Ph.D. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: In the present study, heat and mass transfer in drying are investigated theoretically and experimentally. In the theoretical part, heat and mass transfer equations governing air drying of cubic, cylindrical and spherical food products are solved numerically. Flow and temperature fields around the rectangular and cylindrical products placed normal to the flow are analyzed at first using the FLUENT CFD package. Using the temperature profiles, the local distributions of the convective heat and mass transfer coefficients along the product surface are determined. It is shown that the local heat and mass transfer coefficients are higher at the left side wall than those at the right side due to the upstream of the drying air.In order to obtain homogeneous drying for the product, the optimum location of inlet and outlet stations of drying air into the convective dryer are investigated. For this purpose, five different cases are comparatively examined. The optimum air inlet from the bottom of the convective dryer and outlet from the top of the convective dryer are determined to be the optimum locations in terms of homogeneous drying and the shortest drying time. In the experimental part, the effects of air velocity, temperature and relative humidity on drying characteristic of kiwi and cherry laurel are investigated. It is observed that increasing the air velocity and temperature and decreasing the air relative humidity decreases the drying time. The effects of drying air temperature and relative humidity on the vitamin C are also investigated. It is observed that increasing the air temperature at a constant relative humidity or decreasing the relative humidity of air at a constant temperature decreases the content of vitamin C in the product. Finally, a thermoeconomic analysis is made for the horizontal convective dryer at different drying air conditions for drying of kiwi fruits. It is disclosed that the drying air with a temperature of 50oC and a relative humidity of 25% presented the most economical drying.Key Words: Convective Drying, Heat and Mass transfer, Fluent, Vitamin C, Kiwi, Cherry Laurel.
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