Optimum design parameters of Pin-Fin heat sink using the grey-fuzzy logic based on the orthogonal arrays

The effects of design parameters and the optimum design parameters for a Pin-Fin heat sink (PFHS) with the multiple thermal performance characteristics have been investigated by using the grey-fuzzy logic based on the orthogonal arrays. Various design parameters, such as height and diameter of pin-fin and width of pitch between fins are explored by experiment. The average convective heat transfer coefficient, thermal resistance and pressure drop are considered as the multiple thermal performance characteristics. Through the grey-fuzzy logic analysis, the optimization of complicated multiple performance characteristics can be converted into the optimization of a single grey-fuzzy reasoning grade. In addition, the analysis of variance (ANOVA) is applied to find the effect of each design parameter on the each or all thermal performance characteristics. Then the results of confirmation test with the optimal level constitution of design parameters have obviously shown that this logic approach can effective in optimizing the PFHS with the multiple thermal performance characteristics.     

Application of response surface methodology in the parametric optimization of a pin-fin type heat sink

In this paper, an effective procedure of response surface methodology (RSM) has been successfully developed finding the optimal values of designing parameters of a pin-fin type heat sink (PFHS) under constrains of mass and space limitation to achieve the high thermal performance (or cooling efficiency). Various design parameters, such as height and diameter of pin-fin and width of pitch between fins are explored by experiment. The thermal resistance and pressure drop are considered as the multiple thermal performance characteristics. Experiments are performed by a standard RSM design called a central composite design (CCD). The results identify the significant influence factors to minimize thermal resistance and pressure drop. The obtained optimal designing parameters have been predicted and verified by conducting confirmation experiments.     

Modeling and optimization of designing parameters for a parallel-plain fin heat sink with confined impinging jet using the response surface methodology

The parallel-plain fin (PPF) array structure is widely applied in convective heat sinks in order to create extended surface for the enhancement of heat transfer. In the present study, for investigating the influences of designing parameters of PPF heat sink with an axial-flow cooling fan on the thermal performance, a systematic experimental design based on the response surface methodology (RSM) is used. The thermal resistance and pressure drop are adopted as the thermal performance characteristics. Various designing parameters, such as height and thickness of fin, width of passage between fins, and distance between the cooling fan and the tip of fins, are explored by experiment. Those parameters affect the structure arrangement, geometry of fins and the status of impinging jet from an axial-flow cooling fan installed over the heat sink. A standard RSM design called a central composite design is selected as experimental plan for the four parameters mentioned above. An effective procedure of response surface methodology (RSM) has been proposed for modeling and optimizing the thermal performance characteristics of PPF heat sink with the design constrains. The most significant influential factors for minimizing thermal resistance and pressure drop have been identified from the analysis of variance. The confirmation experimental results indicate that the proposed model is reasonably accurate and can be used for describing the thermal resistance and pressure drop with the limits of the factors studied. The optimum designing parameters of PPF heat sink with an axial-flow cooling fan under constrains of mass and space limitation, which are based on the quadratic model of RSM and the sequential approximation optimization method, are found to be fin height of 60 mm, fin thickness of 1.07 mm, passage width between fins of 3.32 mm, and distance between the cooling fan and the tip of fins of 2.03 mm.     

Application of grey-fuzzy logic on the optimal process design of an injection-molded part with a thin shell feature

This paper presents an effective approach for the optimization of machining parameters to an injection-molded part with a thin shell feature (example of cell phone shell consist of PC/ABS material) based on the orthogonal array with the grey relational analysis and fuzzy logic analysis. Through the grey-fuzzy logic analysis, the optimization of complicated multiple performance characteristics can be converted into the optimization of a single grey-fuzzy reasoning grade. In this injection molding process, the machining parameters, namely the mold temperature, melt temperature, filling pressure and filling time are optimized with considerations of multiple performance characteristics including the strength of welding line, the shrinkage and the difference of forming distributive temperature. The experimental results for the optimal setting have obviously shown that the above performance characteristics in the injection molding process can be improved effectively together through this approach.     

Forced Convection of Metallic Foam Heat Sink under Laminar Slot Jet Confined by Parallel Wall

This investigation numerically explores the fluid flow and heat transfer characteristics of the metallic foam heat sink under the laminar slot jet confined by a parallel wall. The Prandtl number is 0.7, and the range of Reynolds numbers is 100–500. The parameters of interest in this work are the porosity (?), pore density (PPI), effective solid conductivity (k _s *), jet nozzle width (W), ratio of the porous sink length to the jet nozzle width (L/W), ratio of the jet-to-sink distance to the jet nozzle width (C/W), and ratio of the porous sink height to the jet nozzle width (H/W). The simulation data reveal that the Nusselt number of the system with a metallic porous heat sink was much better than that of the system without a porous sink, for a given volumetric flow rate and value of (C+H)/W. The porous properties (such as ? and k _s *) and the system configurations (such as L/W and H/W) strongly influenced the cooling performance. The effect of the PPI, W, and C/W values on the heat transfer characteristics of the system was negligible. The effect of the fluid flow on the thermal results was examined. Finally, the correlations of the stagnation Nusselt number and the average Nusselt number were also determined using the numerical data for a system with the size of a common multi-chips module.     

