This book presents a systematic introduction, practical meaning, and measurement of thermo-physical properties (i.e. viscosity, density, thermal conductivity, specific heat capacity, and thermal diffusivity) associated with the Prandtl number. The method of slope linear regression through the data points is presented in this textbook as a methodology for a deeper and insightful scrutinization. The book serves as a reference book for scientific investigators, Teachers of Fluid Mechanics, Experts on Heat and Mass Transfer, Researchers on Boundary layer flows, Mechanical and Chemical Engineers, Physicists, and Postgraduate Students working on transport phenomena who need theoretical and empirical reviews on the impact of increasing the ratio of momentum diffusivity to thermal diffusivity. Features: A systematic overview of the state-of-the-art in statistical methodology for understanding changes between dependent and independent variables. Pointers to some theoretical and empirical reviews on Prandtl number. Presents in-depth analysis of various self-similar flows, emphasizing stretching induced flows, nanofluid dynamics, suction, injection, free convection, mixed convection, and forced convection. Insightful study on thermal radiation, heat sour, heat sink, energy flux due to concentration gradient, mass flux due to temperature gradient, thermo-capillary convection flow, Joule heating, viscous dissipation, thermal stratification, thermophoresis, and Brownian motion of particles.