This book presents select proceedings of the International Conference on Advances in Fluid Flow and Thermal Sciences (ICAFFTS 2021) and summarizes the modern research practices in thermal sciences and engineering. The content of book involves advanced topics in heat transfer science, automobile, refrigeration and air conditioning, cryogenics, non-conventional systems and energy storage. Topics on cutting edge research in the area of hybrid nano-PCM-based systems, solar-based applications, bio-diesel and nano additives-based combustion, fuel cell and thermoacoustic engine are also included. In addition, this book contains recent research in the area of two-phase thermal management of Li-Ion/Li-titanium battery and LED systems using heat sink, heat pipe, pulsating heat pipe and thermosyphon with next-generation refrigerants, PCM and nanofluid. Some thermal aspects of virus/aerosol research, advances in volumetric velocimetry and application of artificial intelligence in thermal systems are also covered. This book is a valuable reference for academicians, researchers and professionals working in the various fields of thermal sciences.