Browsing by Author "Chen, Hong-Long"

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Analysis and experimental verification of weight saving with trapezoidal base heat sink
(2018-03-05)
Chen, Hong-Long
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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
A quick weight saving methodology with trapezoidal base heat sink applicable for electronic cooling application is studied analytically, numerically, and experimentally. The conventional heat sink with rectangular base can be modified into trapezoidal base for material saving. A differential equation capable of describing the temperature distribution of the trapezoidal base is derived and its closed-form analytic expression is derived. It is found that three parameters r(A) (ratio of effective surface area to the base area), r(d) (ratio of chip lateral length to the base length) and h(+) (modified convection heat transfer coefficient) play pivotal roles in balancing the material saving and the performance loss. When r(d) = 0.1, the material saving for r(t) = 0.6 is about 18%; while the corresponding performance loss is 2.93%. When r(d) = 0.2, the material saving for r(t) = 0.6 is about 16%; while the corresponding performance loss is 2.47%. The analytical results are verified with experiments with good agreement. (C) 2017 Elsevier Ltd. All rights reserved.
Analytical analysis and experimental verification of interleaved parallelogram heat sink
(2017-02-05)
Chen, Hong-Long
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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, a novel air-cooled heat sink profile is proposed to compete with the conventional design. The new design is termed as IPFM (Interleaved Parallelogram Fin Module) which features two different geometrical perimeter shapes of fins. This new design not only gains the advantage of lower pressure drop for power saving; but also gains a material saving for less fin surface area. An assessment of flow impedance and performance between the conventional and IPFM heat sink is analytically investigated and experimentally verified. A new modified dimensionless friction factor for triangular region is proposed. The analytical predictions agree with experimental measurements for both conventional and IPFM design. In electronic cooling design, especially for cloud server air-cooled heat sink design, the flow pattern is usually laminar with Reynolds number being operated less than 2000. In this regime, the IPFM design shows 8-12% less of surface than conventional design when the flow rate is less than 10 CFM; yet the thermal performance is slightly inferior to the conventional design when the flowrate is raised towards 25 CFM. Yet in the test range of 5-25 CFM, a 10-15% lower flow impedance is observed. The smaller fin spacing, the more conspicuous reduction of flow impedance is observed. The optimization of cutting angle is around 35 degrees for 10 CFM, and it is reduced to 15 degrees at a larger flowrate of 20 CFM. (C) 2016 Elsevier Ltd. All rights reserved.
Analytical analysis and experimental verification of trapezoidal fin for assessment of heat sink performance and material saving
(2016-04-05)
Chen, Hong-Long
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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
A quick assessment of the performance loss in association with material saving amid rectangular and trapezoidal fin is analytically investigated and experimentally verified. A novel dimensionless parameter - r(t) representing the ratio of the fin tip to base thickness - is used to simplify the fin equation. A dimensionless differential equation is derived based on the formulation and the corresponding closed form solution of the dimensionless temperature and fin efficiency is presented. It is found that the performance drop depends on various rt ratios, and the most pronounced performance difference occurs in the region between M = 1.7 and 2.5. Yet the performance difference between the rectangular and trapezoidal fin are quite insignificant at low velocity region; with the increasing of velocity, the performance loss ratio is gradually discriminated to reach the maximum performance loss between region of M = 1 and 2, then it begins to converge again toward M = 4. The recovering of the ratio is actually associated with the diverging and converging trend of the fin efficiency. The analytical results are in line with the experimental results. At a frontal velocity of 4 m/s, the predicted difference of heat transfer rate between trapezoidal and rectangular fin profile in terms of total heat transfer ratio is only 0.88%. (C) 2015 Elsevier Ltd. All rights reserved.
Analytical and Experimental Verification of Interleaved Trapezoidal Heat Sink
(2017-01-01)
Chen, Hong-Long
;
Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
The objective of this paper is to explore the technique for lowering the contraction and hydraulic developing region pressure drop, in order to gain more airflow for electronic cooling heat sink for the same footprint and fin number. By combining two different geometrical perimeter shapes of fins, odd number is rectangular shape, and even number is trapezoidal shape, this new fin module design gains extra 10% airflow with little loss or equivalent thermal performance. Current data center server is suffering from too little airflow to cool essential chips due to enormous flow impedance for packing too many components inside. This technology is the solution to resolve this bottleneck. The precious extra 10% more airflow not only cools CPU chip itself; but also quite beneficial to cool other heating components inside servers. Also, this new design excels in low velocity of 2 m/s for thermal performance compared to original design. Lower velocity is equal to lower RPM of fan that leads to the advantage of energy saving.