Subcooled boiling is important heat transfer regime in nuclear reactor engineering. In subcooled boiling flow, the bubbles are generated from the heater wall, then transported along the fluid channel during condensation. In this study, Ultrasonic Velocity Profile (UVP) method is used to measure vapor bubble condensation rate and bubble velocity, which are important parameters to calculate interfacial condensation heat and mass transfer in the subcooled boiling flow. Two transducers were installed to measure the top and bottom surface velocities of bubbles and then the condensation rate and velocity of bubbles are calculated. In order to confirm the applicability of UVP method to measure bubble surface velocities, the results are compared with the results of optical visualisation method.
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