The Effect of Radiation Heat Transfer on the Thermal Conductivity Measurement of the Infrared Transmitting Materials

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.

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Convection–radiation heat transfer study of moving fin with temperature-dependent thermal conductivity, heat transfer coefficient and heat generation

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2016.04.121 ◽

2016 ◽

Vol 103 ◽

pp. 705-712 ◽

Cited By ~ 44

Author(s):

A.S. Dogonchi ◽

D.D. Ganji

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Heat Generation ◽

Radiation Heat Transfer ◽

Radiation Heat ◽

Temperature Dependent ◽

Temperature Dependent Thermal Conductivity ◽

Transfer Study

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Heat Transfer Across Opaque Fibers

Journal of Heat Transfer ◽

10.1115/1.4006035 ◽

2012 ◽

Vol 134 (7) ◽

Cited By ~ 1

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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