Department of Mechanical Engineering
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- ItemOpen AccessAirflow and Heat Transfer Analysis within Flat-top Roofs Heated from Below(The University of the West Indies St. Augustine , Trinidad, 2021) Kamiyo, O.Natural convection in attic of non-conventional rooftops has received considerable attention in recent years due to its importance in thermal management of modern pitched- roof buildings. In this study, a finite -volume numerical investigation of laminar fluid dynamics and heat transfer of air within the attic of a flat- top roof structure has been predicted for bottom isothermal heating at varying pitch angle. The heat transfer between the walls results in multiple thermal plumes and multi-cellular flow structure with the number, size and strength of the counter -rotating cells reducing with increasing pitch angle. The results further show that the peculiar shape of the roof has significant effect on the fluid flow and heat transfer. Particularly, the truncated triangular architecture of the roof prevents the formation of large, dominating and upper-row cells at the midsection of the attic. At low pitch, the intensity of the vortices results in thorough mixing of air and, hence, uniform temperature distribution within the attic. The averaged Nusselt number for the hot ceiling wall which depicts the rate of convective heat transfer into the attic is in negative - gradient quasilinear relationship with the roof pitch. The practical significance of the predicted results is that, due to the peculiarity of the flat-top roof structure, heat loss to the attic is minimized when the roof pitch is relatively high; particularly not less than 300 and made as low as possible if the attic is to be used for drying of food crops
- ItemOpen AccessALTERNATE ENERGY SOURCES FOR CI ENGINES: A FOCUS ON NIGERIA(Energy Technology & Management Conference ETMCon, University of Ibadan., 2012) Omoregbee, HenryThe supply of energy through sources that have been adjudged not to be amenable to cleanliness and supportive of emission control, which are also finite, necessitates the search for alternative sources of energy. This becomes particularly important for transportation, specifically Internal Combustion Engines. It is also applicable to developing countries like Nigeria, which have the desire to develop technologically and would benefit from alternative technological paths to ensure the development, deployment and utilization of environmentally friendly technological products. Nigeria, a country rich in oil resources, would benefit from proper study and development of alternative products, specifically Compressed Natural Gas, which she has in abundance. CNG has shown a variety of capacities and adaptability, which makes it suitable to address endemic problems such as emissions, energy efficiency and thrift of conventional fuels like Gasoline and Diesel. It then becomes imperative that the pace of development and deployment of CNG consuming engines be fast-tracked. In this research, we hope to facilitate this process by comparing alternative power units, CNG units with conventional gasoline units. And also we hope that by employing the design principles and other factors that have made gasoline vehicles dominant in the passenger vehicle market, we shall arrive at an efficient and reliable CNG powered solution for passenger vehicles.
- ItemOpen AccessAnalysis of the thermal performance of single and multi-layered microchannels with fixed volume constraint(Proceedings of the Romanian Academy, 2018) Adewumi, O.O; Bello-Ochende, T.; Meyer, J.PThis study presents a numerical analysis of forced convection heat transfer and steady, laminar, incompressible fluid flow through single-, two- and three-layered microchannels with different flow arrangements and fixed total volume constraint. Previous studies on multi-layered microchannel heat sinks have shown that these types of heat sinks perform better than single-layered microchannel in terms of reducing thermal resistance and pressure drop, but this is obtained with increased total volume of the solid substrate because equal volumes of the single-layered microchannel are stacked to obtain the number of desired layers. In this paper, the total volume of the solid substrate for all the microchannels considered was fixed at 0.9 mm3 and the geometries of the different microchannels were optimised based on the objective of maximising the thermal conductance using a computational fluid dynamics package with a goal-driven optimisation tool. The results show that for a fixed total volume and fixed inlet fluid velocity, the pumping power of the two-layered microchannel with the different flow arrangements was 10% less than that required for the single-layered microchannel but was increased by about 12% when the number of layers was increased to three. The results obtained from this study show that the multi-layered microchannels give very good results without increasing the total volume of the solid substrate as presented in previous investigations.
