Heat and Mass Transfer Analysis in Newtonian and non-Newtonian Fluids Using Finite Difference Approach
This dissertation is an attempt to analyze the heat and mass transfer in Newtonian and non-Newtonian nanofluids flowing in different physical channels and sheets. The non-Newtonian nanofluid models of micropolar fluids are employed to highlight the thermal transportation in such fluids. Single phase nanofluid model; Tiwari-Das and Buongiorno nanofluid models are used in the study. Water is used as the base fluid in single phase models and the nanoparticles used are Cu and Al2O3. Magnetic field is used to influence the nanofluid flow and its impact on the heat transfer is observed. The application of magnetic field prompts Joule heating effect which is added to the mathematical modeling of the models. Also viscous dissipation effect is considered in all the three problems to find out the internal heat generated during the movement of the fluid. An additional equation of angular momentum is used to observe the impact of microstructures present in the micropolar fluid. The Maxwell equations of electromagnetism are included to tackle the induced magnetic field effects. Other aspects of the study involve convective boundary conditions and the induced magnetic field effects. The governing equations of mathematical models are nondimensionalized into the ordinary differential equations by applying suitable similarity transformations. The system of ordinary equations are then solved by a valuable finite difference scheme called the Keller box method.The Matlab code for Keller box method is developed and its verification is done by reproducing the work already published in different journals. The numerical results are analyzed by variation in important parameters using line, 3D graphs and tables of numerical values.
It is observed that an increase in the volume fraction of nanoparticles decreases the temperature of the nanofluid flowing between two parallel plates with upper plate moving vertically and lower plate stretching horizontally. Greater Brownian motion of the nanoparticles rises the temperature but decreases the concentration of the nanofluids, in a flow of micropolar nanofluid pertaining over a stretching sheet. However for a flow of micropolar nanofluid between parallel plates, the linear as well as the angular velocity of the nanofluid diminishes with a rise in the rotational viscosity parameter.