脂肪酸甲酯降膜蒸发器沸腾传热性能

利用传统的多管排列式蒸发器对高黏度、易结垢的混合物进行蒸发，容易造成布液器堵塞，且结垢后的传热管难以清理。因此根据物料特性，本文设计了一种新型的降膜蒸发器，采用大降液孔加倾斜环板进行布膜，利用内径较大的锥筒作为传热壁面，并以粗甲酯作为试验工质对蒸发器的降膜蒸发传热系数随蒸发器筒体半锥度角、液膜流动雷诺数以及输入热通量之间的关系进行了试验研究。结果表明：该型蒸发器对于上述工质具有较好的适用性，蒸发系统能够在保持较高的传热系数的条件下，连续运行而不发生堵塞；蒸发器筒体锥度角有效地强化了降膜蒸发传热过程，而较大的热通量及进料流量在一定程度上却不利于蒸发传热。最后建立了降膜蒸发传热系数随蒸发器筒体半锥角和流动准数之间的经验关联式。

Boiling heat transfer characteristics of fatty acid methyl ester(FAME) in falling film evaporator

Using conventional line-tube heat exchanger for evaporation of high viscosity and easy-to-scaling mixture can easily block liquid distributor and make the cleaning of foul tube impossible. Therefore,a new type of falling film evaporator was designed,which used large liquid orifice plus tilt ring plate for liquid distribution and took larger diameter of conical shell as heat transfer wall. The variation of boiling heat transfer coefficients with shell's taper angle,Reynolds number and heat fluxes were determined by a pilot scale falling film evaporation system,using the FAME mixture as liquid model. Result showed that this type of evaporator worked well for FAME,the system could work smoothly with high heat transfer efficiency for a long time and without the occurrence of clogging. The evaporator shell's taper angle can intensify heat transfer process. The increase of heat flux and feed flow had a negative influence on heat transfer coefficient. Experimental correlation for boiling heat transfer coefficients with consideration of Reynolds number and taper angle of evaporator shell was established.