A Study of Heat Transfer Calculation Method of Reactor Vessel Metallic Insulation

2014 ◽  
Author(s):  
Yan Dapeng ◽  
Ying Luo
Keyword(s):  
Heat Transfer ◽  
Computational Model ◽  
Complex Geometry ◽  
Effective Conductivity ◽  
Radiation Heat Transfer ◽  
Reactor Vessel ◽  
View Factor ◽  
Main Mode ◽  
Modified Model ◽  
Test Result

Metallic insulation is commonly used in reactor vessel because of its resistance to radiation and corrosion. Since the main mode of heat loss of reactor vessel is thermal radiation, the ability to prevent radiation heat transfer is important for metallic insulation. But the thermal conductivity of metallic insulation is difficult to calculate owing to their complex geometry. This article uses FLUENT 14.0 to obtain the important parameter “view factor”, and then develops a computational model of effective conductivity of metallic insulation. Heat transfer test of metallic insulation was done, and the numerical simulation of metallic insulation was also performed. Based on results of test and simulation, the computational model is modified. The modified model can fit the test result better. Based on the modified model, the effective conductivity of metallic insulation increases with the increase of temperature of hot side and cold side, among which the temperature of hot side influences more. And when the temperature is high, the effective conductivity increases much faster.

Validation of the Isis-3D Computer Code for Simulating Large Pool Fires Under a Variety of Wind Conditions

2003 ◽  
Author(s):  
Miles Greiner ◽  
Ahti Sou-Anttila
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Temperature Response ◽  
Diffuse Radiation ◽  
Computer Code ◽  
Time Dependent ◽  
Fuel Vapor ◽  
View Factor ◽  
Pool Fires ◽  
Fuel Evaporation

The Isis-3D computational fluid dynamics/radiation heat transfer code was developed to simulate heat transfer from large fires. It models liquid fuel evaporation, fuel vapor and oxygen transport, chemical reaction and heat release, soot and intermediate species formation/destruction, diffuse radiation within the fire, and view factor radiation from the fire edge to nearby objects and the surroundings. Reaction rate and soot radiation parameters in Isis-3D have been selected based on experimental data. One-dimensional transient conduction modules calculate the response of simple objects engulfed in and near the flames. In this work, Isis-3D calculations were performed to simulate the conditions of three experiments that measured the temperature response of a 4.66-m-diameter culvert pipe located at the leeward edge of 18.9-m and 9.45-m diameter pool fires in crosswinds with average speeds of 2.0, 4.6 and 9.5 m/s. The measured wind conditions were used to formulate time-dependent velocity boundary conditions for a rectangular Isis-3D domain with 16,500 nodes. Isis-3D accurately calculated characteristics of the time-dependent temperature distributions in all three experiments. Accelerated simulations were also performed in which the pipe specific heat was reduced compared to the measured value by a factor of four. This artificially increased the speed at which the pipe temperature rose and allowed the simulated fire duration to be reduced by a factor of four. A 700 sec fire with moderately unsteady wind conditions was accurately simulated in 10 hours on a 2.4 GHz LINUX workstation with 0.5 GB of RAM.

Modeling the Effect of Infrared Opacifiers on Coupled Conduction-Radiation Heat Transfer in Expanded Polystyrene

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
A. Akolkar ◽  
N. Rahmatian ◽  
S. Unterberger ◽  
J. Petrasch
Keyword(s):  
Heat Transfer ◽  
Refractive Index ◽  
Effective Conductivity ◽  
Cell Model ◽  
Radiation Heat Transfer ◽  
Expanded Polystyrene ◽  
Sample Mean ◽  
Mean Error ◽  
Oblate Spheroids ◽  
Similar Density

Heat transfer properties of two expanded polystyrene (EPS) samples of similar density, one without (white) and one with graphite opacifier particles (gray), are compared. Tomographic scans are used to obtain cell sizes of the foams. Using established models for closed-cell polymer foams, the extinction coefficient and the effective thermal conductivity are obtained. The effect of opacifiers is modeled using (1) an effective refractive index for the polystyrene walls within a cell model for the EPS and (2) a superposition of extinction due to a particle cloud upon extinction predicted by the cell model, where particles are modeled as oblate spheroids, or equivalent volume, surface, or hydraulic diameter spheres. Modeled effective conductivities are compared with measurements done on a guarded hot-plate apparatus at sample mean temperatures in the range from 0 °C to 40 °C. Typically, cells of the gray EPS are about 40% larger than those of the white EPS and the cell walls in the gray EPS are thicker. The refractive index mixing model and the model with graphite opacifier particles as oblate spheroids overpredict extinction, however, the mean error in the effective conductivity predicted by the oblate spheroids model is only 2.7%. Equivalent volume/surface sphere models underpredict extinction, but still yield a low mean error in effective conductivity of around 4%. While the oblate spheroids model has a lower mean error, the computationally less expensive equivalent volume or equivalent surface models can also be recommended to model the inclusions.

