- 期刊
- OpenAccess
柿餅加工乾燥機特性分析
The Analysis of a Dryer for Persimmon Process
摘要
具有熱能回收裝置的乾燥系統能降低乾燥所需的能量，為了分析此乾燥系統的最佳操作條件，測試其風扇轉速對於乾燥室內溫度、風速和熱能回收裝置效能的影響，歸納出風扇最佳運作應是在加熱啟動階段應用最快轉速，到達穩定階段後，以較低轉速可提升乾燥機的性能。經由建立的重量即時量測系統量測整批柿果在乾燥過程中的重量變化，得到熱能回收機械系統的平均乾燥速率為0.14 kg/min，但隨著乾燥時間遞減，顯示柿果在熱風乾燥機內為減率乾燥期，每次適當的熱風乾燥時間長度約為70~80分鐘。在均化階段，除了第一次和捻壓階段之外，柿果重量變化很小，顯示柿果水分的排出主要在熱風乾燥階段，均化階段則是使柿果內部水分均勻擴散到整顆柿果。加工作業中的捻壓程序，會造成柿果內部水分往表皮擴散，促使水分蒸發，所以捻壓在加工的意義上，除了定型之外尚可促進水分的蒸散。
並列摘要
Energy requirement for drying could be reduced by a dryer with a heat recovery device. In order to analyze the optimum operation conditions, the effect of fan speed on the temperature, airflow distribution and effectiveness of the heat recovery device was investigated in the drying system. The optimum fan speed would be at maximum speed during initial heating stage and at lower speed during steady stage in order to improve the performance. Via development of real-time weighing system, the variation of persimmon weight could be obtained. By analysis of the weight during drying process, the average drying rate was 0.14 kg/min and decreased with time, which indicated that the persimmon was in the falling rate period during drying process. The appropriate duration of hot air drying for each drying cycle is 70~80 minutes. The weight of persimmon was slightly reduced during tempering stage except the first cycle and squeeze period, which showed that the moisture removal of persimmon was mostly occurred in the drying period and the moisture diffused through the whole fruit in the stage of tempering. The squeezing process resulted in the moisture diffusing to the surface of the fruits, and thus increasing themoisture evaporation. Therefore, the meaning of squeeze is to enhance the moisture removal in addition to shaping the persimmon.