Thermal And Flow Analysis Of Piezoelectric Fans For Cooling LEDS Packages

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. Komputer, pakej LED dan alatan elektronik mudah-alih, seperti komputer riba mini, tablet, telefon sel, meningkat dengan ketara dari segi bentuk, ringan, nipis, dan lebih padat dengan fungsi yang tinggi bagi memenuhi permintaan pelangan. Pertumbuhan yang ketara ini dalam elektronik termaju memerlukan penyelesaian moden bagi menyesuaikan dengan cabaran baru pengurusan terma. Salah satu daripada penyelesaian terma terbaru adalah kipas piezoelektrik, yang mana baru-baru ini dianggap sebagai alat yang amat sesuai bagi penyejukan generasi hadapan dalam alatan mikroelektronik umum

Infrared thermographic analysis of LED lights on a ceramic layer

LED svetila intenzivno nadomeščajo žarnice z volframovo žarilno nitko, pri čemer je poleg doseganja dobrih optičnih lastnosti pomembno zagotavljati njihovo učinkovito hlajenje. V tej nalogi obravnavamo infrardečo termografsko analizo dveh različnih LED svetil na keramični plasti z debelinami od 0,25 mm do 5 mm. Razvita je bila eksperimentalna proga, ki omogoča napajanje LED svetila z omejevanjem električnega toka in napetosti ter sočasno spremljanje porabe električne moči in merjenja temperature s pomočjo hitrotekoče infrardeče kamere. V okviru meritev smo analizirali segrevanje keramičnih plasti različnih debelin, vpliv orientacije LED svetila, dinamični odziv segrevanja in čas, potreben za doseganje ustaljenega temperaturnega stanja pri različnih električnih močeh. Prikazani so tudi temperaturni profili in dvodimenzionalna temperaturna polja. Rezultati meritev kažejo, da razviti merilni postopek omogoča vrednotenje segrevanja LED svetil in določanja maksimalne dovoljene električne moči, da zadostimo temperaturnim omejitvam.LED lamps intensively replace incandescent lamps, and in addition to achieving good optical properties, it is important to ensure their efficient cooling. In this paper, the infrared thermographic analysis of two different LED lamps on a ceramic layer with thicknesses from 0.25 mm to 5 mm is considered. An experimental track has been developed that enables the power supply of LED lights by limiting current and voltage, while simultaneously monitoring electrical power consumption and temperature measurement using a high-speed infrared camera. As part of the measurements, the heating of ceramic layers of different thicknesses, the influence of LED light orientation, the dynamic heating response and the time required to achieve a steady-state temperature at different electrical powers were analyzed. Temperature profiles and two-dimensional temperature fields are also shown. The measurement results show that the developed measurement procedure enables the evaluation of the heating of LED lights and the determination of the maximum allowable electrical power in order to meet the temperature limits

Optimization of multiple piezoelectric magnetic fans for electronic cooling system

Air cooling system for electronics is still preferable due to its simplicity and reliability. To date, some researches on air cooling showed that a piezoelectric fan is more efficient than natural convection with minimum power consumption. However, a single piezoelectric fan can only cover a small cooling area and more power might be consumed if multiple piezoelectric fans are applied. A multiple piezoelectric magnetic fan (MPMF) has proven to have a high potential to replace the existing rotary fan. Initially, the MPMF was designed in line/array (APMF). However, the deflection of the MPMF needs to be improved in fundamental analysis and validated by the experimental data from previous studies. Hence, the first objective of the study is to propose a new mathematical model for MPMF to include the location of magnet and distance between magnets to length ratio. A centripetal force is introduced as the contributing parameter to the equation of deflection of a radial piezoelectric magnetic fan (RPMF). The second objective is to optimize the multiple piezoelectric magnetic fan parameters using Response Surface Method (RSM). The experimental setup consisted of two divisions; parameters optimization and thermal analysis. The theoretical results of the fan deflection were compared with experimental data and the thermal performance of the proposed RPMF was compared with the benchmarked paper. The results showed that an optimal magnet location was on the Mylar blade, 44mm from the origin (63.8% of original length). The new location of magnet has led to increment of Reynolds Number to 924. The distance between magnets to length ratio is in the range of 14.5mm to 15.6mm (21%-22.6% of the fan length). By fixing the distance between magnets at 14.5mm, the resonant frequency and deflection of RPMF and APMF were 42.66Hz, 11.6mm and 40.68Hz, 9.4mm respectively. By varying the orientation of MPMF, the Reynolds number of RPMF was improved 32% compared to APMF. The heat convection coefficient increased by 8.07% to enhance the heat transfer performance by 8.06%. The thermal resistance reduced by 7.6% which led to 5% increment of overall thermal efficiency. In conclusion, the relocation of magnet has improved the overall performance of MPMF. The RPMF has been found to have a better cooling performance compared to APMF. Thus, RPMF has a high potential to be applied in electronics cooling system

