Abstract
The technology of Light Emitting Diodes (LEDs) has rapidly developed in recent years from indicators to illumination applications. With the features of long-term reliability, environmental friendliness and low power consumption, the white light LED is viewed as a promising alternative for future lighting products. Nevertheless, the rate of heat generation increases with the illumination intensity. This issue will become a challenge for thermal engineers to design the indoor LED illumination. Conventionally a passive cooling method like natural convection from heat sinks is no longer adequate for today’s high brightness of LEDs. To solve the thermal problems of LED, the electrohydrodynamics (EHD) technique is utilized to enhance the heat transfer from the heat sinks in the present study. The electric field is generated by parallel wire electrodes with different arrangements charged with DC high voltage. It is found that the heat transfer coefficients under electric fields are greater than those under natural convection by 1.6 ~ 3 times in the test range of 1 ~ 16 kV. Besides, the enhancement of heat transfer increases with the supplied voltage but decreases with raising the Rayleigh number. In addition to the supplied voltage, the electrode polarity also influences the performance of EHD. The negative polarity slightly outperforms the positive one by 6% due to its higher current density between the electrodes and the grounded surface. In the present study, EHD has been proven as a good cooling technique by showing improved heat transfer at the expense of small power consumption.