Discrete Ordinates Method for Transient Radiation Transfer in Cylindrical Enclosures

2003 ◽  
Author(s):  
Kyunghan Kim ◽  
Zhixiong Guo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat ◽  
Radiation Transfer ◽  
Radiation Heat Transfer ◽  
Discrete Ordinates ◽  
Radiation Heat ◽  
Discrete Ordinates Method ◽  
Transient Radiation ◽  
Tissue Welding

The Discrete Ordinates Method (DOM) for solving transient radiation transfer equation in cylindrical coordinates is developed for radiation heat transfer in participating turbid media in pico-scale time domain. The application problems addressed here are laser tissue welding and soldering. The novelty of this study lies with the use of ultrashort laser pulses as the irradiation source. The characteristics of transient radiation heat transfer in ultrafast laser tissue welding and soldering are studied with the DOM developed. The temporal distribution of radiative energy inside the tissue cylinder as well as the radiative heat flux on the tissue surface is obtained. Comparisons are performed between laser welding without use of solder and laser soldering with use of solder. The use of solder is found to have highly concentrated radiation energy deposition in the solder-stained region and reduce the surface radiative heat flux accordingly. Comparisons of transient radiation heat transfer between the spatially square-variance and Gaussian-variance laser inputs and between the temporally Gaussian and skewed input profiles are also conducted.

scholarly journals Reduced Order Modeling Applied to the Discrete Ordinates Method for Radiation Heat Transfer in Participating Media

2016 ◽  
Author(s):  
John Tencer ◽  
Kevin Carlberg ◽  
Roy Hogan ◽  
Marvin Larsen
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Practical Interest ◽  
Accurate Solution ◽  
Discrete Ordinates ◽  
Test Problems ◽  
Radiation Heat ◽  
Reduced Basis ◽  
Participating Media ◽  
Discrete Ordinates Method

Radiation heat transfer is an important phenomenon in many physical systems of practical interest. When participating media is important, the radiative transfer equation (RTE) must be solved for the radiative intensity as a function of location, time, direction, and wavelength. In many heat transfer applications, a quasi-steady assumption is valid. The dependence on wavelength is often treated through a weighted sum of gray gases type approach. The discrete ordinates method is the most common method for approximating the angular dependence. In the discrete ordinates method, the intensity is solved exactly for a finite number of discrete directions, and integrals over the angular space are accomplished through a quadrature rule. In this work, a projection-based model reduction approach is applied to the discrete ordinates method. A small number or ordinate directions are used to construct the reduced basis. The reduced model is then queried at the quadrature points for a high order quadrature in order to inexpensively approximate this highly accurate solution. This results in a much more accurate solution than can be achieved by the low-order quadrature alone. One-, two-, and three-dimensional test problems are presented.

On the Entropy Generation Formula of Radiation Heat Transfer Processes

2005 ◽  
Vol 128 (5) ◽  
pp. 504-506 ◽  
Author(s):  
L. H. Liu ◽  
S. X. Chu
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Radiative Heat ◽  
Radiation Heat Transfer ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Discrete Ordinates ◽  
Local Entropy ◽  
Radiation Heat ◽  
Local Entropy Generation

Because thermal radiation is a long-range phenomenon, the local radiative heat flux is dependent on the temperature distribution of the entire enclosure under consideration and is not determined by the local temperature gradient. In the community of heat transfer, traditionally, the conduction-type formula of entropy generation rate is used to calculate the entropy generation rate of radiation heat transfer. In the present study, three counterexamples are considered. The discrete ordinates method is employed to solve the radiative transfer equation and then solve the radiative entropy generation rate. The results show that the traditional formulas of entropy generation rate for heat transfer generally cannot be used to calculate the local entropy generation rate of radiation heat transfer. Only in optically extremely thick situations, the traditional formula of entropy generation rate for heat transfer can be approximately used to calculate the local entropy generation rate of radiation heat transfer.

Investigation of Luminous/Nonluminous Radiation in a Vortex Engine

2007 ◽  
Author(s):  
M. H. Saidi ◽  
M. Kargar ◽  
A. Ghafourian
Keyword(s):  
Heat Transfer ◽  
Outer Surface ◽  
Direct Contact ◽  
Radiative Heat ◽  
Radiation Heat Transfer ◽  
Axial Flow ◽  
Chamber Wall ◽  
Radiation Heat ◽  
Insulating Material ◽  
Quartz Window

Investigation of radiation heat transfer In vortex engine is an important and new phenomenon in combustion for scientists and combustion researchers. In this research some parts of the combustion chamber wall are insulated using Blanket as a high insulating material. The rate of radiative heat transfer to the chamber wall is calculated using temperature difference between inner and outer surface of chamber. In the experiments this parts are protected from direct contact with hot combustion media using quartz window. The luminous radiative transfer per volume of chamber and also volume of flame in a vortex engine are compared with that in a similar axial flow type engine. A detector sensitive to emission from C2* excited radically is utilized for the measurement of chemiluminescence emission at the centerline of chamber along all axial positions. The filtered photographs of flame are used to compare total C2* emission from flame.

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