A coupled mathematical model for simultaneous microwave and convective drying of wheat seeds

Faster drying techniques are preferred to prevent spoilage of harvested wheat seeds. Microwave (MW) drying may be used as an alternate technique for faster drying of crops with efficient utilisation of time and energy. The objective of this study was to develop a mathematical model to simulate the drying condition of wheat seeds during drying in a MW oven. A coupled mathematical model was developed for simultaneous MW and convective drying of wheat seeds in a domestic MW oven, resulting in a system of non-linear equations. Wheat samples with initial moisture levels of 15e25% wet basis were dried under MW power ranging from 245 to 910W for 3 min. The temperature and the relative humidity of drying air was 23 degC and 27%, respectively. The results revealed that the rate of drying increased with increase in the initial moisture content of wheat seeds. The germination percentage of wheat seeds decreased with the increase of the MW power at each initial moisture content. The predicted temperature of grain during drying with the MW power at 910W was within the range of 65-70 degC. The experimental results of moisture content of wheat seeds undergoing MW drying were in good agreement with the moisture content of wheat seeds predicted by the coupled mathematical model

Numerical investigation of thermal characteristics of confined rotating multi-jet

For using the swirling jet for air conditioning and heating in the premises, knowledge of the thermal characteristics is more than necessary. It is for this objective that the experimental and numerical study was realized. To conduct this study, we designed and built an experimental facility to ensure proper conditions of confinement in which we placed five air blowing devices with adjustable vanes, providing multiple swirling turbulent jet with a swirl number S = 0.4. The jets were issued in the same direction and the same spacing defined between them. This study concerned the numerical simulation of the thermal mixing of confined swirling multi-jets, and examined the influence of important parameters of a swirl diffuser system on the performance characteristics. The experimental measurements are also realized for a confined domain, aiming to determine the axial and radial temperature field. The CFD investigations are carried out by an unstructured mesh to discretize the computational domain. In this work, the simulations have been performed using the finite volume method and FLUENT solver, in which the standard k-ε, K-ε realizable, k-ε RNG and the RSM turbulence model were used for turbulence computations. The validation shows that the K-ε RNG model can be used to simulate this case successfully

Common applications of thin layer drying curve equations and their evaluation criteria

In this study, thin layer drying curve equations commonly used in the literature between 2003 and 2013 are systematically discussed and evaluated in terms of their applications and selection for thin layer drying processes by considering the model evaluation criteria. As a result of this study, serious complications, confusions, and conflicts in the applications of thin layer drying curve equations and their evaluation criteria are noticed. Consequently, it is recommended that the drying curve equations should be applied in accordance with the forms commonly used in the literature. Also, it is determined that the following drying curve equations give the best results for thin layer drying processes which are the Midilli-Kucuk, Page, Logarithmic, Two-term, Wang and Singh, Approximation of diffusion, Modified Henderson and Pabis, Modified Page, Henderson and Pabis, Two-term exponential, and Verma et al. © Springer International Publishing Switzerland 2014