Determination of Radiative Fluxes in an Absorbing, Emitting, and Scattering Vapor Formed by Laser Irradiation

1991 ◽  
Vol 113 (4) ◽  
pp. 939-945 ◽  
Author(s):  
P. Erpelding ◽  
A. Minardi ◽  
P. J. Bishop
Keyword(s):  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Heat Fluxes ◽  
Radiative Properties ◽  
Medium Temperature ◽  
Radiative Fluxes ◽  
Factors Affecting ◽  
Axial Heat ◽  
Significant Factors

A two-dimensional computer model is developed to determine the radiative heat flux distributions within the vapor formed above a metal target irradiated by a laser beam. An axisymmetric cylindrical enclosure containing a radiatively participating medium is considered. Scattering is assumed to be isotropic and allowances are made for variation of the radiative properties of the medium and boundaries. The P-1 and P-3 spherical harmonics approximations are used to solve the integro-differential radiative transfer equation. The resulting equations are then solved for the radial and axial heat fluxes using a finite-difference algorithm. The most significant factors affecting the results obtained from both the P-1 and P-3 approximations were the optical thickness of the medium and the type of laser profile incident upon the medium. Using different wall reflectivities and scattering albedos had a smaller effect. Changing the medium temperature had an insignificant effect as long as medium temperatures were below 20,000 K.

scholarly journals Assessing the Role of Particles in Radiative Heat Transfer during Oxy-Combustion of Coal and Biomass Blends

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Caitlyn Wolf
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Test Facility ◽  
Biomass Combustion ◽  
Radiative Fluxes ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Fuel Fragmentation

This study assesses the required fidelities in modeling particle radiative properties and particle size distributions (PSDs) of combusting particles in Computational Fluid Dynamics (CFD) investigations of radiative heat transfer during oxy-combustion of coal and biomass blends. Simulations of air and oxy-combustion of coal/biomass blends in a 0.5 MW combustion test facility were carried out and compared against recent measurements of incident radiative fluxes. The prediction variations to the combusting particle radiative properties, particle swelling during devolatilization, scattering phase function, biomass devolatilization models, and the resolution (diameter intervals) employed in the fuel PSD were assessed. While the wall incident radiative flux predictions compared reasonably well with the experimental measurements, accounting for the variations in the fuel, char and ash radiative properties were deemed to be important as they strongly influenced the incident radiative fluxes and the temperature predictions in these strongly radiating flames. In addition, particle swelling and the diameter intervals also influenced the incident radiative fluxes primarily by impacting the particle extinction coefficients. This study highlights the necessity for careful selection of particle radiative property, and diameter interval parameters and the need for fuel fragmentation models to adequately predict the fly ash PSD in CFD simulations of coal/biomass combustion.

Radiative Heat Transfer Using Isotropic Scaling Approximation: Application to Fibrous Medium

2004 ◽  
Author(s):  
Herve´ T. Kamdem Tagne ◽  
Dominique Doermann Baillis
Keyword(s):  
Heat Transfer ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Scattering Problem ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Fibrous Medium

The applicability of the isotropic scaling approximation to heat transfer analysis in fibrous medium is discussed. The isotropic scaling model allows the transformation of an anisotropic scattering problem to an isotropic one. The scaled parameters are derived for general anisotropic scattering and for radiative properties dependent of the incidence direction such as for fibrous medium. The fibers are randomly oriented either in space or parallel to the boundaries of the medium. The radiative transfer equation is solved with the discrete ordinate method and comparisons between the exact and the isotropic scaling problems for several Gauss quadrature are studied.

ΕΞΕΤΑΣΗ ΦΑΙΝΟΜΕΝΩΝ ΘΕΡΜΙΚΗΣ ΑΚΤΙΝΟΒΟΛΙΑΣ ΣΕ ΕΣΤΙΕΣ ΣΤΕΡΕΟΥ ΚΑΥΣΙΜΟΥ

1998 ◽  
Author(s):  
Ιωάννης Μαράκης
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Operating Conditions ◽  
Radiative Properties ◽  
Band Model ◽  
Combustion Chambers ◽  
Practical Applications

