The development of three-dimensional heat transfer and fluid flow in a square channel rotating in a parallel-mode has been investigated numerically. The duct is partially occupied by a foam material of high porosity ε≥0.89 and subjected to a uniform wall heat flux. In regards to the influence of rotation, both the centrifugal buoyancy and Coriolis forces are considered in the current study. The generalised model is used to mathematically simulate the momentum equations employing the Boussinesq approximation for the density variation. Moreover, thermal dispersion has been taken into account with considering that fluid and solid phases are in a local thermal non-equilibrium. The governing equations are discretised according to the finite volume method with employing a hybrid differencing scheme. Computations are performed for a wide range of parameters including the hollow ratio (0≤S≤1), foam porosity (0.89≤ε≤0.97), pore density (5PPI≤ω≤40PPI), solid to fluid thermal conductivity ratio (250≤κ≤4000), Reynolds number (250≤Re≤2000), and rotation number (0≤Ro≤1), while the values of characteristic temperature difference and Prandtl numbers are maintained constant at ΔTc=1000°C and Pr=0.7, respectively. Results reveal that flow resistance and heat transport are augmented with either decreasing the hollow ratio and foam porosity or increasing Reynolds and rotation numbers, while two contradictory trends are found for the impact of increasing pore density on heat transfer; either enhancing or suppressing depending on the size of hollow zone. In addition, both rotation and thermal dispersion have dominant roles in enhancing heat transfer at the higher levels of porosity or the lower values of conductivity ratios. However, these roles are reduced gradually with decreasing the foam porosity or increasing thermal conductivity ratio, but do not completely vanish. Eventually, the worth of using high porosity fibrous media in enhancing the heat transported through rotating channels has been inspected. An overall enhancement parameter is compared for the current study with a previous work regarding turbulent flow in a rotating clear channel, where it has been confirmed that the current proposal is practically justified and efficient.
06-05-2015Ahmed Alhusseny A5, George Begg Building, Sackville Street Manchester, M60 1QD (+44) 7876340153 ahmed.alhusseny@postgrad.manchester.ac.uk
International Journal of Heat and Mass TransferThe current research presents a numerical simulation of the three-dimensional fluid flow and heat transfer in a square channel rotating around a parallel axis. The duct is partially occupied by metal foam of high porosity (ε≥ 0.89) and subjected to a uniform wall heat flux. Both the centrifugal buoyancy effect and Coriolis forces are considered regarding to the rotation effect in the current study.The generalised model is used to mathematically simulate the momentum equations employing the Boussinesq approximation for the density variation. Moreover, thermal dispersion has been taken into account w...
In this paper, flow field and heat transfer performance in stationary and rotating wavy channels with different shapes were numerically investigated. Three different geometries were generated through three different values of phase-shift angles of = 0, 90 and 180 degrees between ∅ the two opposite wavy walls. A cell-centred finite-volume technique was employed to solve the three-dimensional governing equations based on the SIMPLE algorithm technique. Besides, the Menter k-SST turbulence model was used to simulate the turbulent flow in the current study. The wavelength and wave amplitude of the channel examined were L w =20 mm and a=2 mm, respectively. Numerical simulations were carried out over a range of design and operating conditions including the phase-shift angle of = 0-180 degrees, Reynolds number of Re=1,000-∅ 10,000, and rotating speed of 0-1000 rpm. The results showed that the surface-averaged Ω = Nusselt number increases as Re increases for all shapes of the wavy channel, however, at the expense of the raised pressure losses. Also, the wavy channel with a phase-shift of = 0 deg ∅ showed the highest enhancement in the performance of heat transfer followed by that of 90 ∅ = and 180 deg, respectively. The rotation had a strong impact on the flow field and heat transfer performance. With the increase of rotating speed, lower wall heat transfer coefficient significantly increased, while the upper wall heat transfer coefficient exhibited a slight increase, indicating that those three different geometries of the wavy channels had a good versatility at various values of rotating speeds. The numerical results were compared with those available in the literature, and the results were in a good agreement.
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