Integrity Analysis of Electrical Penetration With Intense Radiation Heat Transfer by Hydrogen Diffusion Flame

2017 ◽  
Author(s):  
Gaofeng Huang ◽  
Kun Zhang ◽  
Jiayun Wang
Keyword(s):  
Heat Transfer ◽  
Diffusion Flame ◽  
Hydrogen Diffusion ◽  
Hot Spot ◽  
Radiation Heat Transfer ◽  
Hydrogen Release ◽  
Heat Radiation ◽  
View Factor ◽  
Containment Vessel ◽  
Integrity Analysis

While hydrogen release into large compartment from confined compartment, hydrogen diffusion flame is easy to occur. There is intense heat radiation effect on electrical penetration from diffusion flame. Aim to evaluate the influence of diffusion flame on electrical penetration, systematic method is constructed, including computing view factor of electrical penetration, assessment of hot spot of containment vessel and research of heat transfer for electrical penetration. Research results give theory basis for determining location of venting which can generate hydrogen diffusion flame. The method can be extended to use in the influence evaluation of personnel hatch and equipment hatch in the containment vessel.

A Numerical Investigation of Ray Tracing Method in a View Factor Calculation Procedure for Zonal Radiation Heat Transfer in Complex Systems

2009 ◽  
Author(s):  
German Malikov ◽  
Vladimir Lisienko ◽  
Roman Koptelov ◽  
Jakov Kalugin ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Ray Tracing ◽  
Direct Method ◽  
Radiation Heat Transfer ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
View Factor ◽  
Radiation Heat ◽  
Zonal Method ◽  
Metallurgical Furnaces

In this paper a variety of well known computer graphics algorithms (Binary Spatial Partitioning-BSP, Bounding Box-BB, and direct method of sequential search) for ray tracing are studied numerically in the context of the view factor calculations for the zonal method of radiation heat transfer analysis in complex industrial furnace geometries. The paper reports on a modified BSP algorithm which takes into account the specific types of obstructions and their arrangement in different types of metallurgical furnaces. The modified algorithm enhances the ray tracing calculations by two to three orders of magnitude. An universal algorithm to obtain an intersection with a polyhedron obstruction is developed. The method is tested for simple three dimensional and complex furnace geometries.

scholarly journals Radiation Heat Transfer in a Complex Geometry Containing Anisotropically-Scattering Mie Particles

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3986 ◽  
Author(s):  
Ali Ettaleb ◽  
Mohamed Abbassi ◽  
Habib Farhat ◽  
Kamel Guedri ◽  
Ahmed Omri ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fly Ash ◽  
Complex Geometry ◽  
Radiation Heat Transfer ◽  
Solid Particles ◽  
Isotropic Scattering ◽  
Isotropic Case ◽  
Radiation Heat ◽  
Radiation Heat Flux

This study aims to numerically investigate the radiation heat transfer in a complex, 3-D biomass pyrolysis reactor which is consisted of two pyrolysis chambers and a heat recuperator. The medium assumes to be gray, absorbs, emits, and Mie-anisotropically scatters the radiation energy. The finite volume method (FVM) is applied to solve the radiation transfer equation (RTE) using the step scheme. To treat the complex geometry, the blocked-off-region procedure is employed. Mie equations (ME) are applied to evaluate the scattering phase function and analyze the angular distribution of the anisotropically scattered radiation by particles. In this study, three different states are considered to test the anisotropic scattering impacts on the temperature and radiation heat flux distribution. These states are as: (i) Isotropic scattering, (ii) forward and backward scattering and (iii) scattering with solid particles of different coals and fly ash. The outcomes demonstrate that the radiation heat flux enhances by an increment of the albedo and absorption coefficients for the coals and fly ash, unlike the isotropic case and the forward and backward scattering functions. Moreover, the particle size parameter does not have an important influence on the radiation heat flux, when the medium is thin optical. Its effect is more noticeable for higher extinction coefficients.

