Abstarct: Abstract Due to the increase in global energy consumption in various sectors, especially in dryers to dry agricultural products, as well as the limited resources of non-renewable energy, the use of solar energy is important because it is cheap. However, the intermittent nature of the sun during the day and its absence at night, causes the dryer to remain unstable and reduce the temperature, and as a result, reduce the quality of the product. Thermal storage of latent heat by Phase Change Matrial (PCM) during the day, and heat release during hours when the sun is not available; It stabilizes the dryer temperature at night and maintains the quality of the products. In this research, numerical simulation of solar dryer using thermal storage system, for: calculation of energy stored in the storage section, investigation of thermal distribution and energy input to solar dryer, with the help of Fluent software. Examining the previous research, the equations related to both parts were extracted. To simulate the storage system, a cylindrical tank with a spiral coil containing paraffin was used. Water with temperature dependent on laboratory data, from the solar collector, for every local hour from 7 am to 7 pm, entered the tank and after heat exchange with paraffin as a phase change material, left the tank. The maximum stored heat was related to 14:00, which was 0.406 MJ. The average temperature of paraffin at this time was 351 K. The water leaving the tank enters the heat exchanger and after exchanging with the air that enters from the environment; Returns to the collector. The heat exchanger was tested in a laboratory by researchers. To simulate the solar dryer, a cubic chamber with an expansion inlet with three perforated rectangular trays was used. The exhaust air from the heat exchanger enters the solar dryer for every local hour from 7 am to 24 pm and leaves the drying room after exchanging heat with the walls and trays. The maximum heat energy input to the dryer occurred at 14:00 with the highest amount of sunlight, the amount of which was 1.039 MJ. The amount of energy stored in the tank and the amount of heat energy input to dryer for each local hour were validated by previous research. Simulation of the storage section, due to: the use of melting and freezing models and complex computational volume, consumes a lot of time; And to do that, you need powerful computers. Using the temperature effects of the storage section and the heat exchanger in the form of mathematical functions for each hour is a good alternative to simulate these sections. The mean relative error between the dryer simulation using input mathematical functions and the simulation using input data was 0.41%. By providing unique mathematical functions for each phase change material, according to the conditions and geometry of the tank and heat exchanger, as well as its application in solar dryers, the dryer performance can be investigated by spending a short time and reducing the volume of calculations. And predicted for each phase change material.