Optimization of pin-fin heat sinks using entropy generation minimization

In this study, an entropy generation minimization, EGM, technique is applied as a unique measure to study the thermodynamic losses caused by heat transfer and pressure drop in cylindrical pin-fin heat sinks. The use of EGM allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general expression for the entropy generation rate is obtained by considering the whole heat sink as a control volume and applying the conservation equations for mass and energy with the entropy balance. Analytical/empirical correlations for heat transfer coefficients and friction factors are used in the optimization model, where the characteristic length is used as the diameter of the pin and reference velocity used in Reynolds number and pressure drop is based on the minimum free area available for the fluid flow. Both in-line and staggered arrangements are studied and their relative performance is compared on the basis of equal overall volume of heat sinks. It is shown that all relevant design parameters for pin-fin heat sinks, including geometric parameters, material properties and flow conditions can be simultaneously optimized.     

Least-energy optimization of forced convection plate-fin heat sinks

A coefficient of performance (COP/sub T/) analysis for plate fin heat sinks in forced convection is presented and shown to provide a viable technique for combining least-material optimization with the entropy minimization methodology. The COP/sub T/ metric relates the heat sink cooling capability to the invested fan pumping work and the thermodynamic work required to manufacture and assemble the heat sink. The proposed optimization methodology maximizes the forced convection cooling that can be achieved by a heat sink occupying a specified volume, with a fixed energy investment and entropy generation rate. In addition, the study identifies the presence of an optimal resource allocation ratio, providing the most favorable distribution of existing energy resources, between heat sink manufacturing and operation, over a fixed product life cycle.     

Optimal numerical design of forced convection heat sinks

The objective of this paper is to describe the development of a computationally efficient computer-aided design (CAD) method, which uses a finite element numerical model (FEM) coupled with empirical correlations, to create an optimum heat sink design, subject to multiple constraints. A thermal optimization "challenge" problem, representative of anticipated heat sink requirements in the near future, is solved to demonstrate the proposed methodology. Particular emphasis is placed upon micro-processor central processing unit (CPU) chip cooling applications where, in addition to thermal requirements, the heat sink design specification includes constraints upon size, total mass, and air coolant pressure drop across the heat sink.     

Optimization of plate fin heat sinks using entropy generationminimization

The specification and design of heat sinks for electronic applications is not easily accomplished through the use of conventional thermal analysis tools because “optimized” geometric and boundary conditions are not known a priori. A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with heat transfer and fluid friction. All relevant design parameters for plate fin heat sinks, including geometric parameters, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature. In addition, a novel approach for incorporating forced convection through the specification of a fan curve is integrated into the optimization procedure, providing a link between optimized design parameters and the system operating point. Examples are presented that demonstrate the robust nature of the model for conditions typically found in electronic applications. The model is shown to converge to a unique solution that gives the optimized design conditions for the imposed problem constraints     

Thermal design methodology for high-heat-flux single-phase and two-phase micro-channel heat sinks

This paper explores several issues important to the thermal design of single-phase and two-phase micro-channel heat sinks. The first part of the paper concerns single-phase heat transfer in rectangular micro-channels. Experimental results are compared with predictions based on both numerical as well as fin analysis models. While the best agreement between predictions and experimental results was achieved with numerical simulation, a few of the fin models are found to provide fairly accurate predictions. The second part of the paper focuses on predicting the incipient boiling heat flux. A comprehensive model based on bubble departure and superheat criteria is developed and validated with experimental data. The incipience model is capable of predicting the location, shape and size of bubbles departing in rectangular micro-channels. In the third part of the study, an analytical model is developed to predict pressure drop across a two-phase micro-channel heat sink. This model provides a detailed assessment of pressure drop concerns with two-phase micro-channels, including compressibility, flashing and choking. Overall, the present study provides important guidelines concerning practical implementation of micro-channel heat sinks in high-heat-flux electronic cooling applications.     

电子产品散热器的设计

对电子产品使用的散热器的散热原理、主要影响因素进行了分析,建立了数理模型,并对如何选择散热器提供了一些可行的依据.     

U- and L-shaped heat pipes heat sinks for cooling electronic components employed a least square smoothing method

Heat pipes-heat sink modules transfer heat from a heat source to the heat pipes, and then to the heat sink and out into the surrounding ambient, and are suitable for cooling electronic components through a forced convection mechanism. The configuration and thermal performance of the heat sinks with inserted heat pipes were studied in the present paper. This article uses experimental procedures to investigate the thermal performance of two embedded U-shaped heat pipe and six embedded L-shaped heat pipe thermal modules with different fan speeds and heat source areas. And via the superposition method and least-square estimators in experimental data, the performance curves of individual U- and L-shaped heat pipes were derived and predicted. Results show that the lowest thermal resistances of U- and L-shaped heat pipe-heat sinks are respectively 0.246 °C/W and 0.166 °C/W given dual fans operating at 3000RPM and 30 × 30 mm² heat sources. Results for a single U-shaped heat pipe are 0.04 °C/W at 78.85 W, while sequential results for L-shaped heat pipes are 1.04 °C/W, 2.07 °C/W, 2.76 °C/W, 2.19 °C/W and 1.7 °C/W between 34 W and 40 W.     

