Experimental Study of the Influence of a Blowing Grid on Turbulent Jets Applied to Air Conditioning Systems

Maiga, A. M.; Khelil, A.; Braikia, M.; Khelil, M.; Belguebli, E.; Fellague Chebra, A.

doi:10.47176/jafm.18.8.3334

Experimental Study of the Influence of a Blowing Grid on Turbulent Jets Applied to Air Conditioning Systems

Document Type : Regular Article

Authors

University of Chlef, Laboratory of Control, Testing, Measurement and Mechanical Simulation, B. P. 151, 2000 Chlef, Algeria

10.47176/jafm.18.8.3334

Abstract

To overcome the challenges associated with homogenising the aerodynamic parameters of turbulent air jets, special attention must be given to the design of air jet distribution systems. This study aimed to evaluate the performance of two air jet distribution systems, one (AG) equipped with a blowing grid and the other (SG) without, at different frequencies. The frequency parameter was selected due to its proportional relationship with velocity, which allowed for precise control over the inlet flow velocity. Experiments were conducted in a controlled environment using a wind tunnel connected to a test chamber at the Control, Testing, Measurement, and Mechanical Simulation Laboratory of the University of Chlef. The results showed that in the axial direction, the blowing grid caused a reversal in velocity trends, indicating recirculation zones, especially at a frequency N₁=40Hz. Conversely, the gridless configuration exhibited a more uniform velocity distribution. At a frequency N₂=50Hz, the increase in instabilities induced turbulence and flow disturbances, leading to a degradation of the velocity distribution. In the radial direction, the blowing grid improved the diffusion of kinetic energy, resulting in a more homogeneous jet spread and a uniform velocity distribution, especially further from the nozzle. The turbulence intensity in the AG configuration increased by 4% near the chamber wall, a finding that was consistent with shear-induced effects. The system equipped with the blowing grid proved more effective in promoting a consistent radial distribution of airflow. This enhanced flow uniformity is essential for applications requiring precise control of aerodynamic parameters. Ultimately, the blowing grid configuration emerged as the optimal solution for achieving a more homogeneous and stable airflow profile.

Keywords

Main Subjects

Mixing and Jets

References

Albayrak, M., Sarper, B., Saglam, M., & Birinci, S. (2023). The role of jet-to-crossflow velocity ratio on convective heat transfer enhancement in the cooling of discrete heating modules. Thermal Science and Engineering Progres, 37, 101549. https://doi.org/10.1016/j.tsep.2022.101549

Anderson, E. A., & Spall, R. E. (2001). Experimental and numerical investigation of two dimensional parallel jets. Transactions of the ASME, 123(2), 401-406. https://doi.org/10.1115/1.1363701

Aziz, M. A., Gad, I. A. M., Mohammed, E. S. F. A., & Mohammed, R. H. (2012). Experimental and numerical study of influence of air ceiling diffusers on room air flow characteristics. Energy and Buildings, 55, 738–746. https://doi.org/10.1016/j.enbuild.2012.09.027

Bennia, A., Fellouah, H., Loukarfi, L., & Naji, H. (2020). Experiments and large-eddy simulations of lobed and swirling turbulent thermal jets for hvac's applications. Journal of Applied Fluid Mechanics, 13(1), 103-117. https://doi.org/10.29252/jafm.13.01.29970

Bennia, A., Loukarfi, L., Khelil, A., Mohamadi, S., Braikia, M., & Naji, H. (2016). Contribution to the experimental and numerical dynamic study of a turbulent jet issued from lobed diffuser. Journal of Applied Fluid Mechanics, 9(6), 2957–2967. https://doi.org/10.29252/jafm.09.06.25953

Bouhamidi, Y., Khelil, A., Hadj Meliani, M., Said, N., & Loukarfi, L. (2020). Numerical investigation of the geometry influence on the aerodynamic fields of the free turbulent jets. Structural Integrity And Life, 20, (3), 219–224.

Bragança, P. (2017). Ventilation par mélange utilisant des dispositifs de diffusion munis d’inserts lobés : analyse des écoulements moteurs et du confort thermique induit [PhD thesis, University of Rochelle].

