DEPARTMENT OF MECHANICAL ENGINEERING
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Item Numerical investigation of forces and acceleration for air-sea unmanned aerial vehicle in transition(2023) Chukwuemeka, E. C.; Ames, F.; Kazeem, R. A.; Petinrin, M. O.; Ikumapayi, O. M.; Akinlabi, E. T.The air-sea UAV is made to be able to fly, change from land to water, and navigate through submerged water. However, as it moves from the air to the water, it experiences a significant impact force. The UAV’s structure and components run the risk of being harmed by this strong impact force. The accelerations and forces involved in the transition process must therefore be understood through quantitative research. The method was created using computational fluid dynamics (CFD), which can manage the process of water entry. The simulation and calculations were carried out using the Fluent software suite from ANSYS Inc. The research examined the UAV’s wing and center bodies independently and separately. 3-D models were used for the analyses of the center body, while 2-D models were used for the wing-body analyses. The transition flow and submerged methods were taken into consideration in obtaining the impact load that a body experiences when transitioning into water. Because it was substantiated using experimental results from prior studies, the transient-time analysis-based transition techniquewas shown to be reliable. The steady-state analysis of the submerged flowmethod can be used to quickly comprehend the pressure and velocity distribution over a body immersed in or entering the water. However, because it fails to account for the water’s initial acceleration upon entry, the steady-state simulation underestimates the drag force. The submerged flow method’s findings indicate that a sharp nose centre body diminishes drag more successfully. The transition method evaluations for the UAV slender body reveal controllable drag and impact forces. Furthermore, the study demonstrates that wedge-shaped leading edges for the wing-body reduce impact but may not be optimal when considering airlift. As a result, this research provides useful data for air-sea UAV structural design and movement conditions.Item Forced convection heat transfer in micro heat sinks with square and circular configuration(2023-06) Godi, N. Y.; Zhengwuvi, L. B.; Petinrin, M. O.This paper reports the results of three-dimensional numerical optimisation of microchannel heat exchanger with square and circular cooling channels. The objective of the optimisation is to maximise the global thermal conductance or minimise global thermal resistance. Response surface optimisation methodology (RSM) is used in the numerical optimisation. A high-density heat flux (2.5×106𝑊/𝑚2) is imposed at the bottom surface of the unit cell microchannel and numerical simulation carried out using ANSYS Fluent commercial software package. The elemental volume and axial length 𝑁=10 𝑚𝑚 of the microchannel were all fixed, while the width was free to morph. The cooling technique employs single-phase water which flows through the rectangular block microchannel heat sink to remove the heat at the bottom of the microchannels in a forced convection laminar flow regime. The velocity of the fluid pumped across the microchannel axial length is the range 400≤𝑅𝑒𝑤≤500. Finite volume method (FVM) is used to descretised the computational domain and computational fluid dynamic (CFD) code employed to solve a series of governing equations. The effect of channel hydraulic diameter and Reynolds number of water-flow on peak wall temperature and minimised temperature are investigated and reported. The numerical results show that the microchannel with square cooling channel has the highest maximised global thermal conductance than the micro heat sink with circular configuration. The result of the numerical study agrees with what is in the open literature.Item Heat transfer analysis in constructal designed microchannels with perforated micro fins(The Institution of Engineers (India), 2023-04) Godi, N. Y.; Petinrin, M. O.This paper documents 3-D numerical optimisation of combined microchannel heat sink with solid and perforated rectangular fins. Constructal design technique is deployed to construct a geometry with reduced material substrate and the effect on the heat transfer is examined. The goal of the study is to minimise the peak temperature or maximise global thermal performance. The axial length and volume of the microchannel are fixed, while the width is allowed to morph. The microelectronic device placed at the bottom of the combined heat sink emits heat flux q″ and the heat deposited at the bottom is removed using a single-phase fluid (water) of Reynolds number Re w in a forced convection laminar regime. The computational domain is descretised and the mathematical equations that govern the fluid flow and heat transfer are solved using the CFD code. Three unique cases were considered in this study. The influence of design parameters (channel width, external shape, and velocity of fluid applied) on the performance of the combined microchannel heat sink is discussed. The study revealed that the solid material substrates used in the manufacturing of the combined microchannel heat sink can be reduced without necessarily compromising the heat transfer at certain applied Re w . The global thermal conductance of the combined microchannel with no perforation on fins increases by 1.1% higher than the microchannel with 1-rectangular perforation on fins and 0.8% above the heat sink with 2-rectangular perforations on fins. The numerical results validation agrees with what is in the open literature.Item Flow and heat transfer characteristics in channels with piriform dimples and protrusions(Global Digital Central, 