Wyznaczanie wspolczynnika dyfuzji masy w procesie konwekcyjnego suszenia buraka cwiklowego

Paper presents the methods for determination of mass diffusion coefficient a m during the second period of red beet dehydration process. Existing models for cereal grains were used, containing a generalized mass diffusion coefficient within their structure: - based on dehydration index, K; - based on the Fourier number. Results of free convection dehydration kinetics tests of 5 and 10 mm cube shaped beet pieces, at five air temperatures: 50°C, 55°C, 60°C, 65°C, and 70°C were used in the calculations. Test results were processed using Microsoft EXCEL spreadsheet and STATISTICA software. It had been previously believed that the coefficient of water diffusion does not depend on the size of dehydrated materiel sample. The calculations presented herein indicate that the values of water diffusion coefficient are approximately 2.5 times greater for the larger size cubes than for the smaller size (under the same drying agent temperature). Therefore, when limits for the application range for am determination are cited, one should consider not only the content of water, temperature and shape, but also the value of characteristic dimension.

W pracy przedstawiono metody wyznaczania współczynnika dyfuzji masy a m w drugim okresie suszenia buraka ćwikłowego. W tym celu posłużono się istniejącymi modelami dla ziarna zbóż. Do obliczeń wykorzystano wyniki pomiarów kinetyki suszenia, w konwekcji swobodnej, cząstek buraków w kształcie sześcianów, o boku 5 oraz 10 mm, w pięciu temperaturach powietrza suszącego: 50, 55, 60, 65, 70°C.