High Prandtl impinging liquid jet: effect of injector geometry on heat transfer

  • Bai, Xiaohan (IFP Energies nouvelles)
  • Poubeau, Adèle (IFP Energies nouvelles)
  • Vinay, Guillaume (IFP Energies nouvelles)
  • Renon, Clément (P' Institute)
  • Fénot, Matthieu (P' Institute)

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In electric motors, heat losses are generated in different components such as stator windings, rotor magnets or conductors, and limit their power density. Among the different cooling strategies available, an active convection cooling technology is selected for this study, for which a jet of liquid is directly injected onto the stator or the rotor. In order to design and evaluate the performance of such a cooling system, it is necessary to evaluate the heat transfer between the solid part of the engine and the coolant film that covers it. In this study, we numerically investigate with CONVERGE software the heat transfer of a liquid jet impinging a heated wall using a Volume of Fluid (VOF) method for interface tracking. Work has already been done to simulate high Prandtl number liquid jets impinging on a heated flat wall: comparison with experimental measurements has shown very good predictions of surface-averaged heat transfer [1]. In this study, we aim to reproduce the experimental setup described in [2] that offers a wide range of operating conditions (Reynolds number, Prandtl number, nozzle diameter) and allows access to the spatial distribution of heat transfer. Thus, high Prandtl number liquid jets impinging on a heated flat plate are simulated, including flow in the injector. The variations in operating conditions performed numerically and the comparison to spatial distribution of Nusselt number obtained experimentally show promising results, with most physical phenomena being correctly reproduced (impact of Reynolds and Prandtl number, notably). The impact of the injector geometry on the heat transfer distribution is investigated by analysing the velocity profiles along the injector and in the jet. The result is that a change in the nozzle diameter deeply affects the flow development in the nozzle and the subsequent velocity profile at the nozzle exit. In conclusion, characterizing the injector by its diameter alone is not enough; the geometry of the injector as a whole must be considered as it can have an impact on the heat transfer distribution. REFERENCES [1] A. Poubeau; G. Vinay; B. Kekelia; K. Bennion. Conjugate heat transfer simulations of high Prandtl number liquid jets impinging on a flat plate. Submitted to Int. J. Heat Mass Transfer, 2022. [2] C. Renon; M. Fénot; M. Girault; S. Guilain; B. Assaad. An experimental study of local heat transfer using high Prandtl number liquid jets. International Journal of Heat and Mass Transfer, Vol. 180,