Two-phase cooling of light emitting diode for higher light output and increased efficiency

A temperature controller for high power light emitting diodes based on resistive heating and liquid cooling

“…In Equation (6) DQ H , C, h, A, T amb and DT are constants for both cooling and heating. The power of the convective heat transfer increases when the temperature difference between the heat sink and the ambient increases.…”

“…6. Step responses for the À20 K temperature change at the heat sink and at the p-n junction of the LED. DQ H ¼ C h DT À hA½TðtÞ À T amb Dt ¼ PDt À hA½TðtÞ À T amb Dt; (6) where t is time, C h is the heat capacity of the heat sink, DT is the temperature change of the heat sink, h is the convective heat transfer coefficient, A is the area of the heat sink, T is the heat sink temperature, T amb is the ambient temperature, and P is the heating power.…”

“…in LED lamps is up to 3 W and inside of an average 10 W LED lamp, there are 4e10 LEDs producing a notable heating power. LEDs are cooled to keep their temperatures below the maximum operating temperature of 400 K. At the temperatures above 400 K, the luminous flux of an LED starts to drop rapidly [6] and at the temperatures above 420 K, the LED normally fails [4].…”

“…In recent years, the development of semiconductor materials and thermal management of high-power LEDs have led to luminous efficacies higher than 276 lm/W [1]. The junction temperature of an LED has a large effect on the LED parameters such as forward voltage [2], spectrum [3], lifetime [4], maximum output power [5], and luminous efficacy [6]. The electrical power of the LEDs used e.g.…”

Experimental investigation of copper-grooved micro heat pipes (MHPs)

“…To enhance the thermal behavior of MHPs, researchers have introduced a series of methods. Ye H [17] fabricated a fluid channel by wet etching and wafer bonding with silicon and glass. The phase transition of coolant allowed the package temperature to remain below 115°C with LED power up to 2.8 W. Dean R. N [18] presented a MHP constructed from a micromachined base and lid that were bonded together after charging.…”