Thermosyphon is wickless heat pipe and also know as gravity-assisted heat pipe. It contains a small amount of working fluid for heat transfer [1]. In addition for basic principle (see in Fig.1), heat is supplied to evaporator where working fluid pool inside, to changing phase into vapor. Then, temperature and pressure are cause of vapor to flow toward the condenser. The vapor adjacent to condenser releases its latent heat, afterward become condensed liquid and then came back to evaporator owing to gravity force [2].