學術出版;;Publications

Permanent URI for this communityhdl:11536/1

收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

Browse

Now showing 1 - 3 of 3

Augmentation of natural convection heat sink via using displacement design
(2020-06-01)
Abbas, Ali
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
Miniaturization of electronic devices demands an effective thermal management system for efficient cooling. Still, many electronic industries use natural convection cooling techniques like plate-fin heat sinks as far as no moving part (noise) and reliability is concerned. In this study, the widely-used plate fin heat sink is augmented by a novel fin displacement amid fin array. Yet the effect of fin displacement between alternate fins is experimentally and numerically investigated under natural convection condition. In the meantime, the effects of fin spacing, length, height, and heat flux on the heat sink performance subject to fin displacement is also studied. For the smaller fin pacing, introducing the fin displacement will delay the merging of boundary layers, and reduce the length of fully developed region accordingly. Smaller fin spacing can also entrain the outside air into the fin array at the upper portion of heat sink for offering additional enhancement. The fin displacement is especially effective for a smaller fin spacing. This is because fully developed flow prevails at a smaller fin spacing. On the other hand, the fin displacement may impair the performance when a very wide fin spacing is used. Similarly, the increase in the fin length also enhances the heat transfer performance under the fin displacement conditions. It is also found that the effect of fin height on the thermal performance is small and the effect of heat flux is negligible. The maximum reduction in the thermal resistance is 56% by adopting the displacement design. A drop in fin temperature at the upper portion with the displacement design may lead to a reduction in heat transfer coefficient. For the comparison containing the fixed volume, the heat sink with fin displacement offers a 30% heat transfer enhancement ratio, 28.7% reduction in total mass, and 27.4 % reduction in surface area when compared to the conventional heat sinks. (C) 2020 Elsevier Ltd. All rights reserved.
Investigation of performance augmentation for natural convective heatsink with the help of chimney
(2020-09-01)
Abbas, Ali
;
Qasrawi, Fatima
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
The effect of adding a plastic chimney on the top of upward horizontal rectangular heatsink under natural convection was investigated experimentally and numerically. The effect of the chimney height, length, depth, inclination, view factor, and conductivity for different fins array dimensions were investigated as well. The presence of low thermal conductivity chimney induces airflow by creating effective pressure difference between the edge and the center of the chimney. Yet higher chimney height results in larger pressure difference. Yet the pressure difference is accentuated with a sharp edge chimney. A smooth edge chimney reduces the pressure gradient and entrained airflow. The chimney with low thermal conductivity is capable to entrain more airflow into the heatsink when comparing with high thermal conductivity chimney (aluminum). The entrained airflow can be as much as 25% higher than the metal chimney. A smaller fin spacing may block the airflow and reversed the heat transfer. For the present configuration, it is found that the chimney is only effective when the heatsink is placed horizontally upward. By employing a transparent chimney, the view factor of the heatsink can be appreciably improved when comparing with opaque chimney.
Numerical investigation of thermal and hydraulic performance of shell and plate heat exchanger
(2020-02-25)
Abbas, Ali
;
Lee, Howard
;
Sengupta, Mash
;
Wang, Chi-Chuan
;
機械工程學系
Detailed single-phase performance of the shell and plate heat exchangers is presented in this study with corresponding chevron angles (beta) of 45 degrees and 75 degrees, respectively. Unlike those conventional plate heat exchanger, the thermofluids characteristics perform quite differently between shell and inner channel. For a larger chevron angle (75 degrees), the friction factor is comparable amid shell and inner channel. Yet the friction factor in the shell channel is much lower than that in inner channel at a smaller chevron angle (45 degrees). The shell channel contains more unidirectional flow pattern while some flow re-circulation may occur at the entrance/exit port of the inner channel. The flow pattern and temperature distribution in the shell channel are generally more uniform than those in inner channel. The shell channel with beta = 45 degrees shows a better overall performance for its much lower friction factor when the Reynolds number is low. The heat transfer performance for shell channel exceeds the inner channel appreciably when the chevron angle is high (75 degrees). The heat transfer performance depends on the corrugation aspect ratio, and an optimum ratio is derived. For the inner channel, the optimum value is around 0.75 while it is 0.53 for the shell channel.