The requirements of European regulations on energy efficiency of buildings, the use of renewable energy sources and the phase out of fluorinated hydrocarbons demand urgent changes in the design of refrigeration systems and heat pumps. Refrigeration systems are designed and optimized for the refrigerant they use. Majority of refrigerants currently used are fluorinated hydrocarbons, whose application by 2030 will have to be reduced to 21% of the 2014 consumption level, which poses a problem to the industry that needs to develop new systems. Costs for the development of new systems adapted to new emerging refrigerants can be reduced by applying numerical simulations, provided that detailed numerical simulation models are developed whose degree of complexity provides results that provide a good picture of the possibility of applying some of the refrigerant in the refrigerating system or a heat pump of a certain construction and purpose. Former scientific research and the experience of the proposed project team on the development of numerical simulation models will enable the project to achieve the goal of producing stationary and dynamic detailed modular simulation models that enable the various components of the cooling system to be included in models of different types and capacities of refrigeration units and heat pumps to obtain new scientific contribution to the justification of the application of certain novel refrigerants in new systems or the replacement of refrigerants in existing systems. Part of the results of the developed numerical models will be tested experimentally in the laboratories of the Faculty of Engineering of the University of Rijeka, laboratories of other universities and industrial laboratories. It is planned to draw up doctoral dissertations within the project, publication of course and scientific books and significant number of papers in A-rated journals and international conferences.