1. Understand the thermal resistance Rjc of the lamp bead, which can be measured or obtained by the supplier. If it is not, it is generally estimated that the temperature difference of the crust is 15-20 °C.

2. Choose an aluminum substrate or a fiberglass panel?

3. Choose thermal grease or ordinary quick-drying glue? Still nothing?

4. What heat sink material is selected?

It seems that the thermal conductivity of various heat-dissipating materials varies greatly, but the main bottleneck in the heat transfer path is not in the material, so the worst-case ceramic is used, and the temperature difference is only 2.6 °C. Die-cast aluminum can be used to meet the requirements.

The T8 lamp heat transfer path is simplified as shown below: The main conduction heat resistance is on the thin walls on both sides, assuming a wall thickness of 1 mm. The length of the tube is 1200mm. The temperature difference is calculated as follows:

5. Need a heat pipe?

The thermal conductivity of the heat pipe is very high, about 1000 W/mK. For high power devices in COB packages, the use of heat pipes is necessary, especially when designing outdoor luminaires >50W.

However, in terms of interior lighting design, there are few more than 30W. Moreover, most of the indoor lamps are evenly distributed with small power lamps, and the heat flow density is small. So there is no need to use a heat pipe.

6. Need a fan?

From the current fan reliability, at 60 ° C (contact with the temperature of the heat sink), the life of the fan must be 45000 (5 years, 24 hours non-stop) without failure, and dustproof, anti-aging (sun exposure, high Humidity) is very difficult.

In the previous analysis of the influence of common materials on heat dissipation, the following analysis of the influence of the shape of the heat sink, taking the solar heat radiator and the straight tooth radiator as an example. Just a qualitative analysis can be used as a guide for heat sink design.

Myth 1: The greater the number of heat sinks, the better.

in conclusion:

1. Meshing has a great influence on the calculation of temperature and net radiation. The same heat sink has different mesh divisions and will have a difference of 1-2 °C. And don't think of this difference as the difference in the number of FINs.
2. For the sunflower type heat sink, the number of heat sinks exceeds a certain number, and the improvement effect on heat dissipation is not large, and the weight is increased. In the example, there are no more than 15 FIN films, and the distance between the roots of the two FINs is 8 mm.

Myth 2: The smaller the gap, the better.

The two FINs are placed symmetrically on one side of the plate, changing the gap, and studying the effect of the gap on convection, radiation and temperature.

Convection + radiation

Pure convection

Pure radiation

in conclusion:

1. When both convection and radiation are present, the gap is increased to 30 mm and the temperature of the heat sink is minimized.
2. Simple convection, the gap is increased by 10mm, and the convection efficiency is the highest.
3. With pure radiation, the radiation efficiency also increases with the increase of the gap.