International Journal of Engineering Research in Africa Vol. 52

Abstract: In this article, the 75Fe₃C-20W-5Co alloy is developed by the powder metallurgy technique in order to study the microstructure and the mechanical properties obtained after solid phase sintering. The mechanical grinding of the mixture of these Fe3C-W-Co powders lasted 6 hours.The powders were compressed by cold isostatic pressing (CIP) at different compaction pressures (5MPa, 10MPa, 15MPa and 18MPa). The green compacts obtained were sintered at a temperature equal to 1350 °C, followed by a heat treatment at different temperatures (850 °C, 950 °C and 1100 °C). The samples were then cooled in different baths (oil and water). The characterization of this sintered steel alloy was carried out by X-ray diffraction (XRD) and with an optical microscope. The results reveal that the structure of these sintered alloys consisted of the Fe matrix phase and the W-Co solid solution phase. The compaction pressure influences the number and size of the pores. Hardness and wear resistance increase with increasing compaction pressure.

Abstract: The intermittent nature of photovoltaic (PV) generation causes the voltage to fluctuate and may lead to instability, especially, in case of high penetration. In this paper, a methodology is proposed to control the reactive power generation of PV-inverters. The objective is to mitigate the voltage fluctuations at the point of common coupling (PCC) resulted from increasing or decreasing the active power output of PV plants which is dependent on solar radiation level. The generic PV-inverter models developed and recommended by the Renewable Energy Modeling Task Force (REMTF) of the Western Electricity Coordinating Council (WECC) is used to analyze the effect of high PV penetration on the dynamic voltage stability of distribution networks. Then, the tested distribution network with the embedded PV plants is modeled and simulated using PSS/E software. Levels of control that are built-in PV-inverters are tested in the case of normal operation and during disturbances. Comparison results show that the most suitable control methodology in case of disturbances and after fault clearance is the local voltage control. While the plant voltage control with coordinated V/Q control is the most preferable control methodology during normal operation.

Abstract: Pleurotus as a fluid loss control additive in synthetic based mud for oil and gas operations was conducted in the laboratory in accordance with API standards using high temperature-high pressure filter press. The effectiveness and compatibility of Pleurotus to synthetic based mud was also evaluated. Its rheological properties were also carried out. Sodium Asphalt Sulfonate was used as a control sample. Synthetic base mud was formulated and the concentrations of 2ppb, 4ppb, 6ppb and 8ppb of Pleurotus were used in four mud formulations with the same materials and in equal concentrations. 4.6ml, 4.0ml, 3.5ml and 3.1ml of fluid loss volumes were obtained respectively. 1mm thick filter cake, with increase in electrical stability was observed. From the laboratory measurement, the optimum effective concentration of Pleurotus to be applied as a fluid loss control agent for fresh non-aqueous mud for field operation is 2ppb which gave the fluid loss volume less than 5ml. The result was compared with the field standard of less than or equal to 5ml fluid loss volume. These results were comparable with control sample and field standard. Also, the thin impermeable filter cake obtained reflects one of the qualities of a good fluid loss control agent. It also showed that Pleurotus contribute very minimal effect on the rheological properties of the synthetic base mud. Improved electrical stability which is the function of emulsion stability confirmed the compatibility property of Pleurotus as fluid loss control additive in the synthetic based mud. The volume of the filtrate improved in geometric progression with the concentrations of the additive applied which summarizes the characteristics of a good fluid loss control agent.

Abstract: Construction waste is a serious challenge that requires particular attention from construction managers to improve the performance of their projects and survive in a highly competitive market. Simulation modeling provides decision-makers with a controllable operating system and a more cost-effective environment which allows a better understanding of construction processes deficiencies. The current paper aims to assess waste in a bricklaying process using ARENA. Data used for simulation modelling were collected through field observations and video recording techniques. Using EasyFit, goodness-of-fit tests were performed to identify the best probabilistic density functions for each construction operation in the studied process. Simulation outputs show that non-value-added (NVA) activities dominate the bricklaying process with 85.2 % of the total cycle time. These results indicate a strong potential for optimizing the process under study by reducing these sources of waste especially regarding waiting time that holds the highest share of waste with 72.5 %.

Abstract: This paper focuses on the fault blocking analysis and operational issues associated with MTDC systems incorporated in an AC network. The dynamic modelling of a line-commutated converter based bipolar multi-terminal direct current (LCC MTDC) system are shown, and the dynamic response of the converter during a DC converter fault is discussed. The converter controller design for both rectifiers and the inverters system was modelled for a realistic active power and extinction angle (γ) control with consideration to the VI characteristics of all the converter stations. An overall power controller was modelled for both converter pole. Two operational scenarios of converter fault were simulated using PSCAD EMTDC. The converter firing angle and extinction angle, as well as the voltage-dependent current order limiter, was monitored and plotted on a graph. Results show that the MTDC link became unstable during the full deblocking stage with a continuous occurrence of commutation failure. Furthermore, the results presented in this paper show that during partial converter de-blocking showed a favourable performance, as the power system remains stable and commutation failure of the MTDC system is prevented.

