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Effect of pressure work on the energy separation in air vortex tube: dimensional analysis and numerical investigation.

Number: 2112

Author(s) : LAGRANDEUR J., CROQUER S., PONCET S.

Summary

In this work, a two-dimensional computational fluid dynamics (CFD) model of air vortex tube is used to investigate the effect of the pressure work from turbulence, which transfers energy in the direction of the strong outward pressure gradient generated by the swirling flow. The pressure work is considered by adding a term modelling it as an energy source in the CFD model. Prediction of the cold outlet temperature is good at high cold mass fractions, but some discrepancies remain at lower values. In addition, the inclusion of the pressure work inverts the radial static temperature profile near the inlet. Without it, the static temperature gets higher in the core, while it becomes lower with the additional term. To better understand where the pressure work is dominant inside the vortex tube and how it scales up with turbulence, the energy equation solved by ANSYS Fluent with the additional term is non-dimensionalized. The pressure work is proportional to the ratio of the pressure gradient divided by the local pressure (ΔP~P). The pressure work, the heat transfer and the shear stress term all scale up with the turbulent viscosity ratio, meaning that turbulence level does not impact the relative importance of each of these terms. In the CFD model, the pressure work term is more important than the heat transfer and the shear stress term almost everywhere in the radial direction into the main tube. This highlights that it is important to model pressure work in future CFD simulations. However, the two-equation turbulence models do not predict the swirl decay adequately in the vortex tube. Consequently, the temperature gradient could be dominant in some additional areas near the hot end. New simulations may benefit from using advanced turbulence models which take into account both curvature and rotational effects in high swirling flows.

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Pages: 10 p.

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  • Original title: Effect of pressure work on the energy separation in air vortex tube: dimensional analysis and numerical investigation.
  • Record ID : 30030469
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

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