• Journal of computational fluids engineering
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• v.5 no.1
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• pp.27-32
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• 2000

This study investigates the problem of phase change from liquid to solid in the inviscid stagnation flow. The instantaneous location of the solid-liquid interface is fixed for all times by a coordinate transformation. Finite difference method is used to obtain the solution of the unsteady problem, and the growth rate of solid and the transient heat transfer from the surfaces of solid are investigated. The transient solution is dependent on the three dimensionless parameters, but the final steady state is determined by only one parameter of temperature ratio/conductivity ratio. It is observed that the instantaneous heat flux at the surface of solid can be obtained with sufficient accuracy by measuring the thickness of the solid or vice versa.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.653-663
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• 2000

A lot of hazardous wastes are discharged as by-products of working process by industrial development. Hazardous wastes is physical characteristics of difficult destruction at hight temperature. Numerical simulation and combustion experiment performed of dump incinerator for hazardous waste incineration. For the numerical simulation, the SIMPLEST algorithm was used to ensure rapid converge A K-$\varepsilon$ model was incorporate for the enclosure of turbulence flow. Combustion model was used by ESCRS (extended simple chemically reacting system) model available of CHEMKIN thermodynamic data for the source term of species conservation equation or energy equation. Radiation model is used by six flux model. A parametric screening studies was carried out through numerical simulation and experiment. Residence time and concentration in the incinerator was strongly dependent on the parameters of mixture velocity, mixture equilibrium ratio, surrogate velocity and surrogate equilibrium ratio.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.2
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• pp.10-15
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• 2011

A ground loop heat exchanger for the ground source heat pump system is the core equipment determining the thermal performance and initial cost of the system The length and performance of the heat exchanger is dependent on the ground thermal conductivity, the operation hours, the ground loop diameter, the grout, the ground loop arrangement, the pipe placement and the design temperature. The result of this simulation shows that higher thermal conductivity of grouting materials leads to the decrease length of geothermal heat exchanger from 100.0 to 84.4%.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.4
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• pp.479-485
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• 1996

Volatile organic compounds are air pollutants exhausting from industrial process, evaporation of solvent, and so on. Most of VOCs are the combustible gas of low calorific value as it is diluted by air. The systems burning such a hazardous gas need to increase enthalpy in order to increase flame stability. In this study an incinerator with reciprocating flow in the honeycomb ceramic has been used for the experiment of VOCs control. By the reciprocating flow system, the enthalpy of combustion gas is effectively regenerated into the enthalpy increases of the combustible gas through the honeycomb ceramic, which provides a heat storage. The position of the reaction zone is strongly dependent on the parameters of mixture velocity and time frequency. Flame front is changed to the point where burning velocity is coincided with burning velocity in the honeycomb ceramic. In this system it is important that flame front should be located symmetrically at the center of honeycomb ceramic for the purpose of increasing the reaction rate at one point. Peak temperature becomes higher with decreasing time frequency, at which the flow direction is regularly reversed.

• Bulletin of the Korean Chemical Society
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• v.21 no.12
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• pp.1187-1192
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• 2000

Ternary (Mo-Ru-Pd) and binary (Mo-Ru, Mo-Pd) alloys have been prepared using an Ar arc melting furnace. Mo and the noble metals, Ru and Pd, are the constituents of metallic insoluble residues, which were found in the early days of post-irradiation studies on uranium oxide fuels. In the present study, the structure of the alloys was evaluated using a powder X-ray diffractometer. Unit cell parameters were determined by least squares refinements of powder X-ray diffraction data. Scanning electron microscopic analyses of the surface of the alloys indicated that surface morphology was dependent on the crystallographic structure as well as its composition. Measurements of the magnetic susceptibility of the alloys showed evidence of superconducting transition from 3 to 9.2 K. Among the ternary and binary alloys, the ${\sigma}-phase$ showed the highest superconducting transition temperature,~9.2 K.

