LED heat sink and graphite heat sink process technology development with vibration cooling fluid characteristics

This study investigated the heat transfer characteristics of LED heat sink and the development process technology of graphite heat sink with micro-sized metal powders. Employing the reverse engineering technology, the three-dimension LED heat sink entity was rebuilt and the heat transfer characteristics of LED heat sink were analyzed by CFD numerical simulation and experimental measurement. The numerical results were validated with experimental results and it showed a good agreement. The experimental and simulation results showed that the heat dissipation of LED device could be removed by natural convection effectively. The difference between the maximum temperature and minimum temperature of cooling efficiency was 10 oC. For the process technology development of LED graphite heat sink, the graphite powder, metal powder and resin were mixed in specific ratios. The vacuum casting, vacuum pressure casting and rapid die technology were used to manufacture LED graphite heat sink. The experimental results showed that the LED graphite heat sinks developed in this study have advantages of low cost, light weight and attractive appearance as compared with the heat sink of aluminum alloy, and the overall heat transfer capacity is still within acceptable range

Experimental Study on Active Cooling Systems Used for Thermal Management of High-Power Multichip Light-Emitting Diodes

The objective of this study was to develop suitable cooling systems for high-power multichip LEDs. To this end, three different active cooling systems were investigated to control the heat generated by the powering of high-power multichip LEDs in two different configurations (30 and 2 × 15 W). The following cooling systems were used in the study: an integrated multi-fin heat sink design with a fan, a cooling system with a thermoelectric cooler (TEC), and a heat pipe cooling device. According to the results, all three systems were observed to be sufficient for cooling high-power LEDs. Furthermore, it was observed that the integrated multifin heat sink design with a fan was the most efficient cooling system for a 30 W high-power multichip LED. The cooling system with a TEC and 46 W input power was the most efficient cooling system for 2 × 15 W high-power multichip LEDs

Diseño óptimo de un disipador de calor para luminaria LED mediante moderación modelación computacional

Resumen: En el presente trabajo se desarrolla una selección de materiales y simulación térmica en el diseño de disipadores de calor para sistemas de iluminación de estado sólido (SSL) mejor conocidos como luminarias LEDs. Se desarrolló un modelo matemático con la capacidad de predecir el comportamiento térmico de la luminaria cuando se encuentra en operación. El modelo matemático fue resuelto mediante un software de distribución libre el cual permite resolver ecuaciones diferenciales mediante el método de elemento finito. Los resultados obtenidos en el modelo matemático planteado fueron validados con los resultados obtenidos mediante experimentación usando imágenes termográficas. Palabras clave: LEDs, Diseño asistido por computadora, modelación computacional, Selección computacional de materiales

A Thermal Management System to Reuse Thermal Waste Released by High-Power Light-Emitting Diodes

© 1963-2012 IEEE. In this article, a comprehensive and efficient thermal management system is proposed to harvest and reuse the thermal waste of high-power light-emitting diodes (HP-LEDs) for the first time. Besides a conventional cooling system, including a thermoelectric (TE) cooler (TEC), a heatsink, and a fan, the proposed thermal management system also employs a TE generator (TEG), a temperature sensor, a voltage boost converter, and a microcontroller for thermal waste recycling. In this system, some of the thermal waste released by the HP-LED is harvested by the TEG and converted into electrical energy. With the help of a voltage boost converter, the harvested electrical power is used to power a temperature sensor for monitoring the surface temperature of the HP-LED. The entire system is regulated by the microcontroller. The system is elaborately established, tested, and the results are discussed. The experimental results show that the proposed system has an output electrical power of approximately 696.5μW , which is used to power a temperature sensor as a demonstration. The sensor works well, and the discrepancy of the surface temperature of the HP-LED measured by the sensor and by a thermometer is less than 5.38%, which validates the proposed thermal management system

LED heat sink and graphite heat sink process technology development with vibration cooling fluid characteristics

