Numerical Simulation of a Specialty Optical Fibre Drawing Process

2002 ◽  
Author(s):  
Katja Lyytika¨inen ◽  
Peter Ra˚back ◽  
Juha Ruokolainen
Keyword(s):  
Heat Transfer ◽  
Optical Fibre ◽  
Cross Sections ◽  
Radiation Heat Transfer ◽  
Drawing Process ◽  
Cross Sectional ◽  
Mass And Heat Transfer ◽  
Sectional Structure ◽  
Fibre Drawing ◽  
Surface Calculation

The present study investigates the mass and heat transfer in the optical fibre fabrication process where a specialty optical preform with a non-homogeneous cross-sectional structure is drawn into a fibre. A finite element method was used to model the steady state fibre drawing process. The model included free surface calculation of the neck-down shape of the preform coupled with a two-dimensional heat transfer equation. The enclosure model was used for the radiation heat transfer. In addition to the silica preform the model took into account the graphite-resistance furnace structure and the inert gas surrounding the preform. Fibre designs with axisymmetric cross-sections with radial variations in material properties were modeled, including air silica structures. The effect of internal air structures was found to have a significant impact on temperature distribution. The effects of drawing parameters such as draw speed, preform diameter, draw temperature and furnace structure were also studied.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Heat Transfer in Triangular Microchannels

2003 ◽  
Author(s):  
J. Todd Dickey ◽  
Tung T. Lam
Keyword(s):  
Heat Transfer ◽  
Porous Material ◽  
Cross Sections ◽  
Flow Characteristics ◽  
Microchannel Flow ◽  
Geometric Aspect ◽  
Rectangular Microchannel ◽  
Cross Sectional ◽  
Numerical Heat Transfer ◽  
Fluid Flow Characteristics

A numerical heat transfer solution is compared with an analytical solution for a microchannel flow. The analytical derivation is based upon the porous material assumption as put forth by various investigators. While extensive work exists for the rectangular microchannel cross sectional area, other cross sections have not received the same attention. It is the intent of this paper to investigate the applicability of the porous material assumption to a triangular “saw tooth” cross section microchannel with respect to heat transfer and fluid flow characteristics. The results are presented in nondimensionalized form applicable to any fluid and geometric aspect ratio combination presented herein.

Thermo-hydraulic assessment of non-Newtonian MWCNT nanofluid flows inside microchannels with different cross-sections

2021 ◽  
pp. 095440622110560
Author(s):  
AR Ramezan ◽  
A Ahmadpour ◽  
MR Hajmohammadi
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Thermal Performance ◽  
Cross Sections ◽  
Volume Fraction ◽  
Thermal Conditions ◽  
Geometrical Shape ◽  
Newtonian Viscosity ◽  
Two Phase ◽  
Cross Sectional

In the present study, the convective heat transfer of MWCNT/water nanofluid was investigated along microchannels with different cross-sectional geometries. This class of carbon-based nanofluid exhibited a notable non-Newtonian shear-thinning behavior, which made them suitable for different heat transfer applications. A two-phase mixture model with a well-tuned non-Newtonian viscosity function was adapted. The effects of the volume fraction of nanoparticles, Reynolds number, and the geometrical shape of the cross-section were examined on the pressure drop and heat transfer rate across various microchannels. The obtained results showed that the microchannel cross-section geometry had a significant effect on the thermal performance of MWCNT/water nanofluids under certain thermal conditions. Moreover, it was deduced that for all Reynolds numbers and nanoparticle volume fractions considered, the flattened geometry exhibited the most superior thermal performance, which is around 19.03% larger than the circle geometry at Re = 1000 and volume fraction of 2%.

Inverse Estimation of Main Parameters of Spectral Line-Based Weighted Sum of Gray Gases Model With Few Gray Gases to Simulate the Radiation in Nongray Media

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
A. Dehghanian ◽  
S. M. Hosseini Sarvari
Keyword(s):  
Heat Transfer ◽  
Spectral Line ◽  
Cross Sections ◽  
Radiation Heat Transfer ◽  
Noisy Data ◽  
Extreme Case ◽  
Least Square ◽  
Weighted Sum ◽  
Absorption Cross ◽  
Radiation Heat

The aim of this study is to present a reduced spectral line-based weighted sum of gray gases (SLW) model to simulate the radiation heat transfer in nongray media at high temperatures. Inverse approach is used to divide the absorption cross section band into a clear gas with one gray gas and two gray gases, which are called the S-1 and S-2 approaches, respectively. The unknown absorption cross sections are determined from the knowledge of measured total incident intensities received by wall surfaces. In order to simulate the exact solution of radiation heat transfer in nongray gaseous media, the discrete transfer method (DTM) in combination with S-20 model is used, where the nongray medium is replaced with a set of a clear gas and 20 gray gases. The inverse problem is formulated as an optimization problem to minimize a least square objective function, which is solved by the conjugate gradient method (CGM). The accuracy of the present method is verified by comparing with previous researches and the S-20 approach with a large number of gray gases. The effects of noisy data on the inverse solution are investigated by considering an extreme case with large measurement error. The results show that the unknown absorption cross sections are retrieved well, even for noisy data.

