Abstract
Cooling characteristic of the thermosiphon type heat pipe with variable tilt angle is examined. Sodium myristate and potassium oleate those have good hydrophilicity and foamability are used as surfactants and added to pure water. The experimental results show reduction of thermal resistances for surfactant solutions is about 20% with concentration of 10ppm compared to pure water. Further, thermal resistance is reduced with increases in tilt angle θ. However the difference in thermal resistance between θ=30° and 60° is small compared with that between θ=0° and 30°.