LED is a type of photoelectric devices. Take the existing most advanced high-power LED chips for instance, the conversion from electrical energy to optical energy is only 15%-20%, far less than the requirements of most industrial applications and commercial applications. The rest 85%-80% energy will be transformed into heat, keeping LEDs in an over-heated state. That is the reason why most high-power LED lighting products have relatively short service lives. On the other hands, the luminous flux (lumen output) of LED lights will be reduced with the increase of PN junction temperatures. Thus an incompetent cooling design may dramatically cut down the lighting effect and working time of high-power LED tunnel lights.
Currently, there are three major solutions for cooling technology of high-power LED tunnel lights: 1) natural cooling. Adding fans/ventilators and heat pipes/sinks to assist cooling. Natural heat dissipation is base on natural convection and thermal radiation, reliable structure, waterproof, but strict in the structure design, cannot be easily handled. Normally, the practical effects are far less than the theoretical results. 2) Mandatory cooling through fans/ventilators on the base of forced convection. This method can provide a much faster cooling effect, but generate more noise and cost a lot, hard for waterproof. 3) Mandatory cooling through heat pipes/sinks. This technology takes the use of heat pipes to conduct unwanted thermal energy to heat sinks/pins to realize a rapid thermal dissipation. There are no other motion compartments and the entire system is more stable, but correspondingly cost a lot.
Different from ordinary roads, tunnels have many special properties. Mandatory cooling with the help of heat pipes and heat sinks would be the most suitable cooling technology for high-power LED tunnel lights among three. The vertical design of heat dissipation channel can realize the modularization of cooling section. Normally, high-power LED lamps using this cooling method can maintain a working temperature below 70℃, keeping LED chips working in a stable low-light-attenuation state, improving the maintenance factor to save more maintenance costs.
According to the airflow characteristics within tunnels, scientists usually made asymmetry ventilation designs, ensuring the air convection cooling. Meanwhile these asymmetry designs also can reduce the mass of soot and other pollutions generated by vehicles to enter the cooling chamber. These dusts may probably absorbed by cooling devices and reduce heat dissipation effects.