Eight Surfaces of Radiation Heat Transfer Network Model Development

2013 ◽  
Vol 391 ◽  
pp. 191-195 ◽  
Author(s):  
Ummi Kalthum Ibrahim ◽  
Ruzitah Mohd Salleh ◽  
W. Zhou
Keyword(s):  
Heat Transfer ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Radiative Heat ◽  
Radiation Heat Transfer ◽  
Model Development ◽  
Transfer Model ◽  
View Factor ◽  
Radiation Heat

This paper deals with the numerical solution for radiative heat transfer within a heated six wall surfaces baking oven, baking tin surface and bread surface. The radiation heat transfer model is constructed by adopting a radiation network representation analysis. The analysis applies view factor and radiosity in determining the radiation rates for each surface in the oven. The amount of radiation heat, q and temperature, T variables are equivalent to electric current and voltage, respectively. Finite difference method coupled with Gauss-Seidel iteration was selected to solve the equations involved in the analysis. Even though this method is tedious and intractable for multiple surfaces, but it would seem to be the most accurate and suitable approach for radiation analysis in the enclosure.

Optimum Spacing of Vertical Parallel Plates for Maximum Radiation Heat Transfer

2014 ◽  
Author(s):  
Hanry Issavi ◽  
Fred Barez ◽  
Younes Shabany ◽  
Ernest Thurlow
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Radiation Heat Transfer ◽  
Convection Heat Transfer ◽  
View Factor ◽  
Parallel Plates ◽  
Radiation Heat ◽  
Parabolic Distribution ◽  
Optimum Spacing ◽  
Exact Correlation

The reliability of the majority of electrical and electromechanical systems depends on their ability to dissipate heat generated by their internal components. Application of parallel plates for cooling electronic equipment is one of the most common methods of heat dissipation through convection and radiation. Others have investigated the optimum spacing between vertical plates for the case of maximum natural convection heat transfer. The goal of this study was to determine the optimum spacing for the maximum radiation heat transfer. Analytic calculations were carried out to determine the optimum spacing. A mathematical interpolation was used to simplify the view factor correlations and from this an exact correlation was obtained to determine the optimum spacing for radiation heat transfer. It was concluded that for a known plate surface area, the optimum spacing for the maximum radiation decreases when the ratio of height over length of the plates increases. For fixed geometric parameters, the optimum spacing for radiation will display a skewed parabolic distribution when the surface emissivity of the plates was increased.

A Study of GDC-Based Micro Tubular SOFC

2010 ◽  
Vol 638-642 ◽  
pp. 1152-1157 ◽  
Author(s):  
Nigel Sammes ◽  
J. Song ◽  
B. Roy ◽  
K. Galloway ◽  
Toshio Suzuki ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Computational Model ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Species Transport ◽  
Transfer Flow

In this work, we studied a NiO/GDC-GDC-LSCF micro-tubular SOFC system using saturated hydrogen at 450-550 oC. The systems were electrochemically and mechanically tested using a number of different methodologies, and were modeled using a 2D axial symmetric steady state non-isothermal computational model incorporating radiation heat transfer, flow and species transport.

A Flexible Thermal Model for Solar Cavity Receivers Using Analytical View Factors

2021 ◽  
Author(s):  
Jacob A. Kerkhoff ◽  
Michael J. Wagner
Keyword(s):  
Heat Transfer ◽  
Thermal Model ◽  
Radiation Heat Transfer ◽  
Heat Transfer Fluid ◽  
Connectivity Matrix ◽  
Transfer Model ◽  
View Factor ◽  
Fluid Temperature ◽  
Computationally Efficient ◽  
View Factors

Abstract This paper presents advances to a thermal model for a cavity-type receiver that will be integrated into NREL’s System Advisor Model (SAM) software. Traditional concentrated solar power towers make use of an external cylindrical receiver where all active surfaces are fully exposed to the environment, resulting in significant convective and radiative losses. Cavity-type receivers promise to mitigate these losses by instead accepting solar flux through an aperture. In order to allow detailed resolution of the temperature distribution across the cavity, it is necessary to create refined meshes for different cavity geometries and determine the view factor accurately and quickly between any two elements in the mesh. To accomplish this, an analytical function is written to precisely calculate view factors between arbitrary planar polygons without requiring the use of computationally expensive Monte Carlo ray tracing. These view factors are modified using the F-hat method and used as the basis for a two-band radiation heat transfer model. Heat transfer fluid routing is handled through an elemental connectivity matrix, which specifies the elemental fluid temperature variation from inlet to outlet and allows the cavity mesh to interact with the fluid elements. The model is solved iteratively for panel and then fluid temperatures in order to account simultaneously for all energy transfers (convective, long wavelength, short wavelength, and fluid). This approach offers a computationally efficient but still detailed simulation of cavity receiver configurations making it suitable for use in an annual-hourly time series simulation tool such as SAM.

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