Vortex tube shape optimization for hot control valves through computational fluid dynamics

•For hot exit of vortex tube, truncated control valve optimization is performed.•The highest ΔTc of 45.17 K was achieved for ψ = 4 mm and w = 1.36 mm.•Cold temperature difference is improved by raising the nozzles inlet pressure.•Maximum absolute error of 4.12% is found as compared to 2D model.•The numerical and experimental values were less than 2.3% for the 3D. A vortex tube (VT) is a thermofluidic device that generates cold and hot streams from a single injection of compressed gas. This interesting phenomenon of energy separation is due to fluid dynamic effects. In this study, the optimization of the VT geometry was performed to investigate the potential applications of the VT as an expansion device in natural gas processing and air separation industries. A steady-state computational fluid dynamics (CFD) model with the standard k–ɛ turbulence was used to solve the hydrodynamics of the highly compressible, turbulent, and swirling flow within the VT. Velocity streamlines and temperature distributions of the separated air stream were obtained for different control valve shapes located at a hot end. The CFD results showed the effects of the control valve shape, cone valve geometry, and nozzle inlet pressures on the VT performance. A truncated cone control valve with an optimized geometry was found to be the best choice for thermal performance enhancement of the VT. The CFD results were validated with experimental data, and the difference in the cold temperatures between the numerical and experimental values were less than 4.12% for the 2D and 2.3% for the 3D vortex tube models. [Display omitted]