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/Dh = 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.