Abstract
The present study aims to geometrically optimize vortex tube from a conventional straight tube design to enhance thermal separation. The computational analysis of the swirling flow in vortex tube variants: straight, convergent, divergent, and convergent-divergent tubes, is evaluated based on the swirl intensity. A novel approach of evaluating the driving forces such as the swirl intensity (centrifugal force), pressure gradient, and temperature gradient is utilized to predict the thermal separation characteristics. This method is validated with the quantitative energy transfer rate between the hot and cold exit flows. A validated computational model, solving the Reynolds-averaged Navier–Stokes equations with the Re-Normalization-Group k-epsilon turbulence model, analyzes the flow characteristics and resulting energy transfer. The vital role of swirl intensity in predicting thermal separation is analyzed and verified both qualitatively and quantitatively. The convergent and the convergent-divergent tubes show a subsonic radial expansion reaching up to a temperature ratio of 0.6 and pressure ratio of 0.08 in vortex chamber. This is regarded as a combined effect of vortex tube effect and flow expansion. Further expansion in cold exit nozzle yields a temperature drop of nearly 170 K in both designs, identifying them as optimal outcomes of the study. Additional optimization on angle of convergence and divergence with varying inlet pressure ratios is warranted. Numerical data shows a hot exit with isenthalpic flow and a cold exit with polytropic flow (nearly isentropic), providing novel validation for a previous hypothesis.
Published Version
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