Tray dryers are usually designed with simplistic scaling rules that do not account for all the transport phenomena associated with drying. The use of computational fluid dynamics coupled with response surface methodology can be a powerful tool to evaluate how different tray dryer design parameters affect the drying process. In this work, two tray dryers, one with a lateral air inlet and another with a bottom air inlet, were parameterized for the position of the air inlet, the dryer length, and the distance between the trays. A central composite design was chosen to determine the sample points, and the average turbulence viscosity and effective thermal conductivity as well as the homogeneity index were calculated. With these values, a response surface curve was constructed. The effective thermal conductivity and its homogeneity index were improved (80 % and 11 %, respectively) with an increased distance between trays and an air inlet located in the middle of the inlet face in the best scenario. In addition, the reductions in effective thermal conductivity outcomes were minimal due to the scale-up process in terms of the dryer length.

This paper presents the development of theoretical and experimental models for the study of rotodynamic behavior of a multistage rotor. The transfer matrix method, which includes the characteristics of stiffness and damping for the supports and the stages respectively as well as the characteristics of unbalance in the stages, is used for the theoretical model. The data from a physical model was employed as a way of validating the theoretical results. The first two critical speeds were determined with the theoretical model and they differ in a low percentage with respect to the values measured experimentally. Moreover, the vibration level recorded in the physical model rises 2.5 times when the multistage rotor approaches the first two critical speeds. In addition to this, significant displacements of the lateral critical speeds are noticeable when an increase in mass imbalance is induced in several of the rotor impellers.