THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

online first only

Research on heat transfer characteristics of fractal-generated turbulence based on large eddy simulation

ABSTRACT
Turbulence plays an important role in the fields of heat and mass transfer and enhanced chemical reaction. In order to explore the effect of grid-generated turbulence on flow heat transfer, in this paper, three different fractal grid structures with the same blocking ratio σ, effective mesh size Meff and thickness ratio tr=tmax/tmin (case1: The grid cross-section is a triangle, case2: the grid cross-section is an inverted triangle,case3:the grid cross-section is square ,case4:no grid) and without the grid were simulated based on large eddy simulation(LES). The aim of this simulation is to explain the evolution characteristics and heat transfer mechanism of turbulent flow field under the four cases. The results show that,in the same initial condition, case 2 can generate the highest turbulence intensity and the feature of heat transfer on the cylindrical surface is more uniform. In case3, the boundary layer in the flow field is separated earlier, and more vortices are excited to enhance the heat transfer than other cases in the boundary layer region. The surface average Nusselt number is 1.3 times than that of case4.
KEYWORDS
PAPER SUBMITTED: 2018-11-22
PAPER REVISED: 2019-03-06
PAPER ACCEPTED: 2019-03-20
PUBLISHED ONLINE: 2019-04-07
DOI REFERENCE: https://doi.org/10.2298/TSCI181122108D
REFERENCES
  1. G. Melina., Heat transfer in production and decay regions of grid-generated turbulence, Int. J. Heat Mass Transfer, 109 (2017), 2, pp. 537-554
  2. G.F. Hewitt., Heat Exchanger Design Handbook, Begell House, New York, USA, 2008
  3. Hurst, D., et al., Scalings and decay of fractal-generated turbulence, Phys. Fluids., 19(2007), ID 035103
  4. G. Melina., P.J.K. Bruce., J.C. Vassilicos., Vortex shedding effects in grid-generated turbulence, Phys. Rev. Fluids., 1(2016), 4, ID 044402
  5. Torrano, M. Tutar., et al., Comparison of experimental and RANS-based numerical studies of the decay of grid-generated turbulence, Journal of Fluids Engineering., 137 (2015), 6, ID, 061203.
  6. R. J. Hearst., P. Lavoie., Decay of turbulence generated by a square-fractalelement grid, Journal of Fluid Mechanics., 741 (2014), 2, pp. 567-584.
  7. J.Panda, A. Mitra, A. Joshi, H. Warrior, Experimental and numerical analysis of grid generated turbulence with and without mean strain, Experimental thermal and fluid science., 98 (2018), 11, pp. 594-603.
  8. Risberg, D., et al., Computational fluid dynamics simulation of indoor climate in low energy buildings computational set up, Thermal science., 21(2017), 5, PP, 1985-1998
  9. Alammar, K, N., Turbulent flow and heat transfer characteristics in U-tubes: a simulation study, Thermal science., 13(2009), 4, PP, 175-181
  10. M.C. Smith., et al., Effects of turbulence on laminar skin friction and heat transfer, Phys. Fluids., 9 (1966), 12, pp. 2337-2344
  11. J. Kestin., et al., The influence of turbulence on mass transfer from cylinders, J. Heat Transfer., 93 (1971), 4, pp. 321-327
  12. G.W. Lowery., R.I. Vachon., The effect of turbulence on heat transfer from heated cylinders, Int. J. Heat Mass Transfer., 18 (1975), 6, pp. 1229-1242
  13. C. Sak., et al., The role of turbulence length scale and turbulence intensity on forced convection from a heated horizontal circular cylinder, Exp. Therm. Fluid Sci., 31 (2007), 4, pp. 279-289
  14. B.G. Van Der Hegge Zijnen., Heat transfer from horizontal cylinders to a turbulent air flow, Appl. Sci. Res., 7 (1958), 2-3, pp. 205-223
  15. Tian L T., et al., A comparative study on the Air-side performance of wavy fin-and-tube heat exchanger with Punched delta winglets in staggered and in-line arrangements. International Journal of Thermal Sciences., 48 (2009), 9, pp. 1765-1776
  16. Fiebig, M., et al., Wing-type vortex generators For fin-tube heat exchangers. Experimental Thermal and Fluid Science., 7 (1993), 4, pp. 287-295
  17. Biswas G., et al., Heat transfer enhancement in Fin-tube heat exchangers by winglet type vortex generators. International Journal of Heat and Mass Transfer., 37 (1994), 2 pp.283-291
  18. Jacobi, A. M., et al., Heat transfer surface enhancement, Through the use of longitudinal vortices - a review of recent progress. Experimental Thermal and Fluid Science., 11 (1995), 3, pp. 295-309
  19. Gentry M C., et al., Heat transfer enhancement by delta Wing Vortex generators on a flat plate: vortex interactions with The boundary layer. Experimental Thermal and Fluid Science., 14 (1997), 3, pp. 231-242
  20. Mushatet., Khudheyer S., Simulation of turbulent flow and heat transfer over a backward -facing step with ribs turbulators, Thermal science., 15(2011), 1, pp.245-255
  21. Panda J.P., Warrior, H. V., Maity, S., Mitra A., Sasmal, K., An improved model including length scale anisotropy for the pressure strain correlation of turbulence, ASME Journal of Fluids Engineering., 139(2017), 1, ID. 044503.
  22. Mishra, A., Girimaji, S., Toward approximating non-local dynamics in single-point Pressure-strain correlation closures, Journal of Fluid Mechanics., 811(2017), 25, pp. 168-188.
  23. Panda, J.P. and Warrior, H.V., A Representation Theory-Based Model for the Rapid Pressure Strain Correlation of Turbulence., Journal of Fluids Engineering., 140 (2018), 8, ID.081101.
  24. A. A. Mishra., S. S. Girimaji., Pressure-strain correlation modeling: towards achieving consistency with rapid distortion theory, Flow, turbulence and combustion., 85 (2010), 3-4, pp.593-619.
  25. W.Q. Tao., Numerical Heat Transfer., Xi'an Jiaotong University, Xi'an., China,2001
  26. ZOU L., et al., Large-eddy simulation of flow around cylinder arrays at a subcritical Reynolds number, Journal of hydrodynamics, 20 (2008), 4, pp. 403-413
  27. ChuWen Guo., et al., Engineering fluid mechanics., Jiang Su., China, 2010