Papers by Adekunle Adelaja
Partial Differential Equations in Applied Mathematics, 2021
World Journal of Engineering
Purpose Inclination angle has been reported to have an enhancing effect on the thermal-hydraulic ... more Purpose Inclination angle has been reported to have an enhancing effect on the thermal-hydraulic characteristics and entropy of some thermal systems. Therefore, this paper aims to numerically investigate the effects of inclination angle, volume concentration and Reynolds number on the thermal and hydraulic characteristics and entropy generation rates of water-based Al2O3 nanofluids through a smooth circular aluminum pipe in a turbulent flow. Design/methodology/approach A constant heat flux of 2,000 Watts is applied to the circular surface of the tube. Reynolds number is varied between 4,000 and 20,000 for different volume concentrations of alumina nanoparticles of 0.5%, 1.0% and 2.0% for tube inclination angles of ±90o, ±60o, ±45o, ±30o and 0o, respectively. The simulation is performed in an ANSYS Fluent environment using the realizable kinetic energy–epsilon turbulent model. Findings Results show that +45o tube orientation possesses the largest thermal deviations of 0.006% for 0.5%...
This paper investigates the heat transfer and pressure drop characteristics of mango bark-CO2 nan... more This paper investigates the heat transfer and pressure drop characteristics of mango bark-CO2 nanofluid. The physical model comprises flow in a pipe under a constant heat flux of-10W/m 2. The inclination angle varies between-90 o and +90 o , and volume fraction between 0% and 2.0% for Reynolds numbers of 50 and 100. The numerical code is validated using three research studies on heat transfer coefficient, Nusselt number, and pressure drop. Results show that the heat transfer coefficient and pressure increase with nanofluid volume concentration and Reynolds number. However, the heat transfer coefficient varies nonlinearly with the inclination angle and has a maximum occurring when the inclination angles are-30 o and +60 o while the pressure drop is relatively constant.
In this work, a numerical study is conducted to investigate the effects of hybrid nanofluid (Al2O... more In this work, a numerical study is conducted to investigate the effects of hybrid nanofluid (Al2O3-Cu/water) on the thermal and hydraulic performance of a three-dimensional double-layer counterflow microchannel heat sink. The heat sink comprises a silicon block to which a constant heat flux of q = 1.0 MW/m 2 is applied at the base. Different volume concentrations of alumina and copper nanoparticles are considered, with the Reynolds number varying between 200 and 1000. The conjugate heat transfer problem is solved numerically using the two-phase Eulerian-Eulerian model in ANSYS-Fluent environment. Experimental validation shows a good agreement between the numerical models and the experiment. Nanofluids exhibit higher heat transfer coefficients and pressure drops than the base fluid; however, nanoparticle hybridization has a minimal effect on the pressure drop.
This study employs machine learning techniquesrandom forest and extra trees-to predict the fricti... more This study employs machine learning techniquesrandom forest and extra trees-to predict the frictional pressure gradient during convective condensation in an inclined in-tube heat exchanger. The experimental data matrix (663) includes conditions for saturation temperatures of 30, 40, and 50 o C, mass velocity 100-400 kgm-2 s, quality 10-90%, and thirteen inclination angles between-90 o and +90 o for a smooth tube of an internal diameter of 8.38 mm. Based on statistical analysis, the extra trees outperforms the random forest. The average deviation (AD) and mean average deviation (MAD) are 2.88% and 6.72%, respectively, for random forest (RF) and 0.25% and 2.97%, respectively, for extra trees (ET).
Microfluidics and Nanofluidics
ITEGAM
This study presents the optimum design of the radial heat sink for light-emitting diode (LED) und... more 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 () 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 ≤̇≤ 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 ̇= 1900 / 2 , 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.
Journal of Emerging Trends in Engineering and Applied Sciences, 2011
This paper presents biodiesel production from non-edible jatropha oil by transesterification proc... more This paper presents biodiesel production from non-edible jatropha oil by transesterification process on a bench scale using sodium hydroxide (NaOH) as catalyst for the methanolysis of the jatropha oil. This study evaluated the effect of the concentration of the basic catalyst on the biodiesel yield. The biodiesel was evaluated for fuel properties and compared with the American Society for Testing and Material (ASTM) specification for biodiesel according to its physical, chemical and mechanical properties such as viscosity, flash point, density, sulphur content. The results show that the properties of the biodiesel produced was found to be within the limit of the ASTM specifications for biodiesel. At a catalyst concentration of 0.8%, reaction temperature of 65%, reaction time of 1 hour and methanol to oil molar ratio 5:1, the amount of biodiesel produced was 95.5%.
