Browsing by Author "Lin, Wei-Keng"

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A NOVEL LIQUID-PACKAGING TECHNOLOGY FOR HIGHLY RELIABLE UV-LED ENCAPSULATION
(2019-01-01)
Zhang, Wen-Hua
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Lin, Wei-Keng
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Yeh, Chih-Ting
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Chiang, Song-Bor
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Jao, Chih-Sheng
This paper proposes a liquid-packaging technology for UV LED. Unlike the traditional packaging methods that involve thermosetting silicon or quartz glass, the proposed method primarily uses silicon oil to directly contact the chip, which prevents erosion due to moisture or oxygen. In this study, UV LEDs with high heat dissipation technology were selected, and the experimental results of optical and thermal management were compared between the general packaging and liquid-packaging structures, respectively. The results of the optical experiments showed that the proposed method increases the extraction efficiency by 9.5%. The results of the heat dissipation experiments showed that the liquid-packaging technology can reduce the thermal resistance of the UV-LED package by 31%.
Performance evaluation of a tube-in-tube CO2 gas cooler used in a heat pump water heater
(2014-04-01)
Yu, Pei-Yu
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Lin, Wei-Keng
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Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
In this study, investigation of the performance of a tube-in-tube counter-flow water-cooled CO2 gas cooler operating above and near critical pressure is presented using a heat pump water heater with CO2 flowing in the annulus side. A tube-in-tube heat exchanger model applicable for supercritical fluid CO2 and water was also developed and validated. The measured total heat transfer capacity ranged from 1.31 to 4.06 kW at various test conditions. The calculations show good agreement with the experimental results. The results demonstrate that the variation of CO2 temperature tends to show very slow decreasing near the pseudo-critical region when compared to the inlet region. Yet this phenomenon becomes more pronounced as the inlet pressure is close to the critical pressure (73.8 bar). The calculation also reveals a peculiar phenomenon that the local heat transfer rate of the heat exchanger peaks within the heat exchanger near the pseudo critical region due to the drastic rise of specific heat (C-p value). (C) 2014 Elsevier Inc. All rights reserved.
Performance of a tube-in-tube CO2 gas cooler
(2012-11-01)
Yu, Pei-Yu
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Lin, Kai-Hsiang
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Lin, Wei-Keng
;
Wang, Chi-Chuan
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機械工程學系
In this study, a tube-in-tube heat exchanger model applicable to supercritical CO2 and water was developed. The developed model is first validated with some existing measurements. Normally, the variation of the heat transfer rate for a constant-property working fluid shows a monotonic decrease from the inlet of minimum heat capacity flow rate (C-min). By contrast, the CO2 may present a local minimum and a local maximum along the length of the heat exchanger, provided CO2 passes through the pseudo-critical temperature, and this phenomenon becomes more and more pronounced when the pressure is close to the critical pressure. In contrast, it is possible for a local maximum heat transfer rate to occur near the inlet of C-min even when the CO2 does not pass through the pseudo-critical point. This happens when C-min is on the water side and the property variation of CO2 is taken into account. The calculation also shows that the effect of the inlet pressure on the variation of the CO2 temperature is not as apparent as the effect of the inlet pressure on the heat transfer rate, even when there is a significant change in the overall heat transfer coefficient, implying that the heat transfer characteristics of CO2 near the pseudo-critical region is similar to normal refrigerants, which show an invariant temperature at the condensation point. Hence, it would be beneficial to extend the influence of the pseudo-critical region when taking the heat transfer augmentation into consideration. (C) 2012 Elsevier Ltd and IIR. All rights reserved.
Zr-MOF/Polyaniline Composite Films with Exceptional Seebeck Coefficient for Thermoelectric Material Applications
(2019-01-23)
Lin, Chih-Chien
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Huang, Yi-Chia
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Usman, Muhammad
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Chao, Wen-Hsuan
;
Lin, Wei-Keng
Controlling the polymerization of aniline in the presence of zirconium-based metal-organic frameworks (Zr-MOFs) using polystyrene sulfonic acid as a dopant resulted in the formation of a new type of freestanding thermoelectric composite film. Polyaniline chains interpenetrate into the Zr-MOFs to enhance the crystallinity of polyaniline, resulting in an improved degree of electrical conductivity. In addition, the inherent porosity of the Zr-MOFs functions to suppress the increase in thermal conductivity, thus dramatically promoting a negative Seebeck coefficient. When 20 wt % Zr-MOF was used, a power factor of up to 664 mu W/(m K-2) was obtained, which was accompanied by a surprisingly large, negative Seebeck coefficient. The new class of MOF-based composites offers a new direction for developing new types of efficient thermoelectric materials.