University of Khartoum

PID Control of DC-Motors

PID Control of DC-Motors

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Title: PID Control of DC-Motors
Author: Ahmed, Waleed Ahmed Mohammed Hussein
Abstract: Experiments of thin layer solar drying of banana slices were conducted at the Workshop of the Dept. of Agriculture Engineering, Faculty of Agriculture, University of Khartoum, Sudan. The objectives of the study were: 1) determination of the drying characteristics of banana slices and 2) simulation of thin layer solar drying of banana slices. Fresh banana was brought from Omdurman Local Market, Sudan. A representative sample of peeled banana was used for the determination of the banana initial moisture content. The method used for moisture content determination was that described by AOAC (1965). In this method two grammes of banana flesh were placed inside an air-oven set at 80°C for 24hours. Another five banana fingers were also peeled and cut into slices with a thickness of 10 mm. Five banana slices from that lot were used in carrying out the thin layer solar drying tests. A previously constructed convective solar dryer was used for drying banana slices. Temperature of ambient air, air inside absorber, inlet air and outlet air from solar dryer were recorded at intervals of one hour. The relative humidities of ambient air, inlet air and outlet air were obtained by intersecting dry-bulb and wet-bulb air temperature on a psychrometric chart. The weights of banana slices during the drying tests were recorded at intervals of one hour. The drying experiment was run for three consecutive days starting from 09:00 to 18:00. For simulating thin layer solar drying of banana slices, three drying models were tested. These models were namely; Lewis, Page and Henderson and Pabis. A computer programme was written into Turbo Pascal programming language for Windows, version 1.5 for each of the three tested drying models and the programmes were run on a personal computer (PC). Results showed that the convective solar dryer heated the drying air efficiently. This efficiency can be depicted by the maximum attained temperature difference between the air inside the dryer absorber and the ambient air which was found to be 56.2°C. Also the efficiency can be noticed by the maximum attained relative humidity difference between inlet air and outlet air from dryer which was found to be 16.8%. Thin layer solar drying of banana slices took place during the falling drying rate period and the effective drying of banana slices occurred during the first day while a steady state was attained during the second and the third days of the drying experiment. The three tested drying models predicted the thin layer solar drying of banana slices satisfactorily but Henderson and Pabis model was in a close agreement with the measured data. This close agreement of Henderson and Pabis model was shown by the high values of probability of being wrong if the null hypothesis is rejected (P = 94%) and the coefficient of determination (R2 = 91%).
Description: 87page
URI: http://khartoumspace.uofk.edu/123456789/16080
Date: 2015-09-14


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