Analysis of enhanced heat transfer on a passive heat sink with high-emissivity coating

Heat sinks are widely used for cooling electronic devices and LED lights, etc. Heat sinks without fans are preferred especially for mini-sized devices due to their compact size without noises or the need for power. Under these circumstances, natural convection and radiation are main means to dissipate the generated heat. Thus, enhancing radiation heat transfer becomes important. In this paper, a high-emissivity coating (ε = 0.934) with additives of carbon materials and SiO2 was put on the surface of an aluminum heat sink. Experiments and simulations were performed to study the influence of the high-emissivity coating on the heat transfer performance. It is proved that the high-emissivity coating effectively reduces the equilibrium temperature of the heat sink. In experiments, the maximum temperature difference between the heat sink (base size: 100*60 mm) with and without coating reached 26 °C at a heating power of 18 W. The simulation results showed that radiation with coating greatly contributed to heat transfer and occupied 38% of the total dissipated power. The coating increased the total heat transfer coefficient by 23% and decreased thermal resistance by 18%. The heat sink partly coated on outer surfaces remains good thermal properties and could reduce the coating cost. In conclusion, the high-emissivity coating enhances heat transfer of passive heat sinks and has a promising prospect as an excellent thermal management material.