Abstract:The pump design is facilitated by the development of computational fluid dynamics and the complex internal flows in water pump impellers can be well predicted. Various parameters affect the pump performance and energy consumption. The impeller outlet diameter, the blade angle and the blade number are the most critical. The present paper describes the simulation of the flow into the impeller of a laboratory pump in a parametric manner. In this study, the performance of impellers with the same outlet diameter having different outlet blade angles is thoroughly evaluated. The one-dimensional approach along with empirical equations is adopted for the design of each impeller. The predicted performance curves result through the calculation of the internal flow field and a successful correlation of local and global parameters. The numerical solution of the discretized three-dimensional, incompressible Navier-Stokes equations over an unstructured grid is accomplished with a commercial CFD finite-volume code. For each impeller, the flow pattern and the pressure distribution in the blade passages are calculated and finally the head-capacity curves are compared and discussed.
a b s t r a c tThe objective of the present work is to study the drying kinetics of quince slices during convective drying. The details of the laboratory-scaled convective dryer are presented. Experiments were carried out at air temperatures 40 C, 50 C and 60 C and 2 m s À1 bulk velocity. The whole process occurred within the falling rate period. Results showed that the temperature of the air stream has a significant effect on the drying curves. In particular, a temperature increase from 40 to 60 C produced a decrease of the total time of drying of about 54%. Eight thin-layer drying models were used to fit the temporal distributions of the moisture data using non-linear regression analysis. Among the various models, the Weibull formula was best fitted to measurements. For the range of the drying temperatures examined, Fick's law of diffusion was used to determine the effective moisture diffusivity, which varied between 3.23 Â 10 À10 m 2 s À1 and 7.82 Â 10 À10 m 2 s À1 . Assuming an Arrhenius type model for the drying process, a value of 38.291 kJ mol À1 was estimated for the activation energy.
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