Thermal and flow analysis of piezoelectric fans for cooling leds packages

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Date
2014
Authors
Farid Shaker, Sufian
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Computers, LED packages and portable electronic devices, such as minilaptops, tablets, and cellular phones, are rapidly emerging in lighter, slimmer, and more compact forms with high functionalities to meet consumer demands. This tremendous growth in advance electronics necessitates modern solutions to be adapted with the new challenges of thermal management. One of the recent thermal solutions is piezoelectric fans, which recently considered as a very strong candidate for cooling the next generation in general microelectronic devices. Piezoelectric fans (vibrating fans) are microvibrating machines that can be potentially used as airflow generators to help dissipate heat in microelectronic devices. They are reliable, have longer life span, consume low power, noise-free and it’s adaptable in very small spaces. In this work, a combination of experimental and numerical analyses (CFD) was performed to investigate the performance of piezoelectric fans on heat dissipation function. Laser vibrometer study was carried out to determine the resonance frequency of vibrating fans. Particle image velocimetry study presented the flow field induced by combination of different vibrating fans arrangements. 3D simulations based on a dynamic meshing scheme were performed in FLUENT and ABAQUS with the use of code coupling interface MpCCI to investigate transient changes on the temperature and flow fields achieved by vibrating fans. The results of single vibrating fan orientations showed that the vertical orientation to the heated surface had significant enhancement on the heat transfer. The effects of vibration phase difference between the fans corresponding to in-phase (Φ=0°) and out-of-phase (Φ=180°) vibrations were explored in terms of transient temperature and flow fields. Computed results show that the single fan enhanced heat transfer performance within approximately 2.3 times for the heated surface. By contrast, the dual fans enhanced heat transfer performance within approximately 2.9 for out-of-phase vibration (Φ=180°) and 3.1 for in-phase vibration (Φ=0°). This successful approach was then exploited as a cooling device to dissipate heat from high power LEDs package. The LEDs package were directly exposed to the dual vibrating fans arranged according to configuration A (for edge to edge fans arrangement), and configuration B (for face to face fans arrangement). It was found that the dual fans enhanced heat transfer performance approximately by 2.3 times for configuration A and 2.4 for configuration B. Combination of heat sink with dual and quadruple vibrating fans to cool the LEDs package for maximizing the heat dissipation was also explored. The quadruple vibrating fans with heat sink demonstrated significant reduction in the junction temperature of the LEDs (Tj = 319K) over a dual fans (Tj = 324K), natural convection with heat sink (Tj = 344K) and natural convection only MCPCB substrate without heat sink (Tj = 390K). This research has established the ability of piezoelectric fans for thermal management of LEDs arrays and recommends it for use as commercial cooling of LEDs chips.
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