连续式微波干燥机腔体内流场仿真分析与验证

为提高发芽糙米在连续式微波干燥机内干燥均匀性和干燥品质,采用流体动力学软件SolidWorks Flow simulation建立微波干燥机干燥腔室流体仿真模型,研究其内部气流场分布规律,对不同结构干燥腔室内部气流分布作仿真分析。结果表明,在微波干燥机进风口加装均风网板和在出料口同端面加设出风管,可使腔体内部气流更加平稳,风速平稳区域占干燥腔室内料层区域45%,可降低进料口气体流量损失;出风管上端面距离干燥腔室顶端320 mm,尺寸为800 mm×1220 mm×200 mm;干燥腔室边角避免圆角过渡,可减少腔室内部气流涡旋,提高气流利用效果。研究结果为连续式微波干燥机结构设计和工艺优化提供理论依据。

Heat and mass transfer of a circular porous moist object located in a triangular shaped vented cavity

Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method.The porous object is considered to be a moist food sample,located in the middle of the cavity with inlet and outlet ports with different configurations of inlet/outlet ports.Convective drying performance is numerically assessed for different values of Reynolds numbers(between 50 and 250),dry air inlet temperature(between 40 and 80℃)and different locations of the port.It is observed that changing the port locations has significant impacts on the flow recirculaitons inside the triangular chamber while convective drying performance is highly affected.The moisture content reduces with longer time and for higher Reynolds number(Re)values.Case P4 where inlet and outlet ports are in the middle of the walls provides the most effective configuration in terms of convective drying performance while the worst case is seen for P1 case where inlet and outlet are closer to the corners of the chamber.There is a 192% difference between the moisture reduction of these two cases at Re=250,T=80℃ and t=120 min.

荔枝红外真空干燥过程火用变特性试验比较

分析了荔枝红外真空干燥热力系统的过程质量、能量变化,导出了果体及腔内干燥介质的火用变式;结合试验参数测定,对比了不同工艺组合干燥荔枝果体及腔内干燥介质的火用变特性。结果表明,改变荔枝红外真空干燥工艺组合条件,果体及腔内干燥介质的火用变特性不同;两种保压方式,荔枝果体火用均增加,保压时果体火用增幅小,其值随辐射距离、红外线源、加热缓苏比不同而改变,变化趋势与非保压时腔内干燥介质的火用变相近,各保压工艺组合干燥,腔内干燥介质火用呈锯齿形变化;非保压、SZ线源、120 mm辐射距离、30 min/15 min加热缓苏比工艺组合干燥,果体火用及干燥效率高。可为物料红外真空干燥的高效、节能加工提供参考。