Browsing by Author "Shen, Han"

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A parametric study on thermal performance of microchannel heat sinks with internally vertical bifurcations in laminar liquid flow
(2018-02-01)
Shen, Han
;
Wang, Chi-Chuan
;
Xie, Gongnan
;
機械工程學系
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Department of Mechanical Engineering
The optimal position of internal vertical bifurcation integrated with a microchannel heat sink (MHS) is investigated numerically in the present research. The corresponding rectangular smooth microchannel is compared with those with internal vertical bifurcation. The optimal position along the streamwise direction for interval distances is studied in detail. The corresponding temperature fields, flow fields, pressure drop and thermal characteristics are presented through verified computational model. The numerical simulation indicates that a clear inflection point of pressure gradient may prevail with the presence of internal vertical bifurcation. It is also found that the microchannel heat sink with a small distance between the tail end of internal vertical bifurcation and the outlet of microchannel shows the best thermal performance instead of those with setting the tail end of internal bifurcation at the outlet of microchannel. The proposed optimal design of internal vertical bifurcation shows improved thermal performance without any pressure drop penalty. (C) 2017 Elsevier Ltd. All rights reserved.
Comparative study for convective heat transfer of counter-flow wavy double-layer microchannel heat sinks in staggered arrangement
(2018-06-05)
Shen, Han
;
Zhang, Yingchun
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Wang, Chi-Chuan
;
Xie, Gongnan
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機械工程學系
This study proposes a modification of double-layer Microchannel Heat Sinks (DMHSs) into wavy configuration with swap of upper and lower layer design. The design can effectively improve the comparatively low cooling effectiveness at the upper layer, yet the swap of flow can promote re-developing of flow field and heat transfer accordingly. Both parallel and counter flow arrangements of the proposed configurations are examined in details. It is found that the staggered wavy DMHSs with opposite amplitude shows superior heat transfer enhancement. Regardless of the types of heat sink being investigated, the maximum temperature for all parallel flow arrangement always occurs at the exit while the maximum temperature for counter flow is in the interior of heat sink but is close to the exit. Interestingly, the swap design of counter flow arrangement (parallel channel or wavy) shows two maximum temperatures in the first and second half of the heat sink. Basically, the counter flow of straight staggered DMHS has the best overall thermal performance among the counter flows of straight parallel DMHS, synclastic wavy staggered DMHS and opposite wavy staggered DMHS. This is because the wavy staggered DMHS incur more pressure drop and pumping power accordingly.
Heat transfer and thermodynamic analysis by introducing multiple alternation structures into double-layer microchannel heat sinks
(2019-11-01)
Shen, Han
;
Xie, Gongnan
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
The study examined the performance of a novel staggered flow alternation structure in the Double-layer Microchannel Heat Sink (DMHS) based on authors' prior work and further detailed and quantitatively influences regarding the effects of the numbers of multiple staggered flow alternation structures are thoroughly investigated. Yet the analysis also contains more in-depth description about the entropy generation caused by heat transfer and liquid flow based on the second-law perspective. The major influential factors combining thermal performance and pressure drop penalty such as Nusselt number, Reynolds number, pumping power and thermal performance factor have been numerically studied. Moreover, the flow directions with parallel/counter stream were also compared in the present work. Through these detailed analysis, the propose multiple novel design offers much superior performance with better thermal uniformity and augment entropy generation number. The results show that the temperature difference of the substrate can be made quite uniformly by adding the number of multiple staggered flow alternation structure, and superior performance of the proposed DMHS can be achieved with affordable pressure drop penalty, while the DMHS with single alternation structure shows higher thermal performance.
Parametric study on thermal performance of microchannel heat sinks with internal vertical Y-shaped bifurcations
(2015-11-01)
Xie, Gongnan
;
Shen, Han
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
In this paper, internal vertical Y-shaped bifurcation plates are integrated with the microchannel heat sink (MHS), and its corresponding thermal and fluid flow characteristics are investigated numerically. The effect of the length of Y-shaped bifurcation and the angles of the arms on the overall performance are examined. A best Y-shaped plate length are firstly screened out from three designs and are compared with the corresponding rectangular smooth microchannel. Based on the best thermal performance with a specific length, the effect of arm angles in terms of five different configurations of Y-shaped plates are further investigated. Through the calculations, the corresponding flow field, temperature field and pressure drop characteristics are reported. It is found that the thermal performance of MHSs with internal Y-shaped bifurcations is much better than that of the traditional rectangular microchannel. The longest internal Y-shaped bifurcation microchannel results in best thermal performance. On the other hand, a larger arm angle leads to a better thermal performance of the internal Y-shaped bifurcation microchannel. (C) 2015 Elsevier Ltd. All rights reserved.
The numerical simulation with staggered alternation locations and multi-flow directions on the thermal performance of double-layer microchannel heat sinks
(2019-12-25)
Shen, Han
;
Xie, Gongnan
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
The novel staggered flow alternation structure (SFAS) proposed in prior study has proved to be an efficient way in improving the overall thermal performance with acceptable pressure drop penalty in Double-layer Microchannel Heat Sinks (DMHSs). Based on the prior design, a further numerical investigation concerning the optimum location of SFAS in DMHSs is presented. The corresponding temperature fields, Nusselt number, flow fields, pressure drop and thermal characteristics are presented through verified computational mode. In addition, the effect of flow arrangements such as concurrent, upper-inlet/lower-inlet countercurrent arrangement on the thermal performance are studied in more details. The best thermal location of SFAS in the DMHSs is found to be based on the alterable locations and multi-flow directions. Yet, changing the location of staggered alternation structure does not lead to an appreciable rise of pressure drop penalty in DMHSs. However, the improvement in thermal performance for upper-inlet countercurrent arrangement is significant. Placing the SFAS in the middle of the DMHSs ensures the best overall thermal performance.
Thermal performance and entropy generation of novel X-structured double layered microchannel heat sinks
(2020-06-01)
Shen, Han
;
Xie, Gongnan
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
A novel X-structured Double layered Microchannel Heat Sink (X-DMHS) is proposed for performance augmentation on the traditional rectangular Double layered Microchannel Heat Sink (DMHS). The overall flow and thermal performances of parallel-flow and counter-flow arrangements on X-DMHSs are studied, and the entropy generation from the second law perspective is also quantitatively analyzed. From the analysis of the pressure drop penalty, thermal performance and entropy generation rate, it is found that the proposed X-DMHSs show much superior performance either from the heat transfer performance or from the second law perspective. The design offers higher entropy generation number and better thermal uniformity on substrate, meaning that proposed X-DMHSs can control the thermal gradients more significantly and lower the highest temperature on the heated substrate more effectively with affordable rise of pumping power as compared with the corresponding traditional DMHS. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.