The refrigerant charge is an important parameter for the thermodynamic conditions of a small-scale refrigeration appliance. This paper analyzes the relationships among the amount of refrigerant charge and other running parameters of refrigerator-freezer such as pressures and temperatures. In order to choose a proper void fraction correlation for the description of two-phase flow conditions, an experiment is done and the results show that Premoli correlation underestimates the charge and Hughmark correlation overestimates the charge for a refrigerator-freezer. As the Premoli correlation and Hughmark correlation are both complex, a simplified correlation is used in the system simulation. How to use the void fraction correlation for dynamic simulation of a refrigerator is also discussed.