scholarly journals The Effect of Radiation Heat Transfer in the Measurement of Thermal Conductivity for the Semitransparent Medium

1976 ◽  
Vol 19 (134) ◽  
pp. 973-979 ◽  
Author(s):  
Masaaki KURIYAMA ◽  
Kozo KATAYAMA ◽  
Yoshiyuki TAKUMA ◽  
Yasushi HASEGAWA
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Semitransparent Medium

scholarly journals Diffusion Approximation to Radiation Heat Transfer in Semitransparent Medium

2016 ◽  
Vol 34 (1-2) ◽  
pp. 25-37
Author(s):  
Harihar Khanal ◽  
Kedar Nath Uprety
Keyword(s):  
Heat Transfer ◽  
Transfer Problem ◽  
Diffusion Theory ◽  
Radiation Heat Transfer ◽  
Coupled System ◽  
Radiation Heat ◽  
Parabolic Pdes ◽  
Highly Nonlinear ◽  
Semitransparent Medium ◽  
Limited Diffusion

Conduction-radiation heat transfer problem is usually formulated with a highly nonlinear integrodifferential equation. In this paper we describe a simple technique for modeling radiation heat transfer in a semi-transparent medium with arbitrary varying spectral absorption coefficient and purpose a computational model (described by a coupled system of elliptic-parabolic PDEs) based on flux limited diffusion theory. Numerical simulations of a glass cooling problem in one dimension show that the proposed method is comparable to a higher order discrete ordinate (S8) method.

scholarly journals Numerical Study of Entropy Generation due to Coupled Laminar and Turbulent Mixed Convection and Thermal Radiation in an Enclosure Filled with a Semitransparent Medium

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
M. Goodarzi ◽  
M. R. Safaei ◽  
Hakan F. Oztop ◽  
A. Karimipour ◽  
E. Sadeghinezhad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Semitransparent Medium

The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNGk-εmodel and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (104) and turbulent flow (108). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible.

Development of hybrid method for coupled conduction-radiation heat transfer in two-dimensional irregular enclosure considering thermo-radiative effects and varying thermal conductivity

2019 ◽  
Vol 30 (4) ◽  
pp. 1815-1837
Author(s):  
Mehdi Zare ◽  
Sadegh Sadeghi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Source ◽  
Radiation Heat Transfer ◽  
Isotropic Scattering ◽  
Two Dimensional ◽  
Radiation Heat ◽  
Content Type ◽  
Irregular Enclosure

Purpose This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source. Design/methodology/approach For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium. Findings DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied. Originality/value In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.

Heat Transfer Across Opaque Fibers

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Krishpersad Manohar ◽  
Gurmohan S. Kochhar ◽  
David W. Yarbrough
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Fiber Diameter ◽  
Radiation Heat Transfer ◽  
Physical Parameters ◽  
Density Range ◽  
Radiation Heat ◽  
Apparent Thermal Conductivity ◽  
Air Conduction

Predicting the thermal conductivity of loose-fill fibrous thermal insulation is a complex problem, when considering the combined conduction, convection, and radiation heat transfer within a scattering, emitting, and absorbing medium. A piecewise model for predicting the overall apparent thermal conductivity of large diameter opaque fibrous materials was developed by considering the radiation heat transfer, solid conduction and air conduction components separately. The model utilized the physical parameters of emissivity, the density of the solid fiber material, the percentage composition and range of fiber diameter, and the mean fiber diameter to develop specific equations for piecewise contribution from radiation, solid fiber conduction, and air conduction toward the overall effective thermal conductivity. It can be used to predict the overall apparent thermal conductivity for any opaque fibrous specimen of density (ρ), known thickness (t), mean temperature (T), and temperature gradient (ΔΤ). Thermal conductivity measurements were conducted in accordance with ASTM C518 specifications on 52 mm thick, 254 mm square test specimens for coconut and sugarcane fibers. The test apparatus provided results with an accuracy of 1%, repeatability of 0.2%, and reproducibility of 0.5%. The model was applied to and compared with experimental data for coconut and sugarcane fiber specimens and predicted the apparent thermal conductivity within 7% of experimental data over the density range tested. The model also predicted the optimum density range for both coconut and sugarcane fibers.

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