With the increasing global demand for more efficient lighting solutions, light emitting diodes (LED’s) have gained widespread adoption in both consumer and industrial lighting markets. While LED’s have proven efficiency and longevity, such performance enhancements are highly correlated to their operating temperatures. While LED’s do not produce infrared (IR) radiation, more than 60% of the input power is lost as heat. In order to maximize LED brightness (lumen output) and lifetime, it is essential to reduce the junction temperature through effective thermal management. Typical thermal management methods include passive heat-sinking and conventional fan cooling. While passive heat-sinks provide a noise-less solution to excess heat, natural convection does not provide sufficient cooling for higher powered LED systems. Fan cooling provides forced convection for effective cooling while taking advantage of well-established heat-sink design guidelines developed by the electronic industry. However, the improvement from fan cooling comes at a trade-off between acoustic noise and fan speed.
Piezoelectric fans can potentially provide low-noise and long-term cooling solutions for modern LED systems. A piezoelectric fan consists of a piezoelectric cantilever beam with a longer mylar blade attached below the beam. When an AC voltage is applied at the beam’s resonant frequency (typically 115V at 60 Hz – 30mW), the tip of the fan experiences a large displacement, resulting in air movement. The vortices flowing from the tip of the blade provide unique airflow patterns for LED cooling applications. Since the frequency of the piezoelectric beams are typically on the lower end of the audible range, acoustic noise from piezoelectric fans are not noticeable. Current research efforts are focused on the design of heat-sinks for cooling LED’s with piezoelectric fans to take advantage of their unique flow patterns. This talk will discuss results from (1) experimental heat transfer analysis, (2) computational design and analysis using COMSOL multi-physics and (3) flow visualization of piezoelectric fans to optimize heat-sink designs.
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