Heat transfer is the movement of thermal energy from one object or substance to another due to a temperature difference. The three primary modes of heat transfer are conduction, convection, and radiation. Conduction occurs through direct contact, where kinetic energy is transferred from high-energy particles to adjacent lower-energy particles. This mode is prevalent in solids, especially metals, due to their tightly packed atomic structure. Convection involves the movement of fluid (liquid or gas) caused by temperature-induced density differences within the fluid. As the fluid heats up, it becomes less dense and rises, while cooler fluid sinks, creating a convective current. This process is critical in many natural phenomena and industrial applications, such as weather systems and heating systems. Radiation is the transfer of energy through electromagnetic waves and does not require a medium. All objects emit radiation proportional to their temperature, with hotter objects emitting more energy. The Sun’s heat reaches Earth through radiative heat transfer. Engineering, environmental science, and energy management are some of the various fields in which heat transfer is applied. They range from designing efficient thermal insulation and electronic cooling systems to improving energy efficiency in buildings and developing sustainable energy technologies. The book aims to shed light on some of the unexplored aspects of heat transfer and the recent researches in this field. Most of the topics introduced in this book cover new techniques and applications of heat transfer. For someone with an interest and eye for detail, this book covers the most significant topics related to heat transfer.