无虹吸管多通道烘缸流体流动及干燥机理的研究

In view of the traditional high energy consumption, dryer of paper machine paper page drying efficiency is low, not suitable for high speed paper machine development bottleneck problem, the study from the traditional dryer drying principle undertook thorough analysis, mentioned a new train of thought that is rainbow straw of draining condensed water energy saving multi channel dryer. In order for the dryer new structure principle analysis and demonstration, the study 1 ) establishment of a multichannel dryer channel within the fluid flow and heat transfer mathematical model, the steam pressure, flow, dryer structure parameters on the flow and heat transfer of the influence law; 2) through the experimental study on rotary channel condensation of steam velocity field, temperature field distribution, the condensation heat transfer coefficient and the paper page drying in the drying cylinder diameter, quantitative, width, channel size, speed and other several important parameters between the influence rules; 3) by numerical simulating the dryer inside the gas-liquid flow field, observation of gas phase concentration area and steam the accumulation condition, analysis of outlet gas volume fraction and overall heat transfer performance, establish the relationship between the paper page drying capacity and energy consumption situation. Based on the fluid flow in the channel and heat transfer analysis for multi channel dryer principle feasibility and provide the theoretical basis for design of structure optimization. This research is helpful to our country papermaking equipment energy saving and high speed paper machine development.

针对传统纸机烘缸能耗高、纸页干燥效率低、不适应高速纸机发展的瓶颈问题，本研究从干燥机理上对传统烘缸进行了深入分析，提出了一种无虹吸管排冷凝水的节能多通道烘缸的新思路。为了对该烘缸的新结构原理进行论证和分析，该研究1）建立多通道烘缸通道内流体流动及传热数学模型，得出蒸汽压力、流量、烘缸结构等参数对流动和传热的影响规律；2）通过实验研究回转通道内蒸汽冷凝的速度场、温度场分布情况，得出凝结换热系数及纸页干燥中定量、幅宽、烘缸直径、通道尺寸、车速等几个重要参数之间的影响规律；3）通过数值模拟烘缸内部的气液两相流场，观察气相的集中区域以及蒸汽的堆积情况，分析出口气体的体积分数及总体的换热性能，建立纸页干燥能力和能耗之间的关系。通过对通道内流体流动及传热分析为多通道烘缸的原理可行性以及结构优化设计提供理论依据。本项目的研究有助于我国造纸装备的节能降耗和高速纸机的发展。

传统纸机烘缸能耗高、纸页干燥效率低，且不适应高速纸机的发展，本研究从干燥机理上对传统烘缸进行了深入分析，提出了一种无虹吸管排除冷凝水的节能多通道烘缸。在2014年至2017年间，我们紧密围绕多通道烘缸的传热特性对其进行研究，通过自主设计搭建多通道烘缸传热特性可视化平台，研究了蒸汽流动参数及多通道烘缸结构参数对多通道烘缸的传热特性、压降特性及通道内气液两相流型的影响；同时由浅入深、依次递进的建立了3类多通道烘缸数学模型，通过实验研究与数值模拟相结合的方法，对多通道烘缸进行了全面的研究，获得的主要研究结果如下：1）研制了矩形小通道单边冷凝换热可视化实验平台，实现了单边换热矩形小通道内的气液两相流模拟流动及流型可视化观测。2）首次对多通道烘缸通道内蒸汽冷凝换热的流型进行了观测，并得到了不同的蒸汽流动参数和通道结构参数对流型转换的影响。3）采用直接测量法（温度、压力及流量等）获得了蒸汽在单边换热的矩形小通道内的冷凝传热特性，并建立了适用于本实验条件的新传热系数关联式及压降关联式，使得预测值与实验值间的误差大幅减小。4）应用数值模拟方法，依次递进的建立了0维多通道烘缸集总参数模型、1维通道分布参数模型和3维CFD旋转模型，对多通道烘缸的结构参数、通道中流型及通道旋转速度对传热性能的影响进行了研究。本项目的研究结果对多通道烘缸后续的理论研究及实际推广具有较为重要的科学意义。