Nigerian Journal of Technological Development

Effects of Geometric Ratios on Heat Transfer in Heated Cylinders: Modelling and Simulation

Sat, 28 Jan 2023 00:00:00 +0000

The application of fluid and heat transfer in electronic and nuclear technology is gaining popularity, particularly in equipment's life span and risk management. However, further study is required for applications involving rectangular cylinders placed inside a square cavity. This study investigates the effects of height ratio (𝐻𝑅), and width ratio (𝑊𝑅) for Prandtl number 𝑃𝑟=0.71 on natural convective heat transfer and the flow field around the annulus of a square domain fitted internally with a heated rectangular cylinder. The square enclosure and the inner rectangular cylinder walls were respectively maintained at cold and hot isothermal conditions. COMSOL Multiphysics (Version 5.6) software was adopted to implement the governing equations and boundary conditions. The results are presented in the form of streamlines, isothermal contours, and Nusselt number (Nu). The study reveals that the combined average Nu of the rectangular cylinder walls improves with 𝐻𝑅, 𝑊𝑅, and Rayleigh number (Ra). The maximum Nu occurred at 𝐻𝑅=0.7, and 𝑊𝑅=0.7; however, height variation at peak average Nu was 37.7% greater than width variation at peak average Nu. This study finds applications in the cooling of electronic chips and aerospace engines.

Effects of Annular-finned Tube Deformation on Thermal Stresses in a Heat Exchanger

M. Kashani, A. Hatami, M. Hosseini — Sat, 28 Jan 2023 00:00:00 +0000

Nowadays, along with the developments in the industry, many machines and structures are exposed to very high-temperature environments, which has caused various types of thermal load in them. These conditions have led to focused studies on thermal stresses in structures. Heat exchangers are among the structures in which the temperature difference causes thermal stress. In this paper, “finite volume” and “finite element” methods are used to solve flow equations and thermal stress equations in solids, respectively. In addition, the effect of changes in the shape of the annular finned pipe on the thermal stresses in the heat exchanger is investigated. The study results on changing the pipe shape from circular to elliptical show that by changing the pipe shape, the thermal stress in the fin can be significantly reduced; for instance, in the cases reviewed in this paper, the thermal stress has decreased by 9%. Furthermore, the results of thermal stress show that the Maximum Effective Stress point, both before and after changing the shape, is still located at the fin’s base. So, according to the results of this study, examining the effect of pipe shape changing on thermal stress is an imperative measure when designing heat exchangers.

Comparison of Errors Caused by Flux Limiters on the Numerical Solution of Advection-Diffusion Problem

Adek Tasri — Sat, 28 Jan 2023 00:00:00 +0000

Flux limiters are widely used in numerical simulations to prevent spurious oscillation in the flow with strong property gradients. However, applying flux limiter on flow without strong property gradient such as advection-diffusion flow can cause errors. This article discusses the errors caused by several flux limiters in advection-diffusion flow solution. A method for applying one-dimensional limiters to two-dimensional unstructured mesh was also suggested. The error was measured by comparing the finite volume solution of a test case with a reference solution. The study shows that the calculation error of second-order finite volume with flux limiter was higher than that of second-order finite volume without limiter. However, the error of third-order finite volume with flux limiter is less than that of second-order without flux limiter. Among the flux limiters tested in this study, Venkatakrishnan’s flux limiter produces the highest error, followed by Van leer’s limiter, EULER and SMART limiter.

Optimization of Cutting Parameters using the RSMDesirability Approach in the MQL-Assisted Turning of AISI 4130

N. C. Ghuge, D. D. Palande, P. B. Belkhode — Sat, 28 Jan 2023 00:00:00 +0000

In this study, the main task is to identify the best cutting parameters to improve the machining performance during MQL-turning with various cutting fluids like coconut oil, ground nut oil, sunflower oil, soyabean oil, and blassocut oil. Cutting temperature and surface roughness were used as performance metrics, with the goal of minimizing these responses. To construct an experimental plan for turning AISI4130 with uncoated brazed carbide, full factorial design for three levels and three factors (33) design of experiments was used. The optimal
cutting parameter was identified using the response surface approach. Aiming to discover the optimum possible cutting settings, the desirability function method was utilized. It was discovered that the best cutting speed, depth of cut, and feed rate for minimizing the temperature and surface roughness are 72.38 m/min, 0.5 mm, and 0.35 mm/rev respectively. According to the ANOVA findings, the feed and depth of cut have a substantial impact on the tool temperature for MQL-soyabean oil.

