The optimization of refrigeration systems involves finding the optimum operating point at which the coefficient of performance of the system is maximum, For most vapor compression refrigeration systems, optimum performance is obtained by proper distribution of the total heat exchanger area between the evaporator and condenser of the system, In this paper, finite time thermodynamic models of a simple vapor compression refrigeration system, a two stage vapor compression refrigeration system (TSS), a dedicated mechanical subcooling vapor compression refrigeration system (DMSS) and an integrated mechanical subcooling vapor compression refrigeration system (IMSS) are presented to study the systems with respect to the heat exchanger parameters. In addition, the model of the TSS is used for investigating the optimum performance with respect to interstage temperature, while the models of the DMSS and IMSS are used for investigating the optimum performance with respect to the subcooler saturation temperature.