CFD SIMULATION OF THERMO-AERAULIC FIELDS IN A CHANNEL WITH MULTIPLE BAFFLE PLATES

Abstract

In this paper, a two-dimensional incompressible flow of a Newtonian fluid through a horizontal duct of rectangular section, where four flat rectangular baffle plates were inserted and fixed to the top and bottom walls in a periodically staggered manner, is examined and analyzed numerically using the finite volume method by means of commercial CFD software FLUENT 6.3. Researchers consider this situation as a significant issue in the field of heat exchangers, for which the fluid flow characterization, heat transfer and skin friction loss distribution, along with the existence and the extension of possible re-circulations must be determined. The aspect ratio of channel width-to-height, channel length-to-hydraulic diameter, baffle spacing-to-channel height ratio, and blockage ratio of baffle height-to-channel height are fixed at W/H = 1.321, L/D_h = 5.137, Pi/H = 0.972, and h/H = 0.547, respectively. The Reynolds-Averaged Navier-Stokes Equations are the governing flow equations for the problem investigated, with the energy equation. In particular, flow and temperature fields, dimensionless axial velocity profiles, skin friction coefficients, local and average Nusselt numbers, and thermal enhancement factor were presented at constant wall temperature condition along the upper and lower channel walls. The presence of the baffle plates in the whole domain analyzed causes a much high skin-friction loss, f/f₀ = 10.829-25.412 but also provides a considerable heat transfer increase in the duct, Nu/Nu₀ = 3.623-5.008, depending on the Re values. The enhancement thermal factor for fluid flowing in the baffled channel with larger flow rate is found to be higher than that with smaller flow rate. The enhancement thermal factor augments with the rise of Reynolds number and thus, the highest Reynolds number value, Re = 32,000, provides maximum thermal performance factor, TEF = 1.783. This indicates that the introducing the flat rectangular baffle plates into the flow in a staggered arrangement can improve the heat transfer efficiency inside the channel.

Keywords

• Computational Fluid Dynamics,Heat Transfer,Friction Loss,Thermal Enhancement Factor,Shell-and-Tube Heat Exchangers,Renewable Energy,Solar Air Collectors

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