Thermal Design and Cooling Performance Evaluation of Electronic Equipment Containing Power Electronic Devices

Categorized Application Technology of Numerical Simulation on Electronic Equipment Thermal Design

Abstract: In order to utilize a numerical simulation on a product development for electronic equipment, not only the simulation techniques themselves, but the application technologies of the simulation in the product design, were examined. The design process of electronic equipment was categorized into four stages, which were a concept, a function, a layout and a parameter design. Each design stage consists of a specifying that a human decide the specification for the next stage and a verification whether the specification satisfy the previous stage requirements. The specifying and the verification are conducted over and over again. Numerical simulation is corresponded to the verification and is used to accelerate this iteration instead of experiments. The examples of numerical simulation corresponding to these four verifications were shown in the present paper. There are few examples in last two type of simulation. The progress of the numerical technology for function and concept verification is expected. The product development process requires not only numerical simulation based on physics but also statistical approach.Copyright © 2009 by ASME

Numerical investigations of using carbon foam/PCM/Nano carbon tubes composites in thermal management of electronic equipment

Abstract: A numerical investigation of predicting thermal characteristics of electronic equipment using carbon foam matrix saturated with phase change material (PCM) and Nano carbon tubes as thermal management modules is presented. To study the effect of insertion of RT65 and Nano carbon tubes in carbon foam matrices of different porosities, three different modules; namely Pure CF-20, CF20 + RT65, and CF-20 + RT65/Nano carbon modules are numerically tested at different values of carbon foam porosities. Mathematical model is obtained using volume averaging technique based on single-domain energy equation and a control volume based numerical scheme. Interfacial effects influencing heat transfer process at enclosure wall, module surface and different interfacial surfaces within the composite have been addressed. Governing equations have been solved using a CFD code (Thetis, http://thetis.enscbp.fr ). Mathematical model is validated by comparing its prediction with previous experimental measurements for pure CF-20 foam and CF-20 + RT65 composite modules. The model is used to predict thermal characteristics of CF-20 + RT65/Nano carbon tubes composite as a thermal management modules. Results reveal that insertion of RT65/MWCNTs in CF-20 leads to a 11.5% reduction in the module surface temperature for carbon foam porosities less than 75%. The reduction decrease to 7.8% for a porosity of 88%. Numerical results of transient and steady state temperature histories at different depths within the module are compared with previous experimental data and fair agreement is obtained.

Thermal Management of Low Profile Electronic Equipment Using Radial Fans and Heat Sinks

Abstract: There is an increasing need for low profile thermal management solutions for applications in the range of 5-10 W, targeted at portable electronic devices. This need is emerging due to enhanced power dissipation levels in portable electronics, such as mobile phones, portable gaming machines, and ultraportable personal computers. This work focuses on the optimization of such a solution within the constraints of the profile and footprint area. A number of fan geometries have been investigated where both the inlet and exit rotor angles are varied relative to the heat conducting fins on a heat sink. The ratio of the fan diameter to the heat sink fin length was also varied. The objective was to determine the optimal solution from a thermal management perspective within the defined constraints. The results show a good thermal performance and highlight the need to develop the heat sink and fan as an integrated thermal solution rather than in isolation as is the traditional methodology. An interesting finding is that the heat transfer scales are in line with turbulent rather than laminar correlations despite the low Reynolds number. It is also found that while increasing the pumping power generally improves the thermal performance, only small gains are achieved for relatively large pumping power increases. This is important in optimizing portable systems where reduced power consumption is a competitive advantage in the marketplace.

Experimental investigation on graphene based nanoparticles enhanced phase change materials (GbNePCMs) for thermal management of electronic equipment

Abstract: The present study focuses on the thermal management of electronic components using nanoparticles enhanced phase change materials (NePCMs) based heat sinks for the reduction in the baseline temperature, to heighten the operational time and ensure the enhanced functionality and reliability of the working system. RT-44HC and RT-64HC are used as the base PCMs along with the incorporation of GNPs (0.002wt%, 0.005wt% and 0.008wt%) for different heating loads i.e. 0.86 KW/m2, 1.44 KW/m2 and 2.40 KW/m2. Results revealed that after 90 min of charging phase, RT-44HC/GNPs (0.008wt%) has depicted best performance with the maximum reduction of 25% in the baseline temperature for 0.86 KW/m2. Subsequently, at 1.44 KW/m2 RT-44HC/GNPs (0.005wt%) and RT-64HC/GNPs (0.008wt%) have shown maximum reduction of 13.6% and 11.8% respectively. For higher heating load i.e. 2.40 KW/m2 RT-64HC/GNPs has revealed best performance with maximum reduction of 16.37% in the temperature. Hence, for low heating loads, RT-44HC composites are best recommended whereas, RT-64HC composites are suitable for higher power levels and high heating loads.

Study on the chimney effect in natural air‐cooled electronic equipment casings under inclination: Proposal of a thermal design correlation that includes the porosity coefficient of an outlet opening

Abstract: Natural air-cooling technologies for electronic equipment have the important advantages of no fan and high reliability. However, natural air cooling has lower cooling capability than fan air cooling, so enhancement of its cooling capability is required. This paper presents the results for experimental casings designed to employ the chimney effect in natural air-cooled electronic equipment. The system casing is inclined to enhance the effectiveness of natural air cooling. Experiments were carried out using a thin laptop PC. We investigated the effect on cooling capability produced by inclining the casing and by varying the outlet positions and numbers and the porosity coefficient of the outlet openings. The results show that the temperatures inside the casing and heater surfaces are slightly diminished by the effect of increased inclination and porosity coefficient of outlet openings. Moreover, the increase in natural circulation flux in the casing was quantitatively proven by experiments. In addition, the experimental data were reduced to a Nusselt number–Rayleigh number correlation, , by using a modified reference length. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 122–136, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20103

Cooling Fan Model for Thermal Design of Compact Electronic Equipment: Improvement of Modeling Using PQ Curve

Abstract: In order to hasten the thermal design for forced convection electronic devices, cooling fans should be modeled to reduce a computational load. A fan-curve-model, which generates volumetric flow rate versus the characteristics pressure difference of a fan, is very simple and usually incorporated into commercial CFD codes. However, this model often results in an erroneous flow rate. In this work, both the experiments and the CFD simulation were performed around small axial-flow-fans of 30 and 40 mm in diameter. The measured PQ curve was applied to the fan model, and compared the result of the simulation to the experimental data. It was clarified that the major reason behind the disagreement was the difference in the pressure definition of the fan model from the PQ curve measured using a chamber. Based on this, a simple method was proposed to correct this definition. Also, the system effect, which is the impact of obstacles on the fan delivery curve, was investigated by setting a cylindrical obstacle at upstream or downstream proximity of the fan.Copyright © 2009 by ASME