The proper design of a refigerator, due to its extensive use, plays a large role in reducing energy consumption in the country. Optimal design with experimentals involves a difficult, time consuming and costly trial and error process. The use of software simulation is one of the most appropriate tools for designing complementary experimental methods at a much lower cost and time. In previous studies, a model with the ability to simulate a refrigerator, taking into account the effects of frosting and defrosting in the Side-Bye-Side refrigerators with compact forced convection condensers, was not available for use by designers. In the present study, a mathematical model is presented to simulate the performance of this refrigerator type. Cycle components were modeled steadily and refrigerator compartment were transiently simulated and the experimental coefficients were calculated by using refrigerator tests in a hot room at ambient temperature of 32 and 43 ° C. Then, by testing the refrigerator and measuring the power consumption, pressure and temperature of different points, the model was validated. By comparing the values ??calculated by the model with the experimental values, the model has the ability to calculate the power consumption, flow rate and the pressure of different points with a maximum error of 10% ??and the temperature of different points of the cycle with a maximum error of 2 ° C. Also, this model can calculate indescribable quantities such as the thickness and mass of the frost formed on the evaporator at any moment. Keywords: Refrigarator, Frost, Defrost, Refrigerator test, Quasi-steady model