scholarly journals A detailed radiation heat transfer study of a dish-Stirling receiver: The impact of cavity wall radiation properties and cavity shapes

2016 ◽  
Author(s):  
Jorge Garrido ◽  
Wujun Wang ◽  
Martin Nilsson ◽  
Björn Laumert
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Cavity Wall ◽  
Radiation Heat ◽  
Radiation Properties ◽  
The Impact ◽  
Transfer Study

scholarly journals Radiation heat transfer between human and cryocabin walls

2021 ◽  
Vol 2119 (1) ◽  
pp. 012146
Author(s):  
I A Burkov ◽  
S I Khutsieva ◽  
V A Voronov
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Human Body ◽  
Transfer Problem ◽  
Radiation Heat Transfer ◽  
Vertical Wall ◽  
Heat Transfer Problem ◽  
Radiation Heat ◽  
The Impact

Abstract The paper considers the particular case of intensive radiation heat transfer in the system consisting of a human body and cryocabin walls of cryosauna. Calculations for three models have been made, namely, human-vertical wall, which is arranged parallel to a human, human-vertical wall, which is positioned at a certain angle, and a human-cryosauna. Analytical calculations are compared with Ansys-bassed numerical calculations. The impact of radiation heat transfer in this radiation-convective heat transfer problem is estimated. Conclusions are drawn about taking into account the radiation heat transfer and a rational method for calculating this heat transfer problem.

scholarly journals Numerical simulation of reacting flow in the combustion chamber and study of the impact of turbulent diffusion coefficients

2020 ◽  
Vol 12 (9) ◽  
pp. 168781402095497
Author(s):  
Evgenij Strokach ◽  
Igor Borovik ◽  
Fang Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Chemical Reactions ◽  
Turbulence Model ◽  
Turbulent Diffusion ◽  
Diffusion Coefficients ◽  
Radiation Heat Transfer ◽  
Mixing Efficiency ◽  
Radiation Heat ◽  
The Impact

A methodology for combustion modeling with complex mixing and thermodynamic conditions, especially in thrusters, is still under development. The resulting flow and propulsion parameters strongly depend on the models used, especially on the turbulence model as it determines the mixing efficiency. In this paper, the effect of the sigma-type turbulent diffusion coefficients arriving in the diffusion term of the turbulence model is studied. This study was performed using complex modeling, considering the conjugate effect of several physical phenomena such as turbulence, chemical reactions, and radiation heat transfer. To consider the varying turbulent Prandtl, an algebraic model was implemented. An adiabatic steady diffusion Flamelet approach was used to model chemical reactions. The P1 differential model with a WSGG spectral model was used for radiation heat transfer. The gaseous oxygen (GOX) and methane (GCH4) operating thruster developed at the Chair of turbomachinery and Flight propulsion of the Technical University of Munich (TUM) is taken as a test case. The studies use the 3D RANS approach using the 60° sector as the modeling domain. The normalized and absolute pressures, the integral and segment averaged heat flux are compared to numerical results. The wall heat fluxes and pressure distributions show good agreement with the experimental data, while the turbulent diffusion coefficients mostly influence the heat flux.

An Experimental Study of Radiation Heat Transfer From Parallel Plates With Direction-Dependent Properties

1970 ◽  
Vol 92 (4) ◽  
pp. 610-615 ◽  
Author(s):  
W. Z. Black ◽  
R. J. Schoenhals
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Radiation Heat Transfer ◽  
Parallel Plates ◽  
Radiation Heat ◽  
Emission Pattern ◽  
Potential Value ◽  
Radiation Properties

An experimental study of radiation heat transfer from opposing parallel plates is described. Surfaces composed of many small grooves were used to fabricate plates having direction-dependent radiation properties. These plates possessed a collimated emission pattern which was found to influence significantly the heat transfer rate, the largest observed effects being approximately 40 percent. It appears that somewhat larger alterations could be achieved with further effort. The measurements obtained in this study establish the potential value of specially prepared surfaces for certain applications requiring improved thermal performance.