• Steel and Composite Structures
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• v.25 no.2
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• pp.187-196
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• 2017

In this work, transient thermo-piezo-elastic responses of an infinite functionally graded piezoelectric (FGPE) plate whose upper surface suffers time-dependent thermal shock are investigated in the context of different thermo-piezo-elastic theories. The thermal and mechanical properties of functionally graded piezoelectric plate under consideration are expressed as power functions of plate thickness variable. The solution of problem is obtained by solving the corresponding finite element governing equations in time domain directly. Transient thermo-piezo-elastic responses of the FGPE plate, including temperature, stress, displacement, electric intensity and electric potential are presented graphically and analyzed carefully to show multi-field coupling behaviors between them. In addition, the effects of functionally graded parameters on transient thermo-piezo-elastic responses are also investigated to provide a theoretical basis for the application of the FGPE materials.

• Smart Structures and Systems
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• v.23 no.3
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• pp.215-225
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• 2019

In the present paper, the nonlocal strain gradient refined model is used to study the thermal stability of sandwich nanoplates integrated with piezoelectric layers for the first time. The influence of Kerr elastic foundation is also studied. The present model incorporates two small-scale coefficients to examine the size-dependent thermal stability response. Elastic properties of nanoplate made of functionally graded materials (FGMs) are supposed to vary through the thickness direction and are estimated employing a modified power-law rule in which the porosity with even type of distribution is approximated. The governing differential equations of embedded sandwich piezoelectric porous nanoplates under hygrothermal loading are derived through Hamilton's principle where the Galerkin method is applied to solve the stability problem of the nanoplates with simply-supported edges. It is indicated that the thermal stability characteristics of the porous nanoplates are obviously influenced by the porosity volume fraction and material variation, nonlocal parameter, strain gradient parameter, geometry of the nanoplate, external voltage, temperature and humidity variations, and elastic foundation parameters.

• Advances in nano research
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• v.7 no.5
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• pp.325-335
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• 2019

In the present study, nonlocal strain gradient theory (NSGT) is developed for wave propagation of functionally graded (FG) nanoscale plate in the thermal environment by considering the porosity effect. $Si_3N_4$ as ceramic phase and SUS304 as metal phase are regarded to be constitutive material of FG nanoplate. The porosity effect is taken into account on the basis of the newly extended method which considers coupling influence between Young's modulus and mass density. The motion relation is derived by applying Hamilton's principle. NSGT is implemented in order to account for small size effect. Wave frequency and phase velocity are obtained by solving the problem via an analytical method. The effects of different parameters such as porosity coefficient, gradient index, wave number, scale factor and temperature change on phase velocity and wave frequency of FG porous nanoplate have been examined and been presented in a group of illustrations.

• Coupled systems mechanics
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• v.13 no.2
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• pp.115-132
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• 2024

This paper introduces an improved shear deformation theory for analyzing the buckling behavior of functionally graded plates subjected to varying temperatures. The transverse shear strain functions employed satisfy the stress-free condition on the plate surfaces without requiring shear correction factors. The material properties and thermal expansion coefficient of the porous functionally graded plate are assumed temperature-dependent and exhibit continuous variation throughout the thickness, following a modified power-law distribution based on the volume fractions of the constituents. Moreover, the study considers the influence of porosity distribution on the buckling of the functionally graded plates. Thermal loads are assumed to have uniform, linear, and nonlinear distributions through the thickness. The obtained results, considering the effect of porosity distribution, are compared with alternative solutions available in the existing literature. Additionally, this study provides comprehensive discussions on the influence of various parameters, emphasizing the importance of accounting for the porosity distribution in the buckling analysis of functionally graded plates.

• Structural Engineering and Mechanics
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• v.16 no.6
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• pp.695-712
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• 2003

The non-linear structural analysis of reinforced concrete beams in fire consists of three separate steps: (i) The estimation of the rise of surrounding air temperature due to fire; (ii) the determination of the distribution of the temperature within the beam during fire; (iii) the evaluation of the mechanical response due to simultaneous time-dependent thermal and mechanical loads. Steps (ii) and (iii) are dealt with in the present paper. We present a two-step computational procedure where a 2D transient thermal analysis over the cross-sections of beams are made first, followed by mechanical analysis of the structure. Fundamental to the accuracy of the mechanical analysis is a new planar beam finite element. The effects of plasticity in concrete, and plasticity and viscous creep in steel are taken into consideration. The properties of concrete and steel along with the values of their thermal and mechanical parameters are taken according to the European standard ENV 1992-1-2 (1995). The comparison of our numerical and full-scale experimental results shows that the proposed mechanical and 2D thermal computational procedure is capable to describe the actual response of reinforced concrete beam structures to fire.