Al-Qadisiyah Journal for Engineering Sciences

Abstract The stability analysis of Marangoni magneto-convection (MMC) is investigated in a two-layer system consisting of an electrically conductive fluid-saturated porous layer overlain by an identical fluid layer, incorporating variable heat sources and a uniform magnetic field. The upper fluid surface is free, allowing surface-tension-driven convection, while the lower porous boundary is rigid. Two thermal boundary conditions are examined: (i) adiabatic–adiabatic (A–A) and (ii) adiabatic–isothermal (A–I). The governing equations are solved analytically using an exact method to obtain the thermal Marangoni number, an eigenvalue, as a function of depth ratio, Darcy number, Chandrasekhar number, internal Rayleigh numbers, wave number, and thermal diffusivity ratio. Graphical results show that the onset of MMC can be either advanced or delayed by appropriate choices of depth ratio and thermal boundary conditions. The novelty of the present work lies in deriving closed-form expressions for a composite fluid–porous system with simultaneous consideration of variable internal heat sources and magnetic effects under dual thermal boundary conditions, and demonstrating how depth ratio and thermal boundary conditions can be strategically tuned to either advance or delay the onset of instability.

Abstract The work aims to investigate the MHD Casson fluid flow over an exponentially long sheet via a thermally stratified permeable medium. All facets of chemical processes, Joule heating, and exponential heat sources are covered in this subject. By using the appropriate similarity conversions, the leading partial differential equations (PDEs) of the model are transformed into a set of nonlinear ordinary differential equations (ODEs). The description of the previous technique was made simpler by applying the Keller Box methodology. The results reveal that when the viscosity factor is increased, the velocity profile improves, but when the thermal profile improves, the opposite trending impact is evident. The temperature profile exhibits the opposite tendency, despite a decline in the number of observations of the Casson fluid constraint. Joule heating parameters allow for more precise measurements of the heat source's properties by raising the temperature. The concentration graph shows a reduction as the number of observations for the chemical reaction parameter increases. The validity of the problem is investigated by computing the Nusselt number for cumulative Prandtl number observations and comparing the results with the literature.

Abstract This study describes a computational model that simulates the behaviour of a solar-powered desalination system. The model incorporates photovoltaic/thermal (PVT) collectors and direct contact membrane distillation (DCMD). A novel DCMD unit model was established and verified using existing data from the literature and the model was incorporated into the TRNSYS library. The effect of feed water mass flow rate and temperature on production was investigated through a parametric analysis. The PVT-DCMD system was modeled, analyzed, and dynamically simulated for the month of June in Algeria using TRNSYS software. Results show that the PVT collector's outlet solar fluid temperature ranges from 20 °C to 85 °C, providing 5000 kJ/hr of useful energy for seawater desalination through a heat exchanger. Meanwhile, the auxiliary heater utilizes around 10,000 kJ/hr of solar energy. The simulation demonstrates the feasibility and effectiveness of using PVT collectors with a DCMD system for seawater desalination, achieving a distillate production rate of approximately 12 L/hr.m2 of membrane.

Abstract Al-Qadisiyah Journal for Engineering Sciences (QJES), E-ISSN: (2411-7773), P-ISSN: (1998-4456), was established in 2008. The Journal, in its current form, is intended to contribute to the state of the art in all engineering research fields. The Journal is a peer-reviewed journal published by The University of Al-Qadisiyah, the College of Engineering. The journal is published quarterly (March, June, September, and December). The QJES has been indexed by Scopus recently, starting in December 2023.

Abstract Numerical investigation of mixed convective in a vented square cavity with fin. The horizontal walls are adiabatic, while the left and right walls are at hot and cold temperatures, respectively. The fluid inlet to the cavity from the lower left open area, and exit from the upper right open area. In this study, a finite element scheme is employed. The analysis is done for specific Prandtl number, Reynolds number, fin length, Richardson number, and the location of the fin. The finding indicates that the increases when high the location of the fin is, the increase at the maximum height of this fin location is estimated to be 17% due to an increase in the area of fluid flow on the hot wall caused by rising convective. The highest heat transfer occurs when the fin length is equal to 0.6 at the location.

Abstract Al-Qadisiyah Journal for Engineering Sciences (QJES) is a scientific Open Access peer-reviewed journal. It publishes papers online and hard copy in all areas of the engineering field, including experimental, theoretical, and computational analysis. The first edition of the QJES was published in 2008. Currently, it is published four times per year at the end of March, June, September, and December at the College of Engineering, the University of Al-Qadisiyah under the Iraqi Ministry of Higher Education and Scientific Research sponsorship.
Based on the evaluation of the editorial and advisory members, the QJES provides essential reference materials and critical feedback into basic and practical contributions in different fields of engineering sciences. All submissions to the journal will be subject to peer review from leading experts in the field from inside and outside Iraq. Their impressions and comments will determine the final decision of the paper, whether accepted or rejected.

Abstract An empirical evaluation of free convective heat transmission was conducted in a rectangular enclosure containing a hybrid nanofluid of (50% CuO-50% Al₂O₃)/water linked to a PCM-containing wall. The enclosure's left and right surfaces were kept at constant warm and cold temperatures, whereas the remaining surfaces were assumed to be isolated. The left side was filled partially with PCM. Several variables were examined, such as the hot-side temperature differential (∆T =10, 15,20 ◦C) and the hybrid nanofluid concentration (Φ=0.03,0.05,0.07)%. The findings show that the rate of heat transmission through natural convection rises as the concentration of nanomaterials rises. Due to its great absorbability and heat storage capacity, PCM was also shown to have the potential to lower the hot side temperature by up to 15.5%. The Nusselt number rises over time as the left cavity is filled partially with PCM. When added hybrid nanofluid is, PCM’s heat-storage efficiency and, by extension, its ability to cool the hot side is greatly improved.

