The experiments were set up to investigate the effects of pipe length on their heat transfer characteristics by tested on different heat input 80 oC and various lengths (300, 450 and 600 mm). The results illustrated in Fig 8, for length of 300, 450 and 600 mm, it has significant influence on heat flux of condenser. It is clear that the heat flux of tested heat pipe with 300 mm section length was higher than the other length (see Fig. 8)