Journal of Engineering

In this paper, the thermal performance of a zig-zag solar air heater (ZZSAH) with and without using steel wire mesh on the absorber plate of the collector is experimentally investigated. The experimental work includes four inclination angles of the collector (20°, 30°, 45°, and 60°) and four air mass flow rates (0.03, 0.04, 0.06, and 0.08 kg/s) under various operating conditions in Baghdad. New correlation equations of the Nusselt number are obtained from experimental results for both types of collectors, considering the effect of varying the inclination angle of the collector. The correlations show good agreement with the present experimental data. Additionally, the effects of mass flow rate and temperature rise on the efficiency of the collector air heater are investigated. The results reveal that the efficiency of the ZZSAH at a 45° inclination angle reaches the highest values among other inclination angles for both types of collectors under study. The results also show that the addition of wire mesh magnifies the effect of the inclination angle.

In this study, the investigation of local natural Iraqi rocks kaolin with the addition of different proportions of bauxite and its effect on the physical and mechanical properties of the produced refractories was conducted. Kaolin/bauxite mixture was milled and classified into various size fractions, the kaolin (less than 105 μm) and the bauxite (less than 70μm). The specimens were mixed from kaolin and bauxite in ranges B1 (95+5)%, B2 (90+10)%, B3 (85+15)%, and B4 (80+20)% respectively. The green specimens were shaped by the semi-dry method using a hydraulic press and a molding pressure of 7 MPa with the addition of (9-12) %wt. of PVA ratio. After molding and drying, the specimens were fired at (1100, 1200 and 1300) °C. Physical properties (density, porosity, water absorption) and mechanical properties (indirect tensile strength and hardness) were measured for all the prepared samples. The results showed that the porosity was increased and the density was decreased, such increase and decrease affected the mechanical properties for refractory. The highest values of indirect tensile strength and hardness were obtained at 20% Bauxite at 1300 °C (0.85386 MPa, 1411Kg / mm²) respectively.

The weather of Iraq has a longer summer season compared with other countries. The ambient temperature during this season reaches over 50°C, making the evaporative cooling system suitable for this climate. In the present work, the two-stage evaporative cooling system is studied. The first stage is indirect evaporative cooling (IEC) represented by two heat exchangers with a groundwater flow rate of 5 L/min. The second stage is direct evaporative cooling (DEC) which represents three pads with groundwater flow rates of 4.5 L/min. The experimental work was conducted in July, August, September, and October in Baghdad. Results showed that the overall evaporative efficiency of the system (two coils with three pads each pad of 3cm) reached 167% with a temperature difference between ambient and supply of 26.2°C. It reached 122.7% (one coil with three pads) with a temperature difference between ambient and supply of 16°C and reduced to 84.88% and 84.36% for IEC and DEC respectively.

Recently, the use of nanofluids represents very important materials. They are used in different branches like medicine, engineering, power, heat transfer, etc. The stability of nanofluids is an important factor to improve the performance of nanofluids with good results. In this research, two types of nanoparticles, TiO₂ (titanium oxide) and γ-Al₂O₃ (gamma aluminum oxide), were used with base fluid water. A two-step method was used to prepare the nanofluids. One concentration of 0.003 vol. % of the nanoparticles was examined. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray diffraction (XRD) were used to accomplish these tests. The stability of the two types of nanofluids is measured by zeta potential and UV-vis spectrophotometer. The results showed that γ-Al₂O₃/water is more stable than TiO₂/water for the same period of time.

A comparative study was done on the adsorption of methyl orange dye (MO) using non-activated and activated corn leaves with hydrochloric acid as an adsorbent material. Scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR) were utilized to specify the properties of adsorbent material. The effect of several variables (pH, initial dye concentration, temperature, amount of adsorbent and contact time) on the removal efficiency was studied and the results indicated that the adsorption efficiency increases with the increase in the concentration of dye, adsorbent dosage and contact time, while inversely proportional to the increase in pH and temperature for both the treated and untreated corn leaves. The equilibrium data is best fitted to Freundlich isotherm for untreated adsorbent, while Langmuir isotherm show best agreement with the data when the treated adsorbent is used. The rate of adsorption was found to follow the pseudo first order kinetic model (PFO) when non-activated adsorbent is used, while the pseudo second order model (PSO) is fitted to the adsorption data using activated adsorbent.