Journal of Thermal Analysis and Calorimetry, 2020
In this study, experiments were conducted for the flow of R-134a condensing in an enhanced inclin... more In this study, experiments were conducted for the flow of R-134a condensing in an enhanced inclined tube at a saturation condensing temperature of 40 °C. The enhanced tube had a helix angle of 14° with a mean internal diameter of 8.71 mm. The mass velocities were varied from 200 to 600 kg m −2 s −1 , while the inclination angles were varied from − 90° to + 90°. It was found that the inclination angle had a considerable effect on the flow patterns and the thermal performance. It was also found that the maximum heat transfer coefficients were obtained at tube inclinations of between − 15° and − 5° (downward flows). By using the experimental data and artificial neural networks (ANN), a model was proposed to predict the heat transfer coefficients during condensation inside the enhanced inclined tube. By using four statistical criteria, the performance of the proposed model was examined against experimental data, and it was found that ANN was a useful tool for the prediction of the heat transfer coefficients based on the effective parameters of vapour quality, mass velocity and inclination angle.
Advanced Materials Research, 2011
The need for renewable and environmentally friendlier energy sources has led to intensified effor... more The need for renewable and environmentally friendlier energy sources has led to intensified efforts with respect to research in that area. One of such endeavours is the production of biofuels from various sources of vegetable oils. Therefore, this work is aimed at producing biodiesel from freshly prepared and clean palm kernel oil and groundnut oil making use of methanol and sodium hydroxide pellets in a base-catalysed trans-esterification reaction. 185g groundnut oil and 187g palm kernel was trans-esterified with 37g of methanol and 0.7g of NaOH pellets at 55°C operating temperature. The result gave a percentage conversion of 91.98% for groundnut oil feedstock and 16.18g of glycerol (i.e. soap) as bye product, while palm kernel oil feedstock gave a yield of 90.53% conversion and 15.20g of glycerol. The biodiesel retained the physical properties of the oil such as smell and colour. The density of the biodiesel from groundnut oil was found to be 850.80kg/m3while that of palm kernel o...
Evaluating convective heat transfer performance in packed beds arising in various engineering pro... more Evaluating convective heat transfer performance in packed beds arising in various engineering problems is a complex issue due to the different parameters involved in the media, such as the bed materials, heat transfer mechanisms, packing structure and heat source. Apart from a number of assumptions made in various correlations developed for determining heat transfer performance in packed beds, literature survey also reveals that more experimental researches were conducted with fluid flowing in and out of the medium than heated fluid confined in an enclosed medium. Noted also is that most of the experimental research found in literature were conducted under forced convection compared with the investigation in the present study conducted under natural convection. In a quest to investigate the particle-to-fluid heat transfer characteristics expected in the proposed new fuel design, a basic unit cell (BUC) model is being developed for the theoretical analysis and applied to determine the heat transfer coefficient, h, of the medium. The model adopted a concept in which a single unit of the packed bed was analyzed and taken as representative of the entire bed; it related the convective heat transfer effect of the flowing fluid with the conduction and radiative effect at the finite contact spot between adjacent unit cell particles. As a result, the model could account for the thermophysical properties of sphere particles and the heated gas, the interstitial gas effect, gas temperature, contact interface between particles, particle size and particle temperature distribution in the investigated medium. Although the heat transfer phenomenon experienced in the experimental setup was a reverse case of the proposed fuel design, the study with the achievement in the validation with the Gunn correlation aided in developing the appropriate theoretical relations required for evaluating the heat transfer characteristics in the proposed nuclear fuel design.
This paper evaluates the feasibility of CO2 storage in depleted hydrocarbon reservoirs using 3-D ... more This paper evaluates the feasibility of CO2 storage in depleted hydrocarbon reservoirs using 3-D seismic and well data with particular reference to the Niger Delta. CO2 sequestration is a fundamental measure for decreasing greenhouse gas emissions. Based on the papers reviewed, the presence of reservoir-seal pairs, traps, faults, lateral continuity of reservoir, appropriate reservoir depth, developed hydrocarbon fields, and availability of massive hydrocarbon fields indicates a high potential for CO2 sequestration in the Niger Delta. The paper concludes that the estimations of the injection rate and injection pressure are essential considerations for CO2 sequestration and highlights the challenges and opportunities of future research.
The need for energy supply, particularly electricity, has been on the increase in the last two de... more The need for energy supply, particularly electricity, has been on the increase in the last two decades in developing countries such as Nigeria. Economic and industrial developments have led to this increase in demand for electricity. In universities, much of the electricity consumption is consumed in air conditioning systems, which are used to overcome the indoor thermal discomfort during harsh seasons. An amount of electricity is also consumed by laboratory equipment and machinery used for practical and demonstrations. Thus, if universities are to achieve the goals of teaching, research and community service, then proper management of electricity supplied to the system is needed in view of its limited availability. Since electrical energy in Nigeria is highly subsidised by the government, monitoring and controlling the energy consumption pattern in a university is a major aim in the country. However, there is still a lack of information about electricity end-use consumption in Nige...
