Numerical Analysis of Enhanced Heat Transfer Using a Pair of Similar Porous Baffles in a Backward-Facing Step Flow

Arthur, James K.; Schiele, Owen

doi:10.11159/jffhmt.2021.024

Cited by 5 publications

(3 citation statements)

References 24 publications

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“…As the adverse pressure gradient decreases, the flow reattaches to the surface. For the case of a BFS channel with no obstacles, the reattachment point is at a distance of five step heights of the step, which is consistent with the results of other studies summarised in [25]. The reattachment point for case 1, located behind the bottom baffle, is slightly closer to the step (X = 4.7).…”

Section: Resultssupporting

confidence: 88%

“…His work examined how variations in the height, width, Darcy number, and thermal conductivity of the baffle affect the performance number if the bottom wall temperature was imposed. Arthur and co-workers [24,25] investigated the inclusion of two porous baffles after the step in a BFS channel, one on the bottom wall and other on the top wall, but used a pore-level approach to model the flow through porous media (while Li et al [22] and Zhao [23] used volume-average models). The bottom wall was kept at a constant temperature, and the dimensions and characteristics of the porous baffles were varied, similar to what was done in the works mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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Multi-objective optimisation of a 2D backward-sfacing step channel with porous baffles

Costa,

Janeiro,

Malico

2024

J Therm Anal Calorim

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Porous baffles can be used to enhance heat transfer in various engineering applications, including electronic cooling, gas turbine blades, and chemical reactors. Also, the backward-facing step is a widely used configuration in fluid dynamics studies due to its simplicity and relevance to real-world geometries. This study examines heat transfer and flow characteristics in a backward-facing step channel featuring a heated bottom wall and two porous baffles. A computational fluid dynamics model, validated against prior research, is used to investigate flow and temperature fields. The innovation of this work lies in the application of multi-objective optimisation to search for a set of solutions that establish a trade-off between the average Nusselt number and the pressure drop. The optimisation specifically considers various parameters of the porous baffles, including height, width, distance from the step, and Darcy number, to identify optimal design configurations. Results show that porous baffles significantly improve heat transfer compared to a backward-facing step channel without them, despite an increase in pressure drop due to their presence. This work offers valuable insights into the trade-off between heat transfer performance and pressure drop, crucial for designing efficient heat transfer systems. By exploring the Pareto-Frontier, which represents various optimal design solutions, the study provides practical guidance when seeking to optimise heat transfer in backward-facing step channels with porous baffles. The findings contribute to advancing the understanding of heat transfer enhancement, highlighting the potential of porous baffles as a viable solution for improving thermal management in engineering systems.

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Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Multi-objective optimisation of a 2D backward-sfacing step channel with porous baffles

Costa,

Janeiro,

Malico

2024

J Therm Anal Calorim

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“…A number of numerical studies have shown the prospect of using porous-like inserts to achieve this purpose at minimal differential pressure cost. However, this has been analysed mostly for laminar flows [1,2]. Studies of turbulent flow with porous inserts in backward-facing step flows are rare [3].…”

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confidence: 99%

Reduction of the Recirculation Region of a Backward-Facing Step Flow

Arthur¹

2022

International Conference on Fluid Flow, Heat and Mass Transfer

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Backward-facing step flow is a common flow phenomenon in engine inlets, combustor flame holders, and turbine blades. The flow is generally associated with an upstream flow that results in a separated shear layer as the flow transcends the step. Beneath this shear layer is a recirculation region characterized by a system of vortices whose extent is a function of the geometry of the flow system and the inlet flow conditions. As the recirculation region can be a zone of unwanted localized heating / cooling and a major contribution to head losses, it is often desirable to reduce the extent of this region through active or passive means. A number of numerical studies have shown the prospect of using porous-like inserts to achieve this purpose at minimal differential pressure cost. However, this has been analysed mostly for laminar flows [1,2]. Studies of turbulent flow with porous inserts in backward-facing step flows are rare [3]. To fill this apparent need, an experimental study of the reduction of the recirculation region for a turbulent flow using a thin porous insert is presented.The study is accomplished using an open channel backward-facing step flow system in a flume. The expansion ratio (i.e. expanded depth to upstream depth ratio) of the system is 1.3 and the aspect ratio (i.e. ratio of channel width to step height h) is 3.1. With a downstream depth of approximately 0.1m and the maximum velocity of the approach flow 0.280m/s, the Froude number and the Reynolds number (based on maximum velocity and step height) is maintained at ~ 0.28 and 6900 respectively. A porous mat is installed behind the step. The mat is of open surface area 40%, filling fraction 3%, length 8h, thickness 0.12h, and covering the entire width of the test channel. The effect of the porous mat is tested by modifying the location of the mat at 6h and 3h respectively. The results are compared with measurements without any porous insert. The measurements are based on velocity data obtained from the application of a high-resolution planar particle image velocimetry in multiple planes within the recirculation region, and along the central span of the channel flow.An examination of the reattachment lengths of the test results show that by locating the porous insert at a streamwise distance of 6h or less behind the step, the streamwise extent of the recirculation region can be reduced. While this reduction is only marginal when the porous insert is located at 6h, it is over 20% at 3h. At the reattachment region, the increment in mean wall-normal velocity due to the porous mat is significant, as are the decrements of turbulence intensities and Reynolds stresses. Consequently, there is a significant cut-back in the production of turbulence kinetic energy due to the presence of the porous insert. Regardless of these differences, the transport of turbulence kinetic energy appears to be unaffected by the presence of a porous insert. Two-point correlations of the velocity fluctuations show that the sizes of the coherent structures and their convection b...

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Numerical investigation of heat transfer characteristics and flow structure inside sudden expansion channel

Mahmood,

Hilal,

Aun

2024

Electromechanical Engineering and Its Applications

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Numerical Analysis of Enhanced Heat Transfer Using a Pair of Similar Porous Baffles in a Backward-Facing Step Flow

Cited by 5 publications

References 24 publications

Multi-objective optimisation of a 2D backward-sfacing step channel with porous baffles

Multi-objective optimisation of a 2D backward-sfacing step channel with porous baffles

Reduction of the Recirculation Region of a Backward-Facing Step Flow

Numerical investigation of heat transfer characteristics and flow structure inside sudden expansion channel

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