International Scientific Journal


The fluid-flow and heat transfer in a buoyancy-driven microcavity heated from below are numerically investigated. In spite of the fact that microcavities are widely used in microelectro- mechanical systems, now a day, more interest in the evacuated cavity on Eqn. solar collectors are very common to reduce heat loss from the system. This paper provides a useful information for engineers to estimate heat transfer in low pressure cavities. The finite volume technique was used to solve the governing equations along with temperature jump and slip flow boundary conditions.The simulations are carried out for various cavity aspect ratios (H/L) and different Rayleigh number for both macroand micro-fluids. The effect of Knudsen number in the rarefied flow regime (microfluidic) has also been investigated. It is shown that for both cases the effect of aspect ratios on heat transfer becomes significant at high Rayleigh numbers and when the aspect ratio is below 5. It was also found that increasing Knudsen number reduces the heat transfer. The interaction between Nusselt, Rayleigh, Knudsen numbers, and the aspect ratio was investigated using the design of experiments, results show that no interaction between these parameters. To help engineers to estimate heat transfer in low pressure cavities, widely used in solar energy applications, a correlation for convection heat transfer coefficient is introduced.
PAPER REVISED: 2017-11-01
PAPER ACCEPTED: 2017-11-02
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  1. Naffouti, T., Djebali, R., Natural Convection Flow and Heat Transfer in Square Enclosure Asymmetrically Heated from Below: A Lattice Boltzmann Comprehensive Study, Computer Modeling in Engineering & Sciences, vol. 88(3), (2012), pp. 211-228.
  2. Globe, S., Dropkin, D., Natural- Convection Heat Transfer in Liquids Confined by Two Horizontal Plates and Heated From Below, Journal of heat transfer, Vol. 81(1), (1959), pp. 24-28.
  3. Alshare, A., Al-Kouz, W., Kiwan, S., Alkhalidi A., Haderd, M., Computational modeling of gaseous flow and heat transfer in a wavy microchannel, Jordan Journal of Mechanical and Industrial Engineering, Vol. 10 (1), (2016), pp. 75- 83.
  4. Al‑Kouz, W., Alshare, A., Alkhalidi, A., Kiwan, S., Two dimensional analysis of low pressure flows in the annulus region between two concentric cylinders, SpringerPlus, 5:529, (2016), DOI 10.1186/s40064-016-2140-6, 2016.
  5. Alkhalidi, A., Kiwan, S., Al-Kouz, W., Alshare, A., Conjugate heat transfer in rarefied gas in enclosed cavities. Vacuum. Vol. 130, (2016), PP.137-145.
  6. Polikarpov, A., Ho, M., Graur, I., Transient heat transfer in a rarefied binary gas mixture confined between parallel plates due to a sudden small change of wall temperatures. International Journal of Heat and Mass Transfer. Vol. 101, (2016), pp. 1292-1303.
  7. Rovenskaya, O., Numerical investigation of gas-surface scattering dynamics on the rarefied gas flow through a planar channel caused by a tangential temperature gradient. International Journal of Heat and Mass Transfer. Vol. 89, (2015), pp. 1024-1033.
  8. Zhou, S., Zhou, L., Du, X., Yang, Y., Heat transfer characteristics of evaporating thin liquid film in closed microcavity for self-rewetting binary fluid. International Journal of Heat and Mass Transfer. Vol. 108, (2017) pp.136-145.
  9. Li, W., Qu, X., Alam, T., Yang, F., Chang, W., Khan, J., Li, C., Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities. Applied Physics Letters. Vol. 110(1), (2017), pp. 014104.
  10. Tatsios G, Vargas MH, Stefanov SK, Valougeorgis D. Nonequilibrium Gas Flow and Heat Transfer in a Heated Square Microcavity. Heat Transfer Engineering, Vol. 37(13-14), (2016), pp. 1085-95.
  11. Rana AS, Mohammadzadeh A, Struchtrup H. A numerical study of the heat transfer through a rarefied gas confined in a microcavity. Continuum Mechanics and Thermodynamics. Vol. 1;27(3), (2015), PP. 433-46.
  12. Sone, Y., Aoki, K. and Sugimoto, H., The Be´nard problem for a rarefied gas: Formation of steady flow patterns and stability of array of rolls, Phys. Fluids, Vol. 9 (12), (1997), PP. 3898.
  13. Stefanov, S., Roussinov V. and Cercignani, C., Rayleigh-Bénard flow of a rarefied gas and its attractors. III. Three-dimensional computer simulations, Phys. Fluids, Vol. 19, (2007), PP. 124101.
  14. Stefanov, S., Roussinov, V. and Cercignani, C., Rayleigh-Be´nard flow of a rarefied gas and its attractors. I. Convection regime, Physics of Fluids, Vol. 14 (7), (2002), PP. 2255.
  15. J.C. Maxwell, on stresses in rarefied gases arising from inequalities of temperature, Philos. Trans. Roy. Soc. Lond. Vol. 170, (1879), pp.231-256.
  16. M. von Smoluchowski, Ueber Wärmeleitung in verdünnten Gasen, Ann. Phys. Chem. Vol.64, (1898), pp. 101-130.
  17. S. Colin, Heat Transfer and Fluid Flow in Minichannels and microchannels: Single-phase gas flow in microchannels, Elsevier Ltd, 2006.
  18. Ansys, Fluent Documentation.
  19. Schaaf S, Chambre P., Flow of Rarefied Gases, Princeton Univ. Press,Princeton, 1961.
  20. Cercignani S, Lampis M, Rarefied gas dynamics, Academic Press, New York, 1974.
  21. Glaser, S. (Red.); Vakuum-Isolierglas (VIG), Abschlussbericht zum Verbund, Verband Deutscher Maschinen- und Anlagenbau e. V. (VDMA), Frankfurt (Hrsg.), 55 S., (2007), FKZ 0327366A-G.
  22. D. Goswami and F. Kreith, Energy Conversion, CRC Press, Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300, 2007.

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