engleski

Heat Transfered of Different Particles Size of Food Products in Gas Fluidized Beds

The obtained results present a significant contribution to the description of functioning of an immersed heat exchanger element. In this process the drying time at lower temperatures is shorter, the product quality is higher and the rehydratation time is shorter as well. This paper comprises a research work on celeriae and potatoes dried in a fluidized bed. First the aerodynamic properties of a fluidizing bed in motion were experimentally investigated and then the particles were dried at given temperatures in different time intervals and at an air flow rate ranging from 0.30 m/s to 4.93 m/s. Two columns of different dimensions were used: a cylindrical column (d= 0.10 m and h= 1.0 m) and a square column (a= 0.09m, b=0.18 m and h=0.83m). Working parameters were: 1. particle dimensions (blanched): 5x5x5 mm and 5x5x10 mm 2. particle mass: 0.200 kg, 0.300 kg and 0.400 kg 3. drying temperature 40°C, 50°C and 60°C Based on the experimental results as well as on the theoretical data, the results of the pressure drop, in relation to the bed height and hot air flow rate, were obtained, as well as in relation to Reynolds, Archimedes and Froude numbers, fluidization number, drying time, drying rate, and to the relative and total humidity of drying. The best results of celeriae drying were obtained with the following dimensions of celeriae: 5x5x5 mm, 200 g, in a cylindrical column at 60°C and at the maximum air flow rate of 4.3 m/s. The best results of potato drying were achieved with the potato dimensions of: 5x5x5 mm, 200 g, in a cylindrical column at 60°C and at the maximum air flow rate of 4.86 m/s. Key words: drying, extended surface of immersed heat exchanger element, fluidization, heat transfer, rehydratation

drying; extended surface of immersed heat exchanger element; fluidization; heat transfer; rehydratation

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