scholarly journals Influence of moist air in copper heat sinks: Analysis through the entropy generation minimization criterion

2015 ◽  
Vol 35 (3) ◽  
pp. 44-52 ◽  
Author(s):  
Jorge Mario Cruz ◽  
Iván Mauricio Amaya ◽  
Carlos Rodrigo Correa
Keyword(s):  
Heat Transfer ◽  
Relative Humidity ◽  
Heat Sink ◽  
Bulk Material ◽  
Heat Transfer Process ◽  
Heat Sinks ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Rectangular Microchannel ◽  
Humidified Air

Many factors affect heat transfer during the cooling of modern electronic devices. Today, knowledge accrues from modeling, simu-lation, and experimentation. This allows predicting and calculating features of heat transfer phenomena, to some extent. Examples include the amount of heat generated and removed, the required physical properties of the working fluid, and the required material properties of the heat sink, among other parameters. This article describes some simulation results of using air with a given relative humidity (10 %, 50 % and 90 %). Its influence on the heat transfer process was also analyzed. Results show a measurable effect of using humidified air instead of dry air and copper as a bulk material. The heat transfer rate increased about 20 % when using air with 90 % relative humidity passing through a rectangular microchannel heat sink made of copper.

Enhanced Thermal Transport in Microchannel Using Oblique Fins

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Y. J. Lee ◽  
P. S. Lee ◽  
S. K. Chou
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Transfer Enhancement ◽  
Microchannel Heat Sinks

Sectional oblique fins are employed, in contrast to continuous fins in order to modulate the flow in microchannel heat sinks. The breakage of a continuous fin into oblique sections leads to the reinitialization of the thermal boundary layer at the leading edge of each oblique fin, effectively reducing the boundary layer thickness. This regeneration of entrance effects causes the flow to always be in a developing state, thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a small fraction of the flow into adjacent main channels. The secondary flows created improve fluid mixing, which serves to further enhance heat transfer. Both numerical simulations and experimental investigations of copper-based oblique finned microchannel heat sinks demonstrated that a highly augmented and uniform heat transfer performance, relative to the conventional microchannel, is achievable with such a passive technique. The average Nusselt number, Nuave, for the copper microchannel heat sink which uses water as the working fluid can increase as much as 103%, from 11.3 to 22.9. Besides, the augmented convective heat transfer leads to a reduction in maximum temperature rise by 12.6 °C. The associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective heat transfer enhancement scheme for a single-phase microchannel heat sink.

Experimental Investigation of Silicon-Based Oblique Finned Microchannel Heat Sinks

2010 ◽  
Author(s):  
Yong-Jiun Lee ◽  
Poh-Seng Lee ◽  
Siaw-Kiang Chou
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Sink ◽  
Leading Edge ◽  
Secondary Flows ◽  
Heat Sinks ◽  
Fluid Mixing ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Silicon Based

Sectional oblique fins are employed in contrast to the continuous fins in order to modulate the flow in microchannel heat sink. Experimental investigation of silicon based oblique finned microchannel heat sink demonstrated a highly augmented and uniform heat transfer performance against the conventional microchannel. The breakage of continuous fin into oblique sections leads to the re-initialization of the thermal boundary layers at the leading edge of each oblique fin, effectively reducing the boundary-layer thickness. This regeneration of the entrance effect causes the flow to be always in a developing state thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a fraction of the flow into the adjacent main channels. The secondary flows thus created improve fluid mixing which serves to further enhance the heat transfer. The average Nusselt number, Nuave, for the silicon microchannel heat sink which uses water as the working fluid can increase as much as 55%, from 8.8 to 13.6. Besides, the augmented convective heat transfer leads to reduction in both maximum chip temperature and its temperature gradient, by 8.6°C and 47% respectively. Interestingly, there is only little or negligible pressure drop penalty associated with this novel heat transfer enhancement scheme in contrast to conventional enhancement techniques.