Braikia, M., Loukarfi, L., Khelil, A., & Naji, H. (2012). Improvement of thermal homogenization using multiple swirling jets. Thermal science, 16 (1), 239-250. https://doi.org/10.2298/TSCI101026131B

Chaour, M., Hamadi, B., Boucherma, D., Boulkroune, S., Achour, T., & Chorfi, S. (2024). Numerical study of the interaction between jets in a reheating furnace. Studies in Engineering and Exact Sciences, Curitiba, 5(2), 01-14. https://doi.org10.54021/seesv5n2-587.

Dia, A. (2012). Simulation de jets d’air lobés pour l’optimisation des Unités Terminales de Diffusion d'Air [PhD thesis, University of Rochelle].

Dimotakis, P. (2000). The mixing transition in turbulents flows. Journal of Fluid Mechanics, 409, 69-98. https://doi.org/10.1017/S0022112099007946

Fellague chebra, A., Khelil, A., Braikia, M., & Bedrouni, M. (2024). Comparative analysis of modified jet diffuser geometry for evaluating the impact of rounded edges and chamfered design on cooling efficiency of electronic components in cross flow and impinging jet. Journal of Thermal Engineering, 10(4), 961−977. https://doi.org/10.14744/thermal.0000849

Gauntner, J. W., Livingood, J. N. B., & Hrycak, P. (1970). Survey of literature on ﬂow characteristics of a single turbulent jet impinging on a ﬂat plate. Technical Report, NASA.

Goldstein, R. J., & Franchett, M. E. (1988). Heat transfer from a flat surface to an oblique impinging jet. Journal of Heat Transfer, 110, 84-90. http://dx.doi.org/10.1115/1.3250477.

Hunter, C., Presz, W., & Reynolds, G. (2002). Thrust augmentation with mixer/ejector systems. 40th AIAA Aerospace Sciences Meeting & Exhibit, 230.

Khelil, A., Naji, H., Braikia, M., & Loukarfi, L. (2015). Comparative investigation on heated swirling jets using experimental and numerical computations. Heat Transfer Engineering, 36 (1), 43–57. https://doi.org/10.1080/01457632.2014.906279

Lieber, L. S., & Weir, D. S. (2007). Comparison of measured low-frequency engine noise with combustion and jet noise predictions for a turbofan engine with an internal lobed mixer nozzle. Turbo Expo: Power for Land, Sea, and Air, 47950, 1511–1520. https://doi.org/10.1115/GT2007-28027

Loukarfi, L. (2021). Thermique appliquée, pages bleues. Algiers. ISBN 978-9947-34-231-2

Massip, Y. Rivas, A., Larraona, G. S., Anton, R., Ramos, J. C., & Moshfegh, B. (2012). Experimental study of the turbulent flow around a single wall-mounted cube exposed to a cross-flow and an impinging jet. International Journal Heat Fluid Flow, 38, 50–71. https://doi.org/10.1016/j.ijheatfluidflow.2012.07.004

Meslem, A., Bode, F., Nastase, I., & Martin O. (2012). Optimization of lobed perforated panel diffuser: numerical study of orifice geometry. Modern Applied Science, 59, 6-12. http://dx.doi.org/10.5539/mas.v6n12p59

Mitchell, M. G., Smith, L. L., Karagozian, A. R., & Smith, O. I. (2016). Emissions measurements from a lobed fuel injector/burner. American Institute of Aeronautics and Astronautics. https://doi.org/10.2514/6.1998-802

Roux, S., Brizzi, L. E., & Dorignac, E. (2009). Dynamics of a round jet impinging a flat wall constrained by acoustic forcing. 19th French Congress of Mechanics Marseille. https://hal.science/hal-03390814v1

Russo, F., & Basse, N. T. (2016). Scaling of turbulence intensity for low-speed flow in smooth pipes. Flow Measurement and Instrumentation, 52, 101–114. https://doi.org/10.1016/j.flowmeasinst.2016.09.012

Shan, G., Zhang, J., & Huang, G. (2011). Experimental and numerical studies on lobed ejector exhaust system for micro turbojet engine. Engineering Applications of Computational Fluid Mechanics, 5(1), 141–148. https://doi.org/10.1080/19942060.2011.11015358

Wildi, T. (2014). Electrical machines, drives, and power systems (5th ed.). Pearson.

Zahout, N., Braikia, M., Khelil, A., & Naji, H. (2024). Thermal and dynamic characterization of a multi-jet system with different geometry diffusers. Journal of Thermal Engineering, 10(2) 404−429. https://doi.org/10.18186/thermal.1456643.