Short-term Study of the Influence of Aggregate Size on the Fire Resistance of Concrete

F. O. Ayodele, O. R. Olulope, I. S. Ayeni — Sat, 28 Jan 2023 00:00:00 +0000

This study aims to investigate the effect of aggregate size on the fire resistance of concrete. The binder for this investigation was 42.5R CEM II/A-L Portland limestone cement, and the crushed granite sizes were 20mm, 12.5mm, and a blend (20 mm + 12.5 mm). The concrete was designed with a mix ratio of 1:2:4 (batching by weight) and 0.55w/c. The workability of the concrete was determined using the slump method. The concrete specimens were cured for 7, 14, and 28 days by immersion and later exposed to heat temperatures of 26.8 °C (Room temperature), 60 °C, 120 °C, 180 °C, and 240 °C. The compressive strength of normal concrete (without heating) had the optimum with concrete produced with blended aggregate size and conversely the least with 20mm aggregate size concrete. When subjected to heat, the optimal performance noted for the influence of aggregate size on fire resistance was also with concrete produced with combined blend (20 mm + 12.5 mm) sizes. The p-value (Prob > F) for the whole model test is less than 0.05, indicating that there is a significant relationship between the grain size, temperature, and strength loss. The use of blended sizes of 12.5 mm and 20 mm is therefore recommended for concrete works and especially when fire resistance is a requirement.

Techno-economic Evaluation of Biodiesel Production from Edible Oil Waste via Supercritical Methyl Acetate Transesterification

Sat, 28 Jan 2023 00:00:00 +0000

This study aimed to assess the economic and engineering feasibility of a large-scale biodiesel manufacturing operation from edible oil waste. The edible oil model used for economic analysis in this study is palm oil waste. Several economic parameters (i.e., gross profit margin (GPM), payback period (PBP), break-even point (BEP), cumulative net present value (CNPV), profitability index (PI)), and internal rate return (IRR) were examined to inform the potential production of biodiesel from edible oil waste in ideal condition. To confirm the feasibility of a manufacturing project, the project is estimated from ideal to worst-case conditions in production activities such as analysis of changing raw material, labor, tax, utility, and selling price costs. Based on an engineering perspective, the result indicated that biodiesel production from edible and non-edible oil is feasible. From an economic perspective, economic analysis shows that biodiesel production from edible oil waste is promising because the economic parameters as analyzed show positive results. Our findings are expected to provide an industrial-scale picture of economic evaluation and layout, particularly in the production of biodiesel, which is commonly used as a renewable energy source for fuel in trucks, trains, ships, and barges.

Assessing Social Sustainability Performance in Textile Industry using Integrated Fuzzy Best-Worst Method and Fuzzy Inference System

T. G. Fadara, K. Y. Wong — Sat, 28 Jan 2023 00:00:00 +0000

The main purpose of the research primarily focused on the development of sustainable social indicators and to test their usefulness and applicability in the Nigerian textile sector in terms of social performance. The integrated Fuzzy Best-Worst method (FBWM) and Fuzzy inference system (FIS) was presented to aid in the evaluation of these indicators. The outcomes demonstrate that employee rights received the highest score of 0.206 in the study. Employee rights are regarded as the most crucial and critical factor. Furthermore, among the indicators, fair salary has the highest global weight. The case company's sustainability performance index was 0.248, which was in the "poor" performance category. A case study was conducted in a Nigerian textile industry to demonstrate the effectiveness and efficiency of the proposed method. These findings will assist managers and policymakers in the textile manufacturing industry, particularly in emerging economies such as Nigeria, in developing strategies to lay the groundwork for social sustainability and transition to truly sustainable textile manufacturing industry.

