Improving thermal performance of miniature heat pipe for notebook PC cooling

Abstract

A miniature heat pipe (MHP) with woven wire wick was used for cooling a notebook PC. The cross-sectional area of the pipe is reduced by about 30% of the original, when the diameter of the MHP is pressed from 4 to 2 mm for packaging in a notebook PC. In the present study, a test of the MHP has been performed in order to review the thermal performance by varying pressed thickness, total length of MHP, wall thickness, heat flux and inclination angle. New wick types were considered for overcoming low heat transfer limits, which occur when the MHP is pressed to a thin plate. Through a performance test, the limiting thickness of pressing is shown to be within the range of 2–2.5 mm. When the wall thickness of 0.4 mm is reduced to 0.25 mm for minimizing conductive thermal resistance through the wall of heat pipe, the heat transfer limit and thermal resistance of the MHP were improved about 10%. While the thermal resistance of the MHP with central wick type is lower than that of the MHP with circular oven wire wick, the thermal resistance of the MHP with composite wick of woven/straight wire is higher than that of the MHP with circular woven wire wick. From the performance test conducted on the MHP cooling modules with woven wicks, it is seen that the T jc (junction temperature of the processor) satisfies a demand condition of being between 0 and 100 ° C. This shows the stability of the MHP as a cooling system of notebook PCs.