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# Modeling of Radiation Heat Transfer in the Drawing of an Optical Fiber With Multilayer Structure

[+] Author and Article Information
Chunming Chen

Department of Mechanical and Aerospace Engineering, Rutgers,  The State University of New Jersey, New Brunswick, NJ 08903

Yogesh Jaluria

Department of Mechanical and Aerospace Engineering, Rutgers,  The State University of New Jersey, New Brunswick, NJ 08903jaluria@jove.rutgers.edu

J. Heat Transfer 129(3), 342-352 (Jul 05, 2006) (11 pages) doi:10.1115/1.2430723 History: Received January 31, 2006; Revised July 05, 2006

## Abstract

A numerical model is developed to study the radiative heat transfer in a furnace for optical fiber drawing with a core-cladding structure in the fiber. The focus is on the effect of the difference in composition and thus the radiation properties in the two regions on radiative transport. The zonal method is applied to calculate the radiative heat transfer within the neck-down region of the preform. The radiative heat transfer between the preform and the furnace is computed by an enclosure analysis. A parallel computational scheme for determining the direct exchange areas is also studied. The radiation model is verified by comparisons with benchmark problems. Numerical results for a pure silica preform, a $GeO2$-doped silica core with a pure silica cladding preform, and a pure silica core with a $B2O3$-doped silica cladding preform are presented. Radiation properties for these are obtained from the literatures and a three-band model is developed to represent the values. It is found that radiative heat flux on the surface of the preform is strongly affected by the differences in the absorption coefficient due to doping. However, changes of about 1% in the refractive index have only a small effect on radiative heat transfer. The basic approach is outlined in order to form the basis for simulating optical fiber drawing processes, which typically involve fibers and preforms with a core and a cladding. Furthermore, the approach can apply to estimate the multi-layer fiber drawing, which is of interest in the fabrication of specialty fibers that have been finding uses in a variety of practical applications. The model can be extended to other similar processes, which involve multiple regions with different radiation properties. The main interest in this study is on the approximate representation of radiation properties and on the modeling of the transport process.

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## Figures

Figure 1

Schematic diagram of a double-layer silica fiber drawing, indicating the radiosities and irradiations on the interfaces

Figure 2

Figure 3

Measured absorption coefficients of pure fused silica with low OH content, GeO2-doped silica and B2O3-doped silica (13-14)

Figure 4

Comparison of ideal speedup and actual speedup in parallel computation of the direct exchange areas

Figure 5

Plot of parallel processing efficiency versus number of processes

Figure 6

Nondimensional radiative heat transfer between two infinite concentric cylinders at radiative equilibrium. Symbols represent benchmark data (20).

Figure 7

Neck-down profiles considered

Figure 8

Comparison of nondimensional radiative heat flux calculated using the three-band model and Myers’s two-band model

Figure 9

Effects of the furnace temperature distribution

Figure 10

Effect of the neck-down profile

Figure 11

Results for different the preform temperature distributions

Figure 12

Comparisons among radiative heat fluxes for pure Silica core with B2O3-doped silica cladding, for GeO2-doped silica core with pure silica cladding, and for pure silica preforms

Figure 13

Effect of refractive index on radiative heat flux for GeO2-doped silica core with pure silica cladding preform

Figure 14

Effect of refractive index on radiative heat flux for pure silica core with B2O3-doped silica cladding preform

Figure 15

Effect of geometry on radiative heat flux for GeO2-doped silica core with pure silica cladding preform; the diameter of the core is 50μm or 62.5μm and the diameter of the cladding is 125μm

Figure 16

Effect of geometry on radiative heat flux for pure silica core with B2O3-doped silica cladding preform; the diameter of the core is 50μm or 62.5μm and the diameter of the cladding is 125μm

## Errata

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