Department of Mechanical Engineering
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Browsing Department of Mechanical Engineering by Author "Adelaja, A.O."
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- 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 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 AccessFlow induced bifurcation and phase-plane stability analysis of branched nanotubes resting on two parameter foundation in a magnetic environment(Elsevier B.V, 2022) Yinusa, A.A.; Sobamowo, M.G.; Adelaja, A.O.This paper explores the nonlinear partial differential equations (PDEs) for transverse and longitudinal vibrations of slightly curved fluid-conveying embedded branched nanotubes operating in a magnetic environment. Using Bernoulli–Euler, Nonlocal and Hamilton theories, equations of motion governing the vibrations of the nanotubes are developed. Thereafter, the developed inimitable equations are solved using the numerical PDE solver and PDE-tool in MATLAB. With the numerical solutions, visualizations and parametric studies were carried out. The results indicate that increasing the branch angle at the downstream decreases quantitative stability. Furthermore, the stability results acquired via simulation point out that the magnetic field has a damping or attenuating influence of about 20%. The solutions as presented in this study match with existing results from previous studies, hence the verifications and validations of this work. It is envisioned that the results obtained will provide better physical insights into the stability criteria for carbon nanotubes and will enhance the designs of nanomechanical carbon nanotubes-based devices that convey fluid and operate in elastic and magnetic environments.
- ItemOpen AccessHeat Transfer Enhancement in a P-Shape Finned Radial Heat Sink Subjected to Natural Convection: Thermal Significance of Slot and Dimples in Fin, Journal of Engineering and Technology for Industrial Applications (ITEGAM-JETIA), 8(34), 12-19(ITEGAM-JETIA, 2022) Fetuga, I.A.; Olakoyejo, O.T.; Adelaja, A.O.; Gbegudu, J.K.This study presents the optimum design of the radial heat sink for light-emitting diode (LED) under natural convection. A radial heat sink with a hollow circular base and a P-shape fin type incorporated with either slots or both slots and dimples was numerically investigated using the ANSYS (Fluent) commercial code, with the aim of achieving better cooling performance at a lower heat sink mass. The average temperature (𝑇𝑎𝑣𝑔) and mass of the HS for various model designs, namely; Type A (HS with plain fin), Type B (HS with slot) and Type C (HS with both dimples and slot) were compared to select the best configuration. The effect of heat flux (700≤𝑞̇≤1900) on average temperature of radial heat sink was investigated. It was found that for all three models, the temperature difference between the HS and the ambient air of the fluid domain linearly increased with heat flux. At 𝑞̇=1900𝑊/𝑚2, when compared to Type A (HS with plain fins), Type C (HS with slot and dimples) models offered the best cooling performance, followed by Type B where the mass and average temperature of the heat sink is reduced by 13.7% and 5.1%, 8.3% and 1%, respectively.
- ItemOpen AccessNatural Convection Heat Transfer and Entropy Generation Analysis in Saltbox Roof under Summer Conditions(FUOYEJET, 2022) Ogwumike, T.E.; Olakoyejo, O.T.; Oloruntoba, F.T.; Musah, A.A.; Oyekeye, M.O.; Oluwatusin, O.; Oluwo, A.A.; Adelaja, A.O.This study investigates numerically the 2D laminar natural convection in a Saltbox roof type geometry under summer climate conditions as obtained in Africa, particularly Nigeria using ANSYS FLUENT to model the boundary conditions. The effects of Rayleigh number (Ra) within the range of 103-107 and pitch angles (top and base) on heat transfer, the flow structure, temperature distribution and entropy generation within the geometry were analysed. Results show that the flow is nearly symmetric at lower Ra, while for higher Ra, the flow becomes asymmetric. The Nusselt number (Nu) has a proportional relationship with the top pitch angle and an inverse relationship with the base pitch angle when the Rayleigh number is fixed. The effect of the Ra on the Nu is insignificant at lower Ra, but becomes noticeable at higher Ra. The total entropy generation increases with an increase in top pitch angle and a decrease in base pitch angles, at fixed Rayleigh numbers. The physical implication is that, for a Saltbox roof type geometry, at fixed Ra, the best convective heat transfer process is achieved by lowering the base pitch angle and increasing the top pitch angle.