Thermal analysis of dual piezoelectric fans for cooling multi-LED packages

This paper reports on the dissipation of heat generated by a high power LED array using piezoelectric fans. Both numerical and experimental studies were carried out to evaluate the heat dissipation efficiency of high power LED package operating under multiple vibrating fans. Two vibrating fans were vertically oriented to the LED package and arranged according to configuration A (for edge to edge arrangement), and configuration B (for face to face arrangement). The junction temperature (Tj), thermal resistance (R ) and average heat transfer coefficient View the MathML sourceh¯ were estimated. The results show that the single fan enhanced heat transfer performance approximately 1.8 times for the LED package. On the contrary, the dual fans enhanced heat transfer performance approximately by 2.3 times for configuration A and 2.4 for configuration B. A significant decrease in the thermal resistance was observed for all the configurations when fan separation distance δ was reduced. The best performance relative to natural convection was found to be at (δ = 0.1) which decreased the thermal resistance using single fan by about 38%, whereas the dual fan accounted for 49.5% in case of configuration A, and 50.6% for configuration B

Numerical Simulations and Optimization Analysis of the Heat Transfer in Piezoelectric Fans

PhD thesisA combined theoretical/computational study is performed to investigate an innovative cooling technology using piezoelectric actuators. The piezoelectric fan is an ultra-low energy air mover which induces unsteady periodic flow. This study focuses on the characteristics of the fluid flow and heat transfer as well as system optimisation in terms of the operational parameters of the piezoelectric fan blade. Regarding the dynamics of piezoelectric fan movements, the fan blades vibrate as a wave-like motion. The fan blade can be simplified as a homogeneous viscoelastic beam with uniform cross-section. In the theoretical analysis, the method of complex orthogonal decomposition is adopted to analyse the blade motions, and the travelling index is proposed to evaluate the curvature of piezoelectric fan blade. The unsteady fluid flow and heat transfer have been studied by computational fluid dynamics based on three-dimensional large-eddy simulation. A parametric study has been performed to investigate the effects of three dynamic parameters of the blade oscillation: oscillating frequency, oscillating amplitude and wave number. In the heat transfer study, a heat source represented by a high temperature wall is added to the computational model. The temperature and the surface Nusselt number of the hot wall serve the purpose of evaluating the characteristics of heat transfer. It is found that the oscillation frequency and amplitude have significant impacts on the fluid flow and heat transfer. In addition, the response surface method facilitates the process of finding the optimal operational parameters of piezoelectric fans. Considering practical limitations imposed by fan geometries and materials, factors determining the optimal operational parameters are outlined as the theoretical optimal operational parameters may not be achievable in practical applications. The results and analyses provide fundamental knowledge to guide the design of a piezoelectric fan system for cooling applications

Development of effective thermal management strategies for LED luminaires

The efficacy, reliability and versatility of the light emitting diode (LED) can outcompete most established light source technologies. However, they are particularly sensitive to high temperatures, which compromises their efficacy and reliability, undermining some of the technology s key benefits. Consequently, effective thermal management is essential to exploit the technology to its full potential. Thermal management is a well-established subject but its application in the relatively new LED lighting industry, with its specific constraints, is currently poorly defined. The question this thesis aims to answer is how can LED thermal management be achieved most effectively? This thesis starts with a review of the current state of the art, relevant thermal management technologies and market trends. This establishes current and future thermal management constraints in a commercial context. Methods to test and evaluate the thermal management performance of a luminaire system follow. The defined test methods, simulation benchmarks and operational constraints provide the foundation to develop effective thermal management strategies. Finally this work explores how the findings can be implemented in the development and comparison of multiple thermal management designs. These are optimised to assess the potential performance enhancement available when applied to a typical commercial system. The outcomes of this research showed that thermal management of LEDs can be expected to remain a key requirement but there are hints it is becoming less critical. The impacts of some common operating environments were studied, but appeared to have no significant effect on the thermal behaviour of a typical system. There are some active thermal management devices that warrant further attention, but passive systems are inherently well suited to LED luminaires and are readily adopted so were selected as the focus of this research. Using the techniques discussed in this thesis the performance of a commercially available component was evaluated. By optimising its geometry, a 5 % decrease in absolute thermal resistance or a 20 % increase in average heat transfer coefficient and 10 % reduction in heatsink mass can potentially be achieved . While greater lifecycle energy consumption savings were offered by minimising heatsink thermal resistance the most effective design was considered to be one optimised for maximum average heat transfer coefficient. Some more radical concepts were also considered. While these demonstrate the feasibility of passively manipulating fluid flow they had a detrimental impact on performance. Further analysis would be needed to conclusively dismiss these concepts but this work indicates there is very little potential in pursuing them further