Thermographic Investigation of the Influence of the Internal Structure on the Heat-Spreading Performance of a Vapor Chamber

In this study, the effect of flow-guide structures on the heat-spreading characteristics of a vapor chamber was systematically investigated using a non-contact thermographic method. The tested vapor chamber had external dimensions of 106 mm × 106 mm × 4 mm (length × width × thickness) and possessed a 1 mm thick wick on its bottom plate. Flow guides with expansion angles of 0°, 22.5°, and 45° were incorporated into the vapor space to control the flow of the vapor-phase working fluid and to enhance structural rigidity. Approximately 6.5 mL of distilled water, corresponding to approximately 130 % of the wick void volume, was charged into the evacuated vapor chamber. The heat-spreading characteristics of the vapor chamber were evaluated in terms of the temperature distribution and the cumulative effective thermal conductivity distribution, measured by non-contact thermographic camera. The vapor chamber exhibited a central region with a uniform temperature distribution and a high effective thermal conductivity within a radial distance of 3.5 cm from the center, whereas in the outer region, the accumulation of excess liquid-phase working fluid resulted in a rapid decrease in both temperature and cumulative effective thermal conductivity. The cumulative effective thermal conductivity increased with heat flux due to the higher mass flow rate of the working fluid at elevated heat fluxes. At a heat flux of 200 W cm^-2, the measured cumulative effective thermal conductivity reached 8 900 W m^-1 K^-1 ± 1 100 W m^-1 K^-1 at an approximately 95 % level of confidence, which corresponded to an approximately tewnty-times higher value than that of copper. The heat-spreading performance of the vapor chamber decreased with increasing expansion angle of the flow guide, mainly due to greater contribution of conduction through the solid flow guide relative to convection of the vapor-phase working fluid.