NUMERICAL SHAPE OPTIMIZATION FOR HIGH PERFORMANCE OF A HEAT SINK WITH PIN-FINS

The design optimization of a 7 × 7 pin-fin heat sink is performed numerically. To achieve higher thermal performance of the heat sink, the thermal resistance at the junction of the chip and the heat sink and the overall pressure drop in the heat sink have to be minimized simultaneously. The fin height (h), fin width (w), and fan-to-heat sink distance (c) are chosen as the design variables, and the pressure drop (ΔP) and thermal resistance (θ _ja ) are adopted as the objective functions. To obtain the optimum design values, we used the finite-volume method for calculating the objective functions, the Broydon-Fletcher-Goldfarb-Shanno method for solving the unconstrained nonlinear optimization problem, and the weighting method for predicting the multiobjective problem. The results show that the optimum design variables for the weighting coefficient of 0.5 are as follows: w = 4.653 mm, h = 59.215 mm, and c = 2.669 mm. The objective functions corresponding to the optimal design are calculated as ΔP = 6.82 Pa and θ _ja  = 0.56 K/W. The Pareto solutions are also presented for various weighting coefficients, and they offer very useful data for designing a pin-fin heat sink.     

基于烟囱效应的通信基站热沉优化设计

利用数值模拟的方法,探究了烟囱效应对通信基站热沉自然对流散热的强化作用,对影响热沉散热性能的主要因素及其机理进行了分析,并以热沉热阻作为优化目标,通过优化翅片间距与隔板间隙的取值提升了热沉的散热性能。在优化设计过程中,通过模糊均值聚类对拉丁超立方抽样所得的样本点进行筛选,快速并有效的缩减了设计区间,使用Kriging模型对新设计区间内的均匀样本点进行拟合,构建了热沉热阻与设计变量间的代理模型,并结合遗传算法寻优,确定了最优设计参数取值。在最优参数布置下,相比于初始热沉,热沉的发热面温度降低了15.23 K,总热阻降低了34.29%。     

On the role of radiation view factor in thermal performance of straight-fin heat sinks

The present study is aimed to experimentally investigate the importance of the effects of thermal radiation and its corresponding view factor on the thermal performance of a straight-fin heat sink designed for electronic cooling under natural convection. The convection heat transfer coefficient between the fins and the ambient air is evaluated in conjunction with the results obtained through the experimental investigation. Three different models are developed to investigate the effects of thermal radiation and its pertinent view factor on the convection coefficient as well as the fin performance of the heat sink. The deviations based on different operating conditions for these models are analyzed and the importance of the effects of thermal radiation and view factor in the thermal analysis of fin arrays are identified and discussed. It can be concluded that the practice of neglecting the radiation view factor in the thermal analysis of fin arrays should be prohibited based on the fact that the errors generated are noticeably larger than those of solely neglecting thermal radiation.     

Optimum Thermal Analysis of a Heat Sink with Various Fin Cross-Sections by Adjusting Fin Length and Cross-Section

A theoretical analysis of a heat sink is presented in this study to pursue the purpose of maximum thermal dissipation and the least material cost. Due to the general derivation, the longitudinal fin arrays on a heat sink can have either square, rectangular, equilaterally triangular, or cylindrical cross-section. By input of the Biot number, Bi, heat transfer coefficient ratio, H, and the shape parameter, γ, the heat transfer equation, which is expressed in implicit form, can be solved by iterative method to calculate the optimum fin length and fin thickness. Meanwhile, the thermal resistance of a heat sink can be obtained to illustrate the cooling performance under various design conditions.     

Optimization design of microchannel heat sink geometry for high power laser mirror

Microchannel heat sink for high power laser mirror with water cooling was analyzed as a function of microchannel geometry and operation parameters. A comparative analysis of the thermal deformation on the mirror surface without cooling and that with cooling revealed that the maximal thermal deformation on the mirror surface could decrease from about 0.115 μm to around 0.040 μm under the laser power of 200 W/cm² by using microchannel heat sink designed. In order to enhance the performance of microchannel heat sink, the effects of channel width, channel depth, fin width, mirror thickness and cooling region were investigated. The results indicated that the heat transfer performance of the microchannel heat sink could be further improved by narrow and deep channel, narrow fin, thin mirror and large cooling region.     