Abstract The gas turbine blade stator is subjected to a severe high temperature of hot incoming gases from the combustor. In order to avoid the melting of the stator, film and internal cooling techniques are applied by using a bypass stream of air from the compressor as a coolant fluid. These techniques have their own merits, but it is limited by some constraints like the value of specific heat of air. In this paper different gases with higher specific heat are used as a coolant in order to increase the thermal capacity of coolant fluid which in turn increases the amount of transferred heat. The selected gases are Helium, Steam, and Ammonia are applied in COMSOL Multiphysics® in order to simulate the cooling process and the temperature distribution. At first, the air is applied and the results show a good agreement with previous literature and then the other coolants to compare their results with the air. The results show that the Helium affects the cooling process strongly and it cools the blade to safer limits rather than air by about 50%, but it increases von Mises stress by about 71% in comparison with air. The two other coolants also have a good and effective cooling performance, but they almost show an identical performance.

Abstract The natural convection heat transfer has many applications in engineering like solar collectors, cooling of electronic equipment and geothermal engineering. The present work demonstrates the recent publications in the last ten years in this specific subject for a body located in complex shapes like rhombic, wavy, trapezoidal, elliptical and Parallelogrammic enclosure. Many parameters like Ra, Nu, number of undulations, the position of the inner body had been addressed and discuss to draw the main conclusions and recommendations.  It is worthy to mention that wavy enclosure had been investigated less than the other simple enclosure shapes due to its complexity. Beside that entropy generation should be included in the future studies in complex shapes of enclosure as this will helps the researchers to extended their studies. The inner bodies inside trapezoidal, parallelogrammic enclosure are very limited and more investigation should be done.

Abstract 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.

Abstract Numerical investigate of double-diffusive natural convection in an inclined porous square. Two opposing walls of the square cavity are adiabatic; while the other walls are, kept at constant concentrations and temperatures. The Darcy–Forchheimer–Brinkman model is used to solve the governing equations with the Boussinesq approximation. A code written in FORTRAN language developed to solve the governing equations in dimensionless forms using a finite volume approach with a SIMPLER algorithm. The results presented in U-velocity and V-velocity, isotherms, iso-concentration, streamline, the average Nusselt number, and the average Sherwood number for different values of the dimensionless parameters. A wide range of these parameters have been used including; Darcy Number, modified Rayleigh number, Lewis number, buoyancy ratio, and inclination angle.  The results show that for opposite buoyancy ratio (N≤-1), the Nu decreases when the Le increases and the Sh increase when the Le increases. For an (N>0), the Nu increases when the Le increases until Le is equal to 1 and then it decreases, also Sh increases when the Le increases

Abstract The characteristics of the conjugate natural convection of (Al₂O₃-water) nanofluid inside differentially heated enclosure is numerically analyzed using COMSOL Multiphysics (5.3a). The enclosure consists of two vertical walls, the left wall has a thickness and maintain at a uniform hot temperature, while the opposite wall at cold temperature and the horizontal walls are isolated. A high thermal conductivity thin baffle has been added on the insulated bottom wall at a different inclination angles. The effect of the volume fractions of nanoparticles (f), Rayleigh number (Ra), solid wall thermal conductivity ratio (Kr), baffle incline angles (Ø) and the thickness of solid wall (D) on the isothermal lines, fluid flow patterns and the average Nusselt number (Nu)  has been investigated. At low Rayleigh number (Ra=10³ to 10⁴) the Isothermal lines are parallel with the vertical wall which is characteristic of conduction heat transfer. on the other hand, when Rayleigh number increase to (Ra=10⁶),  the isotherms lines distribution in the inner fluid become parallel curves with the adiabatic horizontal walls of the enclosure and smooth in this case convection heat transfer becomes dominant. As the Rayleigh number further increases, the average Nusselt number enhance because of buoyancy force become stronger. In addition, the fluid flow within the space is affected by the presence of a fin attached to the lower wall that causes blockage and obstruction of flow near the hot wall, hence the recirculation cores become weak and effect on the buoyant force. The maximum value of the stream function can be noticed in case of nanofluid at (Ø=60), whereas they decrease when (Ø > 60), where the baffle obstruction causing decreases in flow movement. So that the left region temperature increases which cause reduction of the convective heat transfer by the inner fluid temperatures. This is an indication of enhancing of insulation. When the inclination angle increases (Ø >90), the baffle obstruction on flow and fluid resistance becomes smaller and the buoyancy strength increase, as a result, the heat transfer is increasing in this case. As a result of increasing the thermal conductivity from 1 to 10, an increase in the amount of heat transferred through the solid wall to the internal fluid have been noticed. This change can be seen in the isothermal lines, also, there was growth and an increase in the temperature gradient. The increasing of wall thickness from (D=0.1 to 0.4) leads to reduce the intensive heating through the solid wall as well as small heat transferred to the inner fluid. Therefore, it can be noticed that when the wall thickness increases the stream function decrease.