- ItemOpen AccessBiogas production from cassava waste(Trans Tech, Switzerland, 2008-04-15) Kehinde, J.A.; Ojolo, S.J.; Ebiobi, B.Anaerobic digestion is being taken seriously because of increasing concerns about the environmental hazards of wastes. The production of biogas, as an alternative source of energy was investigated in a designed and fabricated 200litre biogas reactor. The digester was operated on a batch-fed basis, and the feed stock was cassava waste which is readily available in Nigerian farms. The main aim was to explore other renewable sources as a means of less dependence on fossil fuels. A total of 1.94dm3/60kg waste of biogas was produced in 40 days of hydraulic retention time (HRT) with the average yield of 0.048dm3/day. The gas burned with a bluish colour indicating presence of methane (CH4). Temperature during the period of experiment varied between 27 and 330C. The pH of the slurry after the experiments averaged 3.21.
- ItemOpen AccessBIOGAS TECHNOLOGY AS A NON-CONVENTIONAL SOURCE OF ELECTRICITY GENERATION(Federal Polytechnic Ilaro., 2010-11) Omoregbee, HenryEfforts by the government to solve the energy crisis in the country over the years with the conventional methods of generating electricity has not yielded the desired result hence the need for alternative source of energy. The paper examines the possibility of exploiting the readily available organic waste (biomass production) and the major benefits over the conventional methods of generating electricity. The impacts of adoption of this alternative source of energy on the environment, the sustainability and renewability of the system were highlighted.
- ItemOpen AccessCharacterization of a Finned Heat Sink for a Power Inverter(Journal of Physics, 2019) Onoroh, F.; Adewumi, O.O.; Ogbonnaya, M.
- ItemOpen AccessCharacterization of a finned heat sink for a power inverter(Journal of Physics:Conference Series, 2019) Onoroh, F; Adewumi, O.O; Ogbonnaya, M.Heat is a by-product which is constantly being generated in the operation of a power inverter and if left unchecked will inevitably lead to the damage of the device. Hence a means to efficiently dissipate this heat has to be employed. In this research, a heat sink is mathematically modelled and its thermal performance was evaluated using ANSYS software and experimentally validated. The optimisation of the heat sink was done with the aid of the FMINCON optimization tool in MATLAB. A K-type thermocouple and a three channel temperature logger, MTM-380SD, with real time data logger were used to obtain temperature data of the heat sink for the purpose of experimental validation. The optimized heat sink parameters are heat sink length and width, number of fins, base thickness, fin height, thickness and spacing. Results show that the percentage deviation between the simulation and experimental temperature results for a pulse load of 300W is 8%, for a pulse load of 460W is 3%, for a pulse load of 600W is 8%, for a pulse load of 1015W is 2%. The maximum simulated and experimented temperatures are 84oC and 85.4oC. Thus the inverter can be safely and reliably operated.
- ItemOpen AccessComparison between the thermal performance of single and two-layer microchannels inserted with micro pin fins(Begel House Inc., 2014-08) Adewumi, O.O; Bello-Ochende, T.; Meyer, J.PThis paper presents a three-dimensional numerical study of steady, laminar, incompressible flow and forced convection heat transfer through a two-layer rectangular microchannel heat sink inserted with pin fins. The objective of the study was to optimise the geometric configuration of the combined two layer microchannel heat sink with micro pin fin inserts for a fixed solid volume so that the peak temperature within the configuration is minimised. The geometric optimisation of the microchannel was carried out using a computational fluid dynamic code with a goal driven optimization workbench tool subject to global constraints. Effects of pressure drop on the minimised peak temperature and maximum thermal conductance for the fixed solid volume were reported. The thermal performance of the single and two-layer microchannel heat sink inserted with micro pin fins based on the minimised peak temperature and maximised global thermal conductance were compared and their results were reported. For a constant solid volume of 0.9mm3 and fixed length of 10mm, it was observed that while the performance of the single microchannel was improved with the micro pin fins, it was not the case with the two-layer microchannel. These results showed that inserting pin fins in a two-layer microchannel does not enhance the heat transfer when the length of the solid substrate is fixed. The thermal performance of the combined design when the axial length of the solid substrate was relaxed was also reported.