This paper proposes improving the structure of the neural controller based on the identification model for nonlinear systems. The goal of this work is to employ the structure of the Modified Elman Neural Network (MENN) model into the NARMA-L2 structure instead of Multi-Layer Perceptron (MLP) model in order to construct a new hybrid neural structure that can be used as an identifier model and a nonlinear controller for the SISO linear or nonlinear systems. Two learning algorithms are used to adjust the parameters weight of the hybrid neural structure with its serial-parallel configuration; the first one is supervised learning algorithm based Back Propagation Algorithm (BPA) and the second one is an intelligent algorithm namely Particle Swarm Optimization (PSO) algorithm. The numerical simulation results show that the hybrid NARMA-L2 controller with PSO algorithm is more accurate than BPA in terms of achieving fast learning and adjusting the parameters model with minimum number of iterations, minimum number of neurons in the hybrid network and the smooth output one step ahead prediction controller response for the nonlinear CSTR system without oscillation.

The concrete industry consumes millions of tons of aggregate comprising of natural sands and gravels, each year. In recent years there has been an increasing trend towards using recycled aggregate to save natural resources and to produce lightweight concrete. This study investigates the possibility of using waste plastic as one of the components of lead-acid batteries to replace the fine aggregate by 50 and 70% by volume of concrete masonry units. Compared to the reference concrete mix, results demonstrated that a reduction of approximately 32.5% to 39.6% in the density for replacement of 50% to 70% respectively. At 28 days curing age, the compressive strength was decreased while the water absorption increased by increasing waste plastic percentage. The leaching test revealed that lead ion extracted from the WLABP-modified concrete was within the acceptable limits. The findings of this study indicated a sustainable alternative solution for reducing the effects on the environment posed by waste plastic from lead-acid batteries.

This investigation presents an experimental and analytical study on the behavior of reinforced concrete deep beams before and after repair. The original beams were first loaded under two points load up to failure, then, repaired by epoxy resin and tested again. Three of the test beams contain shear reinforcement and the other two beams have no shear reinforcement. The main variable in these beams was the percentage of longitudinal steel reinforcement (0, 0.707, 1.061, and 1.414%). The main objective of this research is to investigate the possibility of restoring the full load-carrying capacity of the reinforced concrete deep beam with and without shear reinforcement by using epoxy resin as the material of repair. All beams were tested with a shear span-depth ratio of 2.2. An analytical study was made to show the behavior of a sample of test beams at higher stages of loadings before and after repair. The test results showed that the epoxy resin used for repairing was very efficient in restoring the full capacity of failed beams. Moreover, epoxy resin increased the strength capacity of the original beams by about 14% to 40%. On the other hand, the increase in the longitudinal reinforcement increased significantly the ultimate capacity of deep beams before and after repair.

This study discusses the benefit of adding waste paper as a new cellulose material in mortar mixes. A partial addition of waste paper by cement weight was achieved to produce cement composite mortar. Pulp and paper is the third major industrial dumper of air, soil, and water. In recent years, paper and paperboard constitute a greater portion of many countries’ urban solid discarded generation. Besides, it increases characteristic strength due to the existence of hydrogen links in the microstructure of paper. Furthermore, it consumes better thermal protection. The addition percentages of waste paper used in this work were 5%, 10%, 15%, and 20% by mass of cement to measure and evaluate some properties of the mortar produced (compressive, direct tensile, and flexural strength, thermal properties such as thermal conductivity, and microstructure investigation like scanning electron microscope (SEM)). The results indicated that the fresh mortar properties were affected expressively with higher waste paper percent. The mechanical properties (compression, direct tensile, and flexural strength) were reduced by increasing the content of waste paper, reducing to 74%, 50%, and 86% respectively, with 20% addition of waste paper compared to the reference mix. Moreover, using waste paper with different percentages led to a noticeable decrease in thermal conductivity, especially with increasing addition percentages.

An experimental study is conducted to investigate the effect of heat flux distribution on the boiling safety factor of its cooling channel. The water is allowed to flow in a horizontal circular pipe whose outlet surface is subjected to different heat flux profiles. Four types of heat flux distribution profiles are used during experiments: constant distribution profile, triangle distribution profile with its maximum in channel center, triangle distribution profile with its maximum in the channel

This study offers the elastic response of the variable thickness functionally graded (FG) by single-walled carbon nanotubes reinforced composite (CNTRC) moderately thick cylindrical panels under rotating and transverse mechanical loadings. It’s considered that three kinds of distributions of carbon nanotubes are uniaxial aligned in the longitudinal direction and two functionally graded in the transverse direction of the cylindrical panels. Depending on first-order shear deformation theory (FSDT), the governing equations can be derived. The partial differential equations are solved by utilizing the technique of the finite element method (FEM) with a program built using FORTRAN 95. The results are calculated to investigate the influence of the variable thickness, geometric parameters, rotating velocity, carbon nanotubes (CNTs) volume fraction for different boundary conditions on the non-dimensional deflection of the cylindrical panels. A comparison study has been carried out between the results of the present study and those available in the open literature and found very good correspondence between the two results.