Abstract: Multi-sensor remote sensing data can significantly improve the interpretation and usage of large volume data sources. A combination of satellite Synthetic Aperture Radar (SAR) data and optical sensors enables the use of complementary features of the same image. In this paper, SAR data is injected into optical image using a combining fusion method based on the integration of wavelet Transform and IHS (Intensity, Hue, and Saturation) transform. Not only to preserve the spectral information of the original (MS) image, but also to maintain the spatial content of the high-resolution SAR image. Two data sets are used to evaluate the proposed fusion algorithm: one of them is Pleiades, Turkey and the other one is Boulder, Colorado, USA. The different fused outputs are compared using different image quality indices. Visual and statistical assessment of the fused outputs displays that the proposed approach has an effective translation from SAR to the optical image. Hence, enhances the SAR image interpretability.

Abstract: A steady two-dimensional nonlinear convective flow of a viscous, incompressible, electrically conducting, and non-Newtonian Jeffrey fluid over an inclined stretching sheet with convective boundary conditions and entropy generation is studied under the influence of transverse magnetic field, electrical conductivity and thermal conductivity. The thermal conductivity and electrical conductivity are temperature dependent functions. The governing continuity, momentum and energy equations are transformed to ordinary differential equations (ODEs) using appropriate similarity variables. The resulting coupled ODEs and the corresponding boundary conditions, are solved numerically using Runge-Kutta fourth order method and shooting technique. The velocity, entropy generation rate, temperature and Bejan distributions are presented graphically and discussed. The numerical values of the skin-friction and Nusselt number are obtained and also discussed for various thermophysical parameters through a Table. Furthermore, a comparison with earlier work done with limiting case was carried out and found to be in excellent agreement.

Abstract: Swarm Intelligence algorithms like PSO (Particle Swarm Optimization), ACO (Ant Colony Optimization), ABC (Artificial Bee Colony), Glow-worm swarm Optimization, etc. have been utilized by researchers for solving optimization problems. This work presents the application of a novel modified EHO (Elephant Herding Optimization) for cost optimization of shell and tube heat exchanger. A comparison of the results obtained by EHO in two benchmark problems shows that it is superior to those obtained with genetic algorithm and particle swarm optimization. The overall cost reduction is 13.3 % and 9.68% for both the benchmark problem compared to PSO. Results indicate that EHO can be effectively utilized for solving real-life optimization problems.

Abstract: The rise in the cost of production of beer due to increasing demand for freshwater and high cost of treating wastewater, motivate research interests in resource management in beer production. This study determines and reduces the concentration of the contaminants in the wastewater samples collected from a brewery in Nigeria, to reduce freshwater demand and to save the cost of operation through wastewater reuse using pinch technology. The wastewater samples were analysed for the concentration of Chemical Oxygen Demand using standard procedures. The Total Dissolved Solids were measured using pH-EC-TDS metre. Water Cascade Analysis was used to evaluate the minimum freshwater demand and wastewater generated to design the maximum wastewater recovery network for minimum freshwater demand in the process. The results showed that for 41.54 t/hr of both the freshwater and wastewater used in the brewery operations, the Chemical Oxygen Demand concentration ranged between 0 – 74,775 ppm and the Total Dissolved Solids concentration ranged from 0 – 2,008 ppm. However, with the application of Water Cascade Analysis, the freshwater and wastewater flow rates reduced to 19.88 t/hr based on Chemical Oxygen Demand concentration and 21.54 t/hr based on Total Dissolved Solids concentration. The freshwater saving per annum based on the concentrations of Chemical Oxygen Demand and Total Dissolved Solids were ₦346,560,000:00 ($962,666.67) and ₦319,840,000:00 ($888,444.44), respectively. The study concluded that the application of Pinch Technology to brewery operation is viable because of its capacity to reduce freshwater demand and wastewater generation.

Abstract: Surface cooling water harvesting from air represents an alternative way to provide new potable water sources. In this study, an Extracting Water Machine (EWM) is fabricated, which is a device that can convert water vapor directly into usable and even drinkable water. This study was conducted to evaluate the quantity, chemical quality, and power consumption of condensed water, particularly in areas where the relative humidity is less than 30 %, with an abundance of non-fresh water (i.e., wells, marshes, and others). Three operating strategies were proposed during February, March, April, and May; the experiments were conducted every hour on a particular day of each month for each test using actual climate data of Nasiriya, Iraq in 2020. In the first test, the device operated in dehumidification mode and the ambient air passed directly to the surface of the cooling coil; it has found that the daily condensed water and energy consumption for the four consecutive months under consideration were (16.82, 4.58, 3.93, 4.23) L/day and (0.525, 1.86, 2.175, 2.13) kWh/L, respectively. In the second test, the device also operated on the dry mode, and the air passed through the evaporative cooler and then to the evaporator coil. The results were (36.418, 26.01, 20.895, 19.2) L/day and (0.530, 0.443, 0.550, 0.555) kWh/L respectively. In the last one, the device was run on the cooling mode using an evaporative cooler. The obtained water amounts were (31.93, 38.53, 31.03, 32.29) L/day with (0.530, 0.443, 0.550, 0.555) kWh/L energy consumption for February, March, April, and May. The results indicate the second and third tests are useful under the prevailing climatic conditions. Analysis carried out on the obtained water revealed that some parameters including total dissolved solids and electrical conductivity were within the World Health Organization standard for drinking water.