共查询到20条相似文献,搜索用时 15 毫秒
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Giampietro Fabbri 《Heat and Mass Transfer》2008,44(3):305-314
In the present work, the cooling of a high power electronic device is studied. The device is in contact with a heat dissipator
crossed by air. The air motion through the dissipator is forced by a fan whose supplied power is to be minimized. A finite
element dynamic model of the dissipator is firstly created, taking geometrical and physical properties into account as well
as steady state experimental data. A simplified model is then obtained, which reproduces the time pattern of the maximum dissipator
temperature as a response of the thermal flux removed from the electronic device and the mass flow rate of the air. Afterwards,
the simplified model is utilized to build a control system which allows the electronic device to be correctly cooled at minimum
air ventilation power during transition to steady states. Genetic algorithms are used to find the parameters of the finite
element model and of the control system. Some functioning conditions of the electronic device are lastly considered and discussed. 相似文献
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《International Journal of Solids and Structures》1999,36(1):65-78
Most existing mechanical testers are at most bi-axial and in general too large for microelectronic materials and structures. Existing mini testers are primarily single axis without any active specimen alignment monitoring and adjustment capability. Fundamental investigation needs to be conducted for packaging materials in terms of deformation and fracture processes, constitutive laws, and failure quantities. In this paper, a unique 6-axis sub-micron thermo-mechanical fatigue tester is described, including some calibration work for both load cell and machine stiffness. For the first time, an active specimen alignment monitoring and adjustment was demonstrated on a single lap shear sample, assisted by a high resolution laser moiré measurement system. This paper also presents results for two types of polymer films, one lead-free solder alloy, and some other conventional materials. In particular, deformation and failure mechanisms for two polymer films have been discussed. 相似文献
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多胞材料可通过大变形大量地吸收冲击能量,引入密度梯度可进一步提高其耐撞性。梯度多胞材料的宏观力学响应对材料密度分布极为敏感,不同类型的细观构型的影响也极为不同。已有的研究工作主要局限在对给定的密度梯度分析其动态响应,较少对耐撞性设计方法进行研究。本文针对梯度闭孔泡沫金属材料,基于非线性塑性冲击波模型发展了耐撞性反向设计方法,以维持冲击物受载恒定为目标,运用级数法获得了简化模型和渐近解。利用变胞元尺寸法构建了连续梯度变化的三维Voronoi细观有限元模型,并利用ABAQUS/Explicit有限元软件对理论设计进行数值验证。结果表明,反向设计理论简化模型的渐近解对于梯度闭孔泡沫金属材料的耐撞性设计是有效的,所提出的耐撞性设计方法在控制冲击吸能过程和冲击物受载方面具有指导意义。 相似文献
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Inspired by the wing vein of Lepidoptera, a designment of asymmetric bionic branching channel for electronic chips cooling is developed. Lepidoptera vein D was chosen to measure the angle of first and second branch level. Based on these regular patterns, an asymmetric bionic branching channel is designed in a 35 mm × 35 mm chip. Comparing with fractal-like branching channel, it provides a stronger heat transfer capability, lower pressure drop and lower flow resistance in the experiment. 相似文献
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An experimental investigation has been performed to determine the effects of different arrangements of obstacles on the
cooling of simulated electronic package. The considered simulated electronic package consisted of a channel formed by two
parallel plates. The bottom plate is attached with five identical electrically heated square obstacles, which are perpendicular
to the mean airflow and arranged with different side-to-side distances. The experimental results show that the conventional
equi-spaced arrangement might not be the optimum option and should be avoided. A better thermal performance could be obtained
when the side-to-side distances between the obstacles followed a geometric series. For example, at Re=800, the highest temperature
of the optimum arrangement could be reduced by 12% compare to the equi-spaced arrangement and the maximum temperature difference
among the five obstacles is lower than that of equi-spaced arrangement by 32.1%.