Buffer-aided Relay Selection Technique in a Cooperative Communication Network

S. B. Ajibowu, O. A. Adeleke, I. A. Ojerinde — Sat, 28 Jan 2023 00:00:00 +0000

The goal of cooperative communication is to increase spatial diversity and wireless network coverage. However, in a classical relaying setup, where a single best relay is chosen to receive the source's data in the first time slot and retransmit in the second time slot regardless of channel circumstances, channel mismatch occurs. In this paper, we have developed an enhanced relay selection technique at the relay nodes that incorporates buffers to address the aforementioned problem. The outage probability and throughput computations are derived using closed-form formulas. The results obtained show that the enhanced relay selection technique gives lower values in outage probability and higher values in throughput when compared with the conventional technique, providing it a desirable strategy for use in technical communication.

Numerical Forced Convection Heat Transfer, Fluid Flow and Entropy Generation Analyses of Al₂O₃- Water Nanofluid in Elliptical Channels

Sat, 28 Jan 2023 00:00:00 +0000

This study investigates a three-dimensional elliptical microchannel heat sink for heat dissipation in laminar forced convection. The study seeks to improve thermal performance and overcome overheating associated with excessive temperature commonly experienced in heat-generating equipment, which is beyond the temperature usually specified by the manufacturer. The objective of the study is to evaluate the heat transfer, fluid flow, and entropy generation characteristics of Al₂O₃-water nanofluid in an elliptical cooling channel. The numerical analysis is investigated on the structure experiencing constant volumetric heat generation. The parameters considered are Reynolds number of 100 ≤ Re ≤ 500, nanoparticle concentration ϕ, from 0% to 4% with channel aspect ratio Ar from 1 to 3. The impacts of these parameters on the maximum temperature, heat transfer coefficient, friction factor, and volumetric entropy generation are reported. The study demonstrates that heat transfer is enhanced in the elliptical cooling channel at different aspect ratios, nanoparticle concentrations, and Reynold numbers. The results showed that as the nanoparticle concentration, channel aspect ratio, and Reynolds number (Re) increase, the maximum temperature, and total entropy generation decrease. As the channel aspect ratio increases at a specified Re = 200 and nanofluid concentration, ɸ = 3%, the maximum temperature, and total entropy generation decrease by up to 62% while the heat transfer coefficient increases by up to 78% and the friction factor increase by less than 2% with aspect ratio. However, the friction factor is not sensitive to the nanofluid concentration as a coolant.

Selection of Wireless Communication Technologies for Embedded Devices using Multi-criteria Approach and Expert Opinion

J. A. Adebisi, O. M. Babatunde — Sat, 28 Jan 2023 00:00:00 +0000

Emerging research has shown the significance of communication technologies in the development of embedded systems and devices. Since there are various communication technologies with varying advantages and disadvantages in embedded systems, decision makers in identifying the best alternative can be prejudiced by various features. Hence, making the selection of the most suitable wireless communication technology a multi-criteria problem. To rank the common wireless communication technologies relevant to the development of embedded systems, this paper presents a multi-criteria decision making (MCDM) approach for analyzing experts opinion on the most preferred wireless communication technologies for embedded devices. To accommodate the subjective nature of experts’ responses, a Fuzzy-TOPSIS MCDM approach is proposed for the ranking wireless communication technologies that can be adopted in the development of embedded systems. Based on the aggregation of responses from experts, the results show that the most preferred wireless communication alternative for embedded application is Wi-Fi with a closeness coefficient (𝐶𝐶_𝑖) of 0.52, while the least preferred alternative is Long-Term Evolution (LTE) with a (𝐶𝐶_𝑖) 0.32.

