Abstract
In order to measure the time-dependent pressure change in Oscillating Heat Pipe, we used T-shaped glass tube as flow path, and measured surface temperatures of the glass tube and the operating pressure at the same time. We are confirmed that the frequencies of temperature and pressure oscillation are equal. Also, we tried to insert a thermocouple into flow path so as to measure the temperature of the working fluid directly. A large temperature gradient was found in the liquid column close to vapor-liquid interface, while on the other hand, temperature gradient of vapor phase is very small.