This comprehensive textbook highlights features of two phase flows and introduces the readers to flow patterns and flow maps. It covers a wide range of fundamental and complex subjects focusing on phase change processes like boiling, condensation or cavitation, and boiling phenomenon starting from pool boiling curves to heat transfer under nucleate boiling, film, and flow boiling. It also discusses themes such as numerical techniques for solving boiling and condensation as well as equipment used in industry for evaporation, boiling, and condensation. It includes pedagogical aspects such as end-of-chapter problems and worked examples to augment learning and self-testing. This book is a valuable addition for students, researchers, and practicing engineers.