In all industries which are related to heat, suitable thermal ranges are defined for each device to operate well. Consideration of these limits requires a thermal control unit beside the main system. The Satellite Thermal Control Unit (STCU) exploits from different methods and facilities individually or mixed. The space radiating fin which is combined with a heat pipe can be used to transfer the excess heat from the satellite to outer free space. The finite volume method is employed to simulate numerically the temperature distribution in a space radiating fin and evaluate thermal fin efficiency. Final results are achieved for two different materials (Aluminum and Beryllium) and compared to each other. The present results are compared with the other analytical methods and good agreement is shown.