Vortex Tube

Vortex Tube CFD Simulation, ANSYS Fluent Training

Description

A vortex tube is a mechanical-thermal device that splits a compressed air flow (or any inert gas) into separate hot and cold streams. Its standard components include one or more inlet nozzles, a hot end tube, a vortex chamber, a cold orifice, and a control valve or plug positioned at the hot end, with exits configured on either or both sides.

This project simulates a vortex tube using ANSYS Fluent. Air enters the domain at a static pressure of 7 bar and a total temperature of 300 K, then begins rotating within the tube in a high-speed vortex motion. This rotating gas naturally separates into hot and cold streams, driven by differences in angular momentum between individual gas particles — the hot airflow exits through the outlet chamber, while the cold airflow returns and exits through the opposite (left) side.

The geometry was built in SpaceClaim, with a polyhedral mesh generated using Fluent Meshing, totaling 497,635 elements.

Methodology

A density-based solver was used to model the airflow, with air density defined using the ideal gas law and viscosity modeled via Sutherland's law. Turbulence was captured using the Spalart-Allmaras model.

Conclusion

The results include temperature, pressure, and velocity contours throughout the vortex tube. Flow vectors clearly illustrate the air's rotational motion, showing how lower-momentum air is redirected back toward the cold outlet, while pressure, temperature, and density variations are also evident across the domain.

The simulation confirms the expected vortex tube behavior: the cold outlet registers a temperature below the inlet condition, while the hot outlet registers a temperature above it. The mass-weighted average total temperatures at each boundary were: