Browsing by Author "Rehena Nasrin"

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3D numerical study of thermofluid characteristics of a flat plate solar collector using nanofluid
(Department of Mathematics (Math), 2015-08) Rehena Nasrin; Abdul Alim, Dr. Md.
Solar collector generation is growing quickly around the world to lessen some of the negative environmental impacts of the heating sector. The variability of these renewable sources of heat possesses technical and economical challenges when integrated on a large scale. One of the potential solutions to deal with the variations of renewable energy sources, energy storage is being widely regarded. An elaborate theoretical study on thermofluid characteristics of a nanofluid filled flat plate solar collector (FPSC) has been presented in this thesis. The relevant governing equations have been solved by using finite element method. In this thesis numerical analysis has been performed for better understanding of the heat transfer phenomena of the flat plate solar collector using water as well as water/copper nanofluid. Both 2D and 3D models of the flat plate solar collector (FPSC) have been taken into account. Heat transfer and flow characteristics have been presented for various pertinent parameters. Then comparison in various forms has been shown to check whether 3D study is necessary or not. Two correlations for heat transfer rate and thermal efficiency have been developed from obtained 3D results. Higher heat transfer rate of 3%, mean output temperature of 1.6K and collector efficiency of 5% have been obtained in 3D analysis than that of 2D analysis. Not more than 2% solid volume fraction of water/copper nanofluid has found to be advantageous. Suitable mass flow rate has obtained 0.0248Kg/s from this numerical study. More heat transfer rate of 17% and thermal efficiency of 8% has found for using 2% concentrated water/copper nanofluid than base fluid in 3D simulation. Water based nanofluid having double nanoparticles (copper and silver) has also been used as heat transfer medium instead of nanofluid having single nanoparticle (copper or silver) in 3D study to observe whether thermal efficiency of FPSC increases or not. Also a quadratic form of thermal efficiency has been derived using the results obtained from current 3D numerical study and compared with a survey report for a good FPSC available in the literature.
Effects of temperature dependent thermal conductivity on the coupling of conduction and joule heating with magnetohydrodynamic free convection flow along a vertical flat plate
(Department of Mathematics, BUET, 2009-08) Rehena Nasrin; Abdul Alim, Dr. Md.
In this dissertation, the effects of temperature dq)cndent lhenna1 conductivity on the coupling of conduction and Joule heating with viscous di>sipation and Magnctohydrodynamic free convection flow along a vertical flat plate have been investigated numerically. A steady laminar two dimensional MHD free convection flow is considered here. TIle gc}\'cming equations contain the equation of continuity. momentum and energy. TIlcse equations with associated bOlLndalYconditions for thi, phenomenon are converted to dimensionless fonn using suitable transformations. The transformed nonlinear ordinary differential equations are then solved using the imphcit tillite difference method wilh Keller-box scheme. FORTRAN 90 is used to perform computational job ami the post processing software TECPLOT ha, been used to display the numerical rcslllts graphically, The re,ults III lerms of skin frietioll and surface temperature profile for JOllie heating parameler J and viscou, dissipation parameter N are sho'Wnin tablllar form, Numerical results of the velocity profile, temperalure profile, skin friction coefficient and smfacc temperature profile, have been exhibited graphically for different values of lhe magnetic parameter M, thermal conductivity variation parameter ~ viscous dissipation pararnel~r 11-', JOllIehealing parameter J ,eparately "nd the Prandtl numher Pr as welL