Effects of Channel Aspect Ratio on Convective Heat Transfer in an Electronics Cooling Heat Sink Having Agitation and Fan-Induced Throughflow

2013 ◽  
Author(s):  
Smita Agrawal ◽  
Longzhong Huang ◽  
Terrence Simon ◽  
Mark North ◽  
Tianhong Cui
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Sink ◽  
Single Channel ◽  
Electronics Cooling ◽  
Heat Sinks ◽  
Channel Width ◽  
Channel Height ◽  
Transfer Coefficients ◽  
Multiple Channel

Fan-driven throughflow is frequently used for convective cooling of electronics. Channels with walls behaving like fins are common. In the present study, the flow inside the channels is agitated by means of translationally oscillating plates called agitators. Effectiveness of agitation by oscillating blades is found to be dependent on the channel width, a parameter studied herein. Heat sinks having narrower channels have a greater number of channels in total for the fixed size of heat sink and therefore greater heat transfer area than heat sinks with wider channels. Thus, with the same channel height, as the aspect ratio increases, channel width decreases, and it is found that opportunities for agitation are reduced and the generated turbulence is more strongly damped, thus reducing heat transfer coefficients. A study was carried out to find direction toward an optimal number of channels for a given heat sink using the agitation strategy. As part of the study, fluid damping and power consumption to drive the agitator assembly were addressed. The study was done numerically using ANSYS FLUENT on a representative single channel of the heat sink and the results were extended to the full size, multiple-channel heat sink system. Recommendations for moving toward an optimum geometry, based on thermal performance and agitator power are made.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

CFD Analysis of Flow and Heat Transfer in a Novel Heat Sink for Electronic Devices

2010 ◽  
Author(s):  
Bladimir Ramos-Alvarado ◽  
Peiwen Li ◽  
Hong Liu ◽  
Abel Hernandez-Guerrero
Keyword(s):  
Heat Transfer ◽  
Power Consumption ◽  
Heat Sink ◽  
Electronics Cooling ◽  
Flow Channel ◽  
Heat Sinks ◽  
Temperature Fields ◽  
Pumping Power ◽  
Pressure Losses ◽  
Channel Configuration

Novel flow channel configurations in heat sinks for electronics cooling were proposed in this paper. Computational analyses were carried out to better understand the heat transfer performance, the uniformity of temperature fields of the heat sinking surface, as well as the pressure losses and pumping power in the operation of heat sinks. Comparison of the overall performance regarding to temperature uniformity on the heat sink surface and pumping power consumption was made for heat sinks having novel flow channel configurations and having traditional flow channel configurations. It has been found that the novel flow channel configuration dramatically reduces the pressure loss in the flow field. Giving the same pumping power consumption of an electronics cooling process, the temperature difference on surface of the heat sink which has novel flow channel configuration can be much lower than that of the heat sinks which have traditional flow channel configurations.

Cryogenic Single-Phase Heat Transfer in a Microscale Pin Fin Heat Sink

2013 ◽  
Author(s):  
Eric D. Truong ◽  
Erfan Rasouli ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Single Phase ◽  
Flow Direction ◽  
Heat Sinks ◽  
Variable Cross ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients

A combined experimental and computational fluid dynamics study of single-phase liquid nitrogen flow through a microscale pin-fin heat sink is presented. Such cryogenic heat sinks find use in applications such as high performance computing and spacecraft thermal management. A circular pin fin heat sink in diameter 5 cm and 250 micrometers in depth was studied herein. Unique features of the heat sink included its variable cross sectional area in the flow direction, variable pin diameters, as well as a circumferential distribution of fluid into the pin fin region. The stainless steel heat sink was fabricated using chemical etching and diffusion bonding. Experimental results indicate that the heat transfer coefficients were relatively unchanged around 2600 W/m2-K for flow rates ranging from 2–4 g/s while the pressure drop increased monotonically with the flow rate. None of the existing correlations in literature on cross flow over a tube bank or micro pin fin heat sinks were able to predict the experimental pressure drop and heat transfer characteristics. However, three dimensional simulations performed using ANSYS Fluent showed reasonable (∼7 percent difference) agreement in the average heat transfer coefficients between experiments and CFD simulations.

