THERMAL SCIENCE

International Scientific Journal

TRANSITIONAL FREE CONVECTION FLOW AND HEAT TRANSFER WITHIN ATTICS IN COLD CLIMATE

ABSTRACT
The transitional free convection flow and heat transfer within attics in cold climate are investigated using 3-D numerical simulations for a range of Rayleigh numbers from 103 to 106 and height-length ratios from 0.1 to 1.5. The development process of free convection in the attic could be classified into three-stages: an initial stage, a transitional stage, and a fully developed stage. Flow structures in different stages including transverse and longitudinal rolls are critically analyzed in terms of the location and strength of convection rolls and their impacts on the heat transfer. The transition unsteady flow and asymmetry flow in the fully developed stage is discussed for the fixed height-length ratio 0.5. Various flow regimes are given in a bifurcation diagram in the parameter space of Rayleigh numbers (102 < Ra < 107) for height-length ratios (0.1 < A < 1.5). The time series of heat transfer rate through the bottom wall is quantified for different height-length ratios. The overall heat transfer rate for the low Prandtl fluid (Pr = 0.7) could be enhanced based on 3-D flow structure.
KEYWORDS
PAPER SUBMITTED: 2021-08-26
PAPER REVISED: 2022-03-22
PAPER ACCEPTED: 2022-03-24
PUBLISHED ONLINE: 2022-04-09
DOI REFERENCE: https://doi.org/10.2298/TSCI210826039C
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2022, VOLUME 26, ISSUE Issue 6, PAGES [4699 - 4709]
REFERENCES
  1. R. Kessler, Nolinear transition in three-dimensional convection, J. Fluid Mech. 174 (1987) 357-379.
  2. J. Ma, B.C. Nie, F. Xu, Pr > 1 unsteady thermal flows and heat transfer in a finned cavity with a uniform heat flux, Int. J. Therm. Sci. 129 (2018) 83-93.
  3. H.Y. Zhai, B.C. Nie, B. Chen, F. Xu, Unsteady flows on a roof imposed by a periodic heat flux: 2D simulation and scaling analysis, Int. J. Therm. Sci. 145 (2019) 106002.
  4. E. F. Kent. Numerical computation of laminar natural convection in triangular shaped cavities, Adv. Appl. Mech. XIII 128 (2020) 27-38.
  5. E. F. Kent.Numerical analysis of laminar natural convection in isosceles triangular enclosures for cold base and hot inclined walls, Mech. Res. Commun. 36 (2009) 497-508.
  6. D. Das, M. Roy, T. Basak. Studies on natural convection within enclosures of various (non-square) shapes-A review, Int. J. Heat Mass Transfer 106 (2017) 356-406.
  7. A. Rahimi, A. D. Saee, A. Kasaeipoor, E. H. Malekshah. A comprehensive review on natural convection flow and heat transfer: The most practical geometries for engineering applications, Int. J. Numer. Method. H. 29 (2019) 834-877.
  8. R.D. Flack, Velocity measurements in two free convection air flows using a laser velocimeter, J. Heat Transfer 101 (1979) 256-260.
  9. S.C. Saha, J.C. Patterson, C. Lei, Free convection in attic-shaped spaces subject to sudden and ramp heating boundary conditions, Int. J. Heat Mass Transfer 46 (2010) 621-638.
  10. S.C. Saha, Unsteady free convection in a triangular enclosure under isothermal heating, Energy Build. 43 (2011) 701-709.
  11. S.C. Saha, Scaling of free convection heat transfer in a triangular cavity for Pr > 1, Energy Build. 43 (2011) 2908-2917.
  12. R.D. Flack, T.T. Konopnicki, J.H. Rooke, The measurement of natural convective heat transfer in triangular enclosures, J. Heat Transfer 101 (1979) 648-654.
  13. R.D. Flack, The experimental measurement of free convection heat transfer in triangular enclosures heated or cooled from below, J. Heat Transfer 102 (1980) 770-772.
  14. H. Asan, L. Namli, Laminar free convection in a pitched roof of triangular cross-section: summer day boundary conditions, Energy Build. 33 (2000) 69-73.
