水平管外降膜蒸发液膜流动状态及积垢分析

利用碱法麦草浆黑液作为工质,通过建立湍流数学模型对水平管外降膜黑液蒸发热传递积垢阻力情况进行研究,分析了水平管外降膜黑液蒸发的热传递、浓缩、黑液积垢现象,发现了水平传热管外有效减少黑液积垢和提高生产效率的热边界条件,得出对于一种较高固溶物质量分数的黑液,高Re值、低黑液与加热面温差、低加热温度是提高液体浓缩度和控制可溶物积垢非常有效的方法,同时也显示水平管外降膜黑液的成分越少越好,纯液体的蒸发速率是最好的。这个模型还可用来预测污垢的形成过程及积垢程度。

Flowing state of black liquid falling film evaporation outside horizontal-tubes and its influences on scale fouling

Taking wheat straw black liquor as the working media,the fouling resistance of wheat straw black liquor falling film evaporation outside the horizontal-tubs was studied by using a turbulent mathematical model. The heat transfer,concentration and scale fouling were investigated respectively. The boundary conditions that effectively minimize the black liquor fouling outside the horizontal-tubes and improve productivity were found. The results show that for the black liquid with higher solid solute mass fraction,the high Re value,low temperature difference between black liquor and heating surface and lower heating temperature have a great influence on the concentration and scale fouling. At the same time,the less components of black liquor are formed outside horizontal-tubes,the better evaporation rate will be obtained. The evaporation rate of pure liquid is the optimal. In addition,this model can be used to predict the fouling process and state of scale fouling.