Design and Analysis of High Moisture Content Paddy Drying Simulator
Date Issued
2014
Date
2014
Author(s)
Meng, Yi-Ting
Abstract
High moisture content paddy emergency harvested in rainy season is a serious problem in Taiwan. It might prolong drying time to congest operating schedule of paddy drying centers and also increase drying costs. Currently, commercial circulating dryers are mature commodities. However, various designs and operations might lead to different drying efficiency and energy costs. The purpose of this study is to device a drying simulator based on circulating drying principles to investigate dryer designing and operation for high moisture content paddy. Pre-drying operation tests were conducted in the simulator to dry high moisture content paddy to its critical moisture content. Various parameters were chosen and model of Box Behnken Design (BBD) was adopted under three levels of factors. Levels of paddy layer thickness are 6cm, 9cm, and 12cm; levels of specific air flow rate are 0.3CMM/kg, 0.5CMM/kg, and 0.7CMM/kg; levels of drying time are 10min, 20min, and 30min. It is difficult to measure internal changes in the paddy layer during drying, so heat and mass transfer model was built and simulated by FEM software (Comsol Multiphysics 4.3a) to predict internal changes in the paddy layer. Experimental results showed 98% total energy consumed in drying process being used in heating and desorption of water in grain and the rest being used in air flowing to carry mass and energy. The most efficient way in pre-drying was to dry wet grain to the critical moisture content in one pass. Various passes drying might consume more energy in heating up grain to drying temperature in each pass; besides, the benefit of tempering was insignificant in pre-drying stage. In the range of operations, combinations of specific air flow rate and drying time in 0.3CMM/kg-30min, 0.5CMM/kg-20min, and 0.7CMM/kg-20min with high energy efficiency and high air flow rate, also resulted in high drying rate. Because specific air flow rate was used in experimental design the influence of the paddy layer thickness was not significant. However, simulation results showed that thick layer drying might lead to high moisture content variation along the air flow direction. This phenomenon may affect subsequent drying operation, so it is suggested for further research.
Subjects
乾燥模擬機
高含水率稻穀
有限元素法
反應曲面法
SDGs
Type
thesis
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