Mechanical Engineering-Scholarly Publications

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Browsing Mechanical Engineering-Scholarly Publications by Author "Adewumi, O.O"

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    Open Access
    Analysis 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.P
    This 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.
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    Open Access
    Characterization 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.
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    Open Access
    Constructal 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.P
    This 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.
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    Open Access
    Constructal 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.P
    The 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.
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    Open Access
    Increased heat load effects on the thermal performance of single- and two-layered microchannels with varying axial length and micro pin-fin inserts
    (International Journal of Fluid Mechanics Research, 2016-04-29) Bello-Ochende, T.; Adewumi, O.O; Meyer, J.P
    This study investigates numerically the effect of increasing heat load on thermal performance of six different heat sinks. The heat sinks examined were the single-layered microchannel, two-layered microchannel with parallel and counter-flow configurations, single-layered microchannel with micro pin-fin inserts and the two-layered microchannels with micro pin fins inserts and different flow configurations. The objective of this investigation was to identify the heat sink that performs best under high heat load conditions. The thermal performance was based on two criteria namely, minimised peak temperature and minimised temperature rise on the heated base of the solid substrate. The heat load on the heated base was increased from 100 to 1000 W and results obtained showed that inserting micro pin fins into the microchannels enhances the thermal performance of the heat sink under increased heat load. Also, for the highest heat load of 1000 W and lowest pressure drop of 10 kPa considered, the single-layered microchannel with six rows of micro pin-fin inserts performed best in minimising temperature rise on the heated base while the two-layered microchannel with four rows of micro pin-fin inserts performed best in minimising peak temperature.
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    Open Access
    Numerical investigation into the thermal performance of single microchannels with varying axial length and different shapes of micro pin-fin inserts
    (Heat Transfer Engineering, 2016-09-26) Adewumi, O.O; Bello-Ochende, T.; Meyer, J.P
    This study investigates numerically the thermal performance of combined microchannel heat sink with micro pin-fins with different cross-sectional shapes. The objective of this study is to investigate the best geometric configuration that maximizes the heat transfer from the heated base when the combined heat sink is subjected to a steady, laminar, incompressible convective fluid flow and heat transfer. The axial length of the solid substrate and microchannel is varied from 1 to 10 mm with fixed total volume of 0.9 mm3 while the number of rows of the different shapes of micro pin-fins was varied between three and seven. It was observed that best performance is obtained with a sixth row of circular-shaped micro pin-fins for the optimized combination of the microchannel and micro pin-fin heat sink. Results of the optimal axial length for fixed pressure drop range are also presented.
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    Open Access
    Numerical investigation of the performance of fibre-glass/talc filled epoxy composite as insulator in heating applications
    (Journal of Computational Applied Mechanics, 2019) Zelibe, C.G.; Adewumi, O.O; Onitiri, A.
    This study investigates experimentally and numerically the performance of fibre-glass/talc filled epoxy as an insulator in domestic heating application. The epoxy composites with micro filler (talc) and fibre glass used in this investigation were cured at temperatures of 50°C, 75°C, 100°C, 125°C and 150°C at a constant holding time of 120 minutes. A total of 40 composite specimen were tested and investigated in this paper. Thermal properties of the different composites at their specific cured temperatures are determined using a kd2 pro thermal analyser. The thermo-physical properties measured are the thermal conductivity, volumetric heat capacity and density of the composites. A computational fluid dynamics tool (ANSYS 15.0) was used to model a domestic cooking pot and run various simulations using the thermo-physical properties of the composites to study how the Fibre reinforced polymer (FRP) composites perform when compared Bakelite as the heat insulator handles of the modelled pot. Results obtained showed that 10 of this composites at different cured temperature performed better than Bakelite, with the 2E composite cured at 125°C (125°C- 2E), being the best performing composite out of the 40 specimen investigated, having insulated about 30°C of heat compared to Bakelite with 24.4°C. It was observed that all the composites insulated heat above 20°C which is a considerable value for this form of domestic heating application, and thus fibreglass talc filled epoxy can be recommended for domestic heating insulation over existing material with advantageous qualities such as light weight, naturally occurring, cost effectiveness and availability.
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    Open Access
    Scale analysis and asymptotic solution for natural convection over a heated flat plate at high Prandtl numbers
    (Proceedings of the Romanian Academy, 2018) Adewumi, O.O; Adebusoye, A.; Adeniyan, A.; Ogbonna, N.; Oyediran, A.A
    This study presents a free convection flow over a heated flat plate using Bejan’s method of scale analysis for balancing forces. For Newtonian fluids of large Prandtl numbers, two different layers which are the thermal and velocity boundary layers exist. The thermal boundary layer is thinner than the velocity boundary layer. The method of matched asymptotic expansion is used to obtain the velocity and temperature within the two layers and these quantities are then matched at the interface. A 5–5 matching is used to obtain both inner and outer solutions for velocity and temperature. A natural small parameter in this problem is the inverse of the square root of the Prandtl number multiplying the highest derivative. In the Bejan formulation for large Prandtl number flows, the two dimensionless quantities that emerge are the Rayleigh and Prandtl numbers as opposed to the Grashof and Prandtl numbers obtained in previous works. The results of velocities, temperature, shear stress and Nusselt number presented in this study are for fluids that have Prandtl numbers ranging 10 to 100,000. The Nusselt number predicted as Prandtl number goes to infinity, approaches the same asymptote as in previous works, while there's about 30% difference in the skin friction predicted when the differences in scaling used are not taken into consideration.
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    Open Access
    Thermal model and experimental validation of IRF 3205 MOSFET switches for inverter applications
    (2018-03-05) Onoroh, F.; Enibe, S.O; Adewumi, O.O
    Power inverters operate under dynamic loads; the varying loads cause thermal expansion and contraction, which stress the internal boundaries between the material layers in the semiconductor. Eventually, the stress wears out the semiconductor module which ultimately leads to thermally induced failure. The primary goal of this article is to present thermal model for the IRF 3205 MOSFET chip switching operation for a power inverter. The solution of the models is implemented in MATLAB R2013a environment to obtain the transient temperature profile. The transient device temperatures are recorded with a K-type thermocouple and a three channel temperature logger, MTM-380SD, with real time data logger. Results show that the experimental steady state temperatures are lower than the simulated steady state temperatures by 1.10, 1.52, 1.17 and 0.73% for pulse loads of 460W, 675W, 1015W and 1500W, respectively.