Morphology and Physico-Mechanical Properties of Resin-bonded Palm Kernel Shell and Coconut Shell Grain-based Sandpaper Composites

H. A. Ajimotokan, A. A. Samuel, T. K. Ajiboye, T. S. Ogedengbe, I. O. Alabi — Sat, 28 Jan 2023 00:00:00 +0000

Due to the challenges associated with using crude oil-derived phenolic- or thermoplastics-based materials, agro-based composites have been used as alternative abrasive grains for abrasive tool manufacturing. This paper examines the morphology and physico-mechanical properties of resin-bonded palm kernel shell (PKS) and coconut shell (CNS) grain-based sandpaper composites and their wear performance. The PKS and CNS were collected, pulverised and screened into 250 and 500 μm grainsizes and mixed at ratios of 1:1, 1:2 and 2:1, respectively. Methyl-ethyl-ketone-peroxide and cobalt naphthalene of 1.5 wt. % each were utilised as hardener and catalyst, respectively for proper bonding of the aggregates with unsaturated polyester resin of compositions 12, 15, 18, 21 and 24 wt. %, respectively. To produce the sandpaper samples, the aggregates were compacted at a pressure of 15 MPa and the samples were cured and their morphology, mechanical, and wear properties were investigated.The shatter index, hardness, and compressive strength varied from 66.36% to 95.76%, 6.52 to 11.3 HRB, and 4.41 to 7.24 MPa, respectively. The wear resistance varied from 0.94 to 1.54 mg/m at 50 ^oC, and 1.02 to 2.09 mg/m at 150 ^oC. The properties of the aggregates made from PKS and CNS were found to have much influence on the performance parameters of sandpaper composites.

Nonlinear Time History Analysis for Seismic Effects on Reinforced Concrete Building

A. Hasan, K. I. M. Iqbal, S. Ahammed, A. Ghosh — Sat, 28 Jan 2023 00:00:00 +0000

A typical Reinforced Concrete (RC) building frame comprising of RC columns and connecting beams that participates in resisting the earthquake forces. Due to earthquake, reversal tension generates at both faces of a beam and column; and hence damage occur in the frame for the disability of tension carrying capacity of concrete. Therefore, the structural performance of RC building for seismic load has been analyzed by nonlinear time history analysis method for this study. A residential building located in Dhaka, Bangladesh subjected to various types of gravity load and seismic load was considered to analyze using ETABS software as per the guideline of BNBC (2020). According to the guideline of ATC 40 (1996), the seismic performances like maximum displacement and story drift for RC building were evaluated both at structural and element levels by applying El Centro (1940) ground motion at the base of the structure. Formation of plastic hinges is used as the basis to evaluate the local performance and story drift is used to evaluate the global performance. At first, the considered building was designed only for gravity load, and then for both gravity and seismic load according to BNBC (2020). Further studies have been performed on that building considering double height column at a story level. It was observed that the maximum displacement and story drift exceeds the allowable limit for all the considered cases if seismic load is applied on the structure.

Load Voltage Control of a Wind Turbine-driven Three-phase Squirrel-Cage Induction Generator in an Islanded Microgrid

S. A. Kamilu, L. Olatomiwa, O. M. Longe, S. Ikuforiji — Sat, 28 Jan 2023 00:00:00 +0000

The intermittent nature of the wind resources and reactive power consumptions are major issues associated with squirrel cage induction generator wind power system when operated in an island microgrid mode. The resultant effect of these two issues are continuous fluctuations of load voltage which has adverse effects on electrical devices. This paper proposes a voltage regulation technique based on proportional controller and phase deposition sine pulse width modulation (PDSPWM) for the control of 5-level neutral point clamped multilevel inverter. The instantaneous voltage tracking strategy based on root mean square value of microgrid voltage was adopted to regulate and maintain the output load voltage at 400 𝑉𝑟𝑚𝑠 despite rotor fluctuations with wind speeds. The simulation was carried out in a MATLAB/SIMULINK environment and the performance of the control scheme was found to be excellent.

