The objective of this study is to provide numerical and experimental data that can be used to investigate the performance characteristics of a flat plate fin-tube evaporator in household and commercial refrigerators under frosting conditions. Computer simulations with variations of operating conditions such as air inlet temperature, relative humidity, and geometries were performed to find out optimal design parameters of a fin-tube evaporator for household and commercial refrigerators. The tube-by-tube method was used in the simulation and the frost growth model was considered under frosting conditions. The developed analytical model predicted the decreasing rates of heat transfer capacity and air flow rate ratio within ${pm}$10% compared to the experimental results for a refrigerator under real operating conditions. As a result, the frost thickness at $3^{circ}C$ & 80% is increased 40% than that of $-3^{circ}C$ & 80%, and the frost thickness at $3^{circ}C$ & 90% is increased 30% than that of $3^{circ}C$ & 60%. Accordingly, the operating time of the evaporator in the refrigerator was reduced with the increase of the decreasing rate of air flow rate ratio at each condition.