THERMAL PERFORMANCE OF VERTICAL HEAT SINKS WITH DIFFERENT PIEZOFAN ARRANGEMENTS

2013 ◽  
Vol 37 (3) ◽  
pp. 895-903 ◽  
Author(s):  
Jin-Cherng Shyu ◽  
Jhih-Zong Syu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Enhancement Factors ◽  
Vertical Heat

This study examines various effects on the heat transfer enhancement of several vertical heat sinks with a running piezofan. Both plate-fin heat sink and pin-fin heat sink having a 10-mm-high or 30-mm-high fin array were tested with either a vertical or a horizontal piezofan. Results show that the piezofan tip located at x/L = 0.5 usually yielded the highest heat transfer enhancement. Besides, heat transfer enhancement factors ranged from 1.2 to 2.4 for the present 10-mm-high plate-fin heat sink, and from 1.1 to 2.6 for the 10-mm-high pin-fin heat sink.

Cooling Performance Comparisons of Five Different Plate-Pin Compound Heat Sinks Based on Two Different Length Scale

2011 ◽  
Author(s):  
Feng Zhou ◽  
David Geb ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Cross Section ◽  
Heat Sink ◽  
Heat Sinks ◽  
Length Scale ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
New Type

Plate fin heat sinks (PFHS) are widely used to remove heat from the microelectronic devices. In the present study, a new type of compound heat sink, named as plate-pin fin heat sink (PPFHS), is employed to improve the air cooling performance. With CFD numerical method, PPFHSs with five forms of pin cross-section profiles (square, circular, elliptic, NACA 0050, and dropform) and PFHS were simulated. Two different length scales were adopted to evaluate the performance of six types of heat sinks, including PFHS. One of the length scales is commonly used by many investigators, which is two times of the channel spacing. The other length scale is suggested by volume averaging theory (VAT), which is four times of average porosity divided by specific interface. The influence of pin fin cross-section profile on the flow and heat transfer characteristics was presented by means of Nusselt number, pressure drop and overall efficiency. It is found that the Nu number of a PPFHS is at least 35% higher than that of a PFHS used to construct the PPFHS at the same Reynolds number no matter which length scale was used. It is also revealed that the heat transfer enhancement of square PPFHS is offset by its excessively high pressure drop, which makes it not as efficient as the other types of PPFHS. Circular PPFHS performs similar to the streamline shaped PPFHS when the Reynolds number is not too high. However, with the increase in Re the advantage of the circular cross-section diminishes. Using the streamline shaped pins, not only the pressure drop of the compound heat sinks could be decreased considerably, the heat transfer enhancement also makes a step forward. However, evaluating the performance of heat sinks by using the commonly used length scale, the benefit of streamline shaped types of PPFHSs is a little bit overstated. The VAT suggested length scale is more reasonable to do the performance comparison of different heat sinks, especially when it is difficult to provide a fair and physically meaningful basis for the comparison. In short, the present numerical simulation provides original information of the influence of different pin-fin cross-section profiles on the thermal and hydraulic performance of the new type compound heat sink and emphasizes the importance of choosing a proper length scale when evaluating heat transfer enhancement, which is helpful in the design of heat sinks.

Heat Transfer Enhancement of Vertical Heat Sinks with a Piezofan

2013 ◽  
Vol 284-287 ◽  
pp. 773-777
Author(s):  
Jin Cherng Shyu ◽  
Jhih Zong Syu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
High Heat ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Vertical Heat ◽  
Pin Fins

This study examines several effects, including the piezofan positions, and piezofan arrangements, as well as piezofan height, on the heat transfer enhancement of two typical types of vertical heat sink. Either 30-mm-high or 10-mm-high heat sink having 11 plate-fins or 100 square pin-fins is tested with a running piezofan. The piezofan having Mylar blade is either vertically or horizontally placed above the heat sinks vibrating with resonant frequency of 31 Hz and tip mean-to-peak amplitude of 7.2 mm. The heat transfer coefficient is measured at five different fan locations with fan heights of 12 mm and 16 mm. Results show that the piezofan located at x/L = 0.5 usually performs the highest heat transfer enhancement for a given heat sink, while piezofan located at x/L = 1 usually shows the worst heat transfer enhancement. Depending on the fan arrangements and positions, heat transfer coefficient of the present 10-mm-high plate-fin heat sink shows 1.2 – 2.4 times higher than that under natural convection, while the enhancement factor ranges from 1.1 to 2.6 for 10-mm-high pin-fin heat sink.

