Jos Kunen - Academia.edu (original) (raw)

Papers by Jos Kunen

Recent Advances in Polymer Nanocomposites

IEEE Transactions on Power Electronics, 2015

ABSTRACT This paper studies the thermal influence of a light-emitting diode (LED) driver on a ret... more ABSTRACT This paper studies the thermal influence of a light-emitting diode (LED) driver on a retrofit LED lamp, also reporting on a procedure for its thermal characterization and multiscale modeling. In this analysis, temperature is measured by infrared thermography and monitoring specific locations with thermocouples. Experimental results point out that temperature increases considerably in all lamp parts when the driver is installed in the lamp (up to 15% for LED board). The multiscale simulation approach is set with thermal parameters (thermal conductivity, emissivity, and LED board thermal resistance) measured from several parts of the lamp, reaching an agreement between experiment and simulation smaller than 10%. With this model, the driver temperature is investigated under operational conditions accounting for two alternative thermal designs. First, the driver is completely surrounded with a filling material (air completely removed, Case A), and, second, only the thermal contact between the board and the lamp is improved (air is kept, Case B). In both cases, the heat removal from the driver to the ambient by conduction is enhanced, observing that temperature decreases in its most heated components up to 10 °C in Case A, and up to 7 °C in Case B.

Avui en dia, l'ús de LEDs com a font de llum ofereix una solució més sostenible i eficient co... more Avui en dia, l'ús de LEDs com a font de llum ofereix una solució més sostenible i eficient comparat amb altres tipus d'il·luminació. Tanmateix, l'eficiència de la bombeta ve limitada per l'eficiència de l'electrònica necessària per alimentar els LEDS i els elements òptics necessaris per obtenir llum blanca. Per tant, encara es genera una gran quantitat de pèrdues en forma de calor. En aquest treball doncs, s'han estudiat diverses estratègies per al disseny tèrmic d'una nova bombeta amb el clàssic casquet de rosca E27 i amb una alta capacitat lumínica, aconseguint uns resultats prometedors

Les peintures en dispersion aqueuse presentent un comportement fortement non-newtonien, et il n&#... more Les peintures en dispersion aqueuse presentent un comportement fortement non-newtonien, et il n'est donc pas possible de determiner leur viscosite d'application avec les godets d'ecoulement conventionnels. Sur la base du principe des godets, on a developpe un viscosimetre capillaire a cisaillement intensif operant sous pression gazeuse, qui est peu couteux et facile a utiliser. Les resultats obtenus pour quatre peintures en dispersion aqueuses du commerce concordent bien avec les resultats fournis deux viscosimetres rotatifs.

IEEE Transactions on Power Electronics, 2019

Experimental techniques for the detection of coherent structures in turbulent water flows are eva... more Experimental techniques for the detection of coherent structures in turbulent water flows are evaluated comparatively. The structure of wall-bounded and free turbulence is characterized theoretically; several Eulerian detection techniques (including an autocorrelation method and a second-quadrant analysis method similar to that of Lu and Willmarth, (1973) and a combination of hydrogen-bubble visualization and laser Doppler anemometry (LDA) are applied to

IEEE Transactions on Power Electronics, 2019

19th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), 2013

This work deals with the extraction of key thermal parameters for accurate thermal modelling of L... more This work deals with the extraction of key thermal parameters for accurate thermal modelling of LED lamps: air exchange coefficient around the lamp, emissivity and thermal conductivity of all lamp parts. As a case study, an 8W retrofit lamp is presented. To assess simulation results, temperature is monitored on the lamp by infrared thermography and by monitoring specific locations with thermocouples. As a result, experimental and simulation results show differences below 15%.

19th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), 2013

2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2011

ABSTRACT This work deals with thermal simulation and characterization of solid state lightening (... more ABSTRACT This work deals with thermal simulation and characterization of solid state lightening (SSL) LED Lamp in order to get precise 3D thermal models for further lamp thermal optimization. Simulations are performed with ANSYS-CFX and CoventorWare software tools. The simulated thermal distribution has been validated with thermal measurement on a commercial 8W LED lamp. Materials parametric study has been carried out to discover problematic parts for heat transfer from power LEDs to ambient. The objectives are to predict the thermal management by simulation of LED lamp and environment and to get more insight in the effect of lamp shape and materials used in order to design more effective LED lamps.

