• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.12
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• pp.652-658
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• 2015

The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.69-73
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• 2013

Mass manufacturing of optical fiber includes the process of very thin glass fiber drawing by heating and softening the high purity silica preform and applying the draw tension on the softened tip of preform neck-down profile in a draw furnace. In this computational study, this process is numerically modeled with simplified geometry of the draw furnace which is comprised of essential parts such as concentric graphite heater, muffle tube, and insulation surrounding the heater. The iterative computational scheme is employed between one-dimensional model of neck-down profile prediction and two-dimensional axisymmetric thermo-fluid CFD computation of radiative heating and working gas convection. The computational results show the experimentally observed neck-down profile in heated section of preform, while yielding the reasonable values of draw tension and heater wattage. Also, this study analyzes and discusses the effects of heating conditions such as heater length and temperature on several important aspects of glass fiber drawing process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.975-980
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• 2001

The thermal analysis of the hot roller in a dry film laminator is studied numerically by steady-state two-dimensional heat transfer. In the laminating process for PDP glass or PCB, the temperature distributions in a hot roller are presented considering the effects of the roller rotation speed and the inner and outer radii of the roller. The results show that the temperature distributions are strongly dependent on Peclet number. If Pe number becomes larger, the iso-thermal lines are more concentric about the rotating axis and the temperature difference on the hot roller surface decreases exponentially. It also shows that if the contact angle between the roller and the film becomes smaller the temperature difference becomes smaller. However, the changes of the rollers inner or outer radius have little effect on the temperature difference.