温度振荡条件下固定床传热传质试验研究
毕业论文关键词 固定床 热风对流干燥 干燥理论 模型
Title Heat and mass transfer in fixed-bed under the conditions of oscillating temperature
Abstract The mechanism of convective hot air drying about moist porous particles was described. The development process of drying theory about moist porous particles in terms of driving force was reviewed in brief. Several kind of common drying models in engineering were summarized, including two empirical models and three semi-empirical models and a method to choose the best model was provided. Through analyzing the experimental data, the drying rate of convective hot air drying in the fixed bed at different hot air temperatures and hot air flow rates was discussed. According to the first law of thermodynamics and the conservation of mass, a theoretical model about convective hot air drying in the fixed bed was built. Compared with constant temperature drying, the advantages of variable temperature drying were summarized. The process to construct the test bed about convective hot air drying in the fixed bed was described in brief.
Keywords fixed bed convective hot air drying drying theory model
绪论.11
研究背景及意义.11.1
1.2.1单场驱动理论.2
1.2.2双场驱动理论.2
1.2.3三场驱动理论.3
多孔介质热风对流干燥机理描述..31.3
多孔介质热风对流干燥过程描述..41.4
1.4.1恒速干燥阶段.4
1.4.2降速干燥阶段.4
经验和半经验模型.42
Lewis模型52.1
单参数模型..52.2
双参数模型..52.3
Thompson模型62.4
Herderson模型..62.5
模型评价.62.6
固定床干燥速率影响因素.73
惰性填料.83.1
热风温度.83.2
热风风量103.3
固定床热风对流干燥理论模型的构建133.4
振荡干燥过程分析164
干燥速率184.1
干燥品质194.2
干燥程度204.3
能耗.204.4
固定床试验台的搭建.225
固定床本体部分225.1
加热部分245.2
温度采集部分..245.3
温度振荡条件的实现..255.4
结论..26
致谢..28
参考文献.29
附录A固定床本体结构图.31
附录B固定床试验台系统图..32
绪论 1 研究背景及意义 1.1 含湿多孔介质的固定床干燥是一种低运行费用、低维护成本的干燥方式，其被大范围地应用于农业和化学工程等相关领域。谷物、咖啡、烟草、木材芯、煤炭等众多农业和化工产品通常采用固定床方式进行干燥。我国作为一个传统型的农业大国，粮食产量巨大，如果粮食得不到及时干燥，很容易霉烂变质，尤其是长江以南地区，气候潮湿且存在持续时间较长的梅雨季节，粮食的霉变现象更为严重。 经济的发展与能源的需求量是直接挂钩的，目前我国的经济正处于高速发展阶段，能源的需求量也日益增长。但是化石燃料的储量是有限的，而且大量燃烧化石燃料会造成环境污染问题。深入研究含湿多孔介质在固定床中的传热传质行为，源]自=优尔-·论~文"网·www.youerw.com/ 对整个干燥过程进行控制并加以优化，既可以提高干燥产品的品质，也可以减少能源消耗，缓解我国的能源和环境问题。因此研究含湿多孔介质的固定床干燥意义重大。 国内外研究现状