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This paper performed a three-dimensional numerical analysis of the flow structure and heat transfer enhancement of turbulent airflow through a rectangular channel (without baffles, with baffles). Two partially inclined baffles with different orientations are mounted on the bottom and top walls of the channel. The location of the baffles in the direction of flow through the channel of a heat exchanger is of great importance. It depends mainly on the geometrical parameters and the orientation of the baffles. Hence, our study focused on analyzing the effects of the baffles on the thermal–hydraulic behavior in the exchanger by choosing a flat baffle and four configurations of different orientations. Numerical results are presented in terms of axial velocity U, isotherms (T), turbulent kinetic energy (k), amount of heat dissipated by the channel surfaces (Q), average Nusselt number (Nu), friction factor (f), and thermal performance factor (ƞ). The results show that the insertion of the partially inclined baffles into the channel causes the generation of vortices in the upstream and downstream areas of the baffle location point. Thus the mixing phenomenon occurs, which induces an increase in the heat transfer rate and generates a pressure drop simultaneously. Furthermore, the analysis of the results shows that compared to the smooth case (without baffles), the thermal performance factor (η) is significantly higher in the four configurations with baffles. Thus, for the different cases studied: (2); (3); (4); (5) and (6), the factor (η) is equal to 2.18; 2.16; 2.19; 2.27; and 2.25, respectively, for a Reynolds number equal to 87,300. The results also indicate that the transmitted relative heat quantities are equal to 116.08, 113.93, 118.2, 121.71, and 109.39%, respectively, for the same cases considered. Therefore, the configuration corresponding to case (5) performs better in heat transfer than the others. Finally, new correlations for predicting friction factor and Nusselt number as a function of Reynolds number and configuration are found at the end of this study. [ABSTRACT FROM AUTHOR]

In this paper, the thermal performance improvements of a heat removal system like an electronic system have been analyzed. The studied case is a horizontal channel in which two partially inclined baffles are attached with variable height and number. The channel is crossed by a forced convective flow of a cooling fluid (air). This numerical work evaluates the influences of the height and number of the baffles on the enhancement of the heat transfer rate. The mathematical model of this system is composed of nonlinear partial equations that the analytical solution for them is very complex, hence the need for numerical analysis is mandatory with the aid of a finite volume method. Accordingly, The numerical results are presented in axial and transverse velocity, temperature, local and average Nusselt number, local friction coefficient, pressure drop, heat transfer rate, and turbulence kinetic energy. The results revealed that it is possible to improve the thermal performance of the considered system by adopting designs that allow the maximum heat transfer rate with the minimum energy loss. In addition, results show that at the lowest Reynolds number (Re = 10,000), as the height of baffles rises from 0.01 to 0.03 m (growth by 200%), the heat transfer rate augments about 59.09%. Moreover, at the highest evaluated Reynolds number (Re = 87,300), by increasing the height of baffles up to 200%, the heat transfer rate increases by approximately 50.53%. Furthermore, employing a higher number of baffles leads to more heat transfer rates and a significant pressure drop. [ABSTRACT FROM AUTHOR]

The present study focused on researching a technique that can make a cooling system more efficient in terms of heat transfer. To achieve this, it is possible to modify the thermal conductivity of its cooling fluid or the structure of its flow. In this study, we have opted for the second technique. To do this, we sought to create singularities in the flow by inserting vertical and rotating baffles around the vertical. The study field is a channel of rectangular section, placed horizontally, and crossed by the incompressible and turbulent flow of a fluid (air) in forced convection. Geometrically, the physical problem describes mathematically. A system of hyperbolic equations governs it; Navier–Stokes equations derive from the laws of conservation of mass and momentum and the state's law that derives from the principle of conservation of energy. A finite volume scheme ensures the discretization of the governing equations and the numerical analysis's boundary conditions. The turbulence is modeled using the standard k-ɛ model, while the pressure–velocity coupling problem solves by applying the SIMPLE algorithm. The proposed numerical computational model validates by comparing the computed results with those of literature correlations. The model was then applied to practical cases where a Reynolds number in the range (12,000, 16,000) has chosen. The orientation angle (θ) of the baffles is chosen equal to (0°, 5°, 7°, 13°, 15°) with a different orientation direction. The calculated results are presented in map form for the different physical fields (of axial velocity, temperature) or in graphical form for the different factors and coefficients (friction factor, amount of heat removal, average Nusselt numbers, and thermal performance factor). The results obtained show that the system is made more efficient with a thermohydrodynamic behavior that varies significantly with the baffles' orientation. The heat transfer rate increased, and the pressure drops reduced. For an orientation angle of (θ = 5°), the thermal performance factor is around 2.323, and 2.45, for Re = 12,000, and 16,000, respectively. [ABSTRACT FROM AUTHOR]

In the present paper, we report a numerical study of dynamic and thermal behavior of the incompressible turbulent air flow by forced convection in a two-dimensional horizontal channel. This one contains the complicated form of the deflector which has been studied by varying the inclination angle from φ = 40°, φ = 55° to φ = 65°. The baffles are mounted on lower and upper walls of the channel. The walls are maintained at a constant temperature (375 K), the inlet velocity of air is Uint = 7.8 m/s, and the Reynolds number Re = 8.73 × 104. A specifically developed numerical model was based on the finite-volume method to solve the coupled governing equations and the SIMPLE (Semi Implicit Method for Pressure Linked Equation) algorithm for the treatment of velocity-pressure coupling. For Pr = 0.71, the results obtained show that (i) the streamlines and isotherms are strongly affected by the inclinations angles at Re = 8.73 × 104, (ii) the friction coefficient near the baffles increases under the angle exchange effect, and (iii) for a constant Re, the local Nusselt number at the walls of the channel varies with increasing the inclination angle of the deflector. Furthermore, the deflectors are generally used to change the direction of the structure of flow and also to increase the turbulence levels. We can conclude that the contribution of inclined baffles improves the increase of heat and mass transfer in which the Nusselt number at a certain angle increases noticeably. [ABSTRACT FROM AUTHOR]