苜蓿薄层干燥特性试验研究

以紫花苜蓿为研究对象,在薄层干燥试验台上进行了不同处理、不同热风温度、热风速度和物料初始水分的单因素薄层干燥试验,建立了苜蓿干燥特性曲线。结果表明,苜蓿叶片的干燥速度最快,是未压扁茎的3.5倍,其次为压扁茎杆,压扁切段的干燥速度与叶片的干燥速度最接近;随着介质温度升高,干燥时间缩短,介质温度分别为100、140和180℃时,干燥时间分别为8、4.5和2.5 min,可见介质温度每提高40℃,干燥时间大致缩短一半;热风速度加大使干燥时间缩短,热风速度为0.15、0.4和0.65 m.s-1时的干燥时间分别为10、5和4 min,即热风速度在临界速度以下时,提高热风速度可以缩短干燥时间;物料初始水分为74.98%、50.03%和25.43%时,干燥时间分别为4、2和1 min,即物料初始水分越低,干燥时间越短,物料的初始水分每增加25%,干燥时间成倍增加。

Experimental study on thin layer drying process characteristics of alfalfa

This expetiment was conducted on thin layer drying expetiment table with alfalfa to study single factor thin layer drying test under different treatments,hot air temperature,hot air velocity and initial moistare content,drying characteristic curves of alfalfa was established.The results showed that drying speed of leaves was the fastest,and was 3.5 times of uncrushed stem,then was crushed stem’s,and its drying speed was close to that of leaves.Drying time was shorted with medium temperature increase,when medium temperature was 100,140 and 180 ℃,drying time was 8,4.5 and 2.5 min,respectively,this result showed that drying time was approximately half of original time when medium temperature increased by 40 ℃.Drying time was shorted with hot air velocity increase,when hot air velocity was 0.15,0.4 and 0.65 m.s-1,drying time was 10,5 and 4 min,respectively,showing that drying time was shorted when hot air velocity increased under critical velocity.Drying time was 4,2 and 1 min when initial moistare content was 74.98%,50.03% and 25.43%,respectively,eliciting that the lower the initial moister content was,the shorter the drying time was.Drying time was raised doublely when initial moistare content increased by 25%.