- ItemOpen AccessComputational investigation of thermal behaviors of the automotive radiator operated with water/anti-freezing agent nanofluid based coolant(Federal University of Viçosa, Brazil, 2022) Fetuga, I.A.; Olakoyejo, O.T.; Ewim, D.R.E.; Gbegudu, J.K.; Adelaja, A.O.; Adewumi, O.O.In this study, a 3D computational fluid dynamics (CFD) study was conducted in ANSYS (FLUENT) to examine the thermal performance of an automotive radiator using conventional and hybrid coolant with a Al2O3 nanoparticles (NPs) . A hybrid mixture of pure water H2O and ethylene glycol (EG) in the volumetric proportion of 50:50, was coupled with Al2O3 nanoparticles with volume fraction of 1% - 4% at different inlet temperatures. The Reynolds number was varied from 4 000 to 8 000. From the numerical results obtained, it was found that an increase in nanoparticle volume fraction led to an increase in heat transfer rate and pressure drop in the automotive radiator. Also, it was found that at a Reynolds number of 8 000, using the hybrid mixture as a base fluid increased the Nusselt number by 55.6% in contrast to pure water. However, further suspension of 4% Vol. Al2O3 nanoparticles into existing hybrid mixture increased the Nusselt number by 70%. Furthermore, it was found that an increase in the inlet temperature of the radiator caused more enhancement in the heat transfer rate. For Re=8 000 4% vol. Al2O3-water nanofluid, the heat transfer rate was enhanced by 54.57% when increasing the inlet temperature from 60oC to 90oC. Therefore, it is recommended that automobile radiators be operated at a high inlet temperature with nanofluid containing a very high concentration of suitable nanoparticles and an anti-freezing agent in an adequate volumetric proportion to achieve better thermal performance.
- ItemOpen AccessConstructal conjugate cooling channels with internal heat generation(Elsevier, 2012-04-30) Olakoyejo, O.T.; Bello-Ochende, T.; Meyer, J.P.This paper presents a geometric optimisation of conjugate cooling channels in forced convection with internal heat generation. Two configurations were studied; circular channels and square channels. The configurations were optimised in such a way that the peak temperatures were minimised subject to the constraint of fixed total global volume. The fluid was forced through the cooling channels by the pressure difference across the channels. The structure has one degree of freedom as design variable: channel hydraulic diameter and once the optimal channel hydraulic diameter is found, optimal elemental volume and channel-to-channel spacing result. A gradient-based optimisation algorithm is applied in order to search for the best and optimal geometric configurations that improve thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. This optimiser adequately handles the numerical objective function obtained from CFD simulations. The results obtained show the behaviour of the applied pressure difference on the optimised geometry. There are unique optimal design variables for a given pressure difference. The numerical results obtained are in agreement with the theoretical formulation using scale analysis and method of intersection of asymptotes.
- ItemOpen AccessConstructal design of combined microchannel and micro pin fins for electronic cooling(International Journal of Heat and Mass Transfer, 2013-07-10) Adewumi, O.O; Bello-Ochende, T.; Meyer, J.PThis paper presents a three-dimensional numerical study of steady, laminar, incompressible flow and forced convection heat transfer through a microchannel heat sink with micro pin fin inserts for both fixed and variable axial lengths. The objective of the study was to optimise the geometric configuration of anintegrated microchannel and micro pin fins for different solid volumes so that the peak temperature inthe configuration was minimised. The effect of the micro pin fins on the optimised microchannel was also investigated. The geometric optimisation of the integrated microchannel and micro pin fin was carried out using a computational fluid dynamics (CFD) code with a goal-driven optimisation tool subject to global constraints. The optimisation procedure was carried out in two steps. Firstly, the microchannel configuration was optimised without the micro pin fins inserted and the results were compared with similar work found in the open literature. This optimisation was carried out for both fixed and relaxed lengths. Thereafter, the integrated design of the microchannel and micro pin fins was optimised. The effect of the Bejan number on the solid volume fraction, channel aspect ratio and hydraulic diameter, pin fin aspect ratio, minimised peak temperature and maximised thermal conductance were reported. Results showed that as the Bejan number increased, the minimised peak temperature decreased. Also, the maximum thermal conductance increased with the optimised microchannel structure with three to six rows of micro pin fin inserts. Diminishing return set in when the number of rows of micro pin fin inserts was greater than three for the fixed length but for the relaxed length, as the number of rows increased, the results improved but when it exceeded six diminishing returns set in for a fixed solid volume of 0.9 mm3. For each Bejan number used in this study, there was an optimum channel hydraulic diameter and aspect ratio, solid volume fraction and pin fin aspect ratio that satisfied the global objective.
