The mixed convective heat transfer has many multiple engineering applications, such as solar collectors, electronic equipment cooling and heat exchanger, and geothermal engineering. This work presents comprehensive coverage of a wide range of published studies in terms of convection heat transfer inside the enclosure in recent years. The convective heat transfer in porous media with/without nanofluid, and the effect of stationary/rotating cylinder inside cavities, as well as the position of the cylinder, had been addressed and discuss to draw the main conclusions and recommendations. It is worthy to mention that the mixed convective with the effect of entropy generation with inner bodies in enclosure has been investigated less than the other simple enclosure shapes due to its complexity. The researchers can be extended their future studies by adding the MHD effects with mixed conviction in simple/complex shapes of enclosure. This study gives an important and useful summary for provides researchers of heat transfer in academic and industrial. At the end of this investigation, the governing equations of the 2-D mixed convection in an enclosure filled with porous medium, and nanofluid addressed.
The present study, numerically investigated of mixed convection in a square enclosure with two layers, with Al2O3–water nanofluid (upper layer) and nano-porous medium (lower layer) with an adiabatic rotating circular cylinder at the center of the enclosure. The top and bottom walls are assumed adiabatic, while the left sidewall is heated, and the right sidewall kept cooled. Numerically, COMSOL code based on the Galerkin finite element method used for solved the dimensionless governing equations. The non-dimensional parameters that used in this study are: Rayleigh number (Ra) ranged from 103 up to 106, Darcy number (Da) equal to 10−3, the angular rotational velocity (Ω) ranged (0 and 6000), the solid volume fraction (ɸ=0.06), and the inner circular cylinder radius as (R = 0.2). The results showed that when Rayleigh numbers increase, a noticeable increase in the flow intensity and the steep temperature gradient, while the values increase when the cylinder rotates. The value of the local Nusselt number was high in the upper half of the cavity. The effect of the cylinder rotates is greater on the value of the local Nusselt number when using the low Rayleigh Numbers.
The present study, experimentally investigated the mixed convection in a square enclosure partitioned in two layers. The experiments were performed with Al2O3–water nanofluid (upper layer) and superposed porous medium (lower layer) with an adiabatic rotating cylinder at the center of the cavity. The boundary conditions of the experimental study were; the upper and lower walls were assumed adiabatic, the right wall was heated, and the left wall was cooled. Experimentally, 15 K-type thermocouples and thermal imaging camera were employed to measure the temperatures distribution inside the cavity when the concentration of nanoparticles (ɸ = 0.06), the temperature difference (∆T) between the cold and hot walls was (6, 8, and 10) °C, and angular rotational velocity (-50, -25, 0, 25, and 50) rpm. The results of experimental data showed that in general, the distribution of temperatures was very well along the upper half of the enclosure, while in the lower half the temperature distribution was confined near the hot wall region. When the circular cylinder rotates in counter-clockwise, it noted that the effect of speed is evident in the downside of the cylinder, while the temperature distribution in the left upper part of the enclosure decreasing. When the circular cylinder rotates in the clockwise direction, the results showed that the effect of cylinder rotation was around cylinder only. Moreover, the results demonstrated that the increasing temperature difference leads to a noticeable increment in the intensity of the flow.
Due to its engineering uses in recent years, natural convection within cavities has been studied to enhance heat transfer in various package shapes by infusing the base fluid with nanoparticles. In this paper, we examined natural convection in a square cavity with an inclined roof of Ag-water nanofluid and internal bodies (circular and elliptical cylinders) at the enclosure's center. The (top, bottom, and circular cylinder) walls are assumed to be adiabatic, whereas the (ellipse cylinders and left sidewall) are warmed and the right sidewall is maintained cool. The COMSOL program is based on the "Galerkin finite element approach" in terms of numerical computations. The "Rayleigh number" (Ra) (10 3 -10 6 ) is utilized, as is the solid volume fraction (0.05), the angle of inclination (-45°, -30°, 0°, 30°, 45°), "the inner circular cylinder radius considered as (R=0.15)" and "the radius of the inner ellipse cylinder as (Rx=0.2 & Ry=0.15). At a high "Rayleigh number", the stream function has the lowest value when the caustic angle is tilted to (-30°). While it comes in second place, the angle of inclination (0°) gets the highest value. While at a low "Rayleigh number", there is no effect of the angle of the stream function. There was also a convergence in Nusselt numbers at any angle at the hot left wall, at 30° and 45°, and in the hot ellipse, at 60° and 90°, so we looked at them all.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.