1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Faculty of Science and Technology / Fakulti Sains dan Teknologi

Title:	Heatline analysis of mixed convection in a wavy cavity
Authors:	Fatin Munirah Azizul (P100371)
Supervisor:	Ishak Hashim, Prof. Dr.
Keywords:	Heat -- Convection Heat Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	22-Feb-2022
Description:	The heat transfer mechanism in natural and forced convection has been an important issue in computational fluid dynamics applications, such as architecture, chemical and process engineering, electronics and computer. The advancement of new technology has been taking place to improve heat transfer performances, hence several problems have been investigated in this thesis which involves inner solid blocks, a heat source, nanofluids, magnetohydrodynamics (MHD) and an inner rotating cylinder. The heat transfer behaviour and fluid flow patterns of mixed convection in a complex cavity having wavy wall surfaces have been investigated. Heatline visualisation offers a better illustration between streamlines and isotherms for observing the efficiency heat transfer progression. The trajectory of the heatline presented almost the same pattern with the field lines in a fluid flow on certain parameters. The heatline is mathematically known as the heat function, which is calculated from the concept of stream function, which correlates to the Nusselt number and satisfies the energy transport equation. The flow is considered to be Newtonian, two-dimensional, incompressible and laminar. The Newton's second law and first law of thermodynamics are derived from the conservation principles of mass, momentum and energy and expressed as nonlinear partial differential equations (PDEs) of Navier-Stokes equations. To solve these PDEs numerically, the finite element is used to solve the numerical model equations based on Galerkin weighted residuals in COMSOL Multiphysics software. To verify the computational simulation, validations have been done by comparing the published results and our works. The triangular mesh element, velocity profile fluid flow, temperature behaviour, thermal transportation, local and average Nusselt number are illustrated graphically. First, the impact of the direction of two-sided lid-driven walls on mixed convection in a wavy cavity is considered. The wavy bottom wall is heated, while the top wall is kept cold. The results show that left and right walls moving upwards and downwards, respectively, provide better heat transfer with one undulation designed at the bottom cavity. Secondly, alumina nanofluids inclusion in a wavy cavity with an inner solid block at the centre is considered. The top adiabatic wall moves to the right, while the wavy bottom wall is differentially heated with both vertical walls are in kept cold. The greater the concentration of nanofluids, the higher is the thermal conductivity supplied in the system. Furthermore, the problem is extended by placing an upright heat source at the middle bottom cavity with an upper surface is designed sinusoidal and assumed cold. The obtained result reveals that forced convection is improved at low value of the Richardson number, while natural convection is boosted at a high value of the Richardson number. In the fourth problem, triple fins arranged in the upwards ladder and subjected to a magnetic field with notable inclination is studied numerically. Two wavy surfaces are differentially heated with the left and right walls are in hot and cold temperatures, respectively. The study found that the magnetic field, signified by the Hartmann number, decreases the convective system and weakens the heat transfer rate. Finally, a rotating circular cylinder is placed at the centre of an inclined cavity with a top curved boundary maintained cold, and a wavy bottom wall is heated. It was found that a bigger rotating cylinder with a greater angular velocity narrows the space in the cavity and enhances fluid flow movement, thus improving the heat transfer process system.,Ph.D
Pages:	216
Call Number:	QC327.F338 2022 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.