 The proposed ultrasonic velocity profiler, UVP, uses a single ultrasonic gas-liquid two-phase separation, SUTS, technique to measure the velocity distribution of vapor-liquid boiling bubbly flow. This technique is able to measure the velocity of the vapor bubble and liquid separately in boiling conditions. Experiments were conducted on vertical pipe flow apparatus to confirm the viability of the measurement technique. The ultrasonic transmission and effect of ultrasonic refraction through the pipe wall and water were investigated at ambient temperature until subcooled boiling temperature was reached. The velocity profile in the water at elevated temperature was measured to verify the ability of the technique in this application. Results showed that the proposed technique can effectively investigate the velocity of both phases under various fluid conditions in boiling bubbly flow. This article was authored by Wang Sikorn-Wang Sarage, Heidhara Takahashi, Nettithanan, and others.