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

Year 2018, Volume: 4 Issue: 6, 2481 - 2495, 29.09.2018

Chafika Zidani

https://doi.org/10.18186/thermal.465696

Cited By: 14

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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