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Title:	Numerical simulations of fluid flow and heat transfer in a porous square enclosure
Authors:	Alhashash Abeer (P63568)
Supervisor:	Ishak Hashim, Prof. Dr.
Keywords:	Porous medium Heat transfer Fluid Dissertations, Academic -- Malaysia
Issue Date:	16-Jun-2015
Description:	Understanding of flow, temperature distributions and heat transfer processes in porous medium is valuable in resident environmental, industrial and engineering applications. To fulfill an optimal heat transfer process in residential, industrial and engineering systems by increasing or decreasing the heat transfer rate is a major question for the ordinary people, scientists or engineers. To answer the question, the effects of a wall thickness, thermal conductivity ratio, heat source length, inter-phase heat transfer coefficient, radiation, viscous dissipation, internal heating, exponent of the local heating, inclination angle of the enclosure, nanoparticles types, solid volume fraction were studied in this thesis. Fluid was considered as Newtonian, two-dimensional, incompressible, laminar, and Oberbeck-Boussinesq approximation was used for density variation. Nanoparticles were assumed in a spherical shape, and Rosseland approximation was applied for radiation. As for the porous medium, Darcy law was assumed to hold and the porous material was taken to be homogenous and isotropic. In this thesis, there were four main problems being considered which took into account all the different effects, fluids and medium as mentioned above. All these problems were as discussed in Chapters IV to VII in this thesis. The governing equations and boundary conditions were nondimensionalised to form a system of nonlinear partial differential equations (PDEs). Finite difference method (FDM) with Gaussian scheme was used to solve the elliptic PDE. FDM, with an alternating direct implicit (ADI) scheme and a tridiagonal matrix algorithm (TDMA), was used to solve the parabolic PDE. All the numerical schemes were programmed in MATLAB. Validation studies to the previously published problems were carried out to verify the robustness and the accuracy of the present computations. The numerical results of the flow and the variables of the temperature, as well as the rates of heat transfer, were presented graphically. A critical thickness of the wall existed at the conjugate convection problem, below whereby increasing the thickness increases the average Nusselt number, and above whereby increasing the thickness decreases the average Nusselt number. The thermal radiation and the internal heat generation did not play any crucial role on the critical thickness. In thermal nonequilibrium model, the shape of the isotherms from the solid phase was found to be stagnant by varying the orientation angles at small inter-phase heat transfer coefficient and low modified conductivity ratio. There exists a critical modified conductivity ratio below whereby increasing the modified conductivity ratio increases the average Nusselt number at hot wall, and above whereby increasing the modified conductivity ratio decreases the average Nusselt number at hot wall. Finally, it had been concluded that the significant effect of adding nanoparticles in enhancing a steady heat transfer was obtained at high orientation angle.,Pemahaman mengenai corak aliran, corak suhu dan proses pemindahan haba adalah bernilai bagi sekitaran rumah, penggunaan industri dan kejuruteraan. Untuk mencapai proses pemindahan haba yang optimum dalam sistem perumahan, industri dan kejuruteraan dengan penurunan atau peningkatan kadar pemindahan haba merupakan suatu pertanyaan utama bagi orang awam, saintis dan jurutera. Bagi menjawab pertanyaan itu, kesan dinding berkonduksi, pemanasan boleh berubah, penyejukan Newton, nanobendalir, penjanaan haba dalaman, sinaran dan lesapan likat dikaji dalam tesis ini. Bendalir dipertimbangkan adalah Newtonan, dua dimensi, tidak termampatkan, lamina dan penghampiran Oberbeck-Boussinesq digunakan untuk perubahan ketumpatan. Nanozarah diandaikan berbentuk sfera dan penghampiran Rosseland digunakan untuk sinaran. Untuk medium berliang, hukum Darcy adalah sah dan bahan berliang diandaikan homogen dan isotropik. Dalam tesis ini, terdapat empat masalah utama yang dipertimbangkan dengan mengambil kira kesan bendalir dan mendium berbeza seperti yang dinyatakan di atas. Empat masalah tersebut adalah seperti yang dibincangkan dalam Bab IV hingga VII dalam tesis ini. Persamaan menakluk dan syarat sempadan dinyahdimensikan yang akhirnya membawa kepada sistem persamaan terbitan separa (PTS) tak linear. Kaedah beza terhingga (KBT) dengan skema Gaus digunakan untuk menyelesaikan PTS itu. KBT dengan skema tersirat langsung selang-seli (TLSS) dan al-Khwarizmi matriks tiga pepenjuru (AMTP) diguna untuk menyelesaikan PTS. Seluruh skema berangka diaturcara dalam MATLAB. Kajian pengesahsahihan dengan masalah sebelumnya dilakukan bagi memastikan keteguhan dan ketepatan pengiraan dalam tesis ini. Keputusan-keputusan berangka bagi aliran dan suhu serta kadar pemindahan haba dipaparkan secara bergraf. Ketebalan dinding genting wujud pada masalah olakan konjugat, jika di bawahnya pertambahan ketebalan menaikkan nombor Nusselt purata dan jika melebihinya pertambahan ketebalan menurunkan nombor Nusselt purata. Sinaran terma dan haba dalaman tidak memainkan peranan penting pada ketebalan genting. Untuk model tak seimbang terma, bentuk isoterma daripada fasa pepejal didapati menjadi genang dengan perubahan sudut orientasi pada pekali pemindahan haba antara fasa yang kecil dan nisbah kekonduksian terubah suai rendah. Nisbah kekonduksian terubah suai genting wujud, jika di bawahnya pertambahan nisbah kekonduksian terubah suai menaikkan nombor purata Nusselt pada dinding panas dan jika melebihinya pertambahan nisbah kekonduksian terubah suai menurunkan nombor Nusselt purata pada dinding panas. Akhir sekali, dapat disimpulkan bahawa kesan penambahan nanozarah dalam menaikkan pemindahan haba mantap diperoleh pada sudut orientasi tinggi.,Ph.D
Pages:	140
Call Number:	QC173.4.P67 A439 2015
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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