Abstarct: This thesis describes numerically the modeling of the heat transfer inside the electric vacuum furnaces. In this study, the predominant method of heat transfer inside the furnace is because of the vacuum inside the enclosure. The purpose of this modeling is uniformity of temperature and heat flux inside the furnace chamber, obtaining the necessary input power and the number of appropriate shields and its structure in the high temperature furnace and finally cooling the furnaces. The electric furnace is modeled in a two-dimensional vacuum with a radiation heat transfer mechanism. In this research, low temperature furnaces are studied up to 400 ° C and high temperature furnaces at temperatures of 700 to 1700 ° C in different dimensions. In both types of furnace, the source of heat is the elements that four electric elements are embedded in four facets of geometry and the workpiece is located in the furnace center. In a low temperature furnace, there is ceramic insulator between the heating chamber and the outer wall of the furnace, and the radiation heat transfer is carried out only inside the furnace chamber, and in the insulation section, workpiece, elements and walls, the conductive heat transfer takes place. In a high-temperature furnace, radiation shields are placed between the heat exchanger (thermal enclosure) and the outer wall, instead of the insulation. These shields, like the thermal resistance are placed on the heat transfer path between the outer wall and the elements, reduce the heat transfer rate to the outside, which is also a gap between the shields. As a result, in addition to the heat exchanger (thermal enclosure), heat radiation is transmitted between radiation shields. In this type of furnace, around the outer wall is covered with a stainless steel chamber in which the water coolant fluid is flows. This cooling takes place to save energy and cost so that in addition to reducing the number of shields, the output temperature will be reduced. The geometric and thermal information for modeling is selected from the actual samples made by the knowledge baxse company Artha industry. In each of the furnaces, the independence of the results of the networking of the solution region is studied. Then, the effects of the input power of the elements are checked. The criterion for obtaining the necessary power is when the workpiece inside the furnace reaches the desired design temperature in each type of furnace. Then, in the high-temperature furnace, the number of shields required is determined according to the dimensions of the furnace and material of the shields, as well as the temperature of the outer wall. In this study, the dimensions of the entire furnace and the thermal enclosure are fixed and in the space between the elements and the outer wall of the shields are distributed and designed with a suitable number. Since the uniformity of temperature and heat flux inside the furnaces is the goal of this study, the workpiece is embedded in the various coordinates in the furnace, and the graphs of the temperature and average environmental radiation thermal heat flux are shown. The results show a higher uniformity in smaller furnaces. The effect of the diffusion coefficient change and the thermal conductivity coefficient of the workpiece inside the furnace on the temperature distribution and thermal radiation heat flux have also been investigated. The results show that the distribution of temperature in the furnace depends considerably on the emission factor, and the distribution of thermal heat flux depends on both the emission coefficient and the thermal conductivity. Cooling of high temperature furnace is the final study in this thesis. This part will apply by reducing the number of shields inside the high temperature furnace and studying the cooling effects on the temperature of the external wall of the furnace. The results show that cooling has a significant effect on reducing the temperature of the external wall by 130 to 140 degrees.