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In phosphor-converted light-emitting diodes (pc-LEDs), phosphor heating can lead to decrease of luminous efficiency or even thermal quenching due to local high phosphor temperature. Phosphor scattering model has been used to calculate the phosphor heat generation. Using this model, there are two methods for heating power estimation, one is the subtractive method and the other is the integral method...
In the phosphor coating process of the phosphor-converted light-emitting diodes (pc-LEDs) packaging, the phosphors settle spontaneously due to the density difference between the phosphor particles (YAG-04, about 4800 kg/m3) and the silicone matrix (OE6550 A/B, about 1120 kg/m3). The phosphor sedimentation affects the phosphor distribution and changes the optical performance of pc-LEDs, such as the...
This study quantitatively analyzed the optical and thermal performances of remote quantum dots (QDs)-based white light-emitting diodes (QDs-WLEDs) with the same spectra power distribution (SPD) but reverse packaging structures. The output optical power and PL spectra were measured and analyzed by an integrating sphere system, and the temperature fields were simulated by combing optical measurement...
For light-emitting diode (LED) packages, temperatures, especially junction and phosphor temperature, can greatly affect the optical performance. Thus, measuring the temperatures accurately is of significance for the performance estimation. Among the methods of measuring temperature, physical contact method, represented by thermocouple method, is most convenient and economical. In this paper, we measured...
Logging tools are wildly used in deeper oil and gas wells in which the geothermal temperature can be as high as 200 ¼C. However, a majority of the downhole electronic components can only withstand ambient temperature not exceeding 120 ¼C. Therefore, an effective thermal management system is necessary for logging tools. In this paper, a thermal management based on the combination of the vacuum flask...
Thermal metamaterials have been extensively explored and realized with many discoveries of new heat transfer phenomena and principles. The conventional design method of thermal metamaterials is usually based on the method of transformation thermodynamics, but it is rather complicated and difficult to fabricate in practice. Here, a thermal cloak was designed by alternative layers of copper and silicone...
In our previous study, we investigated the effects of different packaging materials (silicone and phosphor layer) on the reliability of high power light-emitting diodes (HPLEDs) by highly accelerated stress test (HAST). The experimental results showed that the LED samples' lumen maintenance property might have dependence on the silicone amount in the package. In this paper, we further studied the...
In this paper, a water-stirring radiator is presented, which possesses a sealed water chamber and a stirrer. Different from the conventional water-stirring radiators, there are no micro pump and connected channel in the present radiator, but the stirrer driven by a motor stirs water to cool the heat source. A set of experiments and FLUENT simulations were carried out to examine the performances, and...
In this paper, a self-heating model was developed based on Run Hu's light scattering model to calculate the heat generation and an integrated thermal resistance model was established to predict the temperature of phosphor silicone. It is found that the trends of highest temperature along with the phosphor concentration and particles diameters are both non-monotonic with a wave crest. While the temperature...
For multiple-chip high power LED arrays, a high temperature uniformity among LED chips is the guarantee of optical performance, thermal stability and reliability of the devices. Single-layer microchannel heat sink (SMHS) is a good alternative to reach this goal, but its performance is limited because the water temperature may rise at the downstream of the channel. In this paper, a double-layer microchannel...
The phosphor-converted light emitting diodes (LEDs) are the most frequently used white light LED. Due to the Stoke's loss, the silicone/phosphor composites generate a considerable amount of heat. However, as a result of different sedimentation times or coating processes, the phosphor particles present different distributions in the silicone matrix, which has been proved to strongly influence the performance...
Thermal management of the electronic devices who work intermittently with the method of latent heat storage is regarded as one of the most prospective alternative passive thermal management solutions. In this paper, the thermal management performance of the hybrid heat sink with the bottom of the fins immersed in the phase change material (PCM) is studied experimentally. The effect of the melting...
Thermal management has always been crucial for the improving of LED reliability. Most researches focus on the thermal management outside the package like fin optimization, microchannel, microjet cooling, but few refer to the thermal management inside the package. In this paper, a contrast experiment was carried out by an online testing method to explore the LED's optical degradation under conditions...
The effective thermal conductivity (ETC) of silicone matrix embedded with particulate phosphors is of great importance in the thermal management of white light-emitting diode (LED) packages, not only because the mixture provides the heat dissipation path but also because the phosphors may generate heat as well. In this paper, a 2D/3D unit cell method with considering interface resistance was proposed...
The effective thermal conductivity (ETC) of silicone matrix embedded with particulate phosphors is of great importance in the thermal management of white light-emitting diode (LED) packages, not only because the mixture provides the heat dissipation path but also because the phosphors may generate heat as well. In this paper, a 2D/3D unit cell method with considering interface resistance was proposed...
For multiple-chip high power LED arrays, a high temperature uniformity among LED chips is the guarantee of optical performance, thermal stability and reliability of the devices. Single-layer microchannel heat sink (SMHS) is a good alternative to reach this goal, but its performance is limited because the water temperature may rise at the downstream of the channel. In this paper, a double-layer microchannel...
Thermal management has always been crucial for the improving of LED reliability. Most researches focus on the thermal management outside the package like fin optimization, microchannel, microjet cooling, but few refer to the thermal management inside the package. In this paper, a contrast experiment was carried out by an online testing method to explore the LED's optical degradation under conditions...
The phosphor-converted light emitting diodes (LEDs) are the most frequently used white light LED. Due to the Stoke's loss, the silicone/phosphor composites generate a considerable amount of heat. However, as a result of different sedimentation times or coating processes, the phosphor particles present different distributions in the silicone matrix, which has been proved to strongly influence the performance...
Thermal management of the electronic devices who work intermittently with the method of latent heat storage is regarded as one of the most prospective alternative passive thermal management solutions. In this paper, the thermal management performance of the hybrid heat sink with the bottom of the fins immersed in the phase change material (PCM) is studied experimentally. The effect of the melting...
In this paper, a phase change material (PCM) based heat sink was proposed and its geometry was optimized for heat transfer enhancement. The thermal resistance network between the heat source and the control volume was applied to analyze the influence on heat storage performance of the phase change material based heat sink (PCMBHS) and the optimization suggestions were proposed. Besides, the heat storage...
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