Three working-liquid charging methods for miniature heat pipes are introduced, and their advantages and disadvantages are described. Using these methods, two types of ceramic heat pipes were charged and tested. The ceramic heat pipes were made of alumina and have overall dimensions of 89 mm × 12 mm × 2.9 mm and a designed vapor space of 82.5 mm × 4.1 mm × 1.27 mm. Axial micro capillary grooves were provided on the top and bottom or sidewalls inside the heat pipes as wick structures. Water was used as working liquid. More than 20 Watts of heat input was achieved on a 5 mm × 5 mm heating surface. The corresponding heat flux was 80 W/cm2
