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This article numerically investigates the mixed convection of Bingham fluid in a narrow annulus. The temperature of the inner fixed cylinder ( θ i ) is higher than that of the outer one ( θ o ), which rotates at a constant angular velocity. An OpenFOAM solver, icoFoam, which works based on the finite volume method and the PISO algorithm, is modified to perform the simulations. The modified solver can solve unsteady heat transfer problems for Bingham fluids without using regularization methods. After validating the solver, it solves the problem in different conditions to show the effect of relevant parameters, such as Reynolds number, Bingham number, and aspect ratio, on the flow field and thermal performance of the enclosure for constant amounts of Grashof and Prandtl numbers. The results are presented as streamlines and isotherms, the size and shape of the unyielded regions, the local and mean Nusselt number, and the torque coefficient. The results demonstrate that the flow is steady at Re = 10 for all Bingham numbers, and a decrease in the Reynolds number may result in an unsteady flow depending on the value of the Bingham number. The flow's time history reveals that at a fixed Reynolds number, the flow shifts from periodic to steady-state by enhancing the Bingham number so that the flow becomes entirely steady for a given Bingham number. An interesting phenomenon is observed, the formation, movement, and disappearance of the plug zones (unyielded regions) for the periodic flow at Re = 1 and Bn = 5. [ABSTRACT FROM AUTHOR]

In the present study, the mixed convection heat transfer for a nanofluid flow inside solar cell cooling system was numerically investigated. To this end, an inclined two-dimensional channel with insulated walls was taken under study. The solar cells were assumed to locate on one side of channel where the nanofluid enters at constant temperature. The study has been carried out for the Richardson numbers in the range 0.01 ⩽ Ri ⩽ 20, with solid volume fraction 0 ⩽ φ ⩽ 0.04, Reynolds number 100 and for Prandtl number 7.02. The effects of solid volume fraction and solar cells location in terms of Richardson number on the flow and temperature fields and also the heat transfer rate were studied. The results showed that the presence of nanoparticles led to an increase in temperature gradient and heat transfer near the solar cells. It was also observed that the maximum heat transfer in solar cells occurs in minimum inclination angle of channel at a certain relative distance between the cells. [ABSTRACT FROM AUTHOR]

Abstract: This article aims to numerically investigate mixed convection heat transfer in a two-dimensional horizontal channel with an open cavity. A discrete heat source is considered to be located on one of the walls of the cavity. Three different heating modes are considered which relate to the location of the heat source on three different walls (left, right and bottom) of the cavity. The analysis is carried out for a range of Richardson numbers and cavity aspect ratios. The results show that there are noticeable differences among the three heating modes. When the heat source is located on the right wall, the cavity with an aspect ratio of two has the highest heat transfer rate compared to other cavity heating modes. Moreover, when the heat source is located on the bottom wall, the flow field in the cavity with an aspect ratio of two experiences a fluctuating behaviour for Richardson number of 10. The results also show that at a fixed value of Richardson number, all three different heating modes show noticeable improvements in the heat transfer mechanism as the cavity aspect ratio increases. [Copyright &y& Elsevier]

The objective of this paper is to numerically investigate the cooling performance of electronic devices with an emphasis on the effects of the arrangement and number of electronic components. The analysis uses a two dimensional rectangular enclosure under combined natural and forced convection flow conditions and considers a range of Rayleigh numbers. Heat sources in the enclosure generate the natural convection flow and an externally sourced air stream through the enclosure generates the forced convection flow. The results show that increasing the Rayleigh number significantly improves the enclosure heat transfer process. At low Rayleigh numbers, placing more heat sources within the enclosure reduces the heat transfer rate from the sources and consequently increases their overall maximum temperature. The arrangement and number of heat sources have a considerable contribution to the cooling performance. However, increasing the Rayleigh number reduces this contribution. [ABSTRACT FROM AUTHOR]