Abstract:

To investigate the drying characteristics of multi-layer-arrangement cabbage seeds with heat pump drying, a cabbage seed heat pump drying model was built in this paper. It consists of the heat and mass transfer model of both drying air and cabbage seeds. The model was used to simulate the drying characteristics of cabbage seeds with three-layer orderly arrangement. The mean moisture content and temperature of overall cabbage seeds, internal moisture content and temperature of cabbage seeds were calculated and analyzed. Results show that seeds in the top layer dry faster than those in the bottom layer. So, the moisture content of different seeds rises gradually, while temperature decreases both along and across the flow direction of drying air. The moisture contents of seeds in the top layer rise from 12.67% to 12.80% along the flow direction of dry air in 3000 s, with temperatures decrease from 39.8℃ to 39.5℃. And the moisture contents of seeds in the eighth column rise from 12.73% to 12.78% across the flow direction of dry air in 3000 s, with temperatures decrease from 39.7℃ to 39.5℃.

Key words: heat pump, heat transfer, mass transfer, drying, diffusion, numerical simulation

摘要：

为了研究热泵干燥过程中多层种子的干燥特性,建立了包括干燥空气传热与传质模型、种子传热与传质模型组成的白菜种子热泵干燥模型,运用该模型模拟3层规则排列的白菜种子的干燥特性,分析了种子平均含水率与温度、种子内部含水率与温度的分布规律。研究表明,顶层种子干燥更快,在平行和垂直(由顶层到底层)于空气流动方向上,不同位置种子的含水率都逐渐升高,温度都逐渐降低。

关键词: 热泵, 传热, 传质, 干燥, 扩散, 数值模拟