THEMATIC AREA OF THIS THESIS IS THE HEAT TRANSFER IN COMBUSTION CHAMBERS. THE ORIGINALITY ITEMS ARE CONCERNED WITH THE DEVELOPMENT OF ACCURATE METHODS BOTH FOR THE CALCULATION OF THE FLUE GAS AND COMBUSTION PARTICLE RADIATIVE PROPERTIES, AS WELL AS THE SOLUTION OF THE RADIATIVE TRANSFER EQUATION IN FURNACE - LIKE ENCLOSURES. SPECIFICALLY, THIS WORK CONTRIBUTES TO THE EXACT DETERMINATION OF THE INFLUENCE THAT THE TEMPERATURE AND PRESSURE OPERATING CONDITIONS HAVE ON THE RADIATIVE FLUXES AND SOURCE TERMS, THE LATTER BEING THE NET THERMAL ENERGY EMITTED OR ABSORBED PER UNIT VOLUME. THE THESIS INCLUDES THE DEVELOPMENT OF TWO METHODS FOR THE SOLUTION OF THE RADIATIVE TRANSFER EQUATION (A MONTE CARLO VARIANT AND A NEW INTEGRAL METHOD NAMED DIRECT NUMERICAL INTEGRATION),TWO STATISTICAL NARROW BAND AND A WIDE BAND MODEL FOR THE CALCULATION OF THE NON - GRAY GAS SPECTRAL TRANSMISSIVITY, AN ALGORITHM BASED ON MIE THEORY FOR THE DETERMINATION OF THE ABSORPTION AND SCATTERING COEFFICIENTS, THE PHASE FUNCTION AND THE ASYMMETRY PARAMETER OF COAL, CHAR, FLY - ASH AND SOOT PARTICLES AND CORRELATIONS FOR THE RESPECTIVE SPECTRAL OPTICAL PROPERTIES. THE EXACT SOLUTION OF THE THERMAL RADIATION TRANSFER HAS SIGNIFICANT PRACTICAL APPLICATIONS, SUCH AS: 1) DESIGN OF COMBUSTION CHAMBERS AND HEAT TRANSFER SURFACES, 2) DETERMINATION OF THE RADIATIVE FLUX AT THE BOUNDARIES OF A GIVEN GEOMETRY (ABSTRACT TRUNCATED)

scholarly journals The determinational manifestations of individual personality characteristics as factors that influence the motivation of educational activities of adolescents

KANT ◽  
2020 ◽  
Vol 36 (3) ◽  
pp. 263-268
Author(s):  
Anastasia Egorova ◽  
Sergey Bobryshov
Keyword(s):  
Educational Process ◽  
Personality Characteristics ◽  
Educational Activity ◽  
Educational Activities ◽  
Factors Affecting ◽  
Individual Personality ◽  
Gender Characteristics ◽  
And Gender ◽  
Significant Factors

The article is devoted to the problem of determination of the manifestation of a number of individual personality characteristics - the age of students, their temperament, gender, extroversion or introversion-in the aspect of their impact on the formation and expression of parameters of educational motives. The areas of motivational sphere of students in adolescence that are most affected by them are identified. The specific manifestations of these characteristics in schoolchildren as significant factors affecting the motivation of learning are revealed, it is shown how they determine the modality of procedural and content parameters of educational activity. It is proved that the teacher's choice of motives for educational activities to achieve the highest results in it should be based on the whole complex of General and specific age and gender characteristics of the student, key manifestations of his temperament, and attribution to the type of extroverts or introverts. It is argued that the construction of the educational process requires a unified approach to establishing and evaluating the nature of the expression of the presented factors in their inter-determination. Recommendations are given on the choice of ways to account for them, control them, and adapt them to the objective requirements of motivating educational activities.

Effect of Recycle on Radiative Heat Transfer in the Freeboard of a Fluidized Bed Combustor

2005 ◽  
Author(s):  
Nevin Selc¸uk ◽  
Isil Ayranci ◽  
Yusuf Gogebakan
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Method Of Lines ◽  
Heat Fluxes ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Bubbling Fluidized Bed ◽  
Fluidized Bed Combustor

Effect of recycle on radiative heat transfer in the freeboard of a fluidized bed combustor is investigated by applying a previously developed 3-D radiation model to the prediction of incident radiative heat fluxes along the freeboard walls of lignite-fired 0.3 MWt Middle East Technical University (METU) Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) Test Rig and comparing its predictions with measurements. Freeboard is treated as a rectangular enclosure containing gray, absorbing, emitting and isotropically scattering medium bounded by gray and diffuse walls. Radiative properties of the medium are calculated by using Leckner’s correlations for gas and Mie theory for polydisperse particle cloud. Radiative transfer equation for this system is solved by using Method of Lines (MOL) solution of Discrete Ordinates Method (DOM). Experimental data required for application and validation are generated from two runs in which parameters other than recycle ratio was held as nearly constant as possible. Comparisons between predicted incident radiative heat fluxes and measurements with and without recycle reveal that the agreement is excellent and that the effect of recycle on incident radiative heat fluxes is significant. A parametric study is also carried out to investigate the effect of particle load on fluxes. Predictions are found to be relatively insensitive to the particle load but strongly affected by the temperature profile.