Effect of 1D Cu Nanostructures on Heat Transfer Characteristics of Single Phase Microchannel Heat Sink

2011 ◽  
Author(s):  
M. Yakut Ali ◽  
Fanghao Yang ◽  
Ruixian Fang ◽  
Chen Li ◽  
Jamil Khan
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Single Phase ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Heat Transfer Characteristics ◽  
Rectangular Microchannel ◽  
Maximum Enhancement ◽  
Cu Nanowires ◽  
Transfer Characteristics

This study experimentally assesses single phase heat transfer characteristics of a shallow rectangular microchannel heat sink whose surface is enhanced with copper nanowires (CuNWs). The hydraulic diameter of the channel is 672 μm and the bottom wall is coated with Cu nanowires (CuNWs) of 200 nm in diameter and 50 μm in length. CuNWs are grown on the Cu heat sink by electrochemical synthesis technique which is inexpensive and readily scalable. The heat transfer and pressure drop results of CuNWs enhanced heat sink are compared with that of bare copper heat sink using deionized (DI) water as the working fluid at Reynolds Number (Re) ranging from 106–636. The experimental results indicate an enhancement in Nusselt Number (Nu) at all Re with a maximum enhancement of 24% at Re = 106. The enhanced thermal performance is attributed to two properties of Cu nanowire arrays — improvement in surface wettability characteristics and increased heat transfer surface area.

Numerical Simulation of Nanofluids for Improved Cooling Efficiency in Microchannel Heat Sink

2014 ◽  
Vol 695 ◽  
pp. 403-407 ◽  
Author(s):  
Nur Hazwani Mohamad Noh ◽  
Nor Azwadi Che Sidik
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Sink ◽  
Rectangular Cross Section ◽  
Fluid Dynamic ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Rectangular Microchannel ◽  
3 Dimensional

Numerical simulation on 3-dimensional rectangular cross section of microchannel heat sink is conducted to investigate the effect of various type coolant consist of water and different type of nanofluids on the cooling performance of microchannel heat sink. FLUENT, a Computational Fluid Dynamic (CFD) is used as the solver of simulation. A rectangular microchannel with hydraulic diameter of 86um and length of 10mm under the boundary condition of constant heat flux and laminar flow with uniform inlet velocity with five sets of working fluid with different nanofluids. The defined model is validated with previous studies of numerical analysis. Results of present work show that using Diamond-H2O as cooling lead to higher efficiency of heat transfer in microchannel heat sink in comparison to others nanofluid and base fluid. Numerical results show that increasing the thermal conductivity of working fluid can enhanced heat transfer. Nusselt number follows the incremental in Reynolds number.

Performance Comparison of Microchannel Heat Sink Using Boron-Based Ceramic Materials

2021 ◽  
Vol 1163 ◽  
pp. 73-88
Author(s):  
Md Tanbir Sarowar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Sink ◽  
Electronic Devices ◽  
Ceramic Materials ◽  
Substrate Material ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Microchannel Heat Sink ◽  
Small Surface

Microchannel heat sink plays a vital role in removing a considerable amount of heat flux from a small surface area from different electronic devices. In recent times, the rapid development of electronic devices requires the improvement of these heat sinks to a greater extent. In this aspect, the selection of appropriate substrate materials of the heat sinks is of vital importance. In this paper, three boron-based ultra-high temperature ceramic materials (ZrB2, TiB2, and HfB2) are compared as a substrate material for the microchannel heat sink using a numerical approach. The fluid flow and heat transfer are analyzed using the finite volume method. The results showed that the maximum temperature of the heat source didn’t exceed 355K at 3.6MWm-2 for any material. The results also indicated HfB2 and TiB2 to be more useful as a substrate material than ZrB2. By applying 3.6 MWm-2 heat flux at the source, the maximum obtained surface heat transfer coefficient was 175.2 KWm-2K-1 in a heat sink having substrate material HfB2.

Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

2008 ◽  
Author(s):  
Ayman Megahed ◽  
Ibrahim Hassan ◽  
Tariq Ahmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Microchannel Heat Sink

The present study focuses on the experimental investigation of boiling heat transfer characteristics and pressure drop in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 295 μm, width of 254 μm, and a length of 16 mm. Un-encapsulated Thermochromic liquid Crystals (TLC) are used in the present work to enable nonintrusive and high spatial resolution temperature measurements. This measuring technique is used to provide accurate full and local surface-temperature and heat transfer coefficient measurements. Experiments are carried out for mass velocities ranging between 290 to 457 kg/m2.s and heat fluxes from 6.04 to 13.06 W/cm2 using FC-72 as the working fluid. Experimental results show that the pressure drop increases as the exit quality and the flow rate increase. High values of heat transfer coefficient can be obtained at low exit quality (xe < 0.2). However, the heat transfer coefficient decreases sharply and remains almost constant as the quality increases for an exit quality higher than 0.2.