Valorization of Sugarcane Bagasse for Hydrogen-Rich Gas Production using Thermodynamic Modeling Approach

Sat, 28 Jan 2023 00:00:00 +0000

Hydrothermal gasification also known as supercritical water gasification (SWG) has been considered a promising approach for converting wet biomass such as sugarcane bagasse into high-quality syngas. This study presents the thermodynamic modeling of the hydrothermal gasification of sugarcane bagasse using Aspen Plus. The effects of process parameters on the composition and yield of product gases were also investigated. It was found that the effect of temperature and biomass concentration were significant in the production of hydrogen-rich gas, while less impact was observed with pressure. The hydrogen gas (H2) produced with the highest mole fraction (56.70 mol%) and yield (103.26 kmol/kg) was obtained at 750°C and low biomass concentration of 10 wt%, while the lowest yield (1.52 kmol/kg) and mole fraction (2.45 mol%) of H2 were obtained at 450°C and high biomass concentration of 50 wt%. Findings from this study also showed that the highest net calorific value (17.55MJ/kg) was reached at 450˚C and 50 wt% of biomass concentration. This study would help to consolidate research on hydrothermal gasification of sugarcane bagasse and optimization of experimental processes and also serve as an important benchmark in the utilization of biomass as a clean energy source for future projects.

Effect of Thermal Screen Position on Greenhouse Microclimate and Impact on Crop Growth and Yield

Sat, 28 Jan 2023 00:00:00 +0000

Worldwide, researchers are developing methods in which producers can obtain higher yields and conserve more energy in greenhouse crop cultivation. To achieve this, thermal screens are deployed during cold nights and rolled up during the daytime. The positioning of these screens causes a reduction in the amount of solar radiation (SR) received by greenhouses, especially the single span. The impact of thermal screen position on the receipt of SR, temperature, relative humidity (RH), vapour pressure deficit (VPD), fuel consumption, and the consequent effects on crop yield and growth were investigated in this study. Two greenhouses with similar dimensions and structure but different thermal screen positions were designed, namely R-greenhouse (RGH) with thermal screens at the centre of the roof and Q-greenhouse (QGH) at five degrees (5o) Northward. Strawberries were cultivated as study crops. Statistical analysis of the recorded data of greenhouse microclimate parameters, crop growth, and yield showed that both greenhouses performed similarly in energy savings, and there was no significant difference regarding temperature, RH, and VPD. However, there were significant differences in the crop growth and yield obtained in the QGH compared to RGH. This can be attributed to the higher amount of SR received by the QGH than the SR that was received by the RGH, which was achieved because the thermal screen was installed on the north side of the Q greenhouse.

Nigerian Journal of Technological Development

Effects of Geometric Ratios on Heat Transfer in Heated Cylinders: Modelling and Simulation

Effects of Annular-finned Tube Deformation on Thermal Stresses in a Heat Exchanger

Comparison of Errors Caused by Flux Limiters on the Numerical Solution of Advection-Diffusion Problem

Optimization of Cutting Parameters using the RSMDesirability Approach in the MQL-Assisted Turning of AISI 4130

Short-term Study of the Influence of Aggregate Size on the Fire Resistance of Concrete

Techno-economic Evaluation of Biodiesel Production from Edible Oil Waste via Supercritical Methyl Acetate Transesterification

Assessing Social Sustainability Performance in Textile Industry using Integrated Fuzzy Best-Worst Method and Fuzzy Inference System

Buffer-aided Relay Selection Technique in a Cooperative Communication Network

Numerical Forced Convection Heat Transfer, Fluid Flow and Entropy Generation Analyses of Al2O3- Water Nanofluid in Elliptical Channels

Selection of Wireless Communication Technologies for Embedded Devices using Multi-criteria Approach and Expert Opinion

Morphology and Physico-Mechanical Properties of Resin-bonded Palm Kernel Shell and Coconut Shell Grain-based Sandpaper Composites

Nonlinear Time History Analysis for Seismic Effects on Reinforced Concrete Building

Load Voltage Control of a Wind Turbine-driven Three-phase Squirrel-Cage Induction Generator in an Islanded Microgrid

Valorization of Sugarcane Bagasse for Hydrogen-Rich Gas Production using Thermodynamic Modeling Approach

Effect of Thermal Screen Position on Greenhouse Microclimate and Impact on Crop Growth and Yield

Numerical Forced Convection Heat Transfer, Fluid Flow and Entropy Generation Analyses of Al₂O₃- Water Nanofluid in Elliptical Channels