Received on 17 December 1999 相似文献
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High energy demand associated to the massive use of air conditioning systems requires careful consideration of passive cooling strategies, with evaporative cooling being recognized as a useful possibility for that purpose. One important factor that influences the performance of evaporative cooling systems is the media material that supports water evaporation process. In this work evaporative cooling capabilities of different building and textile materials were experimentally determined. The major purpose of the study was to select an evaporative cooling material to be used in a more complex passive cooling unit under research development. A test tunnel was constructed for this particular work and the behavior of several samples was analyzed. Results show that among the studied materials a polyester spacer fabric with honeycomb structure presents best performance. 相似文献
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Experiments were performed by using water and paraffin slurry to investigate thermal characteristics from a test multichip
module. The parameters were the mass fraction of paraffin slurry (0, 2.5, 5, 7.5%), heat flux (10, 20, 30, 40 W/cm2) and channel Reynolds numbers. The size of paraffin slurry particles was within 10–40 μm. The local heat transfer coefficients
for the paraffin slurry were larger than those for water. Thermally fully developed conditions were observed after the third
or fourth row. The paraffin slurry with a mass fraction of 5% showed the most efficient cooling performance when the heat
transfer and the pressure drop in the test section were considered simultaneously. A new correlation for the water and the
paraffin slurry with a mass fraction of 5% was obtained for a channel Reynolds number over 5300.
Received on 25 January 1999 相似文献
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Experimental investigations have been carried out to find out the effect of various configurations of the packing material on the performance of a Fluidized Bed Cooling Tower (FBCT). From the experiments it is observed that the shape of the packing material does have a definite effect on the performance of FBCT and the spherical shape is not the best shape.Modifications of the theoretical predictions based on the single stage equilibrium model in the light of the present experiments help in the predictions of the performance of the FBCT when various shapes of the packing material are used.
Das Verhalten eines Wirbelbett-Kühlturms mit Bettmaterialien verschiedener Konfiguration
Zusammenfassung Es wurden Messungen durchgeführt, um den Einfluß verschiedener Konfigurationen von Füllkörpern auf das Verhalten eines Wirbelschicht-Kühlturms zu untersuchen. Die Experimente zeigten, daß die Form der Füllkörper einen ganz definierten Einfluß auf das Verhalten des Kühlturms hat und daß kugelförmige Füllkörper nicht die besten sind.Modifikationen von theoretischen Analysen, basierend auf dem einstufigen Gleichgewichtsmodell, helfen anhand der vorliegenden experimentellen Ergebnisse bei der Vorhersage des Verhaltens solcher Kühltürme, wenn verschiedene Füllkörperformen verwendet werden.相似文献
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This study presents the experimental investigation of regularly structured Composite Latent Heat Storages. Solid–liquid Phase Change Materials have a low thermal conductivity, resulting in high temperature differences. This drawback is compensated by the combination with specially designed frame-structures made of aluminum to enhance the transport of thermal energy. A prototype is investigated experimentally on a test rig, where the heat load and temperatures are measured while the phase change process is observed optically, and compared to a solid block Phase Change Material. 相似文献
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Nandy Putra YanuarFerdiansyah N. Iskandar 《Experimental Thermal and Fluid Science》2011,35(7):1274-1281
Microprocessor power dissipation is constantly increasing. An increase in microprocessor size has also resulted in higher heat fluxes. The growth of information technology has rapidly increased over the past few years, causing an increase in the demand for a microprocessor that has a very high computing ability. The previous generation of central processing units (CPU) had 1.17 billion transistors planted in it, which indicates that a significant amount of heat was generated. The total heat dissipation resulting from a high end CPU is approximately 110-140 W, which will increase if the CPU voltage and frequency increase. Conventional air-cooled cooling systems are no longer adequate to remove these heat fluxes. For a number of applications, direct air-cooling systems will have to be replaced or enhanced by other high performance compact cooling techniques. In this study, the application of nanofluids as the working fluid on a heat pipe liquid-block combined with thermoelectric cooling is investigated. The type and effect of volume concentrations of nanofluids, coolant temperature, and thermoelectricsystem as heat pumps of a PC on the CPU’s temperature are considered. The results obtained from this technique are compared to those from other conventional cooling techniques. The heat pipe liquid-block combined with the thermoelectric system has a significant effect on heat transfer from the CPU. The higher thermal performance heat pipe liquid-block and thermoelectric cooled system with nanofluids proved its potential as a working fluid. 相似文献
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Development of a portable shear test fixture for low modulus porous (foam) materials 总被引:2,自引:0,他引:2
The shear properties of brittle and highly porous carbon (graphitic) foam cannot be measured reliably with most standard test
methods, such as single rail, double rail, Iosipescu shear, etc. A new testing device has been developed to accurately measure
the shear stiffness and strength of carbon foam or other porous materials. Specimens of cylindrical cross section are used
to reduce the high stress concentration that normally occurs in the vicinity of the grip section. Since strain gages could
not be installed on the specimen surface (due to porosity), the shear strain is determined from the specimen end rotation.
