Parametric analysis of design and operating conditions for energy and particulate matter separation in vortex tubes

The vortex tube (VT) is a device known for separating a compressed gas stream into hot and cold fractions. This study numerically investigates its dual potential for thermal separation and particulate matter (PM) removal. Using computational fluid dynamics, the effects of key design parameters and operating conditions on separation performance are analyzed for uniflow and counterflow vortex tubes. The investigated variables include tube diameter, inlet pressure, particle size (0.05 to 10 µm), and gas injection angle. The thermal analysis reveals a strong dependence of temperature separation (ΔT) on inlet pressure and diameter, with combinations of low pressure and large diameters yielding the highest ΔT, in the range of 60 to 70°C. The PM analysis shows that efficiency is governed by a coupled set of variables. Particle size is the dominant factor, with particles larger than 1 µm achieving over 99% removal efficiency. Inlet pressure has a diameter dependent effect; its increase significantly reduces efficiency in large diameter tubes but has a negligible impact in smaller tubes. A larger gas injection angle monotonically increases PM separation by strengthening tangential momentum. Coordinated selection of diameter, inlet pressure, and injection angle enables application specific tuning for simultaneous energy and particulate separation.