- ItemOpen AccessConstructal Design of Rectangular Conjugate Cooling Channels(Springer, 2013) Bello-Ochende, T.; Olakoyejo, O.T.; Meyer, J.P.The new trend in modern heat transfer for thermal performance is shape and geometric optimisation. Constructal theory and design, ideally, have been adopted as an optimisation technique for the development of a procedure that is sufficiently allocating and optimising a fixed global space constraint using physical law. This work presents a three dimensional geometric optimisation of a conjugate cooling channel in forced convection with an internal heat generation within the solid for a rectangular configuration. The configuration was optimised in such a way that the peak temperature was minimised subject to the constraint of fixed global volume of solid material. The cooling fluid is driven through the channels by the pressure difference across the channel. The structure has channel height, width and channel to channel spacing as degrees of freedom as design variables. The shape of the channel is allowed to morph to determine the best configuration that gives the lowest thermal resistance. A gradient-based optimisation algorithm is applied in order to search for the best optimal geometric configurations that improve thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. This optimiser adequately handles the numerical objective function obtained from CFD simulations. The effect of porosities, applied pressure difference and heat generation rate on the optimal aspect ratio and channel to channel spacing are reported. Results obtained show that the effects of dimensionless pressure drop on minimum thermal resistance are consistent with those obtained in the open literature.
- ItemOpen AccessConstructal design of single microchannel heat sink with varying axial length and temperature-dependent fluid properties(International Journal of Heat and Technology, 2016) Adewumi, O.O; Bello-Ochende, T.; Meyer, J.PThe objective of this numerical study is to investigate the best geometric configuration that maximises heat transfer from the heated base by allowing both the length of the solid substrate and the microchannel heat sink freedom to morph. The thermal performance of the microchannel is based on the minimised peak temperature on the heated surface which gives a global minimised thermal resistance. The optimisation of the geometric parameters of the heat sink and solid substrate is carried out using a computational fluid dynamics code with a goal-driven optimisation algorithm. Results of the effect of Bejan number on the minimised peak temperature and minimised thermal resistance for solid substrate with varying axial lengths of 1 to 10 mm but fixed volume of 0.9 mm3 is presented. Results of optimal channel aspect ratio, solid volume fraction and channel hydraulic diameter of the microchannel were also presented.
- ItemOpen AccessConstructal flow orientation in conjugate cooling channels with internal heat generation(2012-11-06) Bello-Ochende, Tunde; Olakoyejo, Olabode Thomas; Meyer, Josua Prestorius; Bejan, Adrian; Lorente, Silvia
- ItemOpen AccessConstructal heat transfer and fluid flow enhancement optimisation for cylindrical micro-cooling channels with variable cross-section(Wiley, 2021) Olakoyejo, O.T.; Adelaja, A.O.; Adewumi, O.O.; Oluwo, A.A.; Bello, S.K.; Adio, S.A.This study applies constructal theory to conduct a numerical optimization of three‐dimensional cylindrical microcooling channels with the solid structure subjected to internal heat generation. The cylindrical channels are designed as variable cross‐section configurations that experience conjugate heat transfer and fluid flow, where water is used as the coolant. The research aims to optimize the channel configurations subject to a fixed global solid material volume constraint. The key objectives are to minimize the global thermal resistance and friction factor. The coolant is pushed through the channels by pressure drop represented as Bejan number. The main design parameters are the inlet and outlet diameters at a given porosity. The channel configuration and the structure elemental volume are permitted to change to find the best design parameters that minimized thermal resistance and friction factor, so that the cooling effect is enhanced. An ANSYS FLUENT code is used to obtain the best optimal parameter of the configuration that enhances thermal performance. The influence of Bejan number on optimized inlet and outlet diameters led to minimization of thermal resistance and friction factor and maximization of Nusselt number. The results show distinctive optimal inlet and outlet diameters that enhance the overall performance of the system in the range of 1.018 × 10−2 ≤ (din /L) opt ≤ 1.5381 × 10−2 and 1.0838 × 10−2 ≤ (dout /L)opt ≤ 1.6134 × 10−2, respectively.
