Swirl Tube Lab Report

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4. Results In the following we present and discuss results for the flow field, the swirl number, turbulent flow structures and the pressure loss over the swirl tube. Heat transfer results are shown in terms of circumferential averaged Nusselt numbers. The numerics are compared to previously published PIV results [19] and to own heat transfer data obtained using the transient liquid crystal technique [26]. 4.1. Flow field The following section presents the velocity field in terms of axial and circumferential velocity profiles in the swirl tube. Furthermore, we show the turbulent kinetic energy, turbulent flow structures and the swirl number. 4.1.1. Velocity field The non-dimensional axial velocity in the swirl tube is shown in Fig. 11 for seven axial positions compared to experimental data. Additionally, a contour plot of the DES visualizes the flow field. The flow direction is from left to right and the velocity legend is defined on top of each figure. The axial velocity shows an axial flow on the tube periphery, whereas in the core a backflow is visible. The magnitude of the…show more content…
As mentioned above the swirl number is defined as the ratio of the angular momentum (with respect to the cylinder axis) to the axial momentum of the flow, see Eq. (1). Figure 17 shows a swirl number comparison between experiment and DES. As seen for the velocities, the simulation shows the same trend like the experiment and a general good agreement with slight differences in the second half of the tube. The simulated swirl number is a bit higher due to the higher maximum of the circumferential velocity profile seen in Fig. 12. The swirl number decreases within the tube length due to wall friction and dissipation. Additionally, the swirling flow in terms of velocity pathlines is visualized in Fig. 18. A strong swirl near the tube wall with a high circumferential velocity is observed, which leads to high swirl

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