Heat transfer from square pin-fin heat sinks using air impingement cooling

Experimental and numerical results are presented for heat transfer from a C4 mounted organic land grid array (OLGA) thermal test chip cooled by air impingement. Five heat sink geometries were investigated for Reynolds numbers ranging from 9,000 to 26,000. The dimensionless nozzle-to-heat sink vertical spacing z/D was varied between 2 and 12. In this study, we investigate the interactions between heat sink geometry, flow conditions and nozzle setting and how they affect the convective heat transfer and overall cooling of the test chip as measured by total thermal resistance /spl theta//sub ja/. Optimizing fin arrays by minimizing the overall heat sink thermal resistance instead of focusing solely on maximizing the heat transfer from the fins is shown to be a better design criterion. We also provide results that show cooling performance gains can be obtained by inserting a deflector plate above the heat sink.     

Experimental and numerical investigation of circular minichannel heat sinks with various hydraulic diameter for electronic cooling application

This article presents the experimental thermal and hydraulic performances of heat sinks with various channel diameter for cooling electronic components. A heat sink with the length and width of 60 mm and total height of 16 mm fabricated from aluminum material. The heat sink is designed with four circular minichannels and three different values of hydraulic diameter of channel (D = 4 mm, D = 6 mm and D = 8 mm). The minichannel heat sink is heated with a uniform base heat flux. Also, numerical simulation of the problem is performed using Finite Volume Method (FVM). Comparing the experimental and numerical results show that numerical results are in a good agreement with experimental data. The variation of channel diameter affects the heat transfer and pressure drop characteristics of the circular shaped minichannel heat sink. The experimental results show that the increase of channel diameter reduces the pressure drop in the heat sink. Also, the minichannel heat sink with a hydraulic diameter of 4 mm has a much lower thermal resistance than the minichannel heat sinks with a hydraulic diameter of 6 mm and 8 mm. Furthermore, the optimization is done to have the maximum heat transfer coefficient and minimum of pressure drop along the heat sink.     

Optimization study of stacked micro-channel heat sinks for micro-electronic cooling

With smaller inlet flow velocity, a micro-channel stack requires less pumping power to remove a certain rate of heat than a single-layered micro-channel, because it provides a larger heat transfer area. A simple thermal resistance network model was developed to evaluate the overall thermal performance of a stacked micro-channel heat sink. Based on this simple model, in this study, a single objective minimization of overall thermal resistance is carried out using genetic algorithms. The aspect ratio, fin thickness and the ratio of channel width to fin thickness are the variables to be optimized, subject to constraints of maximum pressure drop (4 bar) and maximum volumetric flow rate (1000 ml/min). During the optimization, the overall dimensions, number of layers and pumping power (product of pressure drop and flow rate) are fixed. The study indicates that reduction in thermal resistance can be achieved by optimizing the channel configuration. The effects of number of layers in the stack, pumping power per unit area, and the channel length are also investigated.     

Fluid flow and heat transfer in liquid cooled foam heat sinks for electronic packages

In this paper, the fluid flow and heat transfer of liquid cooled foam heat sinks (FHSs) were experimentally investigated. Eight Open-celled copper foam materials with two pore densities of 60 and 100 PPI (pores per inch) and four porosities varying from 0.6 to 0.9 were bonded onto copper base plates to form the FHSs, which were then assembled on flip chip BGA packages (FBGAs) with a common thermal grease as the thermal interface material. A liquid cooling test loop was established to obtain the pressure drops and overall thermal resistances. For the four 60 PPI FHSs, the one with the lowest porosity of 0.6 is found to possess the lowest thermal resistance level with the largest pressure drop. Generally the FHSs with 100 PPI had slightly lower thermal resistances at the same flowrates but much larger pressure drops than those with 60 PPI. In the overall performance assessment, the thermal resistances of the FHSs are plotted against the pressure drop and the pump power, together with a microchannel heat sink of similar unit cell scale and structural dimensions. The thermal resistances of the FHS with a porosity of 0.8 and pore density of 60 PPI were identified to be the lowest among all the FHSs, which outperformed the microchannel heat sink at large pressure drop and pump power. The reduced heat sink thermal resistance and Nusselt numbers for the present FHSs and microchannel heat sink are also presented and compared with the FHS reported in the literature.     

Heat rejection limits of air cooled plane fin heat sinks for computer cooling

Current desktop computers typically use fan-heat sinks for cooling the CPU, referred to as active heat sinks. This work seeks to determine the heat rejection limits for such fan-heat sinks, within specific fan and heat sink space limits. A fixed volume, 80 /spl times/ 60 /spl times/ 50 mm is chosen as the limiting dimensions, which includes the fan volume. The present work addresses plane fin heat sinks, on which a typical 60 mm fan is mounted. Both duct flow and impinging flow are considered. Analytically based models are used to predict the optimum geometry (minimum convection resistance) for plane fins with duct and impinging flow configurations. Also assessed are the effects of increased fan speed (up to 25%) and heat sink base size (33% increase) on air-cooling limits in duct and impinging flow. Tests on fan-heat sinks are done to validate the predictions. Optimization is also done for an enhanced (offset-strip) fin geometry in duct flow. The plane fin is found to outperform the enhanced geometry.     