Investigation on the Impact of Angle Dependency and Polarization on Radiation Heat Transfer

2021 ◽  
Author(s):  
Mathieu Wijnen ◽  
Jos van Schijndel ◽  
Gunes Nakiboglu
Keyword(s):  
Heat Transfer ◽  
Semiconductor Industry ◽  
Radiation Heat Transfer ◽  
Analytical Approximation ◽  
Radiation Heat ◽  
Modeling Tools ◽  
Increasing Demand ◽  
Radiation Modeling ◽  
Reflecting Surfaces ◽  
The Impact

Abstract In the semiconductor industry there is an increasing demand for thermal stability to optimize the performance of lithography machines. This results in a need for computational tools that are able to accurately model radiation heat transfer, with the ability to include specular and angle dependent reflection and take the influence of the polarization into account. An analytical approximation model of a square passage is formulated, that includes angle dependent reflecting surfaces and the influence of polarization. These problems can be used as benchmarks to verify radiation modeling tools, e.g. COMSOL. The tool is validated by modeling an experiment and comparing the numerical results with the experimental data. The impact of angle dependency and polarization on the heat flux through passages is discussed.

scholarly journals Modeling Loss-of-Flow Accidents and Their Impact on Radiation Heat Transfer

2017 ◽  
Vol 2017 ◽  
pp. 1-15
Author(s):  
Jivan Khatry ◽  
Fatih Aydogan
Keyword(s):  
Heat Transfer ◽  
Fuel Element ◽  
Radiation Heat Transfer ◽  
Nuclear Space ◽  
Radiation Heat ◽  
Uranium Carbide ◽  
Test Reactor ◽  
Fuel Elements ◽  
The Impact

Long-term high payload missions necessitate the need for nuclear space propulsion. The National Aeronautics and Space Administration (NASA) investigated several reactor designs from 1959 to 1973 in order to develop the Nuclear Engine for Rocket Vehicle Application (NERVA). Study of planned/unplanned transients on nuclear thermal rockets is important due to the need for long-term missions. In this work, a system model based on RELAP5 is developed to simulate loss-of-flow accidents on the Pewee I test reactor. This paper investigates the radiation heat transfer between the fuel elements and the structures around it. In addition, the impact on the core fuel element temperature and average core pressure was also investigated. The following expected results were achieved: (i) greater than normal fuel element temperatures, (ii) fuel element temperatures exceeding the uranium carbide melting point, and (iii) average core pressure less than normal. Results show that the radiation heat transfer rate between fuel elements and cold surfaces increases with decreasing flow rate through the reactor system. However, radiation heat transfer decreases when there is a complete LOFA. When there is a complete LOFA, the peripheral coolant channels of the fuel elements handle most of the radiation heat transfer. A safety system needs to be designed to counteract the decay heat resulting from a post-LOFA reactor scram.

scholarly journals A Detailed Numerical Study of NOx Kinetics in Counterflow Methane Diffusion Flames: Effects of Fuel-Side versus Oxidizer-Side Dilution

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Huanhuan Xu ◽  
Fengshan Liu ◽  
Zhiqiang Wang ◽  
Xiaohan Ren ◽  
Juan Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Formation Pathway ◽  
No Formation ◽  
Combustion Properties ◽  
Methane Diffusion ◽  
The Impact

