Investigation on the influence of droplets on the flow characteristics and energy separation in vortex tube based on CFD analysis

Abstract

In industrial sectors such as natural gas, vortex tubes have attracted attention as potential alternatives to throttling devices. Current research on vortex tubes primarily focuses on gas-phase operations, whereas studies on two-phase (gas-liquid) vortex tubes remain scarce. In this study, the mixture of nitrogen and water droplets is used as working fluid. Investigate the influence of adding droplets with different sizes or different volume fractions on the flow characteristics and energy separation in the vortex tube through a three-dimensional computational fluid dynamics model. The research results show that increasing the droplet diameter entering vortex tube reduces the amount of droplets discharged from the cold outlet, thereby improving the gas-liquid separation performance of the vortex tube. An increase in the droplet diameter or the volume fraction entering the vortex tube has a significant negative influence on the energy separation within the vortex tube. Meanwhile, both the tangential and axial velocities inside the tube decrease, and the direction of the radial velocity may change simultaneously. In the range of cold flow fraction from 0.2 to 0.8, cold and hot temperature differences of the vortex tube are at their best when d = 0 μm and δ = 0. When μ = 0.2, the optimal cold temperature difference of 37.80 K is achieved. While when μ = 0.8, the optimal heat temperature difference is 47.86 K.