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Two-phase, Two-component Simulation of Nanofluids in Natural Convection Applying Lattice Boltzmann Method

Hosseini Abadshapoori, Mehdi | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51075 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan
  7. Abstract:
  8. The advances of technology of microelectrical devices and their computational capacity and so, their heat rates, make the thermal control of them more complex. Utilizing nanopfluids is one of proposing options. The current research investigates the effectiveness of using nanoparticles on the heat transfer rate of fluids in the natural convection. A two-component two-phase lattice Boltzmann method (LBM) has been implemented for this purpose. A wide range of Rayleigh number (Ra), namely 103 to 109, 0 to 0.05 volume fraction s of nanoparticles and nanoparticle diameters below 100 nm has been investigated in this research. The method is optimized for complex geometries. Two and three dimensional methods have been developed. Results indicate that volume fraction of nanoparticles increase the overall average Nusselt number (Nu). However, there is an optimum value between 3 to 4% since adding nanoparticles increases viscosity of the fluid. Furthermore, it is shown that increasing nanoparticle size has a deteriorating effect on the Nu number. The effect is supposed to be due to the augment of opposing forces on the nanoparticles. Moreover, the results reveal that among all factors, the effectiveness of nanoparticles depends on the characteristics of the flow and boundary conditions. The effect of boundary condition is studied in two parts. In the mixed convection flow, it is shown that the effectiveness of adding nanoparticles has a reverse relation with the Richardson number. Hence, the natural convection is a better choice for utilizing nanofluids. Different strategies are proposed for different flows in order to maximize the heat transfer rate. Correlations are presented for predicting the enhanced Nusselt number
  9. Keywords:
  10. Lattice Boltzmann Method ; Nanofluid ; Natural Convection ; Mixed Convection ; Richardson Number ; Two-phase Two-Component Modeling ; Complex Geometry

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