Browsing by Author "Tkubet, Habtamu"

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    Simulation of Solar Cereal Dryer Using Trnsys
    (Addis Ababa University, 2007-01) Tkubet, Habtamu; Assefa, Abebayehu (PhD)
    In many countries of the world, the use of solar thermal systems in the agricultural area to conserve vegetables, fruits, coffee and other crops has shown to be practical, economical and responsible approach environmentally. Solar heating systems to dry food and other crops can improve the quality of the product, while reducing wastes produce and traditional fuels - thus improving the quality of life. However the availability of good information is lacking in many of the countries where solar food processing systems are most needed. This work presents the performance of several individual, medium and large-scale food processing systems, which incorporate solar drying. A general purpose of solar crop dryer for drying of various agricultural products such as coffee, fruits, Vegetables, cereals, etc, is simulated. The simulated solar dyer consists of the solar air heater ( solar collector) which uses low emissivity glass cover, weather data, and an integrated dryer chamber attached to the collector where the products to be dried are placed. A thermal solar collector model is developed to determine the available useful energy for heating the ambient air with the available solar radiation. Basic heat transfer equations for single-plate and double glass glazing are drived and techniques for the solution of these questions are presented. A computer program is written to predict the collector outlet temperature, mass flow rate and other engineering variables from the input of the meteorological data and collector parameters and also done for the dryer chamber by using the input from the collector out put and the properties like initial moisture content, initial temperature of cereals and other engineering properties. Results of the system simulation are presented in graphical form suitable for system performance determination. From the incident flux, ambient air temperature and solar collector parameters, the useful energy, collector output temperatures of the out put air are determined. Simulation of Solar Cereal Dryer Using TRNSYS i x The output properties of the collector are the input parameters for the drying chamber. These parameters are used to determine the moisture content, the relative humidity, the mass of water vapor and the output temperature of the air at the out put of the drying chamber.