内插螺旋线强化糖浆立式降膜蒸发传热

Heat Transfer Enhancement of Syrup Vertical Falling-film Evaporation by Spiral Inserts

搭建了新型立式单管蒸汽-糖浆降膜蒸发实验平台,进行连续4 h加与不加螺旋线的降膜蒸发运行对比实验,研究管内插入特定结构和工艺参数的螺旋线对变粘性糖浆降膜蒸发传热性能的影响.结果表明,内插螺旋线可明显改善糖浆降膜蒸发传热效果,相同条件下,内插螺旋线时总传热系数比空管提高了25.9%~82.9%,且随时间延长其下降速率明显低于空管;从管内蒸发侧和管外冷凝侧传热角度分析降膜蒸发传热性能,传热温差增大,管内蒸发侧传热性能变好,管外冷凝侧传热性能变差,增大传热温差改变物料物性(粘度减小)可强化传热效果.在非结垢影响的传热时间内,对管内蒸发侧传热系数进行处理,得到了管内综合传热系数与传热温差的实验关联式.

The new form of vertical single tube steam-syrup falling film evaporation experimental platform was built to study the heat transfer performance of inserting the specific structure and technological parameters＇ spiral in tube for the viscous syrup falling film evaporation, and conducting the 4 h comparative syrup falling film evaporation experiment for added and no added spiral. The results showed that inserting spiral has obviously effect on improving the heat transfer performance of syrup falling film evaporation, under the same experimental conditions, the total heat transfer coefficient improved 25.9%-82.9% than that inserted nothing, and the decline rate of total heat transfer coefficient with time was lower apparently. When the heat transfer temperature difference increased, the heat transfer of the evaporation side for inner tube get better but the condensation side for outer tube get deterioration, material physical properties changes（viscosity reduction） can enhanced heat transfer effect by increasing the heat transfer temperature difference. In the non-fouling affected heat transfer period, further processed was made for the evaporation side heat transfer coefficient, which obtaining the correlation between the inner tube comprehensive heat transfer coefficient and heat transfer temperature difference.