明胶热风干燥特性的实验研究

Experimental study on hot air drying characteristics of gelatin

采用静态法研究了明胶的平衡含湿质量分数,得到了20℃下吸湿和解吸等温线,结果表明,当空气相对湿度在16%—39%,存在吸湿滞后现象。在对流干燥实验台上进行了明胶干燥特性的实验,以不同厚度的明胶块为实验对象研究了热风温度、风速、湿度对干燥过程的影响。实验结果表明:明胶的干燥过程只有降速阶段,提高热风温度、加大风速均可以在前期提高干燥速率,但在干燥后期干燥速率反而降低;明胶块中心温度受胶块厚度、热风温度影响较大,而在实验范围内空气相对湿度的变化对明胶中心温度影响甚微;明胶的相对含湿质量分数随时间呈指数规律下降,提高风温、加大风速后明胶含湿质量分数在开始阶段下降较快,但最终含湿质量分数反而偏高。

The equilibrium moisture mass fraction of gelatin in the different air humidity was investigated by static method.The obtained isotherms of absorption and desorption at 20 ℃ show that the absorption hysteresis phenomenon exists when the relative humidity of air is 16%-39%.In order to research the drying characteristics of gelatin,the drying experiment of gelatin was made in the convective drying apparatus.The results show that in the drying process of gelatin only falling rate period exists.With increasing of air temperature and air velocity,the drying rate can be enhanced in the initial stage,but decreased in the following period.The thickness and air temperature have deep effect on the center temperature of gelatin,but the relative humidity of the hot air has relatively small influence on it.The relative moisture mass fraction of gelatin decreases with time as exponential function.With the increasing of air temperature and air velocity,the moisture mass fraction of gelatin decreases rapidly in the beginning,but the final moisture mass fraction is higher.