This study investigated the heat transfer characteristics of LED heat sink and the development process technology of graphite heat sink with micro-sized metal powders. Employing the reverse engineering technology, the three-dimension LED heat sink entity was rebuilt and the heat transfer characteristics of LED heat sink were analyzed by CFD numerical simulation and experimental measurement. The numerical results were validated with experimental results and it showed a good agreement. The experimental and simulation results showed that the heat dissipation of LED device could be removed by natural convection effectively. The difference between the maximum temperature and minimum temperature of cooling efficiency was 10 oC. For the process technology development of LED graphite heat sink, the graphite powder, metal powder and resin were mixed in specific ratios. The vacuum casting, vacuum pressure casting and rapid die technology were used to manufacture LED graphite heat sink. The experimental results showed that the LED graphite heat sinks developed in this study have advantages of low cost, light weight and attractive appearance as compared with the heat sink of aluminum alloy, and the overall heat transfer capacity is still within acceptable range

Thermal characterisation of insulating layers in metal core PCB

This paper provides a steady-state thermal characterisation of advanced insulating layers for isotropic electroconductive adhesive based Metal Core Printed Circuit Boards. Thermal measurements were conducted using the Thermal Transient Tester to analyse the properties of layers applied onto two different base materials - aluminium and copper. For each base material, four types of insulating layers were characterised. Size of the specimen plate for both base materials was selected as 100mm x 20mm x 1mm. The isotropic electroconductive adhesive was applied onto insulating layers to ensure electrical connection between seven SMD heat-generating components. These components are mounted in the identical distance to each other. The thermal characterisation of power SMD components and the assembling process based on isotropic electroconductive adhesive were evaluated. Application of advanced insulating layer was analysed to assess the thermal performance of complete MCPCB structure. It has been shown that the lowest thermal resistance of the aluminium based insulating layers is 21.1K/W, whereas the lowest thermal resistance of the copper based insulating layer is 15.5K/W

Performance Test and Numerical Simulation of an Adjustable Implant for Treating Vocal Fold Paralysis

Unilateral vocal fold paralysis (UVFP) is one of the most common laryngeal diseases that affect human voice and speech production. It often causes incomplete glottal closure, resulting in voice symptoms including hoarseness, voice fatigue and increased voice effort. One common treatment of UVFP is Thyroplasty Type I, which uses a thyroplasty implant to medialize the paralyzed vocal fold and restore the normal vibration of the vocal fold. However, the surgical outcome is extremely sensitive to the size and shape of the implant. Currently, modifications in the implant size and shape rely upon surgical intuition and experience. The level of voice production restored and satisfaction from patient are variable. Furthermore, the surgical outcome also changes with time as the morphology of the vocal fold changes. In the United States, up to 25% of patients need a revision of the surgery. Therefore, it is desired to have an adjustable implant whose shape and size can be adjusted externally. In this way, the need of reopening the voice box can be permanently removed. This thesis explores employing external forces to control the penetration and shape of the implant. In this way, the contact between the implant and the paralyzed vocal fold can be adjusted as needed. The relationship between the external force, displacement of the implant penetration, and deformation and mechanical stress of the vocal fold was systematically studied in both numerical and experimental ways. Such relationship will inform series of reliably loadings on the device without intensive stress inside the vocal fold. The device is the first step toward a magnetically adjustable implant for Thyroplasty Type I surgery

COMPREHENSIVE ELECTRICAL/OPTICAL/THERMAL CHARACTERIZATIONS OF HIGH POWER LIGHT EMITTING DIODES AND LASER DIODES

Thermal characterizations of high power light emitting diodes (LEDs) and laser diodes (LDs) are one of the most critical issues to achieve optimal performance such as center wavelength, spectrum, power efficiency, and reliability. Unique electrical/optical/thermal characterizations are proposed to analyze the complex thermal issues of high power LEDs and LDs. First, an advanced inverse approach, based on the transient junction temperature behavior, is proposed and implemented to quantify the resistance of the die-attach thermal interface (DTI) in high power LEDs. A hybrid analytical/numerical model is utilized to determine an approximate transient junction temperature behavior, which is governed predominantly by the resistance of the DTI. Then, an accurate value of the resistance of the DTI is determined inversely from the experimental data over the predetermined transient time domain using numerical modeling. Secondly, the effect of junction temperature on heat dissipation of high power LEDs is investigated. The theoretical aspect of junction temperature dependency of two major parameters – the forward voltage and the radiant flux – on heat dissipation is reviewed. Actual measurements of the heat dissipation over a wide range of junction temperatures are followed to quantify the effect of the parameters using commercially available LEDs. An empirical model of heat dissipation is proposed for applications in practice. Finally, a hybrid experimental/numerical method is proposed to predict the junction temperature distribution of a high power LD bar. A commercial water-cooled LD bar is used to present the proposed method. A unique experimental setup is developed and implemented to measure the average junction temperatures of the LD bar. After measuring the heat dissipation of the LD bar, the effective heat transfer coefficient of the cooling system is determined inversely. The characterized properties are used to predict the junction temperature distribution over the LD bar under high operating currents. The results are presented in conjunction with the wall-plug efficiency and the center wavelength shift

