14:50   Complex Flows Study on basic performance of Tesla turbine and application to refrigeration cycle Kosuke Wakimizu, Mitsuhiro Fukuta, Masaaki Motozawa Abstract: The application of Tesla turbine to refrigeration cycles as an expansion device has a possibility to enhance the energy efficiency. Since Tesla turbine has a simple structure, there are many advantages such as low cost, high reliability, and operation without lubrication. Although these features make the turbine suitable for integration into the refrigeration cycle, its operation with two-phase flow during expansion process has been unclear yet. This study aims to investigate the basic performance of Tesla turbine and its applicability to two-phase conditions. The basic performance was evaluated using air as the working fluid. To assess its adaptability to two-phase flow, internal flow behavior in the turbine was visualized. As a result, the maximum output and efficiency under single-phase flow conditions were found to be approximately 16.0 W and 7.5%, respectively. In the visualization experiment under two-phase flow, water was observed to accumulate near the outer periphery of the turbine and rotate along the edge of the disks. Comparing with single-phase operation, the rotational speed decreased. Formation of bifurcating flows and helical structures in the initial region of a round jet using synthetic jets Akinori Muramatsu, Kohei Tanaka, Yuuske Kobayashi Abstract: A round jet is periodically disturbed by synthetic jets at near the exit of a round nozzle. The synthetic jets are formed from holes arranged circumferentially in the round nozzle, because the holes are connected to loudspeakers inputting a sinusoidal wave. The number of holes, namely synthetic jets is 3. When the synthetic jets are driven in the same phase and at the vortex formation frequency of the natural transition of the jet, bifurcating flows can be formed near the nozzle. The number of bifurcating flows is identical to the number of synthetic jets. In this case, the mixing between the jet and surroundings is enhanced near the nozzle exit. The experimental results can be numerically simulated using OpenFOAM. Numerical simulations are also shown that helical structures can be formed in the potential core by driving the synthetic jets in sequence. In this case, the mixing near the nozzle outlet is suppressed. In addition, when six synthetic jets are used, a double helix structure can be formed by driving them with a phase difference, so that the jet breaks down further downstream. This means that mixing of the jet is further suppressed in this case.

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