An Experimental Study of Pin Fin Heat Sinks and Determination of End Wall Heat Transfer

2003 ◽  
Author(s):  
Massimiliano Rizzi ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Optimization Methods ◽  
Heat Sinks ◽  
Base Region ◽  
Transfer Coefficients ◽  
Media Type ◽  
Pin Fin ◽  
Heat Transfer Coefficients

An experimental study of a pin fin heat sink was carried out in support of the development of heat sink optimization methods requiring more detailed measurements be made. Measurements of heat flux and temperature are used to separately determine heat transfer coefficients for the pins and the base region between the pins. Three pitch to diameter ratios (distance from pin center to pin center measured diagonally) were studied: P/d = 3/1, 9/4, 3/2. Heat generation was accomplished using cartridge heaters inserted into a copper block. The high thermal conductivity of the copper ensured that the surface beneath the heat sink would be at a constant temperature. The cooling fluid was air and the experiments were conducted with a Reynolds numbers based on a porous media type hydraulic diameter ranging from 500 to 25000. The channel had a shroud that touches the fin tips, eliminating any flow bypass. The pin surface heat transfer coefficients match the values reported by Kays and London and by Zukauskas. The base region heat transfer coefficients were, surprisngly, larger than the pin values.

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.

An Experimental Study on the Effects of Agitation on Forced-Convection Heat Transfer

2011 ◽  
Author(s):  
Smita Agrawal ◽  
Terrence W. Simon ◽  
Mark North ◽  
Tianhong Cui
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Large Scale ◽  
Single Channel ◽  
Convection Heat Transfer ◽  
Electronics Cooling ◽  
Forced Flow ◽  
Module Design ◽  
Translational Mode ◽  
Enhancing Heat Transfer

Most active electronics cooling modules are cooled by forced flow driven by a rotating fan. Recently, a piezoelectrically-driven plate driven in a flapping mode has been proposed as a replacement. This fan gives both flow movement and agitation. To raise effectiveness, reduce size, and otherwise meet the demands of future electronics cooling devices, better methods are continually being sought. The present research explores the possibility of using a piezoelectric stack to oscillate blades in a translational mode to agitate the flow in a heat sink channel, thus enhancing heat transfer on the channel walls. The aim is to disrupt the thermal boundary layer while introducing strong pressure gradients and channel vorticity. In the present cooling module design, this agitation is used in conjunction with a rotating fan which provides through-flow. The dimensions of actual heat sink channels are small, making detailed heat transfer measurements difficult and inaccurate. Only global averages can be measured. Thus, a Large Scale Mock-Up (LSMU) heat sink channel was created to document agitation enhancement of heat transfer. The LSMU is a single channel arrangement which simulates one channel of a 26-channel heat sink being developed. Results from it complement actual-scale experiments in single and multiple channels. With the LSMU, the effect of frequency and amplitude of agitation on heat transfer along different sections of the channel are assessed. At lower velocities of agitation, the heat transfer coefficient is mainly governed by the velocity of agitation (frequency times amplitude) irrespective of the value of frequency or amplitude. However, at higher velocities, amplitude seems to be somewhat more important than frequency in enhancing heat transfer. The results of the present study show strong effectiveness of plate agitators.

Natural and forced convection heat transfer coefficients of various finned heat sinks for miniature electronic systems

2018 ◽  
Vol 233 (2) ◽  
pp. 249-261 ◽  
Author(s):  
SW Pua ◽  
KS Ong ◽  
KC Lai ◽  
MS Naghavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Cooling Mode ◽  
Heat Transfer Coefficients ◽  
Experimental Heat

Downward lighting light-emitting diodes require cooling with cylindrical fin heat sinks to be mounted on top and cooled under natural convection air cooling mode. Performance simulation would involve specification of the heat transfer coefficient. Numerous methods are available to simulate the performance of conventional plate fin heat sinks including computational fluid dynamics packages. It would be feasible to perform simulation based on conventional flat plate fin heat sinks. A cylindrical fin heat sinks could be simply treated as a plate fin heat sink, if we imagine it cut open and laid out horizontally. A theoretical model is proposed in this paper. An experimental investigation is conducted here to validate its accuracy. Convective heat transfer coefficients were experimentally determined for a horizontally and vertically inclined bare plate operating under natural and forced air cooling modes. In addition, a vertical plate fin heat sink and a vertical cylindrical fin heat sink under natural convection were investigated. Power inputs were kept from 5 to 40 W in order to keep operating temperatures below 100 ℃. Comparison of the experimental heat transfer coefficients and those obtained from well-known existing Nusselt number correlations show that agreement was poor for the bare plate but satisfactory for the plate and cylindrical fin heat sinks. Although they are within the generally accepted range, it would be advisable for actual measurements to be carried out in order to provide more accurate sizing for thermal measurements.

