With the definitive irruption of LED technology in the field of lighting, the main challenge for designers is to effectively manage the heat dissipation produced by LEDs. Its performance and duration over time depend to a large extent on the operating temperature. In this article, we'll look at how to optimize the thermal performance of an LED fixture without sacrificing product design requirements.
Simulation based design
Simulation-based design is a methodology proposed by Siemens Digital Industries Software to integrate thermal simulation in a phase where fundamental design decisions are made, which largely determine the performance and aesthetics of the product.
Unlike the traditional method, this approach allows the designer to experiment with different variants from the start and simulate thermal behavior without leaving the design environment. The prototypes are made digitally, through the creation of digital twins, which make it possible to perfectly simulate the operating characteristics of what will be the real product. This allows designers to select the best options early in the product development process.
· Electronic or mechanical designers finalize a design and deliver it to simulation experts for review and application of eventual changes.
· For each requested change, the different design phases are repeated.
· Each change or variant of the design supposes an increase in costs and time.
· Multiple physical prototypes may be required.
|DESIGN BASED ON SIMULATION
· Electronic or mechanical designers run simulation early in the design process.
· The necessary changes are detected immediately and are carried out in a short time.
· It is possible to experiment more than one variant easily.
· The prototype is made virtually.
Simcenter FLOEFD, from Siemens Digital Industries Software, is the tool par excellence for applying simulation-based design in the lighting industry.
Simcenter FLOEFD revolutionizes LED design in three areas in particular:
Integration with mechanical CAD. Being fully integrated with the main mechanical CADs (Solid Edge, NX, Creo, Catia and Solidworks), there is no need to transfer data between CAD and CFD via files step. Design and CFD models stay in sync, reducing both simulation time and development costs.
Automated parametric studies. They save time for the user, who can focus on model definition instead of manual tasks, by coming up with the optimized design in less time.
dedicated technology. Simcenter FLOEFD can also be used for advanced modeling or to study complex phenomena such as condensation, solar radiation, hot spots, or icing. Also, it is the ideal tool to accurately model LEDs, by importing thermal and optical characterization experimental measurements from the TERALED device (see below).
Thermal simulations of LED lighting with Simcenter FLOEFD; temperature and flow predictions.
Real case: Cariboni Group
An example of the application of this methodology is that of the Cariboni Group, an Italian company leader in the production of outdoor lighting on an international level. In this sector, temperature, color and maintaining good performance over time are essential requirements, which must be respected in highly variable environmental conditions.
In outdoor luminaires, the electronic components are inside a waterproof casing that does not allow air exchange with the outside. This makes dissipation difficult, especially if we take into account that the design requires attractive shapes and not just efficient ones.
By adopting Simcenter FLOEFD and working with Cadlog, Cariboni Group designers were able to avoid physical prototyping and empirical testing, reducing the costs and time required to develop a competitive and successful product. in the market. This approach allowed the team to experiment without limits with numerous variants. Other company products, such as MCPCBs, also benefited from component thermal characterization.
Simcenter T3STER and Simcenter TERALED
Thermal characterization is a fundamental element in the thermal simulation of a project with LEDs. The hardware for thermal/optical characterization Simcenter T3STER and Simcenter TERALED make up a combined test station: electrical, thermal, and radiometric/photometric for LEDs and LED modules. The results of these measurements are compact multi-domain models ready to be used in Simcenter thermal design software.
These LED test stations comply with the JEDEC JESD51-52 standard and follow the CIE 127:2007 and 225:2017 technical reports. Actual thermal resistance and light output metrics are measured based on actual LED junction temperature over a wide range of currents.
The process is fully automated. Third party spectroradiometers help capture emission spectra and provide additional information for accurate modeling of LED package light output properties in lighting design.
Anti-Covid UV-C disinfection simulation
UV-C sanitization of rooms and air conditioning systems is one of the main ways to prevent pandemics such as Covid. Thanks to Simcenter FLOEFD, it is possible to simulate the germicidal effect of UV-C light sources during the system design phase, especially ventilation systems. UV-C rays are a particular range of ultraviolet rays, with a wavelength of between 200 and 280 nanometers. They are capable of penetrating inside microorganisms -such as bacteria, viruses, molds, etc.-, entering their molecules and altering their DNA, inactivating them.
By irradiating objects and fluids, such as air or water, with LEDs based on UV-C rays, it is possible to eliminate the bacteria and viruses present inside them. The main areas of application are sanitizing devices and air conditioning systems, in environments such as hospitals, offices, shopping centers or means of public transport.
Simcenter FLOEFD has a technology dedicated to calculating the effective germicidal dose released by UV-C LEDs and accumulated in fluids, in order to understand if a certain design hypothesis has sufficient germicidal action or not. The integration with the mechanical CAD allows to vary the geometric parameters of the ventilation equipment to simulate the germicidal effect until reaching a sufficient threshold.
An HVAC duct with 11 UVC tubes (60 W) showing germicidal efficacy of irradiation (left) and actual germicidal volume irradiation (right) with flow from left to right.