Novel method of diameter control in optical-fibre drawing process

1977 ◽  
Vol 13 (24) ◽  
pp. 726 ◽  
Author(s):  
Katsuyuki Imoto ◽  
Satoshi Aoki ◽  
Masao Sumi
Keyword(s):  
Optical Fibre ◽  
Drawing Process ◽  
Novel Method ◽  
Diameter Control ◽  
Fibre Drawing

scholarly journals Microfluidics in structured multimaterial fibers

2018 ◽  
Vol 115 (46) ◽  
pp. E10830-E10838 ◽  
Author(s):  
Rodger Yuan ◽  
Jaemyon Lee ◽  
Hao-Wei Su ◽  
Etgar Levy ◽  
Tural Khudiyev ◽  
...  
Keyword(s):  
Cross Sections ◽  
Cell Separation ◽  
Degrees Of Freedom ◽  
Microfluidic Channels ◽  
Drawing Process ◽  
Cross Sectional ◽  
Separation Device ◽  
Chip Format ◽  
External Forces ◽  
Thermal Drawing

Traditional fabrication techniques for microfluidic devices utilize a planar chip format that possesses limited control over the geometry of and materials placement around microchannel cross-sections. This imposes restrictions on the design of flow fields and external forces (electric, magnetic, piezoelectric, etc.) that can be imposed onto fluids and particles. Here we report a method of fabricating microfluidic channels with complex cross-sections. A scaled-up version of a microchannel is dimensionally reduced through a thermal drawing process, enabling the fabrication of meters-long microfluidic fibers with nonrectangular cross-sectional shapes, such as crosses, five-pointed stars, and crescents. In addition, by codrawing compatible materials, conductive domains can be integrated at arbitrary locations along channel walls. We validate this technology by studying unexplored regimes in hydrodynamic flow and by designing a high-throughput cell separation device. By enabling these degrees of freedom in microfluidic device design, fiber microfluidics provides a method to create microchannel designs that are inaccessible using planar techniques.

scholarly journals Cross-sectional structure of the central mitotic spindle of Diatoma vulgare. Evidence for specific interactions between antiparallel microtubules.

1979 ◽  
Vol 83 (2) ◽  
pp. 443-461 ◽  
Author(s):  
K L McDonald ◽  
M K Edwards ◽  
J R McIntosh
Keyword(s):  
Cross Sections ◽  
Specific Interaction ◽  
Near Neighbor ◽  
Optical Diffraction ◽  
Cross Sectional ◽  
Central Spindle ◽  
Square Packing ◽  
Spindle Elongation ◽  
Sectional Structure ◽  
Overlap Region

During the transition from prometaphase to metaphase, the cross-sectional area of the central spindle of Diatoma decreases by a factor of nearly two, both at the poles and at the region of overlapping microtubules (MTs) near the spindle equator. The density of spindle MT packing stays approximately constant throughout mitosis. Optical diffraction analysis of electron micrographs shows that the packing of the MTs at the poles at all stages of mitosis is similar to that expected for a two-dimensional liquid. Analysis of the region of overlap reveals more packing regularity: during prometaphase, a square packing emerges that displays sufficient organization by late metaphase to generate five orders of diffraction; during anaphase the packing in the overlap region shifts to hexagonal; at telophase, it returns to square. From the data provided by serial section reconstructions of the central spindle, it is possible to identify the polarity of almost every spindle MT, that is, to identify one pole with which the MT is associated. Near neighbor analyses of MTs in cross sections of the overlap region show that MTs prefer antiparallel near neighbors. These near neighbors are most often found at a spacing of approximately 40 nm center-to-center, while parallel near neighbors in the zone of overlap are spaced essentially at random. These results are evidence for a specific interaction between antiparallel MTs. In some sections definite bridges between MTs can be seen. Our findings show that certain necessary conditions for a sliding filament model of anaphase spindle elongation are met.

THE INFLUENCE OF HEAT TRANSFER ON PHYSICAL AND MECHANICAL PROPERTIES IN NONCONVENTIONAL PROCESSES OF METALLIC SOLIDS PLASTIC DEFORMATION

2002 ◽  
Vol 16 (04) ◽  
pp. 135-141
Author(s):  
MARIANA POP ◽  
TRAIAN CANTA ◽  
AUREL POP
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Mathematical Model ◽  
Plastic Deformation ◽  
Cross Sections ◽  
Physical And Mechanical Properties ◽  
Variable Cross ◽  
Drawing Process ◽  
Dieless Drawing ◽  
Temperature Strain

The aim of this paper is to present a mathematical model for the steady state of the dieless drawing process. With this model, it is possible to study the influence of various process parameters, such as temperature, strain, strain rate and stress. The paper also presents some elements of the process control for producing variable cross-sections (cone-contour and sinus-contour).

Gender determination of caucasoid hair using image analysis

1993 ◽  
Vol 51 ◽  
pp. 216-217
Author(s):  
T.B. Ball ◽  
W.M. Hess
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Scalp Hair ◽  
The Body ◽  
Equivalent Diameter ◽  
Cross Sectional ◽  
Hair Samples ◽  
Length Width ◽  
Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

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