2023) Oyewola, O. M.; Petinrin, M. O.; Sanusi, H. O.The flow and heat transfer behaviour of channels with dimples and protrusions of spherical and piriform shapes was numerically explored by solving the Navier-Stokes and energy equations with a CFD software, the ANSYS Fluent 19.3, in the range of Reynolds numbers from 8,500 to 59,000. The values of the Nusselt number and friction factors were estimated and the non-dimensional Performance Evaluation Criterion (PEC) was determined to measure the thermal-hydraulic performance. The results reveal that the piriform protruded channel demonstrated a higher thermal performance with Nusselt number values of 36%, 15%, 23%, and 9% than the smooth, spherical dimpled, piriform dimpled, and spherical protruded channels, respectively. This indicates that heat transfer is enhanced by the turbulent mixing caused by the roughened surfaces of the channels. Nevertheless, the smooth channel had the lowest pressure drop with the friction factor of 20%, 7%, 21% and 27% less than that of spherical dimpled, piriform dimpled, spherical protruded, and piriform protruded channels, respectively. In the Reynolds number range, lower Nusselt number ratios and friction factor ratios were observed in the piriform dimpled channel compared to other enhanced-surface channels. The overall performance based on the thermal-hydraulic analysis indicated that the channel with piriform protrusions performed better with the highest PEC value of 3.77 times higher than the smooth-surface channel.Item Climate change mitigation with carbon capture: an overview(2023) Towoju, O. A.; Petinrin, M. O.The world is at the verge of catastrophe occasioned by the effect of climate change. Drastic action needs to be taken to reverse this ugly trend. Some of the proffered solutions to global warming is the adoption of renewable energy usage and a stop of fossil fuels combustion. However, the low capacity factor and energy return has been the bane on the usage of some renewable energy sources. A leeway however, exists in the technology of removal of greenhouse gases referred to as Carbon Capture. The widely adopted method being at point source because of its high concentration favouring easier processes of removal. This technology has received increased attention over the years as evident from data for the past five years. However, this technology alone cannot guarantee atmospheric CO2 levels required to maintain global temperature rise below the 1.50C mark. Negative emission technology processes of which the Direct Air Capture (DAC) is one needs to be developed. The infancy of the DAC technology and the uncertainties that surrounds its cost still pose as challenges. The cost of removing a tonne of CO2 with DAC technology can be as high as $600, this is unsustainable and has to be drastically reduced. While it is projected that DAC technology can take out 980 Metric Tonne (MT) CO2/annum by 2050, current figures stand at 0.008 MT. It is our view that the development of solid adsorbents and the harnessing of the thermal energy inherent in the sun can be a game changer.Item Evaluation of palm kernel oil as cutting lubricant in turning AISI 1039 steel using taguchi-grey relational analysis optimization technique(Elsevier, 2023) Alaba, E. S.; Kazeem, R. A.; Adebayo, A. S.; Petinrin, M. O.; Ikumapayi, O. M.; Jen, T. C.; Akinlabi, E. T.Cutting fluids have a known negative impact on productivity, human health, and the environment in the manufacturing sector. A suitable method for reducing the effect of cutting fluids on human health and the environment is minimum quantity lubrication (MQL). In this experiment, AISI 1039 steel was machined using vegetable oil lubricant and MQL. A chemical method was used to extract vegetable oil from palm kernel seeds. Then, using established techniques, the physicochemical and lubricity properties of palm kernel oil (PKO) were ascertained. The Taguchi L9 (33) orthogonal array served as the basis for the planning of the experimental design. Process parameters such as surface roughness, chip thickness ratio, cutting temperature, and material removal rate were measured during the turning operations. The multi-response outputs from TGRA were considered to simultaneously optimize the cutting parameters namely depth of cut, feed rate, and spindle speed. At a temperature of 55◦C, 180 min, and particle sizes of 0.2–0.5 mm, an oil yield of 55% by weight was obtained. The viscosity at 40◦C, specific gravity, pour, fire, cloud, and flash points of the raw PKO were 117.6 mm2/s, 0.8940 mg/ml, 21◦C, 231◦C, 22.3 ◦C and 227◦C, respectively. The surface roughness and cutting temperature of PKO improved by 44% and 12%, respectively, when compared with mineral oil. The findings of this research confirmed the effectiveness of the integrated Taguchi-grey relational analysis (TGRA) optimization method and established an experimental foundation for the use of PKO minimum quantity lubrication turning.Item Thermodynamic optimisation of solar thermal brayton cycle models and heat exchangers using particle swarm algorithm(Elsevier BV on behalf of Faculty of Engineering, Ain Shams University, 2023) Oyewola, O. M.; Petinrin, M. O.; Labiran, M. J.; Bello-Ochende, T.In this work, three variants of the Brayton cycle incorporating concentrated solar technologies and dual regenerative systems are modeled. The first variant employs reheat, intercooling, and regeneration, the second applies intercooling and regeneration while the third case involves regeneration only. With the application of the entropy generation method and particle swarm algorithm (PSA), processes with the largest irreversibilities are noted, minimized and the geometric parameters of participating components are optimized. Results show that irreversibilities occurring