Refrigeration has become essential in our society and for our standard of living. Though environmental issues regarding the refrigerants that circulate in heating, ventilation and air conditioning (HVAC&R) cycles have resulted in enormous consequences for this technology sector. Twice in the last three decades, phase-out regulations got effective for established refrigerants, which has necessitated the adoption of suitable replacements, related to the need for data on the thermophysical properties of potential alternative working fluids. In this context, molecular simulation has emerged as important compliment to experimental studies, and we here provide an overview on molecular modelling approaches and simulation studies on different generations of refrigerants, though with focus on the current fourth generation of working fluids, i.e. hydrofluoroolefins (HFO). Due to increasing difficulties in meeting all different selection criteria for a specific application by a single component refrigerant, blends are becoming more and more important. We here present recent simulation results for vapor-liquid equilibria of different binary mixtures based on the newly introduced compound trifluoroethene (HFO-1123) as demonstrative example of the benefit of molecular simulation to provide information on mixtures for which no experimental data are available yet. We also discuss studies on conformational isomers and the development of equations of state as further research topics in which molecular simulations are already playing an important role in complementing experimental studies. Finally we highlight some future research directions in which simulation studies can be expected to make an important contribution to the understanding and theoretical modeling of refrigerant properties. (C) 2018 Elsevier B.V. All rights reserved.