Dilution combustion has been widely utilized due to various merits, such as enhanced efficiency, fewer pollutants emissions, and even a promising future in alleviating global warming. Diluents can be introduced through the oxidizer or fuel side to achieve the desired combustion properties, and H2O and CO2 are the most common ones. A comprehensive comparison between the different dilution methods still lacks understanding and optimizes the dilution combustion technologies. This study numerically compared the effects of H2O and CO2 dilution in the oxidizer or fuel stream on counterflow methane diffusion flames, emphasizing NO formation kinetics. Results showed that the impact of different radiation heat transfer models on NO emissions diminishes with increasing the dilution ratio. The calculations of radiation heat transfer were treated in three ways: radiation-neglected, optically thin, and using a nongrey radiation model. When keeping the oxygen content and methane fraction constant, CO2 dilution in the air-side has the most profound influence on NO reduction, and CO2 dilution in the fuel-side has the least. H2O dilution showed a medium impact with a larger degree on air-side than that on fuel-side. To gain a deeper understanding of this effect order, the contributions of different NO formation routes were quantified, and analyses were made based on the diluents’ chemical and thermal effects. It was found that the oxidizer-side dilution and fuel-side dilution affect the NO formation pathway similarly. Still, the influence of H2O dilution on the NO formation pathway differs from that of CO2 dilution.

scholarly journals Assessment of radiation heat transfer influence on parameters of temperature fields of various design fuel rods

Vestnik IGEU ◽  
2021 ◽  
pp. 23-31
Author(s):  
V.A. Gorbynov ◽  
S.G. Andrianov ◽  
S.S. Konovaltseva
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Temperature Fields ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Radiation Heat ◽  
Problem Statement ◽  
Fuel Rods ◽  
Fuel Rod ◽  
The Impact

VVER-1000 reactors use cylindrical smooth-core fuel rods. Previously, a model to determe the fuel rod temperature field in a two-dimensional problem statement has been developed and verified. However, modelling assumptions do not consider the influence of variable thermophysical properties, radiation heat transfer, and the opening in the fuel rod on the final parameters of the temperature fields. The impact assessment is an urgent task to improve the economic efficiency of the fuel cycle and the capacity of power units. To develop models and study the features of energy release in nuclear reactors, a numerical package of thermophysical modeling COMSOL Multiphysics software is used. The simulation of temperature fields is performed based on the heat equation with an internal heat source, under the boundary conditions of the second kind at the ends of the fuel rod and the boundary conditions of the third kind on the side surface of the rod. Аn axisymmetric model in two-dimensional problem statement and a three-dimensional model of the fuel rod are developed. The temperature distribution fields are determined by the finite element method. The results of calculations of various design fuel rods are presented. The results have showen that the radiation heat transfer significantly affects the maximum fuel temperature (UO2). The impact degree of variability of thermophysical properties and radiation heat transfer is determined. It was found that the temperature characteristics under different specified conditions have a difference in the range of 15,5–282,0 K (0,8–14,4 %). The developed models are reliable and confirmed by the previously verified model, the characteristics of the fuel assembly used on the VVER-1000 units. The results presented can be used for mathematical modeling of heat transfer processes, both during the modernization of the equipment in operation, and during the development, design, and operation, which will increase the efficiency of electric energy generation at the power unit of a nuclear power plant.

Investigation of Spectral Radiation Heat Transfer and NOx Emission in a Glass Furnace

2000 ◽  
Author(s):  
B. Golchert ◽  
C. Q. Zhou ◽  
S. L. Chang ◽  
M. Petrick
Keyword(s):  
Heat Transfer ◽  
Glass Furnace ◽  
Radiation Heat Transfer ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Transfer Model ◽  
Radiation Heat ◽  
Spectral Radiation ◽  
Radiation Emission ◽  
The Impact

Abstract A comprehensive radiation heat transfer model and a reduced NOx kinetics model were coupled with a computational fluid dynamics (CFD) code and then used to investigate the radiation heat transfer, pollutant formation and flow characteristics in a glass furnace. The radiation model solves the spectral radiative transport equation in the combustion space of emitting and absorbing media, i.e., CO2, H2O, and soot and emission/reflection from the furnace crown. The advanced numerical scheme for calculating the radiation heat transfer is extremely effective in conserving energy between radiation emission and absorption. A parametric study was conducted to investigate the impact of operating conditions on the furnace performance with emphasis on the investigation into the formation of NOx.

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