Abstarct: In general, solar heat collectors are divided into two general categories: air heaters and solar water heaters. Due to the lack of energy resources as well as environmental approaches, these devices have found an important role in many engineering applications such as building heating, solar dryers, air conditioning and so on. In addition; Simple structure, low cost of construction and maintenance are other advantages of such solar devices. In this dissertation, using a new method by vacuum tube collector, we used the heat absorbed by solar radiation directly to produce hot air. Using numerical solution method, we investigated the numerical modeling of heat transfer in solar air heaters with vacuum tube collector by Ansys Fluent software. We put the desired model in the studied cases. By adding a fan to the part of the collector which is intended as a dryer; We changed the heat transfer current from normal to forced. We obtained the values of changes in temperature and flux of solar radiation and the thermal efficiency of the collector to evaluate the thermal performance of the air heater under different conditions. We observed that the changes in the average temperature of the collector with the change of solar flux during the day, in the unstable state fluctuates slightly compared to the steady state. Also, the thermal performance of the collector in unstable conditions for the duration of the studied time showed very little change compared to the steady state. Examining the heat efficiency of the collector, we found that the average efficiency of the thermal performance of the system during the day for the unstable state is 53.27%. Therefore, due to low temperature fluctuations during daylight hours, the use of hot air produced for drying applications is suitable in these working conditions.