The textbook "Numerical Modelling of Thermoacoustic Heat Pumps and Engines" offers a comprehensive analysis of thermoacoustic systems without stacks, which are considered a promising alternative to conventional stack-based systems. It investigates both theoretically and experimentally how these systems can operate more efficiently and generate more acoustic power. The author, Behrang Asgharian, presents a simplified Lagrange model for analyzing standing waves in stackless thermoacoustic configurations. Additionally, more precise simulations are conducted using Computational Fluid Dynamics (CFD) to optimize the efficiency of these systems. The results show that the second law efficiency can reach up to 55%, and a good agreement is found between the simplified model and the CFD results. This book is aimed at professionals and students in the fields of engineering and IT who are interested in innovative approaches in thermoacoustics.