Thermal analysis of CPU with CCC and copper base plate heat sinks using CFD

This paper describes experimental and theoretical investigations of heat sinks with different base plate material mounted on CPUs. The thermal model of the computer system with heat sinks which is created using Gambit (for preprocessing) and the simulation is carried out using Fluent (for solver execution and post processing). The following parameters are considered: fin thickness, fin height, and number of fins. Primarily in this paper different base plate thickness and base plate materials are optimized for maintaining the cost and thermal performance of a heat sink. In this research work, the thermal model of the computer system with a slot parallel plate fin heat sink design has been selected, and the fluid flow and thermal flow characteristics of heat sinks are studied. The slot parallel plate fin heat sinks have been used with copper base plates and carbon carbon composite (CCC) base plates to enhance the heat dissipation. The results and conclusion obtained in this present work are found to be in good agreement with numerical results. A complete computer chassis with slot parallel plate heat sinks is investigated varying the thickness of base plate, and the performances of the heat sinks are compared. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20342     

Analysis of heat transfer characteristics of double-layered microchannel heat sink

Numerical analysis is performed to examine the heat transfer characteristics of a double-layered microchannel heat sink. The three-dimensional governing equations are solved by the finite volume method. The effects of substrate materials, coolants, and geometric parameters such as channel number, channel width ratio, channel aspect ratio, substrate thickness, and pumping power on the temperature distribution, pressure drop, and thermal resistance are discussed. Predictions show that the heat transfer performance of the heat sink is improved for a system with substrate materials having a higher thermal conductivity ratio. A coolant with high thermal conductivity and low dynamic viscosity also enhances the heat transfer performance. The pressure drop decreases with the channel aspect ratio and channel width ratio. Further, the thermal resistance of the microchannel heat sink can be minimized by optimizing the geometric parameters. Finally, the results show that for the same geometric dimensions, the thermal performance of the double-layered microchannel heat sink is better than that of the single-layered one, by an average of 6.3%.     

Multidisciplinary optimization of a pin-fin radial heat sink for LED lighting applications

In this study, the cooling performance and mass of a pin-fin radial heat sink were optimized. A radial heat sink with pin fins was examined numerically to obtain a lighter heat sink while maintaining a similar cooling performance to that of a plate-fin heat sink investigated in a previous study. Both natural convection and radiation heat transfer were considered. Experiments were performed to validate the numerical model. The average temperature and mass of the heat sink for various types of fin arrays were compared to determine an appropriate reference configuration. The effects of various geometric parameters on the thermal resistance and mass of the heat sink were investigated; these indicated that the system was sensitive to the number of fin arrays, as well as the length of the long and middle fins. Multidisciplinary optimization was carried out using the three design variables to minimize the thermal resistance and mass simultaneously, and Pareto fronts were obtained with various weighting factors. A design for the optimum radial heat sink is proposed, which reduces the mass by more than 30% while maintaining a similar cooling performance to that of a plate-fin heat sink.     

An experimental investigation of forced convective cooling performance of a microchannel heat sink with Al2O3/water nanofluid

Experiments were conducted to investigate forced convective cooling performance of a copper microchannel heat sink with Al₂O₃/water nanofluid as the coolant. The microchannel heat sink fabricated consists of 25 parallel rectangular microchannels of length 50 mm with a cross-sectional area of 283 μm in width by 800 μm in height for each microchannel. Hydraulic and thermal performances of the nanofluid-cooled microchannel heat sink have been assessed from the results obtained for the friction factor, the pumping power, the averaged heat transfer coefficient, the thermal resistance, and the maximum wall temperature, with the Reynolds number ranging from 226 to 1676. Results show that the nanofluid-cooled heat sink outperforms the water-cooled one, having significantly higher average heat transfer coefficient and thereby markedly lower thermal resistance and wall temperature at high pumping power, in particular. Despite the marked increase in dynamic viscosity due to dispersing the alumina nanoparticles in water, the friction factor for the nanofluid-cooled heat sink was found slightly increased only.     

Measurement of performance of plate-fin heat sinks with cross flow cooling

This work assesses the performance of plate-fin heat sinks in a cross flow. The effects of the Reynolds number of the cooling air, the fin height and the fin width on the thermal resistance and the pressure drop of heat sinks are considered. Experimental results indicate that increasing the Reynolds number can reduce the thermal resistance of the heat sink. However, the reduction of the thermal resistance tends to become smaller as the Reynolds number increases. Additionally, enhancement of heat transfer by the heat sink is limited when the Reynolds number reaches a particular value. Therefore, a preferred Reynolds number can be chosen to reduce the pumping power. For a given fin width, the thermal performance of the heat sink with the highest fins exceeds that of the others, because the former has the largest heat transfer area. For a given fin height, the optimal fin width in terms of thermal performance increases with Reynolds number. As the fins become wider, the flow passages in the heat sink become constricted. As the fins become narrower, the heat transfer area of the heat sink declines. Both conditions reduce the heat transfer of the heat sink. Furthermore, different fin widths are required at different Reynolds numbers to minimize the thermal resistance.     