Optimization Under Uncertainty of Manifold Microchannel Heat Sinks

2012 ◽  
Author(s):  
Suchismita Sarangi ◽  
Karthik K. Bodla ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Sinks ◽  
Optimization Under Uncertainty ◽  
Microchannel Heat Sink ◽  
Probabilistic Optimization ◽  
Manifold Microchannel

Conventional microchannel heat sinks provide good heat dissipation capability but are associated with high pressure drop and corresponding pumping power. The use of a manifold system that distributes the flow into the microchannels through multiple, alternating inlet and outlet pairs is investigated here. This manifold arrangement greatly reduces the pressure drop incurred due to the smaller flow paths, while simultaneously increasing the heat transfer coefficient by tripping the thermal boundary layers. A three-dimensional numerical model is developed and validated, to study the effect of various geometric parameters on the performance of the manifold microchannel heat sink. Apart from a deterministic analysis, a probabilistic optimization study is also performed. In the presence of uncertainties in the geometric and operating parameters of the system, this probabilistic optimization approach yields an optimal design that is also robust and reliable. Uncertainty-based optimization also yields auxiliary information regarding local and global sensitivities and helps identify the input parameters to which outputs are most sensitive. This information can be used to design improved experiments targeted at the most sensitive inputs. Optimization under uncertainty also provides a quantitative estimate of the allowable uncertainty in input parameters for an acceptable uncertainty in the relevant output parameters. The optimal geometric design parameters with uncertainties that maximize heat transfer coefficient while minimizing pressure drop for fixed input conditions are identified for a manifold microchannel heat sink. A comparison between the deterministic and probabilistic optimization results is also presented.

Hydrothermal Investigation of a Microchannel Heat Sink Using Secondary Flows in Trapezoidal and Parallel Orientations

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5616
Author(s):  
Safi Ahmed Memon ◽  
Taqi Ahmad Cheema ◽  
Gyu Man Kim ◽  
Cheol Woo Park
Keyword(s):  
Secondary Flow ◽  
Heat Sink ◽  
Performance Enhancement ◽  
Volumetric Flow Rate ◽  
Base Plate ◽  
Secondary Flows ◽  
Heat Sinks ◽  
Microchannel Heat Sink ◽  
Rectangular Microchannel ◽  
Flow Channels

Thermal performance enhancement in microchannel heat sinks has recently become a challenge due to advancements in modern microelectronics, which demand compatibility with heat sinks able to dissipate ever-increasing amounts of heat. Recent advancements in manufacturing techniques, such as additive manufacturing, have made the modification of the microchannel heat sink geometry possible well beyond the conventional rectangular model to improve the cooling capacity of these devices. One such modification in microchannel geometry includes the introduction of secondary flow channels in the walls between adjacent mainstream microchannels. The present study computationally models secondary flow channels in regular trapezoidal and parallel orientations for fluid circulation through the microchannel walls in a heat sink design. The heat sink is made of silicon wafer, and water is used as the circulating fluid in this study. Continuity, momentum, and energy equations are solved for the fluid flow through the regular trapezoidal secondary flow and parallel secondary flow designs in the heat sink with I-type, C-type, and Z-type inlet–outlet configurations. Plots of velocity contours show that I-type geometry creates optimal flow disruption in the heat sink. Therefore, for this design, the pressure drop and base plate temperatures are plotted for a volumetric flow rate range, and corresponding contour plots are obtained. The results are compared with corresponding trends for the conventional rectangular microchannel design, and associated trends are explained. The study suggests that the flow phenomena such as flow impingement onto the microchannel walls and formation of vortices inside the secondary flow passages coupled with an increase in heat transfer area due to secondary flow passages may significantly improve the heat sink performance.

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