The last couple of decades have seen a significant growth in the use of mathematical methods for modelling in natural and engineering sciences. Among a great variety of engineering problems that have successfully been dealt with, the heat transfer problems belong to the most challenging. They can be considered as separate type of engineering problems offering information how industrial objects should be heated or cooled. However, even more frequently, the heat transfer processes are coupled with other physical processes and this results in so-called multi-physic approach to engineering problems. All matter is made up of molecules and atoms. These atoms are always in different types of motion (translation, rotational, vibrational). The motion of atoms and molecules creates heat or thermal energy. All matter has this thermal energy. The more motion the atoms or molecules have the more heat or thermal energy they will have. Heat can travel from one place to another in three ways: Conduction, Convection and Radiation. Both conduction and convection require matter to transfer heat. If there is a temperature difference between two systems heat will always find a way to transfer from the higher to lower system. This book addresses modelling, numerical methods, simulation and information technology with modern concepts and methods to investigates and enhance heat transfer for single and multiphase systems. The combination of fundamental approach with several imperative practical applications of current interest will make this book useful to researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modelling, inverse problems, implementation of recently developed numerical methods in this wide-ranging field along with experimental and theoretical researchers in the field of heat and mass transfer.