Browsing by Author "Mutuku, Winifred Nduku"

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    Analysis of Water, Ethylene and Propylene Glycol-Based Nanofluids for Optimal Radiator Coolant
    (International Journal of Fluid Mechanics & Thermal Sciences, 2023-09) Kisengese, Hilder Mary; Mutuku, Winifred Nduku; Makau, Kimulu Ancent
    Convection is the spontaneous movement of fluid phases, either single or multiple, driven by interactions with heterogeneous material properties and body forces such as density and gravity. This movement of heated fluid facilitates heat transfer within a system. Natural convection finds applications in heat dissipation, air conditioning, and microelectronics. However, industrial fluids commonly used for heat transfer, such as minerals, oil, water, and ethylene glycol (EG), face limitations due to their low thermal conductivities, hindering heat exchange efficiency. The production of efficient cost-effective cooling systems for automotive engines is a significant challenge in the automobile industry. Most engines depend on fluid for cooling and therefore use liquid coolants such as ethylene glycol and water, but with poor heat transmission properties. Nanoparticles, which have been shown to improve thermal conductivity, enhance the thermal properties of the fluids. This study compares six different radiator coolants; water-CuO, Propylene-glycol-CuO, ethylene-glycol-CuO, water-MgO, Propylene-glycol-MgO, and ethylene-glycol-MgO. Nanoparticles exhibit improved thermophysical qualities and therefore nanofluids are used as coolants in various mechanical and engineering contexts, including, but not limited to electronics, vehicles, transformers, computers, and electrical devices. The similarity transformation is utilized to non-dimensionalise the governing equations. The resulting equations are solved using a numerical method with the Runge-Kutta fourth-order method. The results show that water-based nanofluids provide the best coolant. However, when the radiator is close to the magnetic field emerging from the automobile engines, copper oxide or Magnesium oxide nanoparticles should be used with water as base fluid.
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    Double stratification effects on heat and mass transfer in unsteady MHD nanofluid flow over a flat surface
    (SpringerOpen, 2017) Mutuku, Winifred Nduku; Oluwole, Daniel Makinde
    The focus of this work is to theoretically investigate the problem of double stratification on heat and mass transfer in an unsteady hydromagnetic boundary layer flow of a nanofluid over a flat surface. The model employed for the nanofluid transport equations incorporate the effects of Brownian motion and thermophoresis in the presence of thermal and solutal stratification. The governing nonlinear partial differential equations and their associated boundary conditions are initially transformed into dimensionless form by using similarity variables, before being solved numerically by employing the Runge–Kutta–Fehlberg fourth-order method with shooting technique. The effects of different controlling parameters, viz. solutal and thermal stratification, Lewis number, thermophoresis, Brownian motion, magnetic field and unsteadiness on the fluid velocity, temperature, skin friction coefficient, the local Nusselt number, and the local Sherwood number are graphically depicted and quantitatively discussed in detail taking into account the practical applications of each profile. It is noted that thermal stratification reduces the fluid temperature, while the solutal stratification reduces the nanoparticle concentration.
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    Numerical Analysis of Heat Transfer of Eyring Powell Fluid Using Double Stratification of Magneto-Hydrodynamic Boundary Layer Flow
    (Asian Research Journal of Mathematics, 2020) Waswa, Simon Wekesa; Mutuku, Winifred Nduku
    Heat transfer fluids play a vital role in many engineering and industrial sectors such as power generation, chemical production, air-conditioning, transportation and microelectronics. Aim: To numerically investigate the effect of double stratification on magneto-hydrodynamic boundary layer flow and heat transfer of an Eyring-Powell fluid. Study Design: Eyring-Powell fluid is one of the non-Newtonian fluid that possess different characteristics thus different mathematical models have been formulated to describe such fluids by appropriate substitution into Navier-Stoke’s equations. The challenging complexity and the nature of the resultant equations are of great interest hence attract many investigations. Place and Duration of Study: Department of Mathematics and Actuarial Science, Kenyatta University, Nairobi, Kenya between December 2019 and October 2020. Methodology: The resultant nonlinear equations are transformed to linear differential equations by introducing appropriate similarity transformations. The resulting equations are solved numerically by simulating the predictor-corrector (P-C) method in matlab ode113. The results are graphically depicted and analysed to illustrate the effects of magnetic field, thermophoresis, thermal stratification, solutal stratification, material fluid parameters and Grashoff number on the fluid velocity, temperature, concentration, local Sherwood number and local Nusselt number. Results: The results show that increasing the magnetic field strength, thermophoresis, thermal stratification and solutal stratification lead to a decrease in the fluid velocity, temperature, Sherwood number, Nusselt number and skin friction while an increase in the magnetic field strength, thermal stratification, solutal stratification, and thermophoresis increases the fluid concentration. Conclusion: The parameters in this study can be varied to enhance heat ejection of Eyring-Powell fluid and applied in industries as a coolant or heat transfer fluid.
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    Thermal Radiation on Darcy Forchheimmer Flow of a Casson Nanofluid
    (2024-06) Loco, Valerie Sasha; Mutuku, Winifred Nduku
    Owing to Casson nanofluids’ enhanced thermophysical properties, it has a wide range of applications in the fields of mining, drilling operations, material science, metallurgy, food manufacturing, and nanotechnology and bio-engineering. Casson fluid is frequently modelled since the model has a great agreement with the rheological evidence about human blood. Some of its applications in technological, industrial, mechanical, and scientific disciplines include; grain storage, geothermal energy production, designing warm protectors, artificial dialysis, catalytic converters, circulation of water in reservoirs and fermentation processes. On the other hand, radiation heat transfer mechanism has an immense impact in industries, engineering, technological fields where apparatus operate at extremely high temperatures. In this paper, the effects of thermal radiation on Darcy Forchheimer flow of a two- dimensional, steady, incompressible flow of Casson Nanofluid over a linear stretching surface are studied. The equations governing the fluid flow are formulated, then transformed to a system of ordinary differential equations using similarity variables then, the resulting ordinary differential equations are solved using the fourth order Runge- Kutta Method. The model is simulated using MATLAB bvp4c to demonstrate the impact of pertinent parameters on the temperature, velocity, and concentration of the fluid. It was observed that an increase in the thermophoretic parameter leads to an increase of the temperature at the boundary. The concentration of the fluid decreases with an increase porosity parameter value. Increasing the Brownian Motion parameter leads to an increase in concentration. An increase in Schmidt number leads to a decrease in temperature. Schmidt number increases with a decrease in concentration. The velocity and temperature profiles decrease with an increase in porosity parameter and an increase in thermal radiation leads to an increase of heat energy on the surrounding of a system leading to a decrease in fluid’s flow temperature.