In this study, drying behaviour of rough rice stacks up to 30 cm is simulated with several models. The suitability of models is determined by the statistical analysis by examining the values of correlation coefficient, standard deviation and mean squared deviation. The results showed that the best model to explain the drying characteristics of rough rice stack is the Midilli et al. model and the coefficients and exponent in the Midilli et al. model could be expressed as functions of drying temperatures and stack height. Statistical analyses also showed that among the models with two coefficients, that of Page, and among the models with three coefficients, that of Verma et al. and diffusion approach were acceptable models in expressing the drying behaviour of rough rice in stacks. Among the models considered here, the geometric model appeared to be the worst fit.
-In this study, drying behaviour of carrot slices in a microwave dryer was investigated experimentally and drying was modelled by the semi-empirical Page model. Experimental study was conducted for two different slice thicknesses (1cm and 2cm) and three different microwave power levels (350W, 460W, and 600W). During experiments, weight of the carrot samples were recorded at regular intervals of 15s. Experimental results show that drying rate increases considerably with an increase in the microwave power level. The experimental results also show that the effect of carrot thickness on drying rate shows a decrease with an increase in the microwave power level. Finally experimental results indicate that energy consumption during drying shows a decrease by an increase in the microwave power level. The statistical analyses results indicate that the semi-empirical Page model can be used to define the microwave drying behaviour of carrot slices.
Summary
In this work, the performance of a charging mode of a thermal energy storage system is investigated numerically, and results are assessed considering the first law and second law perspectives. The storage unit comprises parallel plates positioned vertically, and the heat transfer fluid flows within the spacing between the plates. The melting process of phase change material inside a rectangular enclosure is simulated considering the natural convection using an in‐house model codded in C++. The proposed model is validated with the numerical and experimental research from the literature. A parametric analysis is carried out to explore the influence of heat transfer inlet temperature and aspect ratio on the unit's first law and second law performance indicators. Analyses are also conducted by disregarding the natural convection to assess the convective mode of heat transfer on the time‐wise variation of the storage effectiveness and stored exergy. The results revealed that for the highest inlet temperature of the heat transfer fluid, the stored energy value increases from 133.85 to 250 kJ then drops to 240 kJ by varying the aspect ratio from 0.25 to 0.50 and from 0.50 to 1.00, respectively, for the natural convection dominated melting. On the other hand, regarding effectiveness, both with and without natural convection modes show the same aspect ratio variations trend. The effectiveness reduces from 0.9 to 0.40 by increasing the aspect ratio from 0.25 to 1.00 for the natural convection‐dominated melting mode. The effectiveness drops from 0.62 to 0.16 for the same variation in the aspect ratio for the conduction‐dominated melting mode. Besides, it is found that the highest stored exergy is observed in Case 9 w/NC situation with a stored exergy value of 13.3 kJ. The exergy efficiency changes approximately between 65% and 81% for all cases.
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