Al-Qadisiyah Journal for Engineering Sciences <p>Al-Qadisiyah Journal for&nbsp;Engineering Sciences&nbsp;(QJES) is a scientific Open Access peer-reviewed journal. It publishes research papers describing different disciplines &nbsp;of engineering sciences online and hard copy every three months since 2007.</p> <p>&nbsp;</p> University of Al-Qadisiyah / Iraq en-US Al-Qadisiyah Journal for Engineering Sciences 1998-4456 Numerical Investigation of the Effect of Baffle Inclination Angle on Nanofluid Natural Convection Heat Transfer in A Square Enclosure <p>The characteristics of the conjugate natural convection of (Al<sub>2</sub>O<sub>3</sub>-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)&nbsp; has been investigated. At low Rayleigh number (Ra=10<sup>3</sup> to 10<sup>4</sup>) 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=10<sup>6</sup>),&nbsp; 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 &gt; 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 &gt;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.</p> Barik AL-Muhjaa Khaled Al-Farhany ##submission.copyrightStatement## 2019-06-29 2019-06-29 12 2 61 71 10.30772/qjes.v12i2.589 Numerical Simulation for the Effect of Biodiesel Addition on the Combustion, Performance and Emissions Parameters of Single Cylinder Diesel Engine <p>This work examines the characteristics of combustion, performance and emissions of single cylinder diesel engine powered by diesel fuel and a different volume percentages of the caster methyl ester (CME). The selected biodiesel is studied numerically using the simulation program diesel-rk. The results reported that peak pressure is closer to the top dead center (TDC), as the percentage of CME. The brake specific fuel consumption (BSFC) is increased slightly as the blending of biodiesel is increased. All the selected biodiesel ratios are found to release higher NOx emission compared to diesel. Dramatic reduction in smoke levels 15.25 %, 35.3 %, 40.7 %, 45.71 %, 49.43 %, and 52.73 % with B10% CME, B20% CME, B30% CME, B50% CME, B70% CME and B100% CME respectively. B20% CME biodiesel was the best remarked ratio which gives slight variations in performance with a good reduction in the carbon emissions compared to diesel fuel. The results are compared with other researchers work and nice convergence is observed</p> Mohammed Salman Edam Mohamed Al - Dawody ##submission.copyrightStatement## 2019-07-02 2019-07-02 12 2 72 78 10.30772/qjes.v12i2.587 Effect of Leachate Recirculation on Biological Stability of Municipal Solid Waste Under Simi-Arid Conditions <p>The present study was conducted to monitor the quality of leachate generated&nbsp; from solid waste landfills operated under different mode over a period of 335 days using a bench scale lysimeters. Sixty six kg waste sample reflecting the typical municipal solid waste (MSW) streams generated in Al-Diwaniyah city open dump was used to fill both sanitary and bioreactor lysimeters&nbsp; to study the influence of leachate recirculation on quality of leachate&nbsp; in landfills located in semi-arid areas. Leachate quality is frequently monitored in terms of pH, electrical conductivity (EC), chemical oxygen demand (COD), chloride, and total Kjeldahl nitrogen (TKN). The results show that pH and electrical conductivity&nbsp; values were clearly fluctuated in the rainy season, while in the dry season the values tend to decrease steadily with a close correlation between the chloride and electrical conductivity parameters. The study reveals that bioreactor landfill with leachate recirculation appears to be the most effective option in the removal of organic matter by 98% removal efficiency compared with 58% removal efficiency in a sanitary landfill. The main difference between recirculation and non-recirculation options is determined through leachate quality.</p> Entessar Hussain Jathwa Al-Ameen ##submission.copyrightStatement## 2019-07-02 2019-07-02 12 2 79–83 79–83 10.30772/qjes.v12i2.596