New generations of vapor compression refrigeration systems use natural refrigerants due to ecological concerns. Carbon dioxide (CO₂ or R744) stands out among them. Its application requires special measures due to high operating pressures and heat dissipation temperatures near and above the critical point. A numerical model of a transcritical refrigeration system with CO₂ has been developed, verified and validated for simulations in transient and steady operating conditions, using real properties for the refrigerant. Each component of the refrigerating system is described by its sub-model. Models of compressors and heat exchangers have been specially developed. Due to the specificity of CO₂ as a refrigerant and the operation of the system in the vicinity of the critical point, currently the most accurate fundamental equation of state of the actual refrigerant and its thermodynamic and transport properties is applied. Submodels were used to prepare simpler and faster models of specific components and were integrated into a simpler model of the entire refrigerating system for accurate, reliable, and much faster numerical simulations. Detailed component models include volumetric compressors: reciprocating compressors, rotary piston compressors and scroll compressors, and fin-and-tube heat exchangers. The models are structured according to the principles of object-oriented programming, in a way that allows flexible assembly of different configurations of transcritical refrigerating systems with CO₂ from its components, without the necessity for extensive external interventions into the structure of numerical simulation code. The developed model of the refrigerating system and its components was validated by comparison with experimental measurements. A very good agreement between the results of numerical simulations and experimental results has been achieved. Validated models were used to gain insight into the properties and efficiency of the system during transient operating conditions and to analyze several simpler improvements of the experimentally investigated CO₂ refrigerating system. Developed and validated models will be used for development of components and entire systems, as well as to determine the necessary data to increase the accuracy of simple and fast approximate models.