High Dense Plate Fin Heat Sinks Characterization and Validation

2005 ◽  
Author(s):  
Guoping Xu ◽  
Chakravarthy Akella ◽  
Lee Follmer
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Turbulent Flows ◽  
Heat Sink ◽  
Analytical Methods ◽  
Parallel Plate ◽  
Electronics Cooling ◽  
Heat Sinks ◽  
Laminar And Turbulent Regimes ◽  
Laminar And Turbulent Flows

Plate fin heat sinks are commonly used in electronics cooling including high end processors. A number of empirical and analytical methods are available to predict their performance but most of the models are valid for fin pitch larger than 3 mm heat sinks in laminar flow. The present work is to investigate high dense plate fin heat sink in both laminar and turbulent regimes. Thermal and hydraulic performance of several dense plate-fin heat sinks were characterized for high end processors in a fully-ducted wind tunnel. All the three heat sinks tested have the same dimensions of 89 mm (L) × 56 mm (W) × 50 mm (H), and fin number varied between 23 and 33. Heat sink base for all heat sinks was made of solid copper, while different fin materials of Aluminum and Copper are used. Several analytical methods for laminar flow from literature were reviewed in this study. A new heat transfer analytical method was proposed for both laminar and turbulent flows. The characterization data from these three parallel plate heat sinks were compared with the analytical methods. Finally, empirical heat transfer correlations were developed for both laminar and turbulent flows.

Heat Transfer of a Double Layer Microchannel Heat Sink

2013 ◽  
Vol 479-480 ◽  
pp. 411-415 ◽  
Author(s):  
Wong Kok Cheong ◽  
Fashli Nazhirin bin Ahmad Muezzin
Keyword(s):  
Heat Transfer ◽  
Double Layer ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Channel Width ◽  
Channel Height ◽  
Physical Parameters ◽  
Microchannel Heat Sink ◽  
Counter Flow

A numerical study is conducted to predict the effects of physical parameters of a double layer microchannel heat sink on heat transfer. The physical parameters investigated are the channel height and channel width for different flow orientation at the upper and lower channels. For the range of Reynolds number investigated, results show that parallel flow configuration leads to better heat transfer performance than counter flow. Lower thermal resistance can be achieved in a double-layered microchannel heat sink with higher channel height and lower channel width.

scholarly journals Nonlocal Modeling and Swarm-Based Design of Heat Sinks

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
David Geb ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Electronics Cooling ◽  
Optimization Methods ◽  
Volume Averaging ◽  
Population Based ◽  
Design Tool ◽  
Heat Sinks ◽  
Optimal Designs ◽  
Traditional Approaches

Cooling electronic chips to satisfy the ever-increasing heat transfer demands of the electronics industry is a perpetual challenge. One approach to addressing this is through improving the heat rejection ability of air-cooled heat sinks, and nonlocal thermal-fluid-solid modeling based on volume averaging theory (VAT) has allowed for significant strides in this effort. A number of optimization methods for heat sink designers who model heat sinks with VAT can be envisioned due to VAT's singular ability to rapidly provide solutions, when compared to computational fluid dynamics (CFD) approaches. The particle swarm optimization (PSO) method appears to be an attractive multiparameter heat transfer device optimization tool; however, it has received very little attention in this field compared to its older population-based optimizer cousin, the genetic algorithm (GA). The PSO method is employed here to optimize smooth and scale-roughened straight-fin heat sinks modeled with VAT by minimizing heat sink thermal resistance for a specified pumping power. A new numerical design tool incorporates the PSO method with a VAT-based heat sink solver. Optimal designs are obtained with this new tool for both types of heat sinks, the performances of the heat sink types are compared, the performance of the PSO method is discussed with reference to the GA method, and it is observed that this new method yields optimal designs much quicker than traditional approaches. This study demonstrates, for the first time, the effectiveness of combining a VAT-based nonlocal thermal-fluid-solid model with population-based optimization methods, such as PSO, to design heat sinks for electronics cooling applications. The VAT-based nonlocal modeling method provides heat sink design capabilities, in terms of solution speed and model rigor, that existing modeling methods do not match.

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