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The hot side of the light Presenter: Pier Angelo Favarolo 18th - - PowerPoint PPT Presentation
The hot side of the light Presenter: Pier Angelo Favarolo 18th - - PowerPoint PPT Presentation
The hot side of the light Presenter: Pier Angelo Favarolo 18th March 2014 1 The zumtobel group Our companies Annual revenues: 1,243.6 million 27.03.2014 2 2 The zumtobel group Production plants 7162 employees in 18 production plants
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The zumtobel group
Production plants 7162 employees in 18 production plants in four continents with one common denominator: The passion for light!
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Modern luminaires contain electronic devices (e.g. drivers) and semiconductors (LEDs, OLED). Their performances and reliability strongly depend on their temperatures: the lower, the better. CFD is a powerful tool to investigate the underlying physics of the problem and hence make suitable design changes.
Thermal management
Why?
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- Anode
Junction Cathode PCB
Light Emitting Diodes
Light generation
The recombination of electrons and holes generate photons
Electrodes
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Light Emitting Diodes
Dice In a typical COB (Chip-On-Board) module the dice have a surface of almost 0.5 mm² and the generated heat and radiant fluxes are of the
- rder of some Megawatts per square meters.
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Light Emitting Diodes
Phosphor conversion InGaN emission
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Light Emitting Diodes
Heat sources Die Phosphor Board
Heat ~ 70% Light ~ 30% of the electrical power
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Light Emitting Diodes
Heat sources The Silicon-Phosphor compound has a poor thermal conductivity.
What happens if some accidentally trapped foreign particle is absorbing the light on the glob-top?
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- Analysis of the thermal behavior of the
glob-top due to the presence of an accidental light absorption.
- Control of the glob-top temperatures in
- rder to avoid alterations of the physical
and optical properties of the Silicon- Phosphor compound.
- Impact of several parameters like the
position and the dimension of the absorbing particles.
Light absorption on the glob-top
Purpose of the investigation Foreign particle
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The simulation model
Physical phenomena
Physical phenomena to be simulated
- Light generated by the dice
- Conversion losses in the phosphor
- Light absorption on the glob-top
- Heat conduction
- Buoyancy-driven convection
- Heat radiation
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Glob-top model
- The glob-top is a compound of Silicon and Phosphor
- The whole glob-top volume is involved in the Stokes‘
shift
The simulation model
Phosphor conversion (Stokes‘ shift) losses The discrete ordinates radiation model (DORM) is adopted in order to take into account the volumetric absorption of the radiation
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The simulation model
Modelling the light
- The multi-band model is used in order to separate
the luminous radiation from the thermal one.
- The spectrum is divided into two bands: one for the
visible and the other one for the IR part of the spectrum
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The simulation model
Modelling the light source
- The dice are modelled as gray bodies
- The radiant temperature and the emissivity are
chosen in order to radiate the desired amount of energy in the visible part of the spectrum.
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The simulation model
Modelling the light source
- The light source has a high temperature used to generate the radiant flux.
- As this temperature is not realistic, it is necessary to isolate thermally, the light source from
the rest of the model → Non-conductive baffles
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The simulation model
Temperature distribution of the glob-top Simulation IR-Camera image
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The simulation model
Temperature distribution
Ø 250 µm Ø 250 µm Ø 1000 µm Ø 500 µm
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