Pin-Fin Heat Sink With Horizontal Base and Blocked Edges

2008 ◽  
Author(s):  
D. Sahray ◽  
H. Shmueli ◽  
N. Segal ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Contact Resistance ◽  
Cross Section ◽  
Heat Input ◽  
Heat Sink ◽  
Numerical Study ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Pin Fin

In the present work, horizontal-base pin fin heat sinks exposed to free convection in air are studied. They are made of aluminum, and there is no contact resistance between the base and the fins. For the same base dimensions the fin height and pitch vary. The fins have a constant square cross-section. The edges of the sink are blocked: the surrounding insulation is flush with the fin tips. The effect of fin height and pitch on the performance of the sink is studied experimentally and numerically. In the experiments, the heat sinks are heated using foil electrical heaters. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks and their environment are modeled using the Fluent 6 software. The results show that heat transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are analyzed for various fin heights. Also assessed are effects of the blocked edges as compared to the previously studied cases where the sink edges were exposed to the surroundings.

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.

Analysis of Heat Transfer Enhancement in Minichannel Heat Sinks With Turbulent Flow Using H2O–Al2O3 Nanofluids

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
T. L. Bergman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Thermophysical Properties ◽  
Heat Sink ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Electronic Heat ◽  
Limited Usefulness

Heat transfer enhancement associated with use of a nanofluid coolant is analyzed for small electronic heat sinks. The analysis is based on the ε-NTU heat exchanger methodology, and is used to examine enhancement associated with use of H2O–Al2O3 nanofluids in a heat sink experiencing turbulent flow. Predictive correlations are generated to ascertain the degree of enhancement based on the fluid’s thermophysical properties. The enhancement is quite small, suggesting the limited usefulness of nanofluids in this particular application.

scholarly journals Heat Transfer Enhancement from Microprocessor

2020 ◽  
Vol 8 (4S4) ◽  
pp. 174-178
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Hydraulic Diameter ◽  
Constant Speed ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Transfer Enhancement ◽  
Pass Through

Experiments were conducted to investigate the cooling of processor to increase the thermal performance by employing a mini channel instead of conventional heat sinks. Now a day’s aluminium fin with fans is used for cooling the processor. Constant speed of the fans is found to be not enough to remove the heat generated by the processor. The experimental investigations were carried out in the channels with the hydraulic diameter of about 1.5x10-3m for the Reynolds number varying from 80 to 1150. The water is allowed to pass through the channel by virtue of which heat is rejected from the processor. The influence of Reynolds number on heat transfer enhancement from the microprocessor is discussed in details. Comparison between heat transfer by air and by water is presented. From the experiment it is disclosed that further increase in heat transfer was observed when compared to air.

Enhancing Heat Transfer of Air-Cooled Heat Sinks Using Piezoelectrically-Driven Agitators and Synthetic Jets

2011 ◽  
Author(s):  
Youmin Yu ◽  
Terrence Simon ◽  
Min Zhang ◽  
Taiho Yeom ◽  
Mark North ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Single Channel ◽  
Synthetic Jets ◽  
Heat Sinks ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Enhancing Heat Transfer

Air-cooled heat sinks prevail in microelectronics cooling due to their high reliability, low cost, and simplicity. But, their heat transfer performance must be enhanced if they are to compete for high-flux applications with liquid or phase-change cooling. Piezoelectrically-driven agitators and synthetic jets have been reported as good options in enhancing heat transfer of surfaces close to them. This study proposes that agitators and synthetic jets be integrated within air-cooled heat sinks to significantly raise heat transfer performance. A proposed integrated heat sink has been investigated experimentally and with CFD simulations in a single channel heat sink geometry with an agitator and two arrays of synthetic jets. The single channel unit is a precursor to a full scale, multichannel array. The agitator and the jet arrays are separately driven by three piezoelectric stacks at their individual resonant frequencies. The experiments show that the combination of the agitator and synthetic jets raises the heat transfer coefficient of the heat sink by 80%, compared with channel flow only. The 3D computations show similar enhancement and agree well with the experiments. The numerical simulations attribute the heat transfer enhancement to the additional air movement generated by the oscillatory motion of the agitator and the pulsating flow from the synthetic jets. The component studies reveal that the heat transfer enhancement by the agitator is significant on the fin side and base surfaces and the synthetic jets are most effective on the fin tips.

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