Effects of kinetic energy and conductive solid walls on the flow and energy separation within a vortex tube

A numerical assessment is carried out to examine the effects of the commonly assumed adiabatic wall boundary conditions via non-adiabatic ones on the predicted temperature differences. Interestingly, the influence of the boundary type is found rather small at low cold fraction values but becomes significant at the high values. This finding completes the current knowledge which is to date somewhat lacking or even contradicting. Coverage of the studies on vortex tube has enabled the authors to identify the dominant dimensionless numbers affecting the flow physics within the device. Hence, a generic correlation which can be easily adapted for a given vortex tube design is proposed. The numerical predictions obtained reveals that the model is capable of mimicking the flow physics in a reasonably good agreement with experimental results provided that sufficiently fine grids are used. The numerical tests also reveal that the global discretisation error for the commercial code is approaching the numerical schemes order. Last but not least, thanks to the control volume thermodynamic analysis carried out in the present study, the authors were able to demonstrate and for the first time, the existing implicit link between the kinetic energy variation within the device and its resulting isentropic efficiency.