Verlängerung der Verarbeitungszeit von Kompositen mit einer neuartigen weißen LED-Arbeitsfeldbeleuchtung

Die meisten lichthärtenden Komposite für Zahnfüllungen enthalten Campherchinon als Photoinitiator und können gezielt von einer Polymerisationslampe mit blauem Licht ausgehärtet werden. Diese Wellenlängen sind auch in dem Licht einer Standard- Behandlungsplatzlampe enthalten, sodass es bei der Modellation zu einer ungewollt frühen Aushärtung kommen kann. Das Material wird oberflächlich spröde und bei einer weiteren Modellation bilden sich Risse in der Oberfläche, sodass das Füllungsmaterial ausgetauscht werden muss. Um dies zu vermeiden, kann die Beleuchtungsstärke der Lichtquelle reduziert werden. Alternativ kann das kritische Spektrum unterhalb von 500 nm herausgefiltert werden oder eine gelbe LED mit einem Spektrum oberhalb von 500 nm verwendet werden. Beide Möglichkeiten, die Verarbeitungszeit zu verlängern, erzeugen eine ungewohnte Beleuchtungssituation und reduzieren die Wahrnehmbarkeit von Kontrasten für den Behandler. Ausgehend von dieser Problemstellung wird in der vorgelegten Arbeit eine Konversions-Leuchtdiode entwickelt, die weißes Licht emittiert und eine längere Verarbeitungszeit von campherchinonhaltigen Kompositen als herkömmliche LED-Kopflampen bietet. Zunächst wird die Anregungs-LED der Konversions- Leuchtdiode mit einem Emissionsmaximum bei 425 nm festgelegt. Sie emittiert Licht in einem Bereich, in dem das Verhältnis zwischen einer geringen Anregung des Photoinitiators Campherchinon und einer hohen Anregung des S-Zapfen im Auge besonders günstig ist. Aufbauend auf dieser LED wurde ein mit ihr zu kombinierender Fluoreszenzstoff ausgewählt, der Licht oberhalb von 500 nm emittiert. Die Bewertung der LEDs erfolgte durch die Verarbeitungszeit von campherchinonhaltigen Kompositen mit einem akustischen Messsystem bei einer Beleuchtungsstärke von 10.000 lx. Dabei werden die Farbtemperatur und die Spektren bei der Analyse der LEDs berücksichtigt. Aufbauend auf den Messergebnissen der Vorversuche wurde eine weiße LED entwickelt und von der OSA Opto Light GmbH als Prototyp produziert. Die Verarbeitungszeit lag mit dieser LED bei einer Beleuchtungsstärke von 10.000 lx für verschiedene Komposite zwischen 6:40 min bis 13:20 min. Im Vergleich zu einer herkömmlichen Kopflampe ist dies eine Verlängerung der Verarbeitungszeit um den Faktor 3 bis 5,5. Die Farbtemperatur beträgt 3.000 K und wird als weiß wahrgenommen. Mit dieser LED können in der klinischen Anwendung in einem ausreichend langen Zeitfenster lichthärtbare Komposite in Ruhe verarbeitet werden. Gleichzeitig wird die Verarbeitung durch die weiße Ausleuchtung des Arbeitsfeldes unterstützt

Energy Efficiency and Sustainable Lighting

The lighting of both exteriors and interiors is a field within electrical and lighting engineering, where important technological changes have been taking place oriented towards environmental sustainability and energy efficiency. LED technology has been gradually gaining ground in the world of lighting over other technologies due to its high lighting and energy efficiency and savings. However, some problems related to overheating or associated regulation are emerging. This has prompted the search for new, more efficient, and sustainable forms of lighting. This book presents successful cases related to energy efficiency and lighting that may be of great interest to those trying to enter the world of scientific research