A high resolution in the rotational measurement is achieved by using a stepper motor with multiple gear reduction. In view
of testing low modulus material, the load cell of the fixture was mounted onto an axial roller to relieve the axial constraint
while twisting the specimens. The accuracy of the measurement and calibration of the test fixture has been demonstrated by
measuring the shear modulus of two plastic (polyvinyl chloride (PVC) and urethane). 相似文献
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In this paper, the improved design of fractal branching channel net that can meet the demand for cooling of rectangular electronic
chip with arbitrary ratio of length to width is presented. A theory model is proposed that can be used to estimate the performance
of heat transfer and pressure drop approximately. It is found that the optimal total branching level is 7 and the ratio of
length to width is 1.87 at the fixed cooling surface for fractal microchannel heat sink. 相似文献
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在实验测试泡沫金属材料的动态性能时,由于其所具有的特殊性能使得传统的SHPB技术的采用遇到较大的困难。为了实验确定泡沫金属材料的初始动力坍塌强度和平台应力,研究其应变率效应,在现有SHPB实验装置的基础上,利用反分析法中的反卷积技术,通过计算机模拟给出了该实验装置的传递函数,完善了SHPB实验的数据处理系统,为实验研究泡沫材料的动态特性提供了一种有效的方法。 相似文献
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In this work, an experimental investigation on cooling performance of using nanofluid to replace the pure water as the coolant in a minichannel heat sink is conducted. The heat sink comprises of four circular channels with hydraulic diameter of 6 mm. Thermal and hydraulic performances of the nanofluid cooled minichannel heat sink are evaluated from the results obtained for the Nusselt number, friction factor, thermal resistance and pumping power, with the volume flow rate ranging from 0.3 to 1.5 L/min. The experimental results show that the nanofluid cooled heat sink outperforms the water-cooled one, having significantly higher average heat transfer coefficient. Despite the marked increase in dynamic viscosity due to dispersing the nanoparticles in water, the friction factor for the nanofluid-cooled heat sink is found slightly increased only. 相似文献
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Within the electronics industry, high degree of integration and enhanced performance has led to high heat dissipation electronic
devices. This has identified the future development of very high heat flux components. In this paper, a novel and high efficient
diffusion welded heat fin-plate radiator (HFPR) was proposed and designed. Various parameters affect the thermal performance
of HFPR. The effect of three parameters: the working fluid filling ratios (8% < FR < 70%), the vacuum degrees (0.001 Pa < VD < 0.1 Pa),
and the air flow velocities (0.5 m/s < u < 6 m/s) were investigated experimentally. Using distilled water and ethanol as working fluids, a series of tests were carried
out to find the influence of the above parameters on steady-state heat transfer characteristics of HFPR. The experimental
results indicated that the filling ratio and vacuum degree had a significant influence on thermal performance of HFPR. Also
compared with cooling performance using distilled water and ethanol, the HFPR cooling component using distilled water had
a stronger heat dissipation capacity for the same filling ratio. The results also can provide a basis for optimal design of
HFPR structure. 相似文献
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This experimental study is concerned with enhancing the buckling characteristics of sandwich structure when the 6061-T6 aluminum skins are replaced by carbon fiber reinforced composite for the same aluminum honeycomb and polyurethane core. Such an improvement can be attributed to the high strength to weight ratio of the composite skin while the softer core material acts on a relative base as a better energy absorbent and hence tends to stabilize the failure. This results in much higher post-buckling loads which corresponds to the remaining strength of the structure after the onset of buckling.Sandwich structures with core made of polyurethane foam with different densities were also tested in compression. The buckling load increased with the density of polyurethane up to 280 kg/m3 while deattachment of the core and skin occurred when the density is decreased below 100 kg/m3. Compatibility of the skin and core material is shown to play an important role in the buckling behavior of sandwich structure. 相似文献
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The transient thermal stress crack problem for two bonded dissimilar materials subjected to a convective cooling on the surface containing an edge crack perpendicular to the interface is considered. The problem is solved using the principle of superposition and the uncoupled quasi-static thermoelasticity. The crack problem is formulated by applying the transient thermal stresses obtained from the uncracked medium with opposite sign on the crack surfaces to be the only external loads. Fourier integral transform is used to solve the perturbation problem resulting in a singular integral equation of Cauchy type in which the derivative of the crack surface displacement is the unknown function. The numerical results of the stress intensity factors are calculated for both the edge crack and the crack terminating at the interface using two different composite materials and illustrated as a function of time, crack length, coefficient of heat transfer, and the thickness ratio. 相似文献