in the systems were largely due to finite temperature differences within components. In all cases, the solar receiver and intercooler are the dominant and modest sources of entropy generation respectively. The regenerative system entropy generation is highest in the first case while decreasing in the second and third cases respectively. An improvement in the exergy availability was observed in the first case, as the first and second law efficiency peaks at 44.9% and 59.68% respectively. Though, with a lower second law efficiency than the former, its percentage network output is equal to the first case at 43%. The aspect ratio, hydraulic diameter, and length of the receiver were observed to vary to enhance greater heat capture and increase the turbine inlet temperature (TIT). The high temperature (HT) regenerator had its geometric properties of a higher magnitude than the low temperature (LT) system as the waste heat recovery is aided by an enhanced heat transfer surface area. In comparison with the single regeneration system, the network output of the dual model was about 33.5% with a significant reduction in the entropy generated, creating a trade-off between operating the system for more power or less generation of irreversibilities.Item Forecast of the trend in sales data of a confectionery baking industry using exponential smoothing and moving average models(2023-02) Kazeem, R. A.; Petinrin, M. O.; Akhigbe, P. O.; Jen, T. C.; Akinlabi, E. T.; Akinlabi, S. A.; Ikumapayi, O. M.Starch-containing foods such as bread, pastries, and cakes are usually baked at a moderately high temperature in an oven. When these products are later exposed to room temperature, the associated gelatinized starch begins to harden which causes retrogradation and molecular realignment. Due to this circumstance, manufacturers need to have a fairly accurate estimate of products demand in order to determine the precise amount of baking powder and additives for use in their production so as not to incur losses in their business arising from the stale and consequentially unsalable products. This research was therefore focused on selecting the best forecasting model using a prominent confectionery firm in Abeokuta, Ogun State, Nigeria as a case study. The study was based on 24-week operational period sales data collected from the company. The moving average model and the exponential smoothing model were the two forecasting models considered in this research. The data obtained was thoroughly reviewed and the results of the forecasting models were compared. The most effective model was the exponential smoothing model as it produced the lowest mean absolute percentage error on the average of 3.7347 for the cumulative days of sales under review as against the 15.1713 for the moving average model. However, the exponential smoothing model was considered the best forecasting model for minimizing forecasting error in this study.Item Crossflow flow and heat transfer characteristics across a cam-shaped tube bank: a numerical study(2022) Petinrin, M. O.; Sikirullahi, B. A.; Olugasa, T. T.; Oyewola, O. M.Tubes are commonly employed in heat exchangers for their ease of production and capacity to sustain high pressure. In this study, the heat and flow transfer behaviour of cam-shaped tube bank in staggered configuration at varying angles of attack 0° to 180° was numerically investigated. The study was carried out by solving the continuity, momentum, energy and realizable k-ε transport equations using the finite volume-based ANSYS Fluent solver. This was performed to acquire the friction factor and heat transfer characteristics in the air inlet velocity range of 9 to 15 m/s. The results showed that the cam-shaped tube bank at varying angles of attack provided enhanced heat transfer characteristics relative to the circular tube bank. Also, camshaped tube banks at angles of attack of 90° and 120° exhibited the maximum heat transfer with 33.9 and 32.1% increase in Nusselt number over the circular tubes. Their friction factor was higher by 183 and 140.7%, respectively. The cam-shaped tube banks generally exhibited higher performance than the circular tube bank. Tube banks at angles of attack of 150° and 180° demonstrated higher thermal-hydraulic performance by 167.6 and 284.3% than the circular tubes, respectively. However, the tube banks at angles 90° and 120° exhibited lesser performance by value of 52.6 and 45.1%.Item Investigation of temperature distribution in a slab using lattice boltzmann method(2022) Petinrin, M. O.; Owodunni, A.; Kazeem, R. A.; Ikumapayi, O. M.; Afolalu, S. A.; Akinlabi, E. T.In this paper, the temperature distribution in a slab was investigated. A model based on the Boltzmann transport equation without heat source was simplified using the Bhatnagar-Gross-Krook (BGK) approximation was applied. This is an example of the Lattice Boltzmann Method. The model was developed based on using a D2Q4 lattice arrangement for the medium of study. To obtain results, the model was tested on different cases: Two box-shaped slabs with different boundary conditions, and a T-shaped and an L-shaped slabs to determine the temperature distributions different times t > 0. The results obtained based on the developed model were validated with the enterprise software COMSOL Multiphysics which is based on the Finite Element Method. For the two cases of box-shaped and the T-shaped slabs, their results were in nearly perfect agreement with the finite element method. However, for the L-shaped slab, there was good agreement at most points apart from the regions where there was change of shape. In conclusion there is high agreement between the results of LBM and using COMSOL, which proves that LBM can be used to determine temperature distribution in a slab accurately.