What kind of power is going in to the unit? I have done some work with customers on LED lighting units, have found a few things that might be useful.
I've found that PCBs for high power LED lighting units normally have either a lot of thick layers with high copper coverage, or have a solid core, so a reasonable assumption to make would be that the board is solid metal. If the models have a large amount of copper tracking on the surface, it might be necessary to model in the thick tracking areas of the model as solid material to better represent the 'heat sink' effect of the tracking. Just using a standard PCB material can give temperature results that are rather high as they lose this 'heat sink' effect of thick / high cover tracking.
Because LEDs are likely to get hot, you may want to consider radiation. In my experience, this drops LED temp by a degree or two, but adds to the run time, so initial runs are probably best left without radiation and the final run with to get more accurate results.
As for the actual flow sim study, I would highly recommend putting control planes in the fully resolve the through thickness of the board and the LED geometry. Five cells through the thickness of the board and LEDs would be a good aim.
I have used both solid geometry and split surfaces to represent the LEDs in the past, and both give comparable results, but solid modelled LED blocks are better as the temperate can average over the volume of the LED.
Lastly, I would be careful what values you use for the wattage of the LEDs, remember that the efficiency of the LED effects the thermal output. The difference in heat values from 35 - 40% efficiency LED can drastically alter the accuracy when comparing to physical data. Below you can see that using a 35% efficiency value for the input changes accuracy from 4% to 1%, so make sure you physically test your LEDs to get accurate efficiency values don't just trust the data sheet!
Hope this helps.
I have done a few simulation using SW Flow sim with EC module. Please share some details which type of Light you want to simulate.? i will help you in this.
Below are steps of doing simulation of this kind of job.
Step 1: Simplify geometry for SW Simulation.
(Remove all lenses or details modeling of LED chip & keep it simple as two rectangular or square blocks as shown in your LED datasheet from mfr. And create a explode view for future)
Step 2: Create your custom LED in two resister components.
(ADD the information in size of L x W x H of Junction & Case in the value box, add the resistance values of junction and case from LED datasheets & save)
Step 3: Apply custom LED to junction with case as per SW two resister component with load in KW.
(Keep in mind, do this exercise for all LEDs individually to get each LED’s temperature behavior)
Step 4: Apply Thermal resistance value of Solder material between all LEDs and MCPCB.
(This values will be in solder material datasheet or from standard material library of silicon materials. use explode view to apply this value between faces, consider MCPCB as metal plate)
Step 5: Apply thermal resistance value of Thermal paste between MCPCB & Heat sink.
(This value should be customized in user defined material of thermal resistance or choose from library of materials like; DOW Corning etc. from interference materials)
Step 6: Specify your goals, surface of global goal for Temperature on LED junction or outer casing etc.
Some important documents required: LED Datasheet, Thermal Paste datasheet, Solder material datasheet & refer image for initial general settings in wizard.
Good one Stephen !!! Thanks...
@Varun, thanks in-advance for your support... I am planning to simulate LED's used in Electronic industry... can you share some of your great works (maybe with Radiation)...
Can you share some 3D models?
I am simulating LED's inside factory/industrial units (eg: Manufacturing factory with LED lighting, machineries, ducting system).... !!!