带水平传热管束的组合加热流化床传热及干燥特性

组合加热流化床干燥机综合了间接加热热效率高及普通流化床热质传递效率高的优点，在高湿含量物料及热敏性物料的干燥中具有优势。本文考察了带水平传热管束的组合加热流化床干燥机中各操作条件对传热系数及干燥机热效率的影响。结果表明，操作气速及床层温度对传热系数及热效率有较大影响，操作气速增大，传热系数先增大后降低，存在一个最大值，而热效率呈单调下降；床层温度升高，传热系数增大，而热效率降低；因此，合理选择这些操作条件，对提高传热系数及热效率是非常重要的。工业装置的运行结果表明，该干燥机的热效率达70％以上，远高于普通流化床干燥机。

Study on heat transfer and drying characteristics of fluidized-bed dryer with combined contact and convective heating

A fluidized-bed dryer with combined contact and convective heating can be used in the drying of high moisture content or heat-sensitive materials due to the advantages of high heat efficiency and high heat(mass) transfer rate. Experiments are conducted to measure the heat transfer coefficient between the horizontal tube bundles and the air-salt fluidized-bed and the heat efficiency in a fluidized bed dryer with combined contact and convective heating . The effects of gas velocity, bed-temperature and inlet moisture content of the salt on heat transfer and heat efficiency are investigated. It is shown that with the gas velocity increasing, the heat transfer coefficient increases firstly.It then decreases and has a maximum value; but the heat efficiency decreases. With the bed-temperature increasing, the heat transfer coefficient increases, but the heat efficiency decreases. The results are useful for the design and operation of this type of dryer.