Performance analysis of heat pipe aided NEPCM heat sink for transient electronic cooling

An experimental investigation on the thermal performance of Nano Embedded Phase Change Material (NEPCM) heat sink with heat pipe has been conducted for electronic cooling in Personal computers. The NEPCM and heat pipe configuration in the heat sink effectively eliminates the use of electronic fan. A flat plate heater was used to simulate the computer's microprocessor. The heat sink configurations were placed above the flat plate heater and tested for multiple head load conditions. The addition of NEPCM increases the heat storage capacity, causes a delay effect on the sensible temperature rise and maintained the core temperature of the heat sink at room temperature for prolonged time. Heat pipe charged with R134a refrigerant placed inside the heat sink cavity for regeneration of NEPCM in heat sink. The results showed that use of heat pipe aided NEPCM heat sink caused a 3 °C decrease in the heater's surface plate temperature during six hours of the operating period without the help of electronic fan or any other forced convection.     

Electrical design inspection: a methodology for using circuitsimulation in the design and development of electronic power supplies

The authors present an electrical design inspection (EDI) methodology that combines advanced power circuit simulation techniques and RISC (reduced instruction set computing) workstation hardware to use simulation in the day-to-day design of electronic power supplies. This methodology makes use of circuit simulation to detect design faults in electronic power supplies and prevent them from propagating further in the product realization process. A hierarchy of inspections which form the basis of EDI methodology, is introduced. The methodology has been embedded in a prototype electrical design inspection system which has been tested on a Sun Sparcserver 4/490 dedicated to circuit simulation. The power of this methodology has been illustrated by its application to a self-oscillating variable-frequency DC-DC power converter with peak current control. It is demonstrated that EDIS can automatically execute inspections requiring an accurate determination of the steady-state solution of the circuit, and process these results. The steady-state accelerator capability within the SIMPLIS circuit simulator has made it possible to achieve this in an unprecedentedly short CPU time     

电子设备机箱的强风冷设计

介绍了电子设备机箱的强迫空气冷却设计中需要考虑的几个方面,并针对电子设备机箱的强制散热设计过程,结合实例从理论上论述了热设计的计算方法,特别是轴流风机的选型计算方法。     

光伏发电电缆敷设优化设计

结合工程实践,在经济性与合理性方面,对光伏发电电缆敷设进行分析.     

Optimal placement of electronic devices in forced convective cooling conditions

An implementation of a genetic algorithm for electronic devices placement optimisation has been done. The study includes a few cases. In the first application electronic devices are placed along a bottom surface of a duct and cooled with forced convection by air stream with velocity U₀. The thermal model is two-dimensional (2D). The algorithm optimizes the order in the view of four thermal criteria. In the second application a genetic algorithm is used to optimize the position of electronic devices on the surface of a Printed Circuit Board (PCB). The thermal model is three-dimensional (3D). Devices have some specified positions on the PCB and permutations are only performed.     

Thermal design and optimization of natural convection polymer pin fin heat sinks

The design and optimization methodology of a thermally conductive polyphenylene sulphide (PPS) polymer staggered pin fin heat sink, for an advanced natural convection cooled microprocessor application, are described using existing analytical equations. The geometric dependence of heat dissipation and the relationships between the pin fin height, pin diameter, horizontal spacing, and pin fin density for a fixed base area and excess temperature are discussed. Experimental results of a pin finned thermally conductive PPS heat sink in natural convection indicate substantially high thermal performance. Numerical results substantiate analytical modeling results for heat sinks within the Aihara et al. fin density range. The cooling rates and coefficient of thermal performance, COP/sub T/, that relates cooling capability to the energy invested in the formation of the heat sink, has been determined for such heat sinks and compared with conventional aluminum heat sinks.     

Parametric optimization of multichanneled heat sinks for VLSI chipcooling

This paper presents an optimization study of multichannel heat sinks for electronic devices. Specifically, we present a method of determining optimum values of the channel diameter, flow rate and number of channels for minimum pumping power or minimum pressure drop. Optimized parameters are expressed in dimensionless form. The calculated results for both laminar and turbulent regimes present several important relationships among the parameters. A criterion for choice of the flow regime to be used is presented. For a current electronic cooling requirement, the optimized diameter of a channel lies in the micro-scale range when water is used as working fluid. Several advantages of an optimized heat sink and its' feasibility toward actual cooling problems are discussed     

Least-energy optimization of air-cooled heat sinks for sustainable development

The development of heat sinks for microelectronic applications, which are compatible with sustainable development, involves the achievement of a subtle balance between a superior thermal design, minimum material consumption, and minimum pumping power. This presentation explores the potential for the least-energy optimization of natural and forced convection cooled rectangular plate heat sinks. The results are evaluated in terms of a heat sink coefficient of performance, relating the cooling capability to the energy invested in the fabrication and operation of the heat sink, and compared to the entropy generation minimization methodology (EGM).