بحوث سكوبس — أوس اكرم محمود العكام

This study numerically investigates mixed convection heat transfer in a ventilated square cavity filled with an MWCNT–Fe3O4/water hybrid nanofluid and partitioned by dual porous layers with distinct properties. Unlike previous works that considered uniform porous media or single-phase nanofluids, the present study focuses on the combined influence of hybrid nanoparticles and multi-layered porous structures under varying Reynolds (50–1000) and Grashof numbers (103–106). Parametric analyses were performed for Darcy number (0.01–100), porosity (0.5–1.8), thermal conductivity ratio (0.2–5.0), and porous thickness (0.1–0.5). The results show that increasing Reynolds number strengthens vortices and enhances thermal dispersion, while higher Grashof numbers shift the system to buoyancy-dominated convection with significantly improved heat transfer. Porous layer thickness has little effect at low Gr but suppresses convection when enlarged (a = 0.5), reducing the average Nusselt number due to flow resistance. This suppression is alleviated by higher Darcy numbers or thermal conductivity ratios, which improve permeability and heat diffusion. At high Gr, increasing the conductivity ratio leads to conduction-dominated transfer. The hybrid nanofluid consistently augments thermal performance across regimes. Overall, the study highlights the synergistic role of hybrid nanofluids and dual porous layers in enhancing mixed convection. The findings provide practical guidance for optimizing porous media and nanofluid design in advanced thermal management applications. © Akadémiai Kiadó Zrt 2025.

This study investigates the airflow behaviour around vortex generators (VG) utilized in air-cooling technologies, considering the impact of rotation. The analysis encompasses a numerical approach to study the flow around vortex generators (conventional and curved delta winglet type) installed inside a duct with a heated wall. The vortex generators' set number effect on the heat transfer behaviour was investigated. Three sets of vortex generators were examined, two-VG set, four-VG set and six-VG set, equally aligned along the duct. The range of Reynolds numbers (Re) from 4000 to 12000, with the rotation number (Ro) fixed at 0.20 is covered. In this study, the thermal behaviour (measured by Nusselt Number (Nu)) and the flow behaviour (represented by) the friction factor (f)) were presented. Validation for the employed numerical model was performed based on the available experimental outcomes. The impact of using the vortex generator was evaluated and compared with the clean duct, the duct with conventional delta winglet and the curved one. The results revealed that installing the vortex generator increases the Nu (by 1.34 times at Re 4000 for four-VG and two-VG sets) and reduces the friction factor. Additionally, using the newly designed curved VG increased Nu by about 1.35. However, as the number of employed VGs enlarged, the rate of increase declined to about 0.9 of the Nusselt number value associated with the conventional VG. Furthermore, f (friction factor) reduces with the number of VG and increases with Re. In all cases, the rotation increases the Nu and f factor and using the curved VG showed a higher rate of increase. The newly designed VGs showed improved heat transfer behaviour, performing best with a four-VG set installed and worst with a six-VG set. © 2025, Semarak Ilmu Publishing. All rights reserved.

Integrating innovative materials and technologies has become imperative in the quest to design energy-efficient and sustainable buildings. Among these, one of the promising solutions to improve indoor spaces' comfort conditions and energy efficiency is the Phase Change Materials (PCMs). The methodology experimentally explores the impact of combining plywood and paraffin wax as a PCM to improve indoor environments' thermal dynamics under Iraqi conditions. Two wooden boxes are used, with one having its wall stuffed with a PCM. A temperature analysis was made for the internal temperature of each box, walls' surfaces, and PCM temperature for seven days. The impact of the box arrangement on the temperature distribution was also considered. The result showed the temperature inside the modified box is lower than the conventional one by about 3.0 during the peak time from 08:00 hr. to 16:00 hr. The night cooling is slower for the box with the PCM than the conventional one. Having the modified and the non-modified box in arrangement improves the insulation of both of them. Moreover, the findings showed that there is no need for all the rooms to be modified for a building with many rooms. The correct position of the room based on the location of the building in the study area will be enough. © 2024 The authors.

This paper presents a method for the assessment of the geometrical properties of the turbine blade after a long running time. This method uses a medical imaging device (CT-Scan) to provide segmentation images of the turbine blade. Image processing technique was employed to produce the cross-sectional properties such as area, centroid, minimum moment of inertia, maximum moment of inertia, and the angle of twist of the principal axes along the blade span. This geometrical information was produced using MATLAB code and validated against Image-J software data. This method can be used as a nondestructive method to evaluate the geometry of the turbine. © 2023 Slovak University of Technology in Bratislava. All rights reserved.

The demand for freshwater is in increasing with time because of global warming. The method of producing freshwater is vast. However, the use of the thermal energy of the sun is one of the promising techniques nowadays. This work proposes a new geometry of the solar still that is used to produce a distilled water out of saline water. The current paper consists of a design of the solar still in V-shape and measurement some of the main performance parameters such as the temperature of the glass cover and water, the subjected solar irradiance, and the water production under Iraqi environment conditions. The results reporting interesting points, such as a continuous rise in the temperature difference between the cover glass and the water (ΔT) with a little reduction from the peak time (14:00 hr) with ΔT =11 ºC and lowest time for solar irradiance at (18:00 hr.) with ΔT =9.0 ºC. moreover, the results showed that the actual solar irradiance that the system captures is much less than the actual amount the earth receives. The current data of this design suggests the need for a new method of efficiency calculation taking into consideration the thermal capacity of the system. © 2022 American Institute of Physics Inc.. All rights reserved.

The pore diameter, type (open or closed), physical properties of Porous alumina ceramic were controlled by varying concentration in the mixture of Polymethylmethacrylate (PMMA) with alumina powder and sintering temperature. The porous alumina ceramic was synthesis by a dry pressing method using a microspheres Polymethylmethacrylate (PMMA) as a pore-forming agent. The properties of the porous alumina were predicted using an experimental approach. Afterwards, the measured data were used to develop a Reduced-order model (Kriging) to enable a fast prediction of the properties for an extended range of parameters variation and further analysis. The experimental results showed that the High porous alumina ceramics is having an open porosity of 72.3%, and a bulk density 1.2 gm/cm3 and these could be fabricated using PMMA microspheres. Kriging model results showed an acceptable prediction of the experimental-derived data with a maximum discrepancy of 0.02% for the apparent porosity. © 2019 Elsevier Ltd. All rights reserved.