermodynamic forces and induce directed fluxes of the mobile components. These fluxes may lead to three basic degradation phenomena of the materials, which are kinetic demixing, kinetic decomposition, and morphological instabilities.

Thermal Property Analysis of 40 mm Long Hollow Cylinders Though Measurements and Analysis of Transient Temperatures (온도 측정과 분석을 통한 40 mm 장축공동실린더의 열적특성 고찰)

  • Shin Nae-Ho;Chung Dong-Yoon;Oh Myoung-Ho;Yoo Sam-Hyeon;Nam Seok-Ryun
    • Tribology and Lubricants
    • /
    • v.22 no.4
    • /
    • pp.190-195
    • /
    • 2006
  • A simple and effective analysis method is presented for gaining a complete transient temperatures on the internal and external surfaces of a 40 mm gun tube subjected to a series of rapid firings. Two series of temperature data for both Hs and As were measured by using two rapid response k-type surface thermocouples near the firing origin and the muzzle. With other available temperature data, patterns of temperature variations of the gun tube as a function of time variable were driven through complete evaluations of the data. It is found that overall temperature gradients which increase exponentially toward saturation temperature, actually consist of a series of linear temperature gradients corresponding to the firing sequences. Under the similar firing sequences, patterns of temperature variations fur both the surface temperatures near the chamber and those near the muzzle were found to have linear temperature gradients with different values and the same response frequencies, i.e. they had peaks and lows in temperatures at the same time. The resultant complete temperature data can be used as the fundamental bases for analysis of thermoelastic properties of the materials such as thermal strain and stress, and f3r the prediction of cannon tube life-time through calculation of wear rate.

GENERATION OF MAGNETIC FIELDS BY TEMPERATURE GRADIENTS

  • OKABE NOBUHIRO;HATTORI MAKOTO
    • Journal of The Korean Astronomical Society
    • /
    • v.37 no.5
    • /
    • pp.547-551
    • /
    • 2004
  • We showed that magnetic fields are generated in the plasma which have the temperature inhomogeneities. The mechanism is the same as the Weibel instability because the velocity distribution functions are at non-equilibrium and anisotropic under the temperature gradients. The growth timescale is much shorter than the dynamical time of structure formation. The coherence length of magnetic fields at the saturated time is much shorter than kpc scale and then, at nonlinear phase, become longer by inverse-cascade process. We report the application of our results to clusters of galaxies, not including hydrodynamic effects.

Numerical Analysis on the Characteristics of Temperature Distribution in an Active Regeneration DPF Type (강제 재생 방식 DPF 내부의 온도 분포 특성에 관한 수치해석)

  • Park, S.C.;Lee, H.S.
    • Journal of the Korean Society of Mechanical Technology
    • /
    • v.13 no.2
    • /
    • pp.55-61
    • /
    • 2011
  • This study analyzed on the characteristics of temperature distribution in an active regeneration DPF using computer simulation. In order to verify the boundary condition of analysis, results of temperature distribution in DPF are compared between experimental and computer simulation. Using this boundary condition, temperature distribution and filter's durability in DPF analyzed according to various operating conditions. The results of computational analysis are agreed well with experimental ones from the tendency of temperature distribution of axis and radius direction. The temperature increases and the axial temperature gradients in DPF according to velocity of exhaust gas are lowered as the high velocity of exhaust gas. But the temperature gradients of radius direction at exit side in DPF are grown as the high velocity of exhaust gas. The results according to inlet temperature of exhaust gas show that the increase ratios of temperature in DPF are grown as the high temperature of exhaust gas.

A Study for Characteristics of Stack Plume Dispersion under Various (다양한 대기풍속 및 대기온도 구배 조건에서의 공장 배출 가스의 확산 특성에 관한 연구)

  • Park, Il-Seouk
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.22 no.11
    • /
    • pp.773-780
    • /
    • 2010
  • The dispersion of plume which is emitted from a chimney is governed by a lot of factors: wind, local terrain, turbulence intensity of atmosphere, and temperature, etc. In this study, we numerically investigate the plume dispersions for various altitudinal temperature gradients and wind speeds. The normal atmosphere has the temperature decrease of $0.6^{\circ}C/100m$, however, actually the real atmosphere has the various altitudinal temperature profiles according to the meteorological factors. A previous study focused on this atmospheric temperature gradient which induces a large scale vertical flow motion in the atmosphere thus makes a peculiar plume dispersion characteristics. In this paper, the effects of the atmospheric temperature gradient as well as the wind speed are investigated concurrently. The results for the developing processes in the atmosphere and the affluent's concentrations at the ambient and ground level are compared under the various altitudinal temperature gradients and wind speeds.

Degradation of Functional Materials in Temperature Gradients - Thermodiffusion and the Soret Effect

  • Janek, Jurgen;Sann, Joachim;Mogwitz, Boris;Rohnke, Marcus;Kleine-Boymann, Matthias
    • Journal of the Korean Ceramic Society
    • /
    • v.49 no.1
    • /
    • pp.56-65
    • /
    • 2012
  • Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (d${\delta}$/dT) ${\approx}$ 1%/K.

Parameterized Extended Finite Element Method for high thermal gradients

  • Zeller, Christian;Surendran, Binu;Zaeh, Micheal F.
    • Journal of Computational Design and Engineering
    • /
    • v.5 no.3
    • /
    • pp.329-336
    • /
    • 2018
  • The Finite Element Method results in inaccuracies for temperature changes at the boundary if the mesh is too coarse in comparison with the applied time step. Oscillations occur as the adjacent elements balance the excessive energy of the boundary element. An Extended Finite Element Method (XFEM) with extrinsic enrichment of the boundary element by a parameterized problem-specific ansatz function is presented. The method is able to represent high thermal gradients at the boundary with a coarse mesh as the enrichment function compensates for the excessive energy at the element affected by the temperature change. The parameterization covers the temporal change of the gradient and avoids the enrichment by further ansatz functions. The introduced parameterization variable is handed over to the system of equations as an additional degree of freedom. Analytical integration is used for the evaluation of the integrals in the weak formulation as the ansatz function depends non-linearly on the parameterization variable.