Characterization of turbulent natural and mixed convection in confined enclosures equipped with a heat source

Characterization of turbulent natural and mixed convection in confined enclosures equipped with a heat source

Sihem Bouzid Yamina Harnane* Abdelhafidh Brima 

Department of Mechanical Engineering, Faculty of Sciences and Applied Sciences, University of Larbi ben M’hidi Oum El Bouaghi, 04000, Algeria

Mechanical Engineering Laboratory (LGM), University of Mohamed Khider Biskra, 07000, Algeria

Corresponding Author Email: 
harnaney@gmail.com
Page: 
63-79
|
DOI: 
https://doi.org/10.3166/I2M.17.63-79
Received: 
|
Accepted: 
|
Published: 
31 March 2018
| Citation

OPEN ACCESS

Abstract: 

In this numerical study two configurations are considered, the first configuration in natural convection corresponds to a closed cavity equipped with a heating bar and the second mixed configuration corresponds to the same cavity but ventilated. The flow is turbulent (GrH = 1,2.108), a choice of model is very important. The turbulence model chosen for natural convection is the low-Reynolds k-ε model. A comparison of the turbulence models led us to choose the RNG k-ε model for mixed convection study, because it is the suitable model for flows in ventilated cavities as well as flows with recirculation. Ventilation effect on natural flow has been studied by analyzing flow dynamic and thermal structure. Nusselt average number on each bar face is found to be improved by jet injection into the ventilated cavity, from about 50% to 60%. This comparison reveals the different velocities influence of the incoming air jet on the confined cavity flow structure, or this jet succeeds in breaking the single-cell flow of natural convection case into a multicellular flow for the other case of mixed convection at high velocities above the heating bar, of which it is the main purpose of this study.

Keywords: 

Fluent, turbulence model, CFD, heat transfer, Closed cavities, ventilated cavities

1. Introduction
2. Mathematical formulation
3. Configurations and boundary conditions
4. Results and discussion
5. Conclusion
  References

Abe K., Kondoh T., Nagano Y. (1994). A new turbulence model for predicting fluid flow and heat transfer in separating and reattaching flows - I. Flow field calculations. Int. J. Heat Mass Tran., Vol. 37, pp. 139-151. https://doi.org/10.1016/0017-9310(94)00252-Q

Abid R. (1993). Evaluation of two-equation turbulence models for predicting transitional flows. Int. J. Eng. Sci., Vol. 31, pp. 831-840. https://doi.org/10.1016/0020-7225(93)90096-d

Betts P. L., Bokhari I. H. (2000). Experiments on turbulent natural convection in an enclosed tall cavity. International Journal of Heat and Fluid Flow, Vol. 21, pp. 675-683. https://doi.org/10.1016/S0142-727X(00)00033-3

Bredberg J. (2001). On two-equation eddy-viscosity models. Department of thermos fluid dynamics. Internal report n°01/8, 2001. Chalmers university of technology, Göteborg, Sweden.

Chang K. C., Hsieh W. D., Chen C. S. (1995). A modified low-reynolds-number turbulence model applicable to recirculation flow in pipe expansion. J. Fluids Eng., Vol. 117, No, 3, pp. 417-423. https://doi.org/10.1115/1.2817278

Cheesewright R., King J. R., Ziai S. (1986). Experimental data for the validation of computer codes for the prediction of two-dimensional buoyant cavity flow. ASME Winter Annual Meeting, Hemisphere HTD, Vol. 60, pp. 75-81.

Chen Q. (1988). Indoor airflow, air quality and energy consumption of buildings. Ph. D Thesis, Delft University of Technology, Netherlands.

Chen Q., Jiang Z. (1992). Significant question in predicting room air motion. ASHRAE Transactions, Vol. 98, pp. 929-939.

Davidson L. (1990). Second-order corrections of the k-ε model to account for non-isotropic effects due to buoyancy. International Journal of Heat Mass Transfer, Vol. 33, No, 12, pp. 2599-2608. https://doi.org/10.1016/0017-9310(90)90195-Z

Djanna F. (2011). Convection naturelle turbulente a grands nombres de Rayleigh: Caractérisation expérimentale des écoulements et des transferts thermiques, étude numérique du couplage convection-rayonnement. Thèse de Doctorat. Institut Pprime, ENSMA Poitier.

Jones W. P., Launder B. E. (1973). The calculation of low-Reynolds number phenomena with a two-equation model of turbulence. Int. J. Heat Mass Tran., Vol. 16, pp. 1119-1130. https://doi.org/10.1016/0017-9310(73)90125-7

Lam C. K., Bremhorst G. K. (1981). A modified form of the k-ε model for predicting wall turbulence. Journal of Fluids Engineering, Vol. 103, pp. 456-460.

Launder B. E., Spalding D. B. (1972). Lectures in Mathematical Models of Turbulence, Academic Press, London. https://doi.org/10.1234/12345678

Launder B. E., Sharma B. I. (1974). Application of the energy-dissipation model of turbulence to the calculation of flow near a spinning disc. Letters in Heat and Mass Transfer, Vol. 1, pp. 131-138. https://doi.org/10.1016/0735-1933(74)90024-4

Murakami S., Kato S., Kobayashi H., Henyu F. (1995). Current status of CFD application to air-conditioning engineering. Pan Pacific Symposium on building and Urban Environmental Conditioning in Asia March 1995, Nagoya, Japan.

Peng S. H. (1998). Modelling of turbulent flow and heat transfer for building ventilation. Ph. D Thesis, Chalmers University of Technology, Sweden.

Shih T. H., Liou W. W., Shabbir A., Yang Z., Zhu J. (1995). A New k-ε eddy viscosity model for high Reynolds number turbulent flows. Computers and Fluids, Vol. 24, No, 3, pp. 227-238. https://doi.org/10.1016/0045-7930(94)00032-T

Tian Y. S., Karayiannis T. G. (2000). Low turbulence natural convection in an air filled square cavity. Part I: The thermal and fluid flow fields. International Journal of Heat and Mass Transfer, Vol. 43, pp. 849-866.

Toulouse M. L. (2004). Analyse et caractérisation de la convection naturelle et de la convection mixte dans des enceintes confines. Thèse de Doctorat. Ecole nationale supérieure de l’aéronautique et de l’espace, ONERA, Centre de Toulouse.

Wang X. (2009). Prédiction et analyse numérique d’écoulements turbulents avec transfert thermique dans des cavités ventilées à l’aide d’un modèle à relaxation elliptique. Thèse de Doctorat. Université de Lille 1.

Yakhot V., Orszag S. A. (1986). Renormalization group analysis of turbulence I. Basic theory J. Sci. Comput, Vol. 11, pp. 1–51.

Yang Z., Shih T. H. (1993). new time scale based k -ε model for near-wall turbulence. American Institute of Aeronautics and Astronautics Journal, Vol. 31, pp. 1191–1198. http://arc.aiaa.org/doi/abs/10.2514/3.11752