The Journal of Engineering and Exact Sciences
In this study, a 3D computational fluid dynamics (CFD) study was conducted in ANSYS (FLUENT) to e... more 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 H2Oand ethylene glycol (EG) in the volumetric proportion of , 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 i...
Correlation models for the prediction of condensation heat transfer performance of inclined smoot... more Correlation models for the prediction of condensation heat transfer performance of inclined smooth tubes are very scarce in literature. Most of the available models are limited to horizontal and vertical tube orientations. This paper presents a correlation model for the prediction of heat transfer coefficient during the convective condensation of R134a in a smooth inclined tube-intube condensing heat exchanger subject to diabatic conditions. The authors, in previous investigations presented the experimental data which have been used for the development of the proposed model. In this particular study, the test matrix comprises 260 data test points for inclination angles varying between -90 degrees (downward flow) and + 90 degrees (upward flow), for mass fluxes between 100 kg/m 2 s and 400 kg/m 2 s, mean vapour qualities between 0.1 and 0.9 at saturation temperature of 40°C. In the developed model, the effects of the independent variables such as mean vapour quality, mass flux and inc...
The need for energy supply, particularly electricity, has been on the increase in the last two de... more The need for energy supply, particularly electricity, has been on the increase in the last two decades in developing countries such as Nigeria. Economic and industrial developments have led to this increase in demand for electricity. In universities, much of the electricity consumption is consumed in air conditioning systems, which are used to overcome the indoor thermal discomfort during harsh seasons. An amount of electricity is also consumed by laboratory equipment and machinery used for practical and demonstrations. Thus, if universities are to achieve the goals of teaching, research and community service, then proper management of electricity supplied to the system is needed in view of its limited availability. Since electrical energy in Nigeria is highly subsidised by the government, monitoring and controlling the energy consumption pattern in a university is a major aim in the country. However, there is still a lack of information about electricity end-use consumption in Nige...
Engineering and Applied Science Letters
The high strength-to-weight ratio and flexibility of single walled carbon nanotubes (SWCNT) make ... more The high strength-to-weight ratio and flexibility of single walled carbon nanotubes (SWCNT) make them of potential use in the control of nanoscale structures for thermal, electrical, structural and mechanical applications. This indicates that they will have a vital contribution to nanotechnology engineering. This paper presents an exact solution to the dynamic response of such CNTs considering the shear force and bending moment under uniformly distributed external pressure. The dynamic behaviour of the SWCNT is modeled by employing the theories of Euler-Bernoulli beam and thermal elasticity mechanics. The developed model that governs the physics of the behaviour of the SWCNT when excited by the aforementioned external agents is solved using Integral transforms. The results of the close form solution in this work were compared with results of past works and excellent agreements were achieved. Furthermore, the dynamic study revealed that a point of maximum shear force on the CNT produced the minimum bending moment at any mode and for any parameter value considered. It is envisaged that this work will enhance the application of SWCNT for structural, electrical and mechanical uses.
Advanced Materials Research, 2011
Most of the attempts made at designing shell and tube heat exchangers have been limited to therma... more Most of the attempts made at designing shell and tube heat exchangers have been limited to thermal hydraulic design. This study however, considers both the thermal and mechanical design of the E-type shell and tube heat exchanger with the aid of computer programming. It involves developing a simple user-friendly computer programme for the heat transfer calculations and ensures that the computational time is kept minimal. The algorithm is designed such that after the conditions for the thermal analysis are satisfied, the programme automatically proceeds to the mechanical design. The programme written in Visual Basic was tested using a model and the simulated result presented.
The present paper reports on the two-phase frictional pressure drop calculated during the condens... more The present paper reports on the two-phase frictional pressure drop calculated during the condensation of R134a in a tube of inner diameter of 8.38 mm at different inclination angles. The pressure drops were calculated using the most recent void fraction model of Bhagwat and Ghajar. The condensation tests were carried out in an experimental test facility with a 1.704 m distance between the differential pressure taps. The operating conditions were for mass fluxes of 200 kg/ms and 300 kg/ms, mean vapour qualities between 0.25 and 0.75, a saturation temperature of 40°C and for inclination angles ranging between -90° (downward flow) and +90° (upward flow). The highest values of the void fractions and frictional pressure drops were obtained during the vertical downward flow while the lowest were obtained during the vertical upward flow. INTRODUCTION In the design and optimization of heat exchangers such as found in refrigeration, petroleum industries, processing, nuclear and thermal powe...
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Papers by Adekunle Adelaja