The heat source is critical for heat transfer. The heat source comes from two parts: the light source and the power source. The heat of the light source part usually pays attention to the effective contact area between the light source PCB and the bonding surface of the heat sink. The larger the effective contact area, the better the heat dissipation. In addition, it should be noted that the heat transfer interface between different media is as smooth as possible; the heat transfer between the heat transfer materials should be tight enough, and the contact surface clearance of the components of the fitting should be as small as possible.
In the heat conduction design of the luminaire, a good heat conduction channel should reduce the thermal resistance between the PCB, the heat transfer medium, the heat sink, and increase the effective contact surface between the three, and select a heat transfer medium with a high thermal conductivity.
Natural convection also requires an effective heat exchange area. Therefore, under normal circumstances, proper roughening of the outer wall of the heat dissipation can increase the effective heat exchange area. In addition, the thickness of the spray and the thermal conductivity and radiation of the paint should be considered when spraying different paints. Performance is good or bad. Generally, in order to increase the heat exchange area of ​​the heat sink, we adopt a fin structure. The usual effective heat exchange area is 50%-60% of the overall area of ​​the luminaire. The "fin" heat sink can determine the effective heat transfer performance according to the fin efficiency and fin spacing.
In natural convection, the power supply will also heat up, because the power of the bulb and the spotlight is generally placed inside the lamp cavity, and the heat can be dissipated by using a medium such as a heat-conductive potting compound or a thermal conductive mud. For the superimposed thermal field, it is recommended to increase the air layer between the power supply and the LED light source and the bonding platform of the PCB to form an air partition and weaken the thermal field superposition effect.
In addition, thermal radiation is an energy transfer that all objects are performing at any time, and different materials have different radiation intensities. Generally, the radiation intensity of a cool object is lower than the radiation intensity of a warm object, and the radiation intensity of a rough object is greater than the radiation intensity of a smooth object. Generally, the radiation heat transfer of bulbs and spotlights is small and can be ignored.
In summary, the cooling of LED bulbs and spotlights needs to consider the reasonable combination of light source, PCB, heat sink and power supply. The selection and design of heat dissipation structure for different lamps and heat dissipation standards should not blindly use large heat sinks or high thermal conductivity materials. It causes unnecessary material and cost waste.
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