- ItemOpen AccessConstructal optimisation of conjugate triangular cooling channels with internal heat generation(Elsevier, 2012-07-17) Meyer, Josua Prestorius; Olakoyejo, Olabode Thomas; Bello-Ochende, Tunde
- ItemOpen AccessDesign and development of a livestock feed pelleting machine(Faculty of Engineering, University of Lagos, Nigeria, 2009) Orisaleye, Joseph Ifeolu; Ojolo, Sunday J.; Fashina, A. B.Feeding pellets to livestock is advantageous to both the livestock and its farmer as it supplies the required nutrients to the livestock and is also economical. However, livestock feed pelleting equipment are known to be expensive and unaffordable particularly to the local farmer. A prototype of the pelleting machine was designed and developed for affordability. The machine was also tested to evaluate its performance. The machine consisted of a screw conveyor, die, barrel and hopper. It can be driven by an electric motor or a prime mover. The machine was tested with broiler’s mash and at different levels of moisture content using 500, 750 and 1000 cm^3 each of water and starch binder as preconditioners. The best pellets were formed using 750 cm^3 of either starch or water. The average specific energy consumption when 750 cm^3 of starch binder was used was 0.69 kWh/kg while it was 0.93 kWh/kg when water was used as preconditioner. The density of the pellets varied between 0.7 and 1 g/cm^3. This machine can be manufactured at a local machine shop for small-scale livestock farmers in developing countries.
- ItemOpen AccessDesign and development of cashew nut shelling machine(Emerald Group Publishing Limited, 2010) Ojolo, Sunday J.; Damisa, O.; Orisaleye, Joseph Ifeolu; Ogbonnaya, C.Purpose The purpose of this paper is to investigate the physical and mechanical characteristics of the roasted cashew nut during fracture, by subjecting the nut to varying impact load tests at different orientations to ascertain the critical impact load that fractures the shell without damaging the kernel within. This load value was correlated with other parameters; shell/kernel moisture content level, average nut mass, to determine the required projection velocity to achieve this force. This projection velocity is the critical factor in sizing and design of the optimum configurations of the shelling impeller. Design/methodology/approach Mechanical properties of roasted cashew nut were first determined to know their fracture points. Each component of the shelling machine was designed. The components were assembled and the machine was tested for performance. Findings Machine throughput capacity was determined as 15.57 kg/h; shelling efficiency was 95 per cent; and whole kernel recovery was 70 per cent. Practical implications The efficiency in terms of whole kernel recovery could be improved by improving the pretreatment measures on the nuts. Originality/value The paper presents a machine which is affordable to peasant farmers and requires little or no training for operation and maintenance. The advantage of reduced unit cost can be derived from large‐scale commercial production of this sheller.
- ItemOpen AccessDesign and development of cashew nut shelling machine(Emerald Group Publishing Limited, 2010-07-29) Ojolo, S.J.; Damisa, O.; Orisaleye, J.I.; Ogbonnaya, C.The purpose of this paper is to investigate the physical and mechanical characteristics of the roasted cashew nut during fracture, by subjecting the nut to varying impact load tests at different orientations to ascertain the critical impact load that fractures the shell without damaging the kernel within. This load value was correlated with other parameters; shell/kernel moisture content level, average nut mass, to determine the required projection velocity to achieve this force. This projection velocity is the critical factor in sizing and design of the optimum configurations of the shelling impeller. Mechanical properties of roasted cashew nut were first determined to know their fracture points. Each component of the shelling machine was designed. The components were assembled and the machine was tested for performance. Machine throughput capacity was determined as 15.57 kg/h; shelling efficiency was 95 per cent; and whole kernel recovery was 70 per cent. The efficiency in terms of whole kernel recovery could be improved by improving the pretreatment measures on the nuts. The paper presents a machine which is affordable to peasant farmers and requires little or no training for operation and maintenance. The advantage of reduced unit cost can be derived from large-scale commercial production of this sheller.
- ItemOpen AccessDesign and development of waste sorting machine(Scholarlink Research Institute, 2011) Ojolo, S. J.; Adelaja, A. O.; Orisaleye, J. I.; Kilankko, O.Nigeria is yet to develop a comprehensive scheme which is required to solve the current and persisting problem of waste management in the country. Whereas the crude methods of sorting wastes practiced may be efficient, it wastes useful time; hence the need for a mechanized sorting machine. An attempt has been made to develop a waste sorting machine, which is conceptualized to sort wastes into light materials, ferrous metals and other heavy materials. The machine is designed with the major components being the fan, the belt conveyor and the magnet. Tests carried out on the machine successfully classified wastes into light materials and heavy materials with inability to sort ferrous metals. Samples of wastes tested weighed 1.15kg and 3.53kg. The wastes consisted of an average of 32% of light materials and the time to sort the waste was 65 minutes per unit mass. This machine separates light materials such as paper, nylon, textile and heavy materials similar to nylon, ferrous and non ferrous metal, glass and paper sorted by the machine developed by Falayi et al. (2007) and the machine designed by Adzimah and Anthony (2009).