This book presents a selection of preliminary sizing procedures for turbomachinery. Applicable to both conventional and non-conventional fluids, these procedures enable users to optimize the kinematics, thermodynamics and geometry of the turbomachinery (in the preliminary design phase) using geometric correlations and losses models; to accurately predict the efficiency of turbomachinery – in most cases, in excellent agreement with CFD calculations; and to consistently analyze all turbomachines (axial and radial turbines, axial and centrifugal compressors, centrifugal pumps). The book is intended for bachelors and masters students in industrial, mechanical and energy engineering, as well as researchers and professionals in the energy systems and turbomachinery sectors, guiding them step by step through the first sizing of turbomachines and the verification of the technological feasibility of turbomachines designed for new conversion systems operating with unconventional fluids.