Optimization of performance and emission characteristics of PPCCI engine fuelled with ethanol and diesel blends using grey-Taguchi method

The performance and emission characteristics of a PPCCI engine fuelled with ethanol and diesel blends were carried out on a single cylinder air cooled CI engine. In order to achieve the optimal process response with a limited number of experimental cycles, multi objective grey relational analysis had been applied for solving a multiple response optimization problem. Using grey relational grade and signal-to-noise ratio as a performance index, a combination of input parameters was prefigured so as to achieve optimum response characteristics. It was observed that 20% premixed ratio of blend was most suitable for use in a PPCCI engine without significantly affecting the engine performance and emissions characteristics.     

Investigation of thermal flow structure and performance heat transfer in three-dimensional circular pipe using twisted tape based on Taguchi method analysis

In the current investigation, the twisted tape inserts are considered as the augmentation thermal technique, the influence of a variety of twisted tape configurations on pressure drop characteristics, temperature differences, thermal performance of fluid flow structure, heat transfer improvement, and friction factor are numerically evaluated. The changed geometrical parameters employed for this study comprise twisted tape width, twisted tape thickness, number of turns, and inward thickness are the input parameters. Design of experiments method is applied to analyze the influence of latter various types of geometrical parameters on hydraulic thermofluid pattern and heat transfer improvement in the twisted tube heat exchanger as the output variables. For the experimental design optimization Taguchi analysis is based on investigate of alterations and performs the orthogonal arrays (OA). Moreover, the OA L16 is chosen as the plan of experimental study. It is found the best design of twisted tape in this study by using computational fluid dynamics numerical methodology complained with Taguchi method the enhancement in heat transfer and hence the overall performance evaluation factor is higher than 1.2.     

Predicting the thermal performance characteristics of staggered vertical pin fin array heat sinks under combined mode radiation and mixed convection with impinging flow

A theoretical and experimental study was carried out investigating the influence of thermal radiation on the thermal performance of a pin fin array heat sink with the purpose of developing accurate predictive capability for such situations, and to determine the particular design parameters and environmental conditions under which thermal radiation might be advantageous to the thermal performance. Several different types of experimental tests were run with the corresponding physical parameter variations including the emissivity of the heat sink, elevated ambient air temperature, the temperature of a visible hot surface, and its radiation configuration factor. A theoretical model, validated by experimental data, which includes the capability of predicting the influence of thermal radiation on the thermal performance of a pin fin array heat sink, was developed by introducing an effective radiation heat transfer coefficient that was added to the convective heat transfer coefficient.     

Numerical study of the heat sink with un-uniform fin width designs

The thermal performances of the heat sink with un-uniform fin width designs with an impingement cooling were investigated numerically. The governing equations are discretized by using a control-volume-based finite-difference method with a power-law scheme on an orthogonal non-uniform staggered grid. The coupling of the velocity and the pressure terms of momentum equations are solved by the SIMPLEC algorithm. The well-known k ? ε two-equations turbulence model is employed to describe the turbulent structure and behavior. The parameters include the five Reynolds number (Re = 5000–25000), three fin heights (H = 35, 40, 45 mm), and five fin width designs (Type-1–Type-5). The objective of this study is to examine the effects of the fin shape of the heat sink on the thermal performance. The results show that the Nusselt number increases with the Reynolds number. The increment of the Nusselt number decreases gradually with the increasing Reynolds number. Furthermore, the effects of fin dimensions on the Nusselt number at high Reynolds numbers are more significant than that at low Reynolds numbers. It is also found that there is potential for optimizing the un-uniform fin width design.     

Heat transfer and pressure loss characteristics of very compact heat sinks with plate fins cooled by jets

High-performance and very compact heat sinks have been developed for effective cooling of VLSIs with high heat-generation densities. Their heat transfer and pressure loss characteristics in air-jet cooling have been experimentally studied. The highly compact heat sinks were plate-fin arrays with a very small fin pitch of 0.4–2.0 mm. The rectangular jet nozzle width that gave the highest cooling performance was 30 to 40% of the streamwise length of the heat sinks. The influence of fin height on heat transfer became weak when the ratio of the height to the thickness of the fin exceeded approximately 35. When the air flow rate was constant, the thermal conductance increased as the fin pitch decreased. For a constant fin pitch, heat sinks with smaller fin thickness showed larger thermal conductance at a given blower power consumption. In our experimental range, the heat dissipation rate per unit heat sink volume increased as the base plate area of the heat sink became small. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(6): 399–414, 1998