  15. T.N. Anderson, M. Duke, J.K. Carson, Experimental determination of free convection heat transfer coefficients in an attic shaped enclosure, Int. Commu. Heat Mass Transfer 37 (2010) 360-363.
  16. E.H. Ridouane, A. Campo, Experimental-based correlations for the characterization of free convection of air inside isosceles triangular cavities with variable apex angles, Exp. Heat Transfer 18 (2005) 81-86.
  17. D. Poulikakos, A. Bejan, Free convection experiments in a triangular enclosure, J. Heat Transfer 105 (1983) 652-655.
  18. D. Poulikakos, A. Bejan, The fluid dynamics of an attic space, J. Fluid Mech. 131 (1983) 251-269.
  19. P.M. Haese, M.D. Teubner, Heat exchange in an attic space, Int. J. Heat Mass Transfer 45 (2002) 4925-4936.
  20. G.A. Holtzman, R.W. Hill, K.S. Ball, Laminar free convection in isosceles triangular enclosures heated from below and symmetrically cooled from above, J. Heat Transfer 122 (2000) 485-491.
  21. E.H. Ridouane, A. Campo, Formation of a pitchfork bifurcation in thermal convection flow inside an isosceles triangular cavity, Phys. Fluids 18 (2006) 074102.
  22. E.H. Ridouane, A. Campo, Numerical simulation of the 3D behaviour of thermal buoyant airflows in pentahedral spaces, Int. J. Heat Fluid Flow 29 (2008) 1360-1368.
  23. C. Lei, F. Xu, J.C. Patterson, Visualisation of free convection in an isosceles triangular enclosure heated from below, Proceedings of 55th Pacific Symposium on Flow Visualisation and Image Processing, Australia (2005).
  24. C. Lei, S.W. Armfield, J.C. Patterson, Unsteady free convection in a water-filled isosceles triangular enclosure heated from below, Int. J. Heat Mass Transfer 51 (2008) 2637-2650.
  25. H. Cui, F. Xu, S.C. Saha, A three-dimensional simulation of transient free convection in a triangular cavity, Int. J. Heat Mass Transfer 85 (2015) 1012-1022.
  26. H. Cui, F. Xu, S.C. Saha, Transition to unsteady free convection flow in a prismatic enclosure of triangular section, Int. J. Therm. Sci. 111 (2017) 330-339.
  27. H. Cui, F. Xu, S.C. Saha, Q. K. Liu, Transient free convection heat transfer in a section-triangular prismatic enclosure with different aspect ratios, Int. J. Therm. Sci. 139 (2019) 282-291.
  28. S.C. Saha, M.M.K. Khan, A review of free convection and heat transfer inattic-shaped space, Energy Build. 43 (2011) 2564-2571.
  29. C. Lei, J.C. Patterson, A direct three-dimensional simulation of radiation-induced free convection in a shallow wedge, Int. J. Heat Mass Transfer 46 (2003) 1183-1197.
  30. S.C. Saha, J.C. Patterson, C. Lei, Free convection in attics subject to instantaneous and ramp cooling boundary conditions, Energy Build. 42 (2010) 1192-1204.
  31. S.C. Saha, J.C. Patterson, C. Lei, Free convection and heat transfer in attics subject to periodic thermal forcing, Int. J. Therm. Sci. 49 (2010) 1899-1910.
  32. K.R. Kirchartz, H. Oertel JR, Three-dimensional thermal cellular convection in rectangular boxes, J. Fluid Mech. 192 (1988) 249-286.
  33. G.M. Horsch, H.G. Stefan, S. Gavali, Numerical simulation of cooling-induced convective currents on a littoral slope, Int. J. Numer. Meth. Fluids 19 (1994) 105-134.
  34. C. Lei, J.C. Patterson, A direct three-dimensional simulation of radiation-induced free convection in a shallow wedge, Int. J. Heat Mass Transfer 46 (2003) 1183-1197.
  35. W.V.R. Malkus, The heat transport and spectrum of thermal turbulence, Proc. R. Soc. Lond. A 225 (1954) 196-212.
  36. S. Grossmann, D. Lohse, Scaling in thermal convection: a unifying theory, J. Fluid Mech. 407 (2000) 27-56.

© 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence