LED chip cooling system using ionic wind induced by multi-wire corona discharge

Abstract

• A T-shaped multi-wire ionic wind pump is developed for cooling a high-power LED chip. • Relationship between air flow in the pump and its electrode configuration is revealed. • Increasing the wire-plate gap in the outlet channel strengthens the reverse discharge effect. • Arranging electrodes in the outlet channel further improves the performance of the T-shaped EHD pump. The high temperature of a light-emitting diode (LED) chip reduces its luminous output and lifetime and can even cause catastrophic damage to the chip. In recent years, ionic wind generators have shown great potential for LED chip cooling owing to their noiselessness, low energy consumption, and compact structure. However, the heat transfer and flow characteristics of ionic wind generated by multi-wire electrodes for LED cooling have not been sufficiently investigated. In this study, a T-shaped multi-wire ionic wind pump, in which each wire electrode corresponds to a pair of parallel plates, was designed for heat dissipation of a 24 W high-power LED chip. The relationship between the air flow characteristics inside the ionic wind pump and the electrode configuration was revealed through numerical simulations. Then, an optimized ionic wind pump was fabricated to test the cooling performance of the LED chip. The results show that each pair of plate electrodes has a critical length, and the average velocity at the pump inlet becomes independent of the plate length when it exceeds this critical value. For fixed wire electrodes in the outlet channel, when their operating voltage remains constant, increasing the wire-plate distance reduces the charge density around these wires, thus strengthening the reverse discharge effect and reducing the average velocity at the pump inlet. When only the wire in the inlet channel discharges electricity at a fixed voltage of 18 kV, the ionic wind pump can stabilize the LED case temperature below its safe temperature (LED operating voltage: 36 V). If all wires discharge electricity at a fixed voltage of 18 kV, the LED case temperature can be further reduced to 74 °C, which is lower than the maximum rated case temperature of 85 °C. In conclusion, when designing multi-wire ionic wind pumps, the electrodes inside them should be elaborately configured to reduce mutual interference and maximize the ionic wind flow rate. The designed ionic wind pump can serve as a noiseless thermal management equipment for high-power LED illumination devices.