Study of heat dissipation characteristics of loop heat pipe with heat sink of composite material

•The average temperature performance is improved after equipped the graphene copper foil heat sink.•The hot spot temperature increases linearly with the increase of inlet water temperature.•With the increase of thermal conductivity in one direction, the optimal heat sink thickness tends to increase.•The hot spot power has a significant impact on the hot spot temperature, but the impact on the temperature by non-hot spot is no different from the various background powers. In this study, a new heat dissipation device with a composite heat sink of a loop heat pipe (LHP) system was evaluated for efficient cooling of electronic components. To improve the heat dissipation ability of the high heat flux chip and its local hot spot area, LHP, which had a gas–liquid phase change as the main mechanism of heat dissipation, was selected to remove heat. The experimental results showed that the average temperature performance was improved after the graphene copper foil heat sink was fitted, and the maximum temperature under the heat loads of 80 W, 90 W, 100 W, and 120 W was reduced by 3.8 °C, 5.7 °C, 6.5 °C, and 7.7 °C, respectively, compared with without a heat sink. The hot spot temperature increased linearly with an increase in the inlet water temperature. Increasing the ambient temperature within a certain range had little effect on the heat-dissipation effect of the hot spots. To interpret the experimental results, the hot spot heat transfer performance of the evaporation section of the LHP with a composite heat sink was set up by the equivalent thermal resistance model. The CFD simulated results were in good agreement with the experimental values. This indicated that the heat sink significantly reduced the hot spot temperature and improved the cooling uniformity largely. When the transverse thermal conductivity of the heat sink is sufficiently high, the increase in longitudinal thermal conductivity is more effective in reducing the hot spot temperature than the transverse thermal conductivity. Moreover, it has been suggested that the hot spots and heating power play a major role in the actual electronic structure and heat dissipation design. In summary, the study proposes a valuable method for improving the uniform cooling of chips, which was conducive to the heat management of the system.