Handbook on Thermal Hydraulics in Water-Cooled Nuclear Reactors: Foundations and Principles is the 1st volume in a three-volume set edited by Professors Francesco D'Auria and Yassin Hassan. Based on the popular 2017 publication, Thermal-Hydraulics of Water-Cooled Nuclear Reactors, this first volume develops, updates and expands the existing chapters to reflect the latest research in the field, providing readers with an unrestricted analysis of the entire spectrum of the topic. End-of-chapter questions and exercises ensure the less experienced readers have a grasp of the content before moving on to more advanced topics. After a summary of the historical aspects of nuclear thermal hydraulics, the team of expert contributors explore balance equations, target phenomena, heat transfer, and guide the reader through various applicable experiments. This book is a valuable reference for graduate and undergraduate students of nuclear or thermal engineering, as well as researchers in nuclear thermal-hydraulics and reactor technology, engineers working in simulation and modeling of nuclear reactors, and engineers and technicians' nuclear settings. Nuclear operators, code developers and safety engineers will also benefit from the practical guidance provided.