2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2011

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2012, 2012

This work deals with a precise 3-D modelling of several LED board technologies mainly focused on ... more This work deals with a precise 3-D modelling of several LED board technologies mainly focused on thermal, thermo-mechanical evaluation and life time prediction to compare their performances. Main role of each LED board is to transport heat from LED die to heat sink and keep the thermal stresses in all layers as low as possible. Thermal stress has been inspected

2012 4th Electronic System-Integration Technology Conference, 2012

ABSTRACT Intelligent LED lighting systems can save up to 80% of energy compared to incandescent l... more ABSTRACT Intelligent LED lighting systems can save up to 80% of energy compared to incandescent lighting systems. In order to provide these products at reasonable costs, integration and miniaturization are important steps [1]. Another attractive feature of LED systems is the claimed long life expectancy. The design lifetime of LED luminaries is typically 25 to 50 thousand hours [2, 3]. The long design lifetime, in combination with short-cycled technological innovations in LED packaging, pose challenges to traditional test-in reliability engineering approaches. Innovations in LED packaging are required to meet future cost target requirements at proven and designed-in lifetimes. Integral design of complex systems — such as LED systems merging optical, thermal, electrical, and mechanical disciplines — becomes more difficult [4, 9] as reliability engineering builds on the higher specialization per discipline. In this work we explore novel approaches for reliability engineering.

Microelectronics Reliability, 2013

ABSTRACT This work presents a comparison of various LED board technologies from thermal, mechanic... more ABSTRACT This work presents a comparison of various LED board technologies from thermal, mechanical and reliability point of view provided by an accurate 3-D modelling. LED boards are proposed as a possible technology replacement of FR4 LED boards used in 400 lumen retrofit SSL lamps. Presented design methodology can be used for other high power SSL lamp designs. The performance of new LED board designs were evaluated by numerical modeling. Modeling methodology was proven by measurement on reference FR4 LED board. Thermal performance was compared by extracting of LED boards thermal resistances and thermal stress has been inspected considering the widest temperature operating range according to standards (-40 to +125 C). Thermo-mechanical and reliability analysis have been performed to study parameters of each LED board technology, using thermal boundary conditions extracted from the thermal simulation of a whole LED lamp. Elastic-plastic analysis with temperature dependent stress-strain material properties has been performed. The objective of the work is to optimize not only the thermal management by thermal simulation of LED boards, but also to find potential problems from mechanical failure point of view and to present a methodology to design SSL LED boards for reliability.

Microelectronics Reliability, 2012

ABSTRACT This work presents a methodology to design an SSL system for reliability. An LED lamp is... more ABSTRACT This work presents a methodology to design an SSL system for reliability. An LED lamp is thermally characterised and its model thermally simulated, indicating that the LED board (FR4 board with thermal vias, copper tracks and LED package) is the thermally most stressed part. Therefore, a thermo-mechanical analysis is performed from a detailed LED board model to study reliability and lifetime limits, using thermal boundary conditions deduced from the thermal simulation of the whole LED lamp. Based on this analysis the weakest spots are identified as the metal vias in the LED package and the interconnection area between the LED package and copper tracks on the FR4 board.

Journal of Fluid Mechanics, 1986

Flow visualization and Reynolds-stress measurement were combined in an investigation of a turbule... more Flow visualization and Reynolds-stress measurement were combined in an investigation of a turbulent boundary layer in a water channel. Hydrogen bubbles were used to visualize the flow; a laser-Doppler anemometer capable of measuring two velocity components was applied to measure the instantaneous value of the Reynolds stress. Owing to the three-dimensional, time-dependent character of the flow it was rather difficult to identify flow structures from measured velocity signals, especially at larger distances from the wall. Despite this difficulty a method based on the instantaneous value of the Reynolds stress could be developed for detecting bursts in the wall region of the boundary layer. By this method the three-dimensional, time-dependent character of the flow is taken into account by attributing to the same burst ejections occurring successively with very short time intervals. This identification procedure is based on a comparison on a one-to-one basis between visualized flow str...

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2012, 2012

This paper summarizes a study into the thermal influence of an LED driver board on an SSL Lamp. F... more This paper summarizes a study into the thermal influence of an LED driver board on an SSL Lamp. Full thermal characterization of an LED lamp and driver board is carried out by infrared thermography and by monitoring specific locations with thermocouples. The experimental results have been used to set up and validate a predictive simulation model for both the SSL

Recent Advances in Polymer Nanocomposites

IEEE Transactions on Power Electronics, 2015

IEEE Transactions on Power Electronics, 2019

19th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), 2013

2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2011

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2012, 2012

2012 4th Electronic System-Integration Technology Conference, 2012

Microelectronics Reliability, 2013

Microelectronics Reliability, 2012

Journal of Fluid Mechanics, 1986

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2012, 2012