An Economic Approach to Abortion Demand

1992 ◽  
Vol 36 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Donna S. Rothstein
Keyword(s):  
Cross Section ◽  
Divorce Rate ◽  
Single Women ◽  
Economic Approach ◽  
Factors Affecting ◽  
Abortion Demand ◽  
Regression Techniques ◽  
Per Capita ◽  
Significant Factors

This paper uses econometric multiple regression techniques in order to analyze the socioeconomic factors affecting the demand for abortion for the year 1985. A cross-section of the 50 states and Washington D.C. is examined and a household choice theoretical framework is utilized. The results suggest that average price of abortion, disposable personal per capita income, percentage of single women, whether abortions are state funded, unemployment rate, divorce rate, and if the state is located in the far West, are statistically significant factors in the determination of the demand for abortion.

Sphere-to-Sphere Radiative Transfer Coefficient for Packed Sphere System

2001 ◽  
Author(s):  
S. H.-K. Lee ◽  
S. C.-H. Ip ◽  
A. K. C. Wu
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Transfer Coefficient ◽  
Radiative Heat Transfer ◽  
Transfer Equation ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Radiative Properties ◽  
Equation Approach ◽  
Packed Sphere

Abstract Rapid sintering is one of the most attractive metalworking technologies due to its ability to fabricate the final product with different microstructure in an economical manner. During this process, the high heating rate would induce a great thermal gradient to the sintering part. Such temperature differences affect the microstructure of the product, which in turn leads to the occurrence of microstructure defects. However, for this non-isothermal sintering, the present Radiative Transfer Equation approach or Units/Cells approach cannot effectively compute the temperature distributions inside the porous media, so as to predict the part defects. Cumbersome computations are needed for the Radiative Transfer Equation approach. For the Units/Cells approach, the use of regular assembly in the model limits the analysis of complex packed sphere systems. This study seeks to simplify the entire computational process for different packed sphere systems. By introducing a Radiative Transfer Coefficient (RTC) approach, the computation of radiative heat transfer within the porous bed can be enhanced. The newly introduced Radiative Transfer Coefficient is defined as the ratio of radiative energy exchange, including direct and indirect exchange, from the emitting sphere to the receiving sphere, which is a function of the system microstructure and radiative properties. A set of energy-balanced algebraic equations can then be established. With an appropriate initial energy guess for each sphere, these equations can be solved by the Gauss-Seidel iteration scheme, thereby computing the radiative heat transfer in packed sphere systems with different microstructures and radiative properties. The temperature for each sphere can therefore be computed right away. This model has been validated in different perspectives. With this RTC approach, the overall computational time required is significantly shorter, providing a set of fine-resolution temperature solution.

Modeling of dynamic mosaicism on ring chromosomes in human fibroblasts and IPSCS

2020 ◽  
pp. 12-13
Author(s):  
Т.В. Никитина ◽  
А.А. Кашеварова ◽  
М.М. Гридина ◽  
А.А. Хабарова ◽  
А.Г. Мензоров ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Human Fibroblasts ◽  
Cellular Heterogeneity ◽  
Mitotic Stability ◽  
Factors Affecting ◽  
Ring Chromosomes ◽  
Cell Clones ◽  
Mitotic Instability ◽  
Mitotic Behavior

Митотическая нестабильность кольцевых хромосом может приводить к появлению клеточных клонов с различной генетической структурой. В качестве модели нестабильности кольцевых хромосом в митозе мы использовали фибробласты от пациентов с r(8), r(13), r(18) и r(22) и полученные из них индуцированные плюрипотентные стволовые клетки (ИПСК). Линии ИПСК с r(22) имели относительно стабильный кариотип на протяжении десятков (до 60) пассажей и сохраняли неизменную структуру кольцевой хромосомы. Кариотип линий ИПСК с r(8) и r(18) на ранних пассажах стабильный, планируется его изучение на поздних пассажах. Наибольшее разнообразие кариотипа выявлено в линиях ИПСК с r(13), в которых наблюдали различные перестройки и выраженную клеточную гетерогенность. Определение факторов, влияющих на митотическую стабильность кольцевых хромосом, может иметь значение для консультирования пациентов. Mitotic instability of ring chromosomes can lead to the appearance of cell clones with different genetic structure. IPSCs from fibroblasts of patients with r(8), r(13), r(18), and r(22) were used as a model of ring chromosomes mitotic behavior. Karyotypes of iPSC lines with r(8) and r(18) have so far been evaluated only in the early passages, lines with r(22) have maintained a relatively stable karyotype up to 60 passages. The occurrence of rearrangements and cellular heterogeneity was found characteristic for r(13) iPSCs. The determination of factors affecting the ring chromosomes mitotic stability would be beneficial for the patient’s prognosis.

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