INFLUENCE OF TRANSIENT HEAT PULSE ON HEAT TRANSFER PERFORMANCE OF VAPOR CHAMBER WITH DIFFERENT FILLING RATIOS

Abstract

Due to the transitional thermal loads of CPU and power elements during the operation of portable electronic devices, traditional uniform structure wicks cannot meet the requirements of working fluid evaporation and reflow under complex heat flow conditions such as pulse heating, thus limiting the heat transfer performance of the vapor chamber (VC). This article proposes a new type of VC to improve the heat transfer performance of dual-heat source electronic devices under complex heat flow conditions. By using copper powders with different particle sizes and shapes in the heat source zone and reflow zone to sinter gradient structure wick, the evaporation and reflow of working fluid under multiple heat sources in complex working conditions could be effectively enhanced. The influence of the gradient structure wick on the heat transfer performance of VC under step heating and pulse heating conditions was analyzed. The results showed that the best heat transfer performance of the VC was achieved at a filling ratio of approximately 90%, under step heating condition, with a minimum thermal resistance of only 0.31°C/W at 45 W. Under pulse heating condition, when the filling ratio was 80% and 100%, the maximum temperature lag was 2.7°C. When the filling ratio was 90%, temperature lag could be eliminated. The research results provided theoretical guidance for the design of VC and the development of efficient heat transfer components under complex working conditions.