The use of centrifugal compressors is widespread in many different industrial applications, namely refrigeration cycles, oil and gas rotating equipments, automotive turbochargers and small aero-engines. Compared to their axial counterpart, centrifugal compressors can provide the same compression ratio within less compression stages, trading-off efficiency with compactness. Current development in this sector involves the tuning of design process to accommodate analysis of turbomachinery operating with non-conventional working fluids that exhibit non-ideal fluid-dynamic behaviour. However, best practices for the preliminary design of centrifugal compressors still rely on the perfect gas assumption. On the other hand, the improvement of the preliminary design tools may result in significant reduction of time and resources spent during the detailed design step by leveraging Computational Fluid Dynamics (CFD). In this scenario, the present research aims to devise guidelines for the preliminary design of centrifugal compressors operating with non-ideal compressible flows by assessing the performance limits of the machine using a meanline design framework, coupled, where possible, to physics-based loss models. Loss models derived from first principles are preferred to semi-empirical loss correlations as they require less tuning with machine-specific (thus, also working fluid-specific) experimental data. In this work, two major loss sources, namely the blade boundary layer loss and the tip leakage loss, are analyzed in detail. For both loss mechanisms, the physics-based loss model are derived, and their results are compared to CFD results to check their validity and accuracy. Due to time constraints, the remaining loss sources are modelled using semi-empirical correlations available in literature. The outcome of this work are design maps for centrifugal compressors operating with different working fluids and thermodynamic conditions, which highlight the impact of non-ideal compressible fluid dynamics (NICFD) on the optimum design region as well as the maximum theoretical stage efficiency. The novel framework could be further extended and replace the traditional design guidelines based on the perfect gas assumption, aiming to improve compressor preliminary design and contribute to the development of next-generation high-performance turbomachinery.