Turbulent flow field and heat transfer in tangentially injected swirl flows in tubes

The turbulent flow field and heat transfer in a tube has been experimentally studied when the fluid is injected tangentially. The experiments were conducted by injecting water through injectors placed on the periphery of an 21.42 mm stainless-steel tube. The tubular test section was electrically heated, and water used as the working fluid. The test section had a length of 1 m and a diameter of 21.42 mm. Heat transfer coefficients were measured over a length of up 1 m. Two injectors of 21.42 mm inside tube diameter and four injectors of 21.42 mm inside tube diameter were used in the two sets of experiments. Injection angle of 70 degrees with the tube axis was studied. In the experiments, the injector axis relative to each other for two injection applications was 180 degrees, and for four injection applications was 90 degrees. Different mass and momentum rates were applied to both experiments, then swirl flow heat transfer experimental results in comparison with plain tube results in the range of Reynolds number between 4806 to 24030. The augmentation of heat transfer was found to be function of the momentum ratio, angles of injectors and number of injectors. With tangential injection, up to twofold increase in average heat transfer coefficient has been observed in the range of experimental parameters studied. The heat transfer coefficient is found to increase to a very large value just downstream of the injection location, and then it decreases nearly exponentially with distance. Flow patterns were observed, using flow visualization tests. The generated data proved the findings.