investigation on the effect of exhaust air recycling in a cabinet solar dryer equipped with a vacuum tube heat pipe solar collector and enhanced with pcm

In the drying process, due to the high moisture content of the products, a lot of energy is consumed. using the independent or combined mechanism of solar system is a common method to dry agricultural products. the drying efficiency due to some reasons such as heat loss and exhaust air from the dryer in the open air flow, is very low. the application of recycling exhaust air flow at the inlet section of the dryer increases the thermal efficiency and reduces the drying time of the product. with recycling system which includes two adjustable valves at the inlet and outlet of the dryer, the amount of return air flow can be controlled. in this study, the effect of recycling exhaust air flow with different fractions (0 25 50 70%), and enhanced with phase change material is simulated by cfd modeling and their effects are investigated on the performance of an indirect solar cabinet dryer.