This book is in two Parts, viz. Cryogenic Engineering: Software solutions – Part-III-A and Part-III B. and deals with the topic: Cryogenic refrigeration systems.Part-III-A contains a brief summary of background theory, formulas and the problems solved with Mathcad. Part-III B contains problems solved with Engineering Equation Solver (EES).In this book, several cryogenic refrigerators are explained briefly under two headings: (i) Refrigerators for temperatures above 2 K and (ii) Refrigerators for temperatures below 2 K.Many Functions are written in Mathcad to simplify the standard and most required calculations, and, several problems solved.Along with this free ebook, two ZIP files are available for free: ‘Cryogenic liquefn. systems – distributables’ and ‘Cryogenic refrign. systems – distributables’. They contain, totally 28 ‘stand- alone’ programs, originally written in EES.Students, teachers, researchers and professionals may find them very useful.