- ItemOpen AccessNumerical study of the thermal performance and pressure drops of water-based Al2O3 - Cu hybrid nanofluids of different compositions in a microchannel heat sink(Microfluidics and Nanofluidics, 2022) Omosehin, O.S.; Adelaja, A.O.; Olakoyejo, O.T.; Oyekeye, M.O.This paper numerically investigates the effects of hybridization of water-based copper-alumina nanofluid on the thermal performance, pressure drop, and the figure of merit (FOM) inside a three-dimensional microchannel heat sink. The heat sink comprises a copper block with the top covered by a polycarbonate plastic (Lexan) to form a closed microchannel. A constant heat flux of 1.0 MW/m2 is applied at the base of the heat sink. The Reynolds number is varied between 400 and 1200 for different volume concentrations of alumina and copper nanoparticles of 0.5–3.0% vol. Simulation in ANSYS Fluent is performed with a two-phase Eulerian-Eulerian model using the finite volume approach to solve the conjugate heat transfer problem. Experimental validations of the numerical models are in very good agreement. Furthermore, the result shows that the higher the relative concentration of copper nanoparticles, the better the thermal enhancement and FOM of the hydridized nanofluid. For design and operational conditions, the maximum FOM favour the concentration of copper nanoparticle ≥ 0.75% for Re of 400 and < 0.75% vol. for Re of 1200.
- ItemOpen AccessThermal Energy Processes in Direct Steam Generation Solar Systems: Boiling, Condensation and Energy Storage(Frontiers, 2019) Dirker, J.; Juggurnath, D.; Kaya, A.; Osowade, E.A.; Simpson, M.; Lecompte, S.; Noori Rahim Abadi, S.M.A.; Voulgaropoulos, V.; Adelaja, A.O.; Dauhoo, M.Z.; Khoodaruth, A.; Obayopo, S.O.; Olakoyejo, O.T.; Elahee, M.K.; De Paepe, M.; Meyer, J.P.; Markides, C.N.Direct steam generation coupled is a promising solar-energy technology, which can reduce the growing dependency on fossil fuels. It has the potential to impact the power-generation sector as well as industrial sectors where significant quantities of process steam are required. Compared to conventional concentrated solar power systems, which use synthetic oils or molten salts as the heat transfer fluid, direct steam generation offers an opportunity to achieve higher steam temperatures in the Rankine power cycle and to reduce parasitic losses, thereby enabling improved thermal efficiencies. However, its practical implementation is associated with non-trivial challenges, which need to be addressed before such systems can become more economically competitive. Specifically, important thermal-energy processes take place during flow boiling, flow condensation and thermal-energy storage, which are highly complex, multi-scale and multi-physics in nature, and which involve phase-change, unsteady and turbulent multiphase flows in the presence of conjugate heat transfer. This paper reviews our current understanding and ability to predict these processes, and the knowledge that has been gained from experimental and computational efforts in the literature. In addition to conventional steam-Rankine cycles, the possibility of implementing organic Rankine cycle power blocks, which are relevant to lower operating temperature conditions, are also considered. This expands the focus beyond water as the working fluid, to include refrigerants also. In general, significant progress has been achieved in this space, yet there remain challenges in our capability to design and to operate high-performance and low-cost systems effectively and with confidence. Of interest are the flow regimes, heat transfer coefficients and pressure drops that are experienced during the thermal processes present in direct steam generation systems, including those occurring in the solar collectors, evaporators, condensers and relevant energy storage schemes during thermal charging and discharging. A brief overview of some energy storage options are also presented to motivate the inclusion of thermal energy storage into direct steam generation systems.
- ItemOpen AccessTransient solution of temperature field of conjugate laminar forced convection heat transfer in functionally graded hollow cylinder(Wiley, 2020-09-06) Fadipe, O; Adelaja, A.O.; Olakoyejo, O.T.this study, the numerical analysis of conjugate heat transfer of laminar flow in a functionally graded hollow cylinder (FGHC) made of metal/ceramic for a two‐dimensional fluid and wall conduction subject to Newton boundary condition is considered. The fluid and FGHC energy equations are coupled through the continuity of temperature and heat flux at the inner wall‐fluid interface while the outer surface is subject to convective heat transfer. The continuity, momentum, and energy equations of the fluid are discretized using the finite volume approach. The effects of fluid and functionally graded material parameters, such as volume fraction index, volume composition, time history, wall‐to‐fluid thermal diffusivity ratio, wall‐to‐fluid thermal conductivity ratio, Biot number, Peclet number, and Prandtl number are investigated on the temperature field in the FGHC. The result shows that on account of the inhomogeneity of the material property, the volume fraction index has a significant effect on the other parameters and the temperature variation along the thickness. The lower the volume fraction index, the higher the inner wall (metal side) temperature, and the temperature gradient along the thickness. However, except for the variation in the wall‐to‐fluid thermal conductivity ratio, the lower the volumetric fraction, the lower the outer wall (ceramic side) temperature distribution.