Numerical analysis of drying kinetics of porous structures with different geometric shapes in a conveyor dryer

In this study, various studies were carried out on the numerical analysis of the hot air-drying process in a conveyor dryer, the studies were developed step by step and the effects of different parameters in the drying process on the drying performance were examined. Food products, especially vegetable and fruit products, were preferred as dried objects, and the properties of the products were taken from previous experimental studies. Numerical studies are discussed for the stationary and moving states of moist bodies in two dimensions and three dimensions. Optimization studies have been carried out for convective drying performance in two-dimensional and three-dimensional cases for the problem of integrated heat and mass transfer in time-dependent channel flow and porous body. First, the moist porous rectangular-shaped body in the stationary state in the channel under two-dimensional laminar flow conditions was considered, and the variation of moisture loss in the body with time was observed under different drying conditions within a certain drying time. Here, drying air inlet speed and temperature are considered as variable parameters. In the first stages of the drying process, it was observed that the moisture loss from the outer surfaces of the object and especially from the corners was at the maximum level. In addition, the surface in front of the duct air flow direction was the surface where the most moisture loss was experienced during drying. The increase in both drying air velocity and temperature values caused an increase in moisture loss. In the same study, the effect of different parameters on drying with a rotating cylinder that affects the flow into the channel was investigated. It was observed that the size of the rotating body, the direction of rotation and its position in the channel affect the flow and drying performance. Depending on the rotation direction of the circular object, the amount of moisture loss on different surfaces of the dried object changed. In addition, as the distance of the cylinder to the object being dried in the channel increases, its effect on drying decreases, and the same effect decreases as the cylinder gets smaller. After that, the drying of more than one cubic object in the three-dimensional channel was discussed, and the effects of the distance between the objects and the placement in the channel were examined. Here, too, it was observed that the moisture loss in the objects behind increased with the increase in the distance between the objects. In the following studies, motion was added to the object in the two-dimensional duct and the effect of the motion of the object in the drying duct was examined together with the effect of air velocity and temperature. The same effect was investigated for the objects in the three-dimensional channel in the next study. There was no negative effect of adding motion to the object on the drying performance. In the study in which the drying performance of different shaped objects was examined, the drying of circle, square and triangular objects was examined numerically. In this study, it was observed that especially the circular shape gave better results in the drying process. In the same study, the drying process with different material properties for this shape was examined, and the drying performance of each material was revealed. In another study, in which the drying of two equi-square objects placed in the channel with different combinations in the channel was examined numerically, an optimization study was carried out to find the placement that will maximize the heat transfer over the objects, and the optimum horizontal and vertical distances of the objects in the channel to each other were obtained. Then, mass transfers were also examined in different parameters, and it was seen that the maximum mass transfer was within the optimum range values. A similar study was then carried out for three cubic congruent bodies in a three-dimensional channel, and the maximum value of mass transfer was obtained at optimum intervals. Artificial Neural Networks (ANN) and Appropriate Orthogonal Discretization (POD) methods were used in the optimization studies. The results obtained from the numerical studies carried out within the scope of the thesis are to reveal the effect of effective parameters on the drying performance for different situations (three-dimensional channel, many moist objects, moist-porous objects in motion, turbulent flow conditions in the channel, etc.) in convective drying. It can be used as a reference in experimental and numerical studies. In particular, the optimization studies developed within the scope of this study provide a great advantage in solving the problem of integrated heat-flow and mass transfer both in the channel and in the porous body, and significantly shorten the simulation time in modeling large-scale drying systems in which many bodies are involved.