Cooling performance of flat plate heat pipes with different liquid filling ratios

The effects of liquid filling ratios and leakage on the cooling performance of flat plate heat pipes (FPHPs) were examined experimentally in this study. With the size of 150 mm × 50 mm × 2.5 mm for all Al 6061 FPHPs filled with acetone (99.87% pure), the results showed that the one with the liquid filling ratio of 25% performed thermally the best. The corresponding maximum heat transport capability, minimum thermal resistance, and maximum effective thermal conductivity were about 47 W, 0.254 K/W, and 3150 W/m K, respectively. In contrast, improper vacuum and leakage would decrease the maximum thermal conductivities greatly to about 200-306 W/m K and 164 W/m K, respectively. The latter was similar to that of an aluminum block and performed the worst among all FPHPs. This situation should be avoided or carefully assessed